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 *Project*                                Anubis

 *Title*                        Making interactive Web sites.

 *Copyright*                Copyright (c) Alain Prouté 2004-2005.
                            Copyright (c) Calexium 2007-2017.
                            Copyright (c) David René 2007-2021.


 *Authors* Alain Prouté
           David René
           Jérémy Larrieu
           Julien Verneuil


 *Revised* May 2015


  *Overview*

   In this file we propose simple tools for making well structured interactive and secured
   web sites.


   ----------------------------------- Table of Contents ---------------------------------

   * (1) Structure of a web site.
      ** (1.1) Three sorts of data.
      ** (1.2) How requests are handled.
      ** (1.3) What web pages are made of.
      ** (1.4) Actions.
      ** (1.5) States.

   * (2) Carrying on.
      ** (2.1) Describing your web sites.
      ** (2.2) Directories on the server's disk.
      ** (2.3) Starting your web sites.

   * (3) The HTML interface.
      ** (3.1) Types used by the HTML interface.
      ** (3.2) ``in form'' versus ``off form''.
      ** (3.3) Defining your own style.
      ** (3.4) Actioners and forms.
      ** (3.5) Local popup.

   ---------------------------------------------------------------------------------------


transmit tools/basis.anubis
read tools/printable_tree.anubis
read tools/base64.anubis
read tools/random.anubis
read tools/avlt_dictionaries.anubis
read system/lists.anubis
read system/string.anubis
read system/logger.anubis
transmit xlib/web/common.anubis
transmit xlib/web/multihost_http_server.anubis
read web/mime.anubis

read xlib/web/cookies.anubis
read xlib/web/json.anubis
transmit xlib/web/web_dump.anubis
transmit xlib/web/web_arg_utils.anubis
transmit xlib/web/web_session.anubis
transmit xlib/web/web_action.anubis

transmit xlib/web/types/web_action_name.anubis
transmit xlib/web/types/making_a_web_site.anubis

//TODO move anywhere


define List(Word8)
/** Test for HTML entity which must be encoded
 * and return the encoded entity if needed
 */
  get_entity
  (
    Word8       _char,
    List(Word8) tail
  )=
  //test for the ampersand
  if      _char = '&' then
    //test if it's already an encoded string like &amp; &lt; etc. In that case we do nothing
    if      insensitive_equal(['&','a','m','p',';'],      tail, 0) then [_char]
    else if insensitive_equal(['&','l','t',';'],          tail, 0) then [_char]
    else if insensitive_equal(['&','g','t',';'],          tail, 0) then [_char]
    else if insensitive_equal(['&','q','u','o','t',';'],  tail, 0) then [_char]
    else
      [';','p','m','a','&']
  //test for '<' etc.
  else if _char = '<'   then  [';','t','l','&']
  else if _char = '>'   then  [';','t','g','&']
  else if _char = '\"'  then  [';','t','o','u','q','&']
  else                        [_char]
.

define String
  _HTML_encode_entities
  (
    List(Word8) source,
    List(Word8) current
  )=
  if source is
  {
    []      then implode(reverse(current)),
    [c . t]  then
      _HTML_encode_entities(t, get_entity(c, t) + current)
  }
.

public define String
  encode_HTML_entities
  (
    String source
  )=
  _HTML_encode_entities(explode(source), [])
.

define List(Word8)
/** Test for HTML entity which must be encoded
 * and return the encoded entity if needed
 */
  get_entity_quote
  (
    Word8       _char,
    List(Word8) tail
  )=
  //test for the ampersand
  if      _char = '&' then
    //test if it's already an encoded string like &amp; &lt; etc. In that case we do nothing
    if      insensitive_equal(['&','a','m','p',';'],      tail, 0) then [_char]
    else if insensitive_equal(['&','l','t',';'],          tail, 0) then [_char]
    else if insensitive_equal(['&','g','t',';'],          tail, 0) then [_char]
    else if insensitive_equal(['&','q','u','o','t',';'],  tail, 0) then [_char]
    else
      [';','p','m','a','&']
  //test for '"' only.
  else if _char = '\"'  then  [';','t','o','u','q','&']
  else                        [_char]
.

define String
  _HTML_encode_quote
  (
    List(Word8) source,
    List(Word8) current
  )=
  if source is
  {
    []      then implode(reverse(current)),
    [c . t]  then
      _HTML_encode_quote(t, get_entity_quote(c, t) + current)
  }
.

public define String
  encode_HTML_quote
  (
    String source
  )=
  _HTML_encode_quote(explode(source), [])
.

   * (1) Structure of a web site.

   First of  all we  need to  explain what  a web site  should be  made of.   Ideally, the
   visitor  (also called  the  'client') should  see the  web  site working  as any  other
   interactive computer software.  So, it should  be clear that a 'session' (i.e.  a visit
   to  the  web site,  including  the  consultation of  several  pages)  is  some kind  of
   conversation  between the  visitor  and the  web site,  and  that the  web site  should
   maintain a 'current state' of this  conversation.  At each new request (click) from the
   visitor, this state must be updated.  This whole conversation is called a 'session' and
   should not be confused with a single request.


      ** (1.1) Three sorts of data.

   All  the data  needed for  putting a  web site  at work  may be  dispatched  into three
   categories:

     1. Constant data  (data that  never change). These  data may  be hard coded  into the
        Anubis source files of the web site.

     2. Permanent data  (data which always exist  independantly of the  users connected to
        the web site). These data are normally recorded into data bases.

     3. Session  data (data  which depend  on a  particular visitor  and which  exist only
        during the  time he  visits the web  site). These  data are stored  into so-called
        'states'.


   It is important to determine which data belongs to which category. This is part of your
   design decisions.


      ** (1.2) How requests are handled.

   We want to  separate the following two functionalities (which are  used at each request
   (click) during a single session):

      - computing the new  state from the previous state and from  the client request, and
        updating the data base,

      - computing the page  to be sent to the  client from the new current  state and from
        the informations in the data base.


   The next picture shows the structure we have in mind:


                request            +---------+         HTML page (with state name in cookie)
               .-------------------| client  |<--------------.
               | .-----------------|         |               |
               | | session         +---------+               |
               | | in cookie                                 |
               | |                                           |          client side
       ............................................................................
               | |                                           |          server side
               | |                                           |
               | | .-------------------.                     |
               | | | previous session  |                     |
               V V V                   |                     |
       +---------------+             +---------------+     +--------------+
       | compute state |             | server's disk |     | compute page |
       +---------------+             +---------------+     +--------------+
           ^     | |                    ^ ^                  ^ ^  ^
           |     | |                    | |                  | |  |
           |     | `--------------------+--------------------' |  |
           |     |   new state            |                    |  |
      read |     `------------------------+--------------------'  |
     write |         new state name                               |
    update V                                                      |
         +-----------+                                            |
         | data base |--------------------------------------------'
         +-----------+              read only


   When the client begins  a session, there is no previous state.  In this case, a default
   'initial state' is used instead.

   The data base  may be updated by 'compute  state' box, but should not be  update by the
   'compute page'  box. The 'compute  page' box  should be allowed  only to read  the data
   base.

   In this file, all  the above stuff is defined, except the  'compute state' and 'compute
   page' boxes. You just  have to provide the function for computing  a new state (compute
   state) and the function for computing the  page (compute page) from the new state.  You
   don't have to worry about state names, saving and retrieving states and the like.


      ** (1.3) What web pages are made of.

   What the client can see in his browser's  window may be called a 'page'. Within a page,
   we have several sorts of components:

      - 'local'  components, i.e.  all  components which  do not  open a  connection, like
        texts, images, etc...  possibly using JavaScript programmation,

      - 'actioners', which, when  clicked upon, open a connection with  our web site; they
        may appear as links or buttons, etc...

      - 'foreign links', which when clicked upon,  open a connection with another web site
        (or ours eventually).

   Of course, what an actioner does is just ask our web site to perform an action. To that
   end, the actioner essentially sends the name of the action to be performed. However, it
   may be necessary to provide additional  informations which may be seen as 'operands' of
   the action.   In order to  attach operands  to an action,  HTML provides the  notion of
   'form'. Indeed, a form contains essentially a set of input fields into which the client
   may put values for  the required operands of the action, and  a submit button, which is
   the actioner  itself. Notice  that a  single form may  contain several  submit buttons,
   which simply  means that  there are several  distincts actions  taking the same  set of
   operands.

   Restrictions  must be  put on  the use  of all  theses gadgets.   Indeed,  for example,
   putting a form within another form  is officially meaningless in HTML, and the client's
   browser may be  seriously disturbed by this.  In this file, we propose  an interface to
   the HTML language,  which forbids such meaningless things, simply  by imposing a strict
   typing of HTML concepts.

   Each web site may be accessible through two communication channels:

      - a non secured channel (HTTP),
      - a secured channel (HTTPS).

   Nevertheless, the whole  thing should be considered as a single  web site. For example,
   you may have a secured page,  obtained through HTTPS, containing public images obtained
   through HTTP.   An actioner in a  non secured page  may open a secured  connection, and
   conversely.

   Summarizing,  a web  page  is made  of  local elements,  foreign  links and  actioners.
   Actioners receive operands from forms, and  they also choose to communicate through the
   non secured or through the secured channel.


       +-------------------+
       | page              |
       |                   |                        +---------------+
       | +--------------+  |                        | next page     |
       | | form         |  |                        | (non secured) |
       | | +----------+ |  |    HTTP                |               |
       | | | actioner |---------------------------->|               |
       | | +----------+ |  |                        +---------------+
       | |              |  |
       | | +----------+ |  |                        +---------------+
       | | | actioner |---------------------------->| next page     |
       | | +----------+ |  |    HTTPS               | (secured)     |
       | |              |  |                        |               |
       | +--------------+  |                        |               |
       |                   |                        +---------------+
       |                   |
       +-------------------+


   Notice that actioners need no be necessarily put into forms. In that case, they work as
   ordinary links, but they still may receive operands as we shall see.


      ** (1.4) Actions.

   The  client  opens a  new  connection  with  our web  site  whenever  he clicks  on  an
   actioner. The  result is that  a request is  sent, essentially made  of a list  of 'web
   arguments'.  Each web argument is a  pair (name,value). One of these web arguments, the
   'action' web argument (whose name is  "a"), determines the action to be performed.  The
   other web  arguments (not including "s", used  to identify the state)  are the operands
   for this action.

   Hence, the  'compute state'  box in the  picture above,  splits naturally into  as many
   sub-boxes  as there are  actions. For  this reason,  we define  the following  type for
   representing actions (where '$State' is the type representing session informations):


   'http_action's  are executed  only under  HTTP, and  'https_action's are  executed only
   under HTTPS. 'http_https_action's may be executed under both types of connections.

   Each action has  a name, which is used  to identify the action. Each action  also has a
   function 'allow'  whose job  is to  verify that the  action is  allowed in  the current
   state, and a function 'do_it' for performing the action.  The function 'do_it' receives
   a lot of informations:

       - 'HTTP informations':
           - the IP address of the client,
           - the URI requested by the client (after redirection),
           - the list of HTTP headers generated by the client's browser,
       - the list  of web arguments sent  by the client  (except "s" and "a"),
       - the previous state (or the 'initial' or 'ticket expired' state if no previous
           state can be found).

   In most cases, HTTP informations are not used. This is the reason why they are gathered
   for simplicity into a unique datum of type 'HTTP_Info'.


   When you  define your web  site, you must  provide the list of  all the actions  of the
   site.  When  a new state  has been computed,  a graphical representation of  this state
   must be  sent to the  client.  To that  end, you must  provide a function  (named below
   'compute_page') of type:

                                   $State -> HTTP_Answer

   where  the type 'HTTP_Answer'  (defined below  in this  file) abstractly  represents HTML
   pages.

//public type HTTP_Answer:...

   It should be clear that states and  pages are deeply linked together. Indeed, we really
   understand the page shown to the client as a representation of the current state of the
   conversation  between the client  and the  web site,  but also  containing informations
   taken from the data bases.


//public type HTML_Partial_Content:...


public define List(HTTP_header)
  make_session_cookie_headers
  (
    String website_name,
    String session_name
  )
  =
    //println("Set-Cookie state_"+website_name+"="+state_name);
    [
      http_header("Set-Cookie", "session_"+website_name+"="+session_name+"; SameSite=Strict")
    ]
  .


   When  a request  arrives, we  need to  retrieve the  previous state  from  the server's
   disk. We receive the name of that state. If the state is out of date, the state file is
   kept 3 days, and then deleted.


define One
  delete_out_of_date_sessions          // for all web sites
  (
    List((String, List(String) -> One))   directories_and_functions
  )=
  if directories_and_functions is
  {
    [ ]     then unique,
    [h . t] then
      since h is (state_directory, function),
      function(directory_list(state_directory,"*"));
      delete_out_of_date_sessions(t)
  }
.

      ** (1.5) States.

   Now, we explain how you can define the  type (say 'State') to be used as an instance of
   the type parameter '$State'. The following is just a suggestion.

   Each  state   determines  a  page  (since   'compute_page'  computes  a   page  from  a
   state). However, some components of the state may be independant of the page. It may be
   the  case  for  example  for  the  indication  of the  natural  language  used  by  the
   client. Hence, a state should be made of (at least) two parts:

      - informations which are the same for all pages,
      - informations which are particular to each page.

   For example, you could define:

   type Page:                // one alternative per page, with particular informations
     login(...),             // in the components
     main_page(...),
     ...etc...

   Now, the type 'State' could be defined as follows:

   type State:
     state(Language,         // informations valid for all pages
           ...,
           Page).            // informations particular to a page

   However, if you are making a secured web site within which clients should be identified
   (by id and  password), it may be a good  idea to have two sorts of  states, one for non
   identified  clients and  one for  identified  clients. In  this case,  define the  type
   'State' as follows (this is just a suggestion):

   type State:
     non_identified(Language),
     identified(String id,
                Language,
                Page).

   When  a  request  arrives,  check  if  the  previous  state  is  'identified(...)'   or
   'non_identified(...)',  and don't  provide access  to certain  pages to  non identified
   clients. This is required for security.

   Some  more words  on security.   If your  site needs  to identify  clients,  define the
   initial state as 'non_identified(...)'.  Construct a 'login' page, and check the id and
   password of the  client. If the id and  password are correct, then change  the state of
   the client to  'identified(...)'. No other action  should be able to do  that.  Now, be
   confident that clients cannot forge states.  The only information they have is the name
   of a state, not the state itself which  is never sent over the network, but only stored
   on the server's disk. The name of the state is constructed using strong cryptographical
   methods (sha1).  If everything (since the  'login' page) is performed under HTTPS, even
   state names  cannot be seen by  a third party. So,  if the system  retrieves a previous
   state of  the form  'identified(...)', you can  be confident  that your client  is well
   identified, and you can send him confidential informations.

   States have a  limited life time. It may happen  that a client clicks on  a button at a
   time its state is  out of date. In this case, this system  considers that the new state
   is a special  state named 'ticket expired'. You must provide  a function producing this
   state when you describe  your web site. The page corresponding to  this state must just
   inform the client that  he/she waited a too long time before  clicking on a button, and
   has to restart (a new conversation) from the begining.


   * (2) Carrying on.

      ** (2.1) Describing your web sites.

   Before you may start your web site, you  must describe it, i.e.  produce a datum of the
   opaque type 'Web_Site'.

public type Web_Site:...

   Producing such a datum may be performed by:

 public define Web_Site
   make_web_site_description
     (
       List(String)                common_names,          // for example: ["www.our-business.com",
                                                          //               "192.168.0.1"]
                                                          // the second one is just for testing
       String                      site_directory,        // where 'public' and other directories are
                                                          // located (should NOT end with '/')
       String                      state_directory,
       One -> One                  init,
       (HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State       initial_state,
       ($State expired,
        Maybe(String),
        HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State   ticket_expired_state,
       (Maybe(String),
        HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State   ticket_lost_state,
       List(Web_Action($State))    actions,
       $State -> HTTP_Answer       compute_page,
       $State -> List(HTTP_header) additional_headers,
       List(HTTP_header)           constant_additional_headers,
       Int                         timeout,               // seconds (todo: minutes)
       Redirections                redirections,
       String                      charset,
       List(String)                journal_extensions,
       List(String)                journal_headers,
       String                      authorization_secret,
       List(MIME)                  known_mime_types,
       (String        action_name,
        List(Web_arg) args)-> One  before_send_file
     ).


   Explanations:

   'common_names' is the list of names of the  site (the name the browser must send as the
   value of the 'Host' HTTP header in order to access the site must be in that list). Such
   a name generally looks like this:

                                       www.somewhere.com

   If you are using  HTTPS, you also have an 'X.509 SSL  server certificate'.  The name of
   the site must  be exactly the same as  the name on the certificate  (which is precisely
   called the 'common name' in the X.509 jargon).  If the two names do not match, the site
   will still work, but the transaction will not be transparent to the client. His browser
   will complain that the name of the certificate does not match the name of the site, and
   he will have to accept the certificate manually.

   'site_directory' is  the absolute path to the  directory where the files  needed by the
   site are located. Usually this directory looks like:

                            my_anubis/web_sites/www.somewhere.com

   However, this  information is not computed  from 'common_name', so that  you can change
   the  common name  (for example  temporarily,  for networking  reasons) without  loosing
   access to the files.

   'ticket_expired_state(expired_state,http_info,lwa,is_https)'  must  produce  the  state
   whose graphical representation  is a page explaining to the user  that its 'ticket' (or
   'session information')  has expired, and that  he/she must close all  popup windows and
   start a  new session.   The arguments  of the function  contain the  previous (expired)
   state and all  current informations concerning the user.  This  arguments may be useful
   for example  for producing the expiration message  in the language chosen  by the user.
   You  can  also (and  this  may  be much  smarter)  send  a  'ticket prolongation  page'
   (including a new  login for example), and resume the same  conversation, since you have
   all the pertinent informations at hand. In  the case the ticket is definitely lost, the
   second fonction 'ticket_lost_state' is used.

   Notice that despite the fact that the  parameter $State is involved in the arguments of
   the above function, the type 'Web_Site' does not depend on this parameter.  This allows
   to produce  lists of web site  descriptions, where each description  may be constructed
   with a different instance of $State.  This is required because distinct sites must have
   distinct types  of session informations.   This is made  possible by the fact  that the
   type  is  obscure,  and  the   constructor  replaced  by  a  function  which  assembles
   'ticket_expired_state', ticket_lost_state', 'actions'  and 'compute_page' into a single
   entity not depending on $State. You should have a look to the private part of this file
   if you want more precisions about this programming technique.

   'charset' is  a string which will  determine the character  encoding to be used  by the
   browser.  Typically, this  string  is one  of:  "UTF-8", "ISO-8859-1",  "Windows-1252",
   etc...

   'before_send_file' is a function which is  executed just before the HTTP server sends a
   file. It gets an  action name and the web arguments received  with the request for that
   file.   Notice that  this  action  name and  these  web arguments  may  be  put into  a
   'private_download'  element, and  will  come back  to the  server  at the  time of  the
   download.


      ** (2.2) Directories on the server's disk.

   The  description of  your site contains  the name  of  the directory  within which  the
   required files are located. This may be for example:

                          my_anubis/web_sites/www.our-business.com/

   This is  called the 'site directory' (for  the given site). Within  the site directory,
   the following directories are created by this program:

          states
          public
          journal
          private_download
          upload_temporary

   The directory 'states'  is used for storing states (session  informations). Out of date
   states are automatically removed after some time.

   The tree rooted  at 'public' contains files that  the server is allowed to  send to the
   clients. For security  reasons, the server never  sends a file which is  not within the
   tree whose root is this 'public' directory (except for the 'private download' mecanism;
   see 'web/multihost_http_server.anubis').   Also, the MIME  type (see 'web/mime.anubis')
   must have been recognized before the file may be sent.

   The  directory  'journal'  contains the  jounal  files.   The  roles of  the  remaining
   directories    'private_download'    and    'upload_temporary'    is    explained    in
   'multihost_http_server.anubis',  where  you  will  also find  further  informations  on
   'public' and 'journal'.


      ** (2.3) Web servers parameters.

   The web servers  have several parameters useful for  administration. They are described
   as follows:

 public type WebServersParameters:
   wsparms(Var(Bool)      shutdown_required,

      ** (2.4) Starting your web sites.

   When you have described all your web sites (you may want to have several web sites, and
   they are distinguished  by their 'common name'), you may start  them all together using
   'start_web_sites' below.  This function returns a result of the following type:

public type Start_Web_Sites_Result:
   cannot_bind_to_port(Word32),
   cannot_bind_to_port(Word32,Word32),
   ok(Server http_server,
      Server https_server).

   Indeed, it may happen  that the system cannot bind (begin to listen)  to one of the two
   ports (or to both). The main reason is that another server is already listening on that
   port. Another reason may be that  'anbexec' has not been correctly installed, i.e. that
   the 's' bit  has not been set for  'user' and 'group' (there is not  such problem under
   Windows). Also notice that the Linux kernel  may need a rather long time (up to several
   minutes) before liberating  a listening port.  Now,  if the system can bind  to the two
   ports, the pair of  the two servers is returned. Two tools  are useful for manipulating
   servers:

      shutdown        of type   Server -> One
      is_down         of type   Server -> Bool

   They are defined in 'predefined.anubis' (together with the type 'Server').


public define Start_Web_Sites_Result
   start_web_sites
     (
       Word32                        ip_address,    // the IP address shared by the web sites
       Word32                        http_port,     // usually: 80
       Word32                        https_port,    // usually: 443
       String                       ssl_certificate_common_name,
       List(Web_Site)               web_sites,     // web sites to be started
       (One) -> Bool                shutdown_required
     ).

   'ip_address' is  the IP  address on which  the two  servers listen. If  you put  0, the
   servers  listen on all  the IP  addresses of  the machine.  This may  be useful  if the
   machine has several network interfaces.

   'ssl_certificate_common_name' is the common name  of the SSL certificate that 'anbexec'
   loads when it starts. One instance of  'anbexec' cannot handle more than one SSL server
   certificate. This is  due to a problem of  conception of SSL itself. See  the book 'SSL
   and TLS' by Eric Rescorla (at Addison Wesley) for more explanations.

   Notice that the  number of servers is always  2, regardless of the number  of web sites
   you are starting.

   The dynamic variable 'shutdown_required' may be used to control the shutdown of the two
   servers from within the web site  (typically the administration part). The servers will
   shutdown as  soon as  this variable contains  'true'.  So  you must provide  a variable
   containing 'false' otherwise your servers will  not run. You may also use the primitive
   'must_restart' (see 'predefined.anubis') to control the restarting of your servers.

   * (3) The HTML interface.

   We propose an interface to dynamic  HTML. Dynamic HTML includes HTML, and a combination
   of CSS (Cascading Style Sheet) and  JavaScript techniques for making HTML elements more
   reactive and attractive on the client side.


      ** (3.1) Types used by the HTML interface.

   For easy reference, we  gather below the definitions of all the  types used by the HTML
   interface, and we comment them immediately.

 //public type HTML_Off_Form:...


public define Printable_tree [HTML_Id      x . Printable_tree y] = str_pt(x.id, y).
public define Printable_tree [HtmlClass    x . Printable_tree y] = str_pt(x.class, y).
public define Printable_tree [WebArgName   x . Printable_tree y] = str_pt(x.name, y).
public define Printable_tree [WebArgValue  x . Printable_tree y] = str_pt(x.value, y).
public define Printable_tree [InitialValue x . Printable_tree y] = str_pt(x.value, y).

public define CoreAttrs   attr(String name, Bool value) = attr(name, if value then "true" else "false").
public define CoreAttrs   attr(String name, Int value)  = attr(name, to_String(value)).


public define InputAttrs   attr(String name, Bool value) = attr(name, if value then "true" else "false").


public define Text_Option
  tooltip(String s) = title(s).

   A list of 'Text_Option' must be given with each text you want to put in your page.

public define CoreAttrs
  tooltip(String s) = title(s).
public define InputAttrs
  tooltip(String s) = title(s).


public type I18n:
  lang  (String),
  dir   (Reading_Way).


  A list of 'DIV_Option' must be given with each DIV you want to put in your page.

public define String
  event_name
  (
    HtmlEvents e
  ) =
  if e is
  {
    onafterprint      then "onafterprint",   //HTML5 Script to be run after the document is printed
    onbeforeprint     then "onbeforeprint",  //HTML5 Script to be run before the document is printed
    onbeforeunload    then "onbeforeunload", //HTML5 Script to be run when the document is about to be unloaded
    onerror           then "onerror",        //HTML5 Script to be run when an error occurs
    onhashchange      then "onhashchange",   //HTML5 Script to be run when there has been changes to the anchor part of the a URL
    onload            then "onload",         //      Fires after the page is finished loading
    onmessage         then "onmessage",      //HTML5 Script to be run when the message is triggered
    onoffline         then "onoffline",      //HTML5 Script to be run when the browser starts to work offline
    ononline          then "ononline",       //HTML5 Script to be run when the browser starts to work online
    onpagehide        then "onpagehide",     //HTML5 Script to be run when a user navigates away from a page
    onpageshow        then "onpageshow",     //HTML5 Script to be run when a user navigates to a page
    onpopstate        then "onpopstate",     //HTML5 Script to be run when the window's history changes
    onresize          then "onresize",       //HTML5 Fires when the browser window is resized
    onstorage         then "onstorage",      //HTML5 Script to be run when a Web Storage area is updated
    onunload          then "onunload",       //      Fires once a page has unloaded (or the browser window has been closed)
    // Form element events
    onblur            then "onblur",         //      Fires the moment that the element loses focus
    onchange          then "onchange",       //      Fires the moment when the value of the element is changed
    oncontextmenu     then "oncontextmenu",  //HTML5 Script to be run when a context menu is triggered
    onfocus           then "onfocus",        //      Fires the moment when the element gets focus
    oninput           then "oninput",        //HTML5 Script to be run when an element gets user input
    oninvalid         then "oninvalid",      //HTML5 Script to be run when an element is invalid
    onreset           then "onreset",        //      Fires when the Reset button in a form is clicked
    onsearch          then "onsearch",       //      Fires when the user writes something in a search field (for <input="search">)
    onselect          then "onselect",       //      Fires after some text has been selected in an element
    onsubmit          then "onsubmit",       //      Fires when a form is submitted
    // Keyboard events (Not valid in base, bdo, br, frame, frameset, head, html, iframe, meta, param, script, style, and title elements.)
    onkeydown         then "onkeydown",      //      Fires when a user is pressing a key
    onkeypress        then "onkeypress",     //      Fires when a user presses a key
    onkeyup           then "onkeyup",        //      Fires when a user releases a key
    // Mouse events (Not valid in base, bdo, br, frame, frameset, head, html, iframe, meta, param, script, style, and title elements.)
    onclick           then "onclick",        //      Fires on a mouse click on the element
    ondblclick        then "ondblclick",     //      Fires on a mouse double-click on the element
    onmousedown       then "onmousedown",    //      Fires when a mouse button is pressed down on an element
    onmousemove       then "onmousemove",    //      Fires when the mouse pointer is moving while it is over an element
    onmouseout        then "onmouseout",     //      Fires when the mouse pointer moves out of an element
    onmouseover       then "onmouseover",    //      Fires when the mouse pointer moves over an element
    onmouseup         then "onmouseup",      //      Fires when a mouse button is released over an element
    onwheel           then "onwheel",        //HTML5 Fires when the mouse wheel rolls up or down over an element
    //Drag Events
    ondrag            then "ondrag",         //HMTL5 Script to be run when an element is dragged
    ondragend         then "ondragend",      //HTML5 Script to be run at the end of a drag operation
    ondragenter       then "ondragenter",    //HTML5 Script to be run when an element has been dragged to a valid drop target
    ondragleave       then "ondragleave",    //HTML5 Script to be run when an element leaves a valid drop target
    ondragover        then "ondragover",     //HTML5 Script to be run when an element is being dragged over a valid drop target
    ondragstart       then "ondragstart",    //HTML5 Script to be run at the start of a drag operation
    ondrop            then "ondrop",         //HTML5 Script to be run when dragged element is being dropped
    onscroll          then "onscroll",       //HTML5 Script to be run when an element's scrollbar is being scrolled
    //Clipboard Events
    oncopy            then "oncopy",         //HTML5 Fires when the user copies the content of an element
    oncut             then "oncut",          //HTML5 Fires when the user cuts the content of an element
    onpaste           then "onpaste",        //HTML5 Fires when the user pastes some content in an element
    //Media Events
    onabort           then "onabort",        //HTML5 Script to be run on abort
    oncanplay         then "oncanplay",      //HTML5 Script to be run when a file is ready to start playing (when it has buffered enough to begin)
    oncanplaythrough  then "oncanplaythrough", //HTML5 Script to be run when a file can be played all the way to the end without pausing for buffering
    oncuechange       then "oncuechange",    //HTML5 Script to be run when the cue changes in a <track> element
    ondurationchange  then "ondurationchange", //HTML5 Script to be run when the length of the media changes
    onemptied         then "onemptied",      //HTML5 Script to be run when something bad happens and the file is suddenly unavailable (like unexpectedly disconnects)
    onended           then "onended",        //HTML5 Script to be run when the media has reach the end (a useful event for messages like "thanks for listening")
    onerror           then "onerror",        //HTML5 Script to be run when an error occurs when the file is being loaded
    onloadeddata      then "onloadeddata",   //HTML5 Script to be run when media data is loaded
    onloadedmetadata  then "onloadedmetadata", //HTML5 Script to be run when meta data (like dimensions and duration) are loaded
    onloadstart       then "onloadstart",    //HTML5 Script to be run just as the file begins to load before anything is actually loaded
    onpause           then "onpause",        //HTML5 Script to be run when the media is paused either by the user or programmatically
    onplay            then "onplay",         //HTML5 Script to be run when the media is ready to start playing
    onplaying         then "onplaying",      //HTML5 Script to be run when the media actually has started playing
    onprogress        then "onprogress",     //HTML5 Script to be run when the browser is in the process of getting the media data
    onratechange      then "onratechange",   //HTML5 Script to be run each time the playback rate changes (like when a user switches to a slow motion or fast forward mode)
    onseeked          then "onseeked",       //HTML5 Script to be run when the seeking attribute is set to false indicating that seeking has ended
    onseeking         then "onseeking",      //HTML5 Script to be run when the seeking attribute is set to true indicating that seeking is active
    onstalled         then "onstalled",      //HTML5 Script to be run when the browser is unable to fetch the media data for whatever reason
    onsuspend         then "onsuspend",      //HTML5 Script to be run when fetching the media data is stopped before it is completely loaded for whatever reason
    ontimeupdate      then "ontimeupdate",   //HTML5 Script to be run when the playing position has changed (like when the user fast forwards to a different point in the media)
    onvolumechange    then "onvolumechange", //HTML5 Script to be run each time the volume is changed which (includes setting the volume to "mute")
    onwaiting         then "onwaiting",      //HTML5 Script to be run when the media has paused but is expected to resume (like when the media pauses to buffer more data)
    //Misc Events
    onshow            then "onshow",         //HTML5 Fires when a <menu> element is shown as a context menu
    ontoggle          then "ontoggle"
  }.


public define Table_Option nude = border(0,0,0,rgb(0,0,0)).


   A list of 'Table_Option' must be given with each table.


   A list of 'Cell_Option'  must be given with each cell and each  row in a table. Options
   given with a row apply to all the cells in the row, but are superseded by options given
   with cells, which apply only to the cell they are given with.


   The parameter $T is later  instantiated either to 'HTML_In_Form' or to 'HTML_Off_Form',
   depending on where  you put your table (within  a form or not within a  form). For your
   convenience, we define the following particular case:

public define HTML_Cell($T)
  cell
  (
    $T content
  )=
  cell([],content)
.

public define HTML_Cell($T)
  cell
  (
    Cell_Option option,
    $T          content
  ) =
  cell([option],content)
.

public define HTML_Header_Cell($T)
   header_cell
     (
       $T content
     ) =
   header_cell([],content).


   Same remark as for 'HTML_Cell($T)'. We define several convenience functions:

public define HTML_Row($T)
  row
  (
    List(HTML_Cell($T)) cells
  )=
  row([],cells).

public define HTML_Row($T)
  row
  (
    HTML_Cell($T) cell
  )=
  row([],[cell]).

public define HTML_Row($T)
  row
  (
    List(Cell_Option) options,
    HTML_Cell($T) cell
  )=
  row(options,[cell]).

public define HTML_Row($T)
  row
  (
    Cell_Option   option,
    HTML_Cell($T) cell
  )=
  row([option],[cell]).

public define HTML_Header_Row($T)
  header_row
  (
    List(HTML_Header_Cell($T)) cells
  ) =
  header_row([],cells).

public define HTML_Header_Row($T)
  header_row
  (
    HTML_Header_Cell($T) cell
  ) =
  header_row([],[cell]).


public define Actioner_Aspect
  immediate_selector
  (
    List(CoreAttrs) core_attrs,
    WebArgName      name,
    Int             size,
    List((List(CoreAttrs),WebArgValue,String)) choices
   )=
   immediate_selector(core_attrs, name, size, choices, failure, "")
   .

public define Actioner_Aspect
  immediate_selector
  (
    List(CoreAttrs) core_attrs,
    WebArgName      name,
    Int             size,
    List((List(CoreAttrs),WebArgValue,String)) choices,
    Maybe(InitialValue) selected
   )=
   immediate_selector(core_attrs, name, size, choices, selected, "")
   .


public define Actioner_Aspect
  link
  (
    List(Text_Option) options,
    String text
  )=
  link(options, text, failure).

public define Actioner_Aspect
  link
  (
    String text
  ) =
  link([], text, failure).


public define Actioner_Aspect
  link
  (
    List(Text_Option) options,
    Int              i
  ) =
  link(options, to_decimal(i), failure).

public define Actioner_Aspect
  link
  (
    Int i
  ) =
  link([], i).

public define Actioner_Aspect
   button
     (
       String  url_img
     ) =
   button(url_img,url_img).

   Actioners are explained in details below.


public define String
  to_String
  (
    CSS_File_Media css_file_media
  )=
  if css_file_media is
  {
    screen      then  "screen",
    tty         then  "tty",
    tv          then  "tv",
    projection  then  "projection",
    handheld    then  "handheld",
    print       then  "print",
    braille     then  "braille",
    aural       then  "aural",
    all         then  "all"
  }.


//public type HTML_Meta:...


public define HTML_Head_Tag
  js_script
  (
    String script_content
  )=
  js_inline(script("text/javascript", script_content))
.
 /* Label with help */


public define HTML_tooltip
  html_tooltip
  (
    String  keyword,
    Int     width
  )=
  html_tooltip("", keyword, width).

public define HTML_tooltip
  html_tooltip
  (
    String  title,
    String  keyword
  )=
  html_tooltip(title, keyword, 0).


public define HTML_Help
  tooltip
  (
    HTML_tooltip  h_tooltip
  )=
  tooltip(h_tooltip, left)
.


  /* It contains
   *  - a List of HTML_Head_Tag representing necessaries head tags for the content. ex: jquery js files, js script, css specific styles, ...
   *  - a HTML_Off_Form representing the HTML code for the part of the page we want to display
   */
//public type HTML_In_Form:...


public define List(HTML_Head_Tag)
  to_HTML_Head_Tag
  (
    List(CSS_File) css_file_list
  )=
  map((CSS_File css_f) |-> css(css_f), css_file_list).

public define List(HTML_Head_Tag)
  to_HTML_Head_Tag
  (
    List(JS_File) js_file_list
  )=
  map((JS_File js_f) |-> js(js_f), js_file_list).


   'HTML_In_Form'  defines all  the  elements  you may  put  within a  form.  We define  a
   convenience function:


public define HTML_In_Form  text_input(HTML_Label label,  HTML_Id id, WebArgName name, InitialValue init, Int width) = text_input([], label, id, name, init, width).

public define HTML_In_Form literal(Printable_tree t) = literal_pt(t).

public define HTML_In_Form image(String url) = image([], url, url).

public define HTML_In_Form image(String url, Int width, Int height) = image([], url, url, width, height).

public define HTML_In_Form
   foreign_link
     (
       Int tsize,
       String url,
       String name
     ) =
   foreign_link([size(tsize)],url,name).

public define HTML_In_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops,
       List(Actioner_Local_Action)  local_actions
  )=
  actioner(conn,targ,asp,action_name(action),extra_ops,local_actions)
.

public define HTML_In_Form
  actioner
  (
       Actioner_Connection       conn,
       Actioner_Target           targ,
       Actioner_Aspect           asp,
       WEB_Action_Name           action,
       List((String,String))     extra_ops
  )=
  actioner(conn,targ,asp,action,extra_ops,[])
.

public define HTML_In_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops
  )=
  actioner(conn,targ,asp,action_name(action),extra_ops,[])
.

public define HTML_In_Form
  actioner
  (
    Actioner_Connection       conn,
    Actioner_Target           targ,
    Actioner_Aspect           asp,
  )=
  actioner(conn, targ, asp, action_name(""), [], []).


public define HTML_In_Form
   text_area
     (
       WebArgName name,
       InitialValue init,
       Int  width,
       Int  height
     ) =
   text_area([], no_label, html_Id(""), name,init,width,height).

public define HTML_In_Form
   text_area
     (
       List(TextAreaOption) options,
       WebArgName name,
       InitialValue init,
       Int  width,
       Int  height
     ) =
   text_area(options, no_label, html_Id(""), name,init,width,height).

public define HTML_In_Form
   table
     (
       List(HTML_Row(HTML_In_Form)) rows
     ) =
   table([],empty,rows,empty).

public define HTML_In_Form
  table
  (
    List(Table_Option)            options,
    List(HTML_Row(HTML_In_Form))  rows
  ) =
  table(options,empty,rows,empty).

public define HTML_In_Form
  table
  (
    HTML_Header_Row(HTML_In_Form)  h_row,
    List(HTML_Row(HTML_In_Form))   rows
  ) =
  table([],h_row,rows,empty).

public define HTML_In_Form
  table
  (
    List(Table_Option)            options,
    HTML_Header_Row(HTML_In_Form) h_row,
    List(HTML_Row(HTML_In_Form))  rows
  ) =
  table(options,h_row,rows,empty).

public define HTML_In_Form
   private_download
     (
       String        abs_path,
       String        name,
       String        extra_ext
     ) =
   private_download(abs_path,name,extra_ext,failure).

public define HTML_In_Form
   private_download
     (
       String        abs_path,
       String        name,
       String        extra_ext,
       String        action_name,
       List((String,String))   args
     ) =
   private_download(abs_path,name,extra_ext,success((action_name,args))).


public define HTML_In_Form
  text
  (
    List(CoreAttrs) l,
    Int             i
  ) =
  text(l, to_decimal(i)).

public define HTML_In_Form
  text
  (
    String s
  )=
  text([],s)
.

public define HTML_In_Form
  text
  (
    Int i
  ) =
  text([], i)
.

public define HTML_In_Form
  div
  (
    HTML_In_Form element
  )=
  div([], [element])
.

public define HTML_In_Form
  div
  (
    List(CoreAttrs) attrs,
    HTML_In_Form   element
  )=
  div(attrs, [element])
.

public define HTML_In_Form
  span
  (
    String s
  )=
  span([],s)
.

public define HTML_In_Form
  span
  (
    Int i
  ) =
  span([], to_decimal(i))
.

public define HTML_In_Form
  radio_button   (List(CoreAttrs) options, HTML_Label label, WebArgName n, WebArgValue value, Bool checked)
  = radio_button (options, label, html_Id(n.name), n, value, checked).

public define HTML_In_Form
  radio_button_r   (List(CoreAttrs) options, HTML_Label label, WebArgName n, WebArgValue value, Bool checked)
  = radio_button_r (options, label, html_Id(n.name), n, value, checked).

public define HTML_In_Form
  check_box     (List(CoreAttrs) options, HTML_Label label, WebArgName n, Bool checked)
  = check_box   (options, label, html_Id(n.name), n, checked).

public define HTML_In_Form
  check_box_r    (List(CoreAttrs) options, HTML_Label label, WebArgName n, Bool checked)
  = check_box_r  (options, label, html_Id(n.name), n, checked).

public define HTML_In_Form
  file_upload     (WebArgName n, Int width)
  = file_upload([], no_label, html_Id(n.name), n, width).

public define HTML_In_Form
  hidden  (WebArgName name, WebArgValue value)
  =
  hidden(html_Id(""), name, value).

public type Input_Type:
button,
checkbox,
color,
date,
datetime_local,
email,
file,
hidden,
image,
month,
number,
password,
radio,
range,
reset,
search,
submit,
tel,
text,
time,
url,
week
.

public type FormMethod:
  get,
  post
.

//public type HTML_Body:...

public define CoreAttrs formaction(WEB_Action_Name action, List((String,String)) extra_ops)   = attr("formaction", format_web_action_name(action, extra_ops)).
public define CoreAttrs formaction(WEB_Action_Name action, (String,String) extra_op)          = attr("formaction", format_web_action_name(action, extra_op)).
public define CoreAttrs formaction(WEB_Action_Name action)                                    = attr("formaction", format_web_action_name(action)).
public define CoreAttrs formmethod(FormMethod method) = attr("formmethod", if method is { get then "get", post then "post"}).


   'HTML_Off_Form' defines all the elements you may put outside any form.


public define CoreAttrs method(String value)      = attr("method", value).
public define CoreAttrs action(WEB_Action_Name action)= attr("action", "/"+format_web_action_name(action)).
public define CoreAttrs action(WEB_Action_Name action, List((String,String)) extra_ops)= attr("formaction", "/"+format_web_action_name(action, extra_ops)).
public define CoreAttrs formmethod(String value)      = attr("formmethod", value).
public define CoreAttrs form(String value)            = attr("form", value).


public define HTML_Off_Form text(List(CoreAttrs) attrs, Int i)  = text(attrs,   to_decimal(i)).
public define HTML_Off_Form text(CoreAttrs attr, Int i)         = text([attr],  i).
public define HTML_Off_Form text(Int i)                         = text([],      i).
public define HTML_Off_Form text(String s)                      = text([],      s).
public define HTML_Off_Form text(CoreAttrs attr, String s)      = text([attr],  s).

public define HTML_Off_Form a(A_href _href)                                                     = a([],     _href, _self, []).
public define HTML_Off_Form a(List(CoreAttrs) attrs, A_href _href)                              = a(attrs,  _href, _self, []).
public define HTML_Off_Form a(List(CoreAttrs) attrs, A_href _href, HTML_Off_Form content)       = a(attrs,  _href, _self, [content]).
public define HTML_Off_Form a(List(CoreAttrs) attrs, A_href _href, List(HTML_Off_Form) content) = a(attrs,  _href, _self, content).
public define HTML_Off_Form a(A_href _href, HTML_Off_Form content)                              = a([],     _href, _self, [content]).
public define HTML_Off_Form a(A_href _href, List(HTML_Off_Form) content)                        = a([],     _href, _self, content).
public define HTML_Off_Form a(List(CoreAttrs) attrs, A_href _href, A_target _target, HTML_Off_Form content) = a(attrs,     _href, _target, [content]).
public define HTML_Off_Form a(CoreAttrs attr, A_href _href, A_target _target, HTML_Off_Form content)        = a([attr],    _href, _target, [content]).
public define HTML_Off_Form a(A_href _href, A_target _target, HTML_Off_Form content)            = a([],     _href, _target, [content]).
public define HTML_Off_Form a(A_href _href, A_target _target, List(HTML_Off_Form) content)      = a([],     _href, _target, content).
public define HTML_Off_Form a(CoreAttrs attr, A_href _href, A_target _target, List(HTML_Off_Form) content)  = a([attr],     _href, _target, content).

  // <article>
public define HTML_Off_Form article(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("article", attrs, content).
public define HTML_Off_Form article(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("article", attrs, [content]).
public define HTML_Off_Form article(List(HTML_Off_Form) content)                         = html_tag("article", [],    content).
public define HTML_Off_Form article(HTML_Off_Form content)                               = html_tag("article", [],    [content]).

  // <aside>
public define HTML_Off_Form aside(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("aside", attrs, content).
public define HTML_Off_Form aside(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("aside", attrs, [content]).
public define HTML_Off_Form aside(List(HTML_Off_Form) content)                         = html_tag("aside", [],    content).
public define HTML_Off_Form aside(HTML_Off_Form content)                               = html_tag("aside", [],    [content]).

  // <b> text in bold face
public define HTML_Off_Form b(String string)                                          = html_tag("b", [], [text(string)]).
public define HTML_Off_Form b(List(CoreAttrs) attrs, HTML_Off_Form content)           = html_tag("b", attrs, [content]).
public define HTML_Off_Form b(CoreAttrs attr, List(HTML_Off_Form) content)            = html_tag("b", [attr], content).
public define HTML_Off_Form b(CoreAttrs attr, HTML_Off_Form content)                  = html_tag("b", [attr], [content]).
public define HTML_Off_Form b(List(CoreAttrs) attrs, String string)                   = html_tag("b", attrs, [text(string)]).
public define HTML_Off_Form b(CoreAttrs attr, String string)                          = html_tag("b", [attr], [text(string)]).

  // <br>
public define HTML_Off_Form br                                                          = html_void_tag("br", []).
public define HTML_Off_Form br(List(CoreAttrs) attrs)                                   = html_void_tag("br", attrs).

  // <button>
public define HTML_Off_Form button(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("button", attrs,   content).
public define HTML_Off_Form button(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("button", attrs,   [content]).
public define HTML_Off_Form button(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("button", [attr],  content).
public define HTML_Off_Form button(CoreAttrs attr, HTML_Off_Form content)               = html_tag("button", [attr],  [content]).
public define HTML_Off_Form button(List(CoreAttrs) attrs)                               = html_tag("button", attrs,   []).
public define HTML_Off_Form button(List(CoreAttrs) attrs, String string)                = html_tag("button", attrs,   [text(string)]).
public define HTML_Off_Form button(List(HTML_Off_Form) content)                         = html_tag("button", [],      content).
public define HTML_Off_Form button(HTML_Off_Form content)                               = html_tag("button", [],      [content]).

  // <canvas>
public define HTML_Off_Form canvas(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("canvas", attrs,   content).
public define HTML_Off_Form canvas(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("canvas", attrs,   [content]).
public define HTML_Off_Form canvas(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("canvas", [attr],  content).
public define HTML_Off_Form canvas(CoreAttrs attr, HTML_Off_Form content)               = html_tag("canvas", [attr],  [content]).
public define HTML_Off_Form canvas(List(CoreAttrs) attrs)                               = html_tag("canvas", attrs,   []).
public define HTML_Off_Form canvas(List(HTML_Off_Form) content)                         = html_tag("canvas", [],      content).
public define HTML_Off_Form canvas(HTML_Off_Form content)                               = html_tag("canvas", [],      [content]).
public define HTML_Off_Form canvas(CoreAttrs cattr, Int width, Int height)              = html_tag("canvas", [cattr,
                                                                                                              attr("width", to_String(width)),
                                                                                                              attr("height", to_String(height))
                                                                                                             ],      []).
public define HTML_Off_Form canvas(List(CoreAttrs) attrs, Int width, Int height)              = html_tag("canvas", [
                                                                                                              attr("width", to_String(width)),
                                                                                                              attr("height", to_String(height)).
                                                                                                              attrs
                                                                                                             ],      []).
  // <datalist>
public define HTML_Off_Form datalist(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("datalist", attrs, content).
public define HTML_Off_Form datalist(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("datalist", attrs, [content]).
public define HTML_Off_Form datalist(List(HTML_Off_Form) content)                         = html_tag("datalist", [],    content).
public define HTML_Off_Form datalist(HTML_Off_Form content)                               = html_tag("datalist", [],    [content]).

  // <div>
public define HTML_Off_Form div(List(CoreAttrs) attrs, List(HTML_Off_Form) content)   = html_tag("div", attrs,  content).
public define HTML_Off_Form div(List(CoreAttrs) attrs, HTML_Off_Form content)         = html_tag("div", attrs,  [content]).
public define HTML_Off_Form div(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("div", [attr], content).
public define HTML_Off_Form div(CoreAttrs attr, HTML_Off_Form content)                = html_tag("div", [attr], [content]).
public define HTML_Off_Form div(List(HTML_Off_Form) content)                          = html_tag("div", [],     content).
public define HTML_Off_Form div(HTML_Off_Form content)                                = html_tag("div", [],     [content]).
public define HTML_Off_Form div(List(CoreAttrs) attrs)                                = html_tag("div", attrs,  []).
public define HTML_Off_Form div(CoreAttrs attr)                                       = html_tag("div", [attr], []).

public define HTML_Off_Form div(String string)                                        = html_tag("div", [],     [text(string)]).
public define HTML_Off_Form div(CoreAttrs attr, String string)                        = html_tag("div", [attr], [text(string)]).
public define HTML_Off_Form div(List(CoreAttrs) attrs, String string)                 = html_tag("div", attrs,  [text(string)]).

public define HTML_Off_Form div(List(CoreAttrs) attrs, HTML_Partial_Content content)  = div(attrs,  [content]).
public define HTML_Off_Form div(List(HTML_Partial_Content) content)                   = div([],     content).
public define HTML_Off_Form div(CoreAttrs attr, HTML_Partial_Content content)         = div([attr], [content]).
public define HTML_Off_Form div(HTML_Partial_Content content)                         = div([],     [content]).

//public define HTML_Partial_Content div(List(CoreAttrs) attrs, HTML_Partial_Content content)  = partial_content([], div(attrs,  [content])).
//public define HTML_Partial_Content div(CoreAttrs attr, HTML_Partial_Content content)  = partial_content([], div([attr], [content])).
//public define HTML_Partial_Content div(List(HTML_Partial_Content) content)            = partial_content([], div([],     content)).
//public define HTML_Partial_Content div(HTML_Partial_Content content)                  = partial_content([], div([],     [content])).

  // <dd>
public define HTML_Off_Form dd(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("dd", attrs, content).
public define HTML_Off_Form dd(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("dd", attrs, [content]).
public define HTML_Off_Form dd(List(HTML_Off_Form) content)                         = html_tag("dd", [],    content).
public define HTML_Off_Form dd(HTML_Off_Form content)                               = html_tag("dd", [],    [content]).

  // <dl>
public define HTML_Off_Form dl(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("dl", attrs, content).
public define HTML_Off_Form dl(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("dl", attrs, [content]).
public define HTML_Off_Form dl(List(HTML_Off_Form) content)                         = html_tag("dl", [],    content).
public define HTML_Off_Form dl(HTML_Off_Form content)                               = html_tag("dl", [],    [content]).

  // <dt>
public define HTML_Off_Form dt(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("dt", attrs, content).
public define HTML_Off_Form dt(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("dt", attrs, [content]).
public define HTML_Off_Form dt(List(HTML_Off_Form) content)                         = html_tag("dt", [],    content).
public define HTML_Off_Form dt(HTML_Off_Form content)                               = html_tag("dt", [],    [content]).

  // <em>
public define HTML_Off_Form em(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("em", attrs, content).
public define HTML_Off_Form em(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("em", attrs, [content]).
public define HTML_Off_Form em(List(HTML_Off_Form) content)                         = html_tag("em", [],    content).
public define HTML_Off_Form em(HTML_Off_Form content)                               = html_tag("em", [],    [content]).

  // <footer>
public define HTML_Off_Form footer(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("footer", attrs, content).
public define HTML_Off_Form footer(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("footer", attrs, [content]).
public define HTML_Off_Form footer(List(HTML_Off_Form) content)                         = html_tag("footer", [],    content).
public define HTML_Off_Form footer(HTML_Off_Form content)                               = html_tag("footer", [],    [content]).

  // <form>
public define HTML_Off_Form form(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("form", attrs, content).
public define HTML_Off_Form form(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("form", attrs, [content]).
public define HTML_Off_Form form(CoreAttrs attr, List(HTML_Off_Form) content)           = html_tag("form", [attr], content).
public define HTML_Off_Form form(CoreAttrs attr, HTML_Off_Form content)                 = html_tag("form", [attr], [content]).
public define HTML_Off_Form form(List(CoreAttrs) attrs)                                 = html_tag("form", attrs, []).
public define HTML_Off_Form form(CoreAttrs attr)                                        = html_tag("form", [attr], []).

public define HTML_Off_Form form(List(HTML_Off_Form) content)                           = html_tag("form", [],    content).
public define HTML_Off_Form form(HTML_Off_Form content)                                 = html_tag("form", [],    [content]).


  // <header>
public define HTML_Off_Form header(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("header", attrs, content).
public define HTML_Off_Form header(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("header", attrs, [content]).
public define HTML_Off_Form header(List(HTML_Off_Form) content)                         = html_tag("header", [],    content).
public define HTML_Off_Form header(HTML_Off_Form content)                               = html_tag("header", [],    [content]).

  // <h1>
public define HTML_Off_Form h1(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h1", attrs, content).
public define HTML_Off_Form h1(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h1", attrs, [content]).
public define HTML_Off_Form h1(List(HTML_Off_Form) content)                         = html_tag("h1", [],    content).
public define HTML_Off_Form h1(HTML_Off_Form content)                               = html_tag("h1", [],    [content]).
  // <h2>
public define HTML_Off_Form h2(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h2", attrs, content).
public define HTML_Off_Form h2(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h2", attrs, [content]).
public define HTML_Off_Form h2(List(HTML_Off_Form) content)                         = html_tag("h2", [],    content).
public define HTML_Off_Form h2(HTML_Off_Form content)                               = html_tag("h2", [],    [content]).
  // <h3>
public define HTML_Off_Form h3(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h3", attrs, content).
public define HTML_Off_Form h3(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h3", attrs, [content]).
public define HTML_Off_Form h3(List(HTML_Off_Form) content)                         = html_tag("h3", [],    content).
public define HTML_Off_Form h3(HTML_Off_Form content)                               = html_tag("h3", [],    [content]).
  // <h4>
public define HTML_Off_Form h4(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h4", attrs, content).
public define HTML_Off_Form h4(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h4", attrs, [content]).
public define HTML_Off_Form h4(List(HTML_Off_Form) content)                         = html_tag("h4", [],    content).
public define HTML_Off_Form h4(HTML_Off_Form content)                               = html_tag("h4", [],    [content]).
  // <h5>
public define HTML_Off_Form h5(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h5", attrs, content).
public define HTML_Off_Form h5(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h5", attrs, [content]).
public define HTML_Off_Form h5(List(HTML_Off_Form) content)                         = html_tag("h5", [],    content).
public define HTML_Off_Form h5(HTML_Off_Form content)                               = html_tag("h5", [],    [content]).

  // <h6>
public define HTML_Off_Form h6(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("h6", attrs, content).
public define HTML_Off_Form h6(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("h6", attrs, [content]).
public define HTML_Off_Form h6(List(HTML_Off_Form) content)                         = html_tag("h6", [],    content).
public define HTML_Off_Form h6(HTML_Off_Form content)                               = html_tag("h6", [],    [content]).

  // <hr>
public define HTML_Off_Form hr                                                      = html_void_tag("hr", []).
public define HTML_Off_Form hr(List(CoreAttrs) attrs)                               = html_void_tag("hr", attrs).
public define HTML_Off_Form hr(CoreAttrs attr)                                      = html_void_tag("hr", [attr]).

  // <iframe>
public define HTML_Off_Form iframe(CoreAttrs _attr, String src, Int width, Int height) =
  html_tag("iframe", [_attr, attr("src",src), width_px(width), height_px(height)], []).
public define HTML_Off_Form iframe(String src, Int width, Int height) =
  html_tag("iframe", [attr("src",src), width_px(width), height_px(height)], []).
public define HTML_Off_Form iframe(String src)                                      = html_tag("iframe", [attr("src",src)], []).

  // <input>
public define HTML_Off_Form input(List(CoreAttrs) attrs)                            = html_void_tag("input", attrs).
public define HTML_Off_Form input(CoreAttrs attr)                                   = html_void_tag("input", [attr]).

public define CoreAttrs type(String value)= attr("type", value).
public define CoreAttrs name(String value)= attr("name", value).
public define CoreAttrs value(String value)= attr("value", value).
public define CoreAttrs init(String value)= attr("value", encode_HTML_entities(value)).
  //-- BEGIN of <input> preset type

  /// Radio button
public define HTML_Off_Form radio(List(CoreAttrs) attrs, String name, String value, String form, Bool checked) = input([type("radio"), attr("name",name), attr("value",value), attr("form", form), bool_attr(checked, "checked") . attrs]).
public define HTML_Off_Form radio(List(CoreAttrs) attrs, String name, String value, String form)  = radio(attrs, name, value, form, false).
public define HTML_Off_Form radio(String name, String value, String form, Bool checked)           = radio([], name, value, form, checked).
public define HTML_Off_Form radio(String name, String value, String form)                         = radio([], name, value, form, false).

  /// hidden value
public define HTML_Off_Form hidden(List(CoreAttrs) attrs, String name, String value, String form) = input([type("hidden"), attr("name",name), attr("value",value), attr("form", form) . attrs]).
public define HTML_Off_Form hidden(CoreAttrs attr, String name, String value, String form)        = hidden([attr],  name, value, form).
public define HTML_Off_Form hidden(String name, String value, String form)                        = hidden([], name, value, form).
public define HTML_Off_Form hidden(String _name, String _value)                                    = input([type("hidden"), name(_name), value(_value)]).

  //-- END  of <input> preset type

  // <img>
public define HTML_Off_Form img(List(CoreAttrs) attrs, String src, String alt)      = html_void_tag("img", attrs + [attr("src",src), attr("alt",alt)] ).
public define HTML_Off_Form img(CoreAttrs _attr, String src, String alt)            = html_void_tag("img", [_attr, attr("src",src), attr("alt",alt)] ).
public define HTML_Off_Form img(String src)                                         = img([], src, "").
public define HTML_Off_Form img(String src, String alt)                             = img([], src, alt).
public define HTML_Off_Form img(List(CoreAttrs) attrs, String src)                  = img(attrs, src, "").
public define HTML_Off_Form img(CoreAttrs attr, String src)                         = img([attr], src, "").
public define HTML_Off_Form img(String src, Int width, Int height)                  = img([attr("width",to_String(width)+"px"), attr("height",to_String(height)+"px")], src, src).
public define HTML_Off_Form img(String src, String alt, Int width, Int height) =
  html_void_tag("img", [attr("src",src), attr("alt",alt), attr("width",to_String(width)+"px"), attr("height",to_String(height)+"px")]).

public define HTML_Off_Form img(List(CoreAttrs) attrs, String src, String alt, Int width, Int height) =
  html_void_tag("img", attrs + [attr("src",src), attr("alt",alt), attr("width",to_String(width)+"px"), attr("height",to_String(height)+"px")]).

public define HTML_Off_Form img(CoreAttrs _attr, String src, String alt, Int width, Int height) =
  html_void_tag("img", [_attr, attr("src",src), attr("alt",alt), width_px(width), height_px(height)]).

  // <label>
public define HTML_Off_Form label(List(CoreAttrs) attrs, List(HTML_Off_Form) content)   = html_tag("label", attrs,  content).
public define HTML_Off_Form label(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("label", [attr], content).
public define HTML_Off_Form label(List(HTML_Off_Form) content)                          = html_tag("label", [],     content).
public define HTML_Off_Form label(HTML_Off_Form content)                                = html_tag("label", [],     [content]).
public define HTML_Off_Form label(String string)                                        = html_tag("label", [],     [text(string)]).
public define HTML_Off_Form label(CoreAttrs attr, String string)                        = html_tag("label", [attr], [text(string)]).
public define HTML_Off_Form label(List(CoreAttrs) attrs, String string)                 = html_tag("label", attrs,  [text(string)]).

  // <li>
public define HTML_Off_Form li(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("li", attrs,   content).
public define HTML_Off_Form li(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("li", attrs,   [content]).
public define HTML_Off_Form li(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("li", [attr],  content).
public define HTML_Off_Form li(CoreAttrs attr, HTML_Off_Form content)               = html_tag("li", [attr],  [content]).
public define HTML_Off_Form li(List(HTML_Off_Form) content)                         = html_tag("li", [],      content).
public define HTML_Off_Form li(HTML_Off_Form content)                               = html_tag("li", [],      [content]).
public define HTML_Off_Form li(String string)                                        = html_tag("li", [],     [text(string)]).
public define HTML_Off_Form li(CoreAttrs attr, String string)                        = html_tag("li", [attr], [text(string)]).
public define HTML_Off_Form li(List(CoreAttrs) attrs, String string)                 = html_tag("li", attrs,  [text(string)]).

  // <main>
public define HTML_Off_Form main(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("main", attrs, content).
public define HTML_Off_Form main(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("main", attrs, [content]).
public define HTML_Off_Form main(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("main", [attr], content).
public define HTML_Off_Form main(CoreAttrs attr, HTML_Off_Form content)               = html_tag("main", [attr], [content]).
public define HTML_Off_Form main(List(HTML_Off_Form) content)                         = html_tag("main", [],    content).
public define HTML_Off_Form main(HTML_Off_Form content)                               = html_tag("main", [],    [content]).

  // <nav>
public define HTML_Off_Form nav(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("nav", attrs, content).
public define HTML_Off_Form nav(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("nav", attrs, [content]).
public define HTML_Off_Form nav(List(HTML_Off_Form) content)                         = html_tag("nav", [],    content).
public define HTML_Off_Form nav(HTML_Off_Form content)                               = html_tag("nav", [],    [content]).

  // <ol>
public define HTML_Off_Form ol(List(CoreAttrs) attrs, List(HTML_Off_Form) content)        = html_tag("ol", attrs, content).
public define HTML_Off_Form ol(List(CoreAttrs) attrs, HTML_Off_Form content)              = html_tag("ol", attrs, [content]).
public define HTML_Off_Form ol(List(HTML_Off_Form) content)                               = html_tag("ol", [],    content).
public define HTML_Off_Form ol(HTML_Off_Form content)                                     = html_tag("ol", [],    [content]).

  // <option>
public define HTML_Off_Form option(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("option", attrs, content).
public define HTML_Off_Form option(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("option", attrs, [content]).
public define HTML_Off_Form option(List(HTML_Off_Form) content)                           = html_tag("option", [],    content).
public define HTML_Off_Form option(HTML_Off_Form content)                                 = html_tag("option", [],    [content]).

  // <p>
public define HTML_Off_Form p(List(CoreAttrs) attrs, List(HTML_Off_Form) content)         = html_tag("p", attrs, content).
public define HTML_Off_Form p(List(CoreAttrs) attrs, HTML_Off_Form content)               = html_tag("p", attrs, [content]).
public define HTML_Off_Form p(CoreAttrs attr, List(HTML_Off_Form) content)                = html_tag("p", [attr], content).
public define HTML_Off_Form p(CoreAttrs attr, HTML_Off_Form content)                      = html_tag("p", [attr], [content]).
public define HTML_Off_Form p(List(HTML_Off_Form) content)                                = html_tag("p", [],    content).
public define HTML_Off_Form p(HTML_Off_Form content)                                      = html_tag("p", [],    [content]).

  // <pre>  preformatted
public define HTML_Off_Form pre(List(CoreAttrs) attrs, List(HTML_Off_Form) content)         = html_tag("pre", attrs, content).
public define HTML_Off_Form pre(List(CoreAttrs) attrs, HTML_Off_Form content)               = html_tag("pre", attrs, [content]).
public define HTML_Off_Form pre(CoreAttrs attr, List(HTML_Off_Form) content)                = html_tag("pre", [attr], content).
public define HTML_Off_Form pre(CoreAttrs attr, HTML_Off_Form content)                      = html_tag("pre", [attr], [content]).
public define HTML_Off_Form pre(List(HTML_Off_Form) content)                                = html_tag("pre", [],    content).
public define HTML_Off_Form pre(HTML_Off_Form content)                                      = html_tag("pre", [],    [content]).
public define HTML_Off_Form pre(String string)                                              = html_tag("pre", [],     [text(string)]).
public define HTML_Off_Form pre(CoreAttrs attr, String string)                              = html_tag("pre", [attr], [text(string)]).
public define HTML_Off_Form pre(List(CoreAttrs) attrs, String string)                       = html_tag("pre", attrs,  [text(string)]).

  // <progress>
public define HTML_Off_Form progress(List(CoreAttrs) attrs, Int value, Int max, List(HTML_Off_Form) content)  = html_tag("progress", [attr("value", value), attr("max", max) . attrs],  content).
public define HTML_Off_Form progress(List(CoreAttrs) attrs, Int value, Int max, HTML_Off_Form content)        = html_tag("progress", [attr("value", value), attr("max", max) . attrs],  [content]).
public define HTML_Off_Form progress(CoreAttrs _attr, Int value, Int max, HTML_Off_Form content)              = html_tag("progress", [attr("value", value), attr("max", max) , _attr],   [content]).
public define HTML_Off_Form progress(Int value, Int max, HTML_Off_Form content)                               = html_tag("progress", [attr("value", value), attr("max", max)], [content]).
public define HTML_Off_Form progress(List(CoreAttrs) attrs, Int value, Int max, String content)               = html_tag("progress", [attr("value", value), attr("max", max) . attrs], [text(content)]).
public define HTML_Off_Form progress(CoreAttrs _attr, Int value, Int max, String content)                     = html_tag("progress", [attr("value", value), attr("max", max), _attr], [text(content)]).
public define HTML_Off_Form progress(List(CoreAttrs) attrs, Int value, Int max)                               = html_tag("progress", [attr("value", value), attr("max", max) . attrs], []).
public define HTML_Off_Form progress(CoreAttrs _attr, Int value, Int max)                                     = html_tag("progress", [attr("value", value), attr("max", max), _attr], []).
public define HTML_Off_Form progress(Int value, Int max, String content)                                      = html_tag("progress", [attr("value", value), attr("max", max)], [text(content)]).
public define HTML_Off_Form progress(Int value, Int max)                                                      = html_tag("progress", [attr("value", value), attr("max", max)], []).


  // <section>
public define HTML_Off_Form section(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("section", attrs, content).
public define HTML_Off_Form section(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("section", attrs, [content]).
public define HTML_Off_Form section(List(HTML_Off_Form) content)                         = html_tag("section", [],    content).
public define HTML_Off_Form section(HTML_Off_Form content)                               = html_tag("section", [],    [content]).

  // <select>
public define HTML_Off_Form select(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("select", attrs, content).
public define HTML_Off_Form select(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("select", attrs, [content]).
public define HTML_Off_Form select(List(CoreAttrs) attrs)                               = html_tag("select", attrs, []).
public define HTML_Off_Form select(List(HTML_Off_Form) content)                         = html_tag("select", [],    content).
public define HTML_Off_Form select(HTML_Off_Form content)                               = html_tag("select", [],    [content]).


  // <span>
public define HTML_Off_Form span(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("span", attrs, content).
public define HTML_Off_Form span(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("span", attrs, [content]).
public define HTML_Off_Form span(CoreAttrs attr, List(HTML_Off_Form) content)           = html_tag("span", [attr], content).
public define HTML_Off_Form span(CoreAttrs attr, HTML_Off_Form content)                 = html_tag("span", [attr], [content]).
public define HTML_Off_Form span(List(HTML_Off_Form) content)                           = html_tag("span", [],    content).
public define HTML_Off_Form span(HTML_Off_Form content)                                 = html_tag("span", [],    [content]).
public define HTML_Off_Form span(Int i)                                                 = html_tag("span", [],    [text(to_decimal(i))]).
public define HTML_Off_Form span(List(CoreAttrs) attrs, String s)                       = html_tag("span", attrs, [text(s)]).
public define HTML_Off_Form span(CoreAttrs attr, String s)                              = html_tag("span", [attr],[text(s)]).
public define HTML_Off_Form span(String s)                                              = html_tag("span", [],    [text(s)]).
public define HTML_Off_Form span(List(CoreAttrs) attrs)                                 = html_tag("span", attrs, []).
public define HTML_Off_Form span(CoreAttrs attr)                                        = html_tag("span", [attr],[]).

  // <strong>
public define HTML_Off_Form strong(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("strong", attrs, content).
public define HTML_Off_Form strong(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("strong", attrs, [content]).
public define HTML_Off_Form strong(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("strong", [attr], content).
public define HTML_Off_Form strong(CoreAttrs attr, HTML_Off_Form content)               = html_tag("strong", [attr], [content]).
public define HTML_Off_Form strong(List(HTML_Off_Form) content)                         = html_tag("strong", [],    content).
public define HTML_Off_Form strong(HTML_Off_Form content)                               = html_tag("strong", [],    [content]).

  // <svg>
public define HTML_Off_Form svg(List(CoreAttrs) attrs)                                  = html_tag("svg", attrs, []).


  // <table>
public define HTML_Off_Form table(List(CoreAttrs) attrs, List(HTML_Off_Form) content)   = html_tag("table", attrs, content).
public define HTML_Off_Form table(List(CoreAttrs) attrs, HTML_Off_Form content)         = html_tag("table", attrs, [content]).
public define HTML_Off_Form table(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("table", [attr], content).
public define HTML_Off_Form table(CoreAttrs attr, HTML_Off_Form content)                = html_tag("table", [attr], [content]).
public define HTML_Off_Form table(List(HTML_Off_Form) content)                          = html_tag("table", [],    content).
public define HTML_Off_Form table(HTML_Off_Form content)                                = html_tag("table", [],    [content]).

  // <thead>
public define HTML_Off_Form thead(List(CoreAttrs) attrs, List(HTML_Off_Form) content)   = html_tag("thead", attrs, content).
public define HTML_Off_Form thead(List(CoreAttrs) attrs, HTML_Off_Form content)         = html_tag("thead", attrs, [content]).
public define HTML_Off_Form thead(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("thead", [attr], content).
public define HTML_Off_Form thead(CoreAttrs attr, HTML_Off_Form content)                = html_tag("thead", [attr], [content]).
public define HTML_Off_Form thead(List(HTML_Off_Form) content)                          = html_tag("thead", [],    content).
public define HTML_Off_Form thead(HTML_Off_Form content)                                = html_tag("thead", [],    [content]).

  // <tbody>
public define HTML_Off_Form tbody(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("tbody", attrs, content).
public define HTML_Off_Form tbody(List(CoreAttrs) attrs, HTML_Off_Form content)         = html_tag("tbody", attrs, [content]).
public define HTML_Off_Form tbody(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("tbody", [attr], content).
public define HTML_Off_Form tbody(CoreAttrs attr, HTML_Off_Form content)                = html_tag("tbody", [attr], [content]).
public define HTML_Off_Form tbody(List(HTML_Off_Form) content)                          = html_tag("tbody", [],    content).
public define HTML_Off_Form tbody(HTML_Off_Form content)                                = html_tag("tbody", [],    [content]).

  // <tfoot>
public define HTML_Off_Form tfoot(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("tfoot", attrs, content).
public define HTML_Off_Form tfoot(List(CoreAttrs) attrs, HTML_Off_Form content)         = html_tag("tfoot", attrs, [content]).
public define HTML_Off_Form tfoot(CoreAttrs attr, List(HTML_Off_Form) content)          = html_tag("tfoot", [attr], content).
public define HTML_Off_Form tfoot(CoreAttrs attr, HTML_Off_Form content)                = html_tag("tfoot", [attr], [content]).
public define HTML_Off_Form tfoot(List(HTML_Off_Form) content)                          = html_tag("tfoot", [],    content).
public define HTML_Off_Form tfoot(HTML_Off_Form content)                                = html_tag("tfoot", [],    [content]).

  // <th>
public define HTML_Off_Form th(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("th", attrs, content).
public define HTML_Off_Form th(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("th", attrs, [content]).
public define HTML_Off_Form th(CoreAttrs attr, List(HTML_Off_Form) content)           = html_tag("th", [attr], content).
public define HTML_Off_Form th(CoreAttrs attr, HTML_Off_Form content)                 = html_tag("th", [attr], [content]).
public define HTML_Off_Form th(List(HTML_Off_Form) content)                           = html_tag("th", [],    content).
public define HTML_Off_Form th(HTML_Off_Form content)                                 = html_tag("th", [],    [content]).
public define HTML_Off_Form th(String string)                                         = html_tag("th", [],     [text(string)]).
public define HTML_Off_Form th(CoreAttrs attr, String string)                         = html_tag("th", [attr], [text(string)]).
public define HTML_Off_Form th(List(CoreAttrs) attrs, String string)                  = html_tag("th", attrs,  [text(string)]).

  // <td>
public define HTML_Off_Form td(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("td", attrs,   content).
public define HTML_Off_Form td(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("td", attrs,  [content]).
public define HTML_Off_Form td(CoreAttrs attr, List(HTML_Off_Form) content)           = html_tag("td", [attr], content).
public define HTML_Off_Form td(CoreAttrs attr, HTML_Off_Form content)                 = html_tag("td", [attr], [content]).
public define HTML_Off_Form td(List(HTML_Off_Form) content)                           = html_tag("td", [],     content).
public define HTML_Off_Form td(HTML_Off_Form content)                                 = html_tag("td", [],     [content]).
public define HTML_Off_Form td(List(CoreAttrs) attrs, String string)                  = html_tag("td", attrs,  [text(string)]).
public define HTML_Off_Form td(CoreAttrs attr, String string)                         = html_tag("td", [attr], [text(string)]).
public define HTML_Off_Form td(String string)                                         = html_tag("td", [],     [text(string)]).
public define HTML_Off_Form td(List(CoreAttrs) attrs, Int i)                          = html_tag("td", attrs,  [text(to_decimal(i))]).
public define HTML_Off_Form td(CoreAttrs attr, Int i)                                 = html_tag("td", [attr], [text(to_decimal(i))]).
public define HTML_Off_Form td(Int i)                                                 = html_tag("td", [],     [text(to_decimal(i))]).

  // <tr>
public define HTML_Off_Form tr(List(CoreAttrs) attrs, List(HTML_Off_Form) content)    = html_tag("tr", attrs, content).
public define HTML_Off_Form tr(List(CoreAttrs) attrs, HTML_Off_Form content)          = html_tag("tr", attrs, [content]).
public define HTML_Off_Form tr(CoreAttrs attr, List(HTML_Off_Form) content)           = html_tag("tr", [attr], content).
public define HTML_Off_Form tr(CoreAttrs attr, HTML_Off_Form content)                 = html_tag("tr", [attr], [content]).
public define HTML_Off_Form tr(List(HTML_Off_Form) content)                           = html_tag("tr", [],    content).
public define HTML_Off_Form tr(HTML_Off_Form content)                                 = html_tag("tr", [],    [content]).


  // <textarea>
  // CoreAttrs for textarea
public define CoreAttrs wrap_lines  = attr("wrap", "hard").
public define CoreAttrs read_only   = bool_attr(true, "readonly").

public define HTML_Off_Form textarea(List(CoreAttrs) attrs, List(HTML_Off_Form) content)  = html_tag("textarea", attrs, content).
public define HTML_Off_Form textarea(List(CoreAttrs) attrs, Int cols, Int rows, List(HTML_Off_Form) content)
        = html_tag("textarea", [attr("cols",to_String(cols)), attr("rows",to_String(rows)) . attrs], content).
public define HTML_Off_Form textarea(List(CoreAttrs) attrs, HTML_Off_Form content)        = html_tag("textarea", attrs, [content]).
public define HTML_Off_Form textarea(List(CoreAttrs) attrs,  Int cols, Int rows, HTML_Off_Form content)
        = html_tag("textarea", [attr("cols",to_String(cols)), attr("rows",to_String(rows)) . attrs], [content]).
public define HTML_Off_Form textarea(CoreAttrs attr, List(HTML_Off_Form) content)         = html_tag("textarea", [attr], content).
public define HTML_Off_Form textarea(CoreAttrs attr, HTML_Off_Form content)               = html_tag("textarea", [attr], [content]).

  // <ul>
public define HTML_Off_Form ul(List(CoreAttrs) attrs, List(HTML_Off_Form) content)      = html_tag("ul", attrs, content).
public define HTML_Off_Form ul(List(CoreAttrs) attrs, HTML_Off_Form content)            = html_tag("ul", attrs, [content]).
public define HTML_Off_Form ul(CoreAttrs attr, List(HTML_Off_Form) content)             = html_tag("ul", [attr], content).
public define HTML_Off_Form ul(CoreAttrs attr, HTML_Off_Form content)                   = html_tag("ul", [attr], [content]).
public define HTML_Off_Form ul(List(HTML_Off_Form) content)                             = html_tag("ul", [],    content).
public define HTML_Off_Form ul(HTML_Off_Form content)                                   = html_tag("ul", [],    [content]).


public define HTML_Off_Form
  form
  (
    String          form_name,
    List(CoreAttrs) options,
    HTML_In_Form    content
  ) =
  form(html_Id(form_name), options, [content]).

public define HTML_Off_Form
  form
  (
    String              form_name,
    List(CoreAttrs)     options,
    List(HTML_In_Form)  contents
  ) =
  form(html_Id(form_name), options, contents).

public define HTML_Off_Form
  form
  (
    String                form_name,
    List(CoreAttrs)       options,
    WEB_Action_Name       action,
    List((String,String)) extra_ops,
    HTML_In_Form          content
  ) =
  form(html_Id(form_name), options, action, extra_ops, [content]).

public define HTML_Off_Form
  form
  (
    HTML_Id               form_id,
    List(CoreAttrs)       options,
    WEB_Action_Name       action,
    List((String,String)) extra_ops,
    HTML_In_Form          content
  ) =
  form(form_id, options, action, extra_ops, [content]).

public define HTML_Off_Form
  form
  (
    String                form_name,
    List(CoreAttrs)       options,
    WEB_Action_Name       action,
    List((String,String)) extra_ops,
    List(HTML_In_Form)    contents
  ) =
  form(html_Id(form_name), options, action, extra_ops, contents).

public define HTML_Off_Form
  form
  (
    String                form_name,
    List(CoreAttrs)       options,
    String                action,
    List((String,String)) extra_ops,
    HTML_In_Form          content
  ) =
  form(html_Id(form_name), options, action_name(action), extra_ops, [content]).

public define HTML_Off_Form
  form
  (
    String                form_name,
    List(CoreAttrs)       options,
    String                action,
    List((String,String)) extra_ops,
    List(HTML_In_Form)    contents
  ) =
  form(html_Id(form_name), options, action_name(action), extra_ops, contents).

public define HTML_Off_Form literal(Printable_tree t) = literal_pt(t).
//public define HTML_Off_Form fixed_size(HTML_Size width, HTML_Size height, String name_of_HTML_file)
//   = fixed_size_2(width,height,name_of_HTML_file).


public define HTML_Off_Form
   foreign_link
     (
       Int tsize,
       String url,
       String name
     ) =
   foreign_link([size(tsize)],url,name).


public define HTML_Off_Form
   actioner
     (
       Actioner_Connection       conn,
       Actioner_Target           targ,
       Actioner_Aspect           asp,
       WEB_Action_Name           action,
       List((String,String))     extra_ops
     ) =
   actioner(conn,targ,asp,action,extra_ops,[]).

public define HTML_Off_Form
   actioner
     (
       Actioner_Connection       conn,
       Actioner_Target           targ,
       Actioner_Aspect           asp,
       WEB_Action_Name           action,
       List((String,String))     extra_ops,
       String                    form_name
     ) =
   actioner(conn,targ,asp,action,extra_ops,[], form_name).

public define HTML_Off_Form
   actioner
     (
       Actioner_Aspect           asp,
       WEB_Action_Name           action,
       List((String,String))     extra_ops
     ) =
   actioner(same, same, asp, action, extra_ops, []).

public define HTML_Off_Form
   actioner
     (
       Actioner_Aspect           asp,
       WEB_Action_Name           action,
       List((String,String))     extra_ops,
       String                   form_name
     ) =
   actioner(same, same, asp, action, extra_ops, [], form_name).

public define HTML_Off_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops,
       List(Actioner_Local_Action)  local_actions
  )=
  actioner(conn,targ,asp,action_name(action),extra_ops,local_actions)
.

public define HTML_Off_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops,
       List(Actioner_Local_Action)  local_actions,
       String                 form_name
  )=
  actioner(conn, targ, asp, action_name(action), extra_ops, local_actions, form_name)
.

public define HTML_Off_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops
  )=
  actioner(conn,targ,asp,action_name(action),extra_ops,[])
.

public define HTML_Off_Form
/* Older call with String as action instead of WEB_Action_Name.
 * This function exists only for compatibility with older project.
 * Please condiser to use above function instead
 */
  actioner
  (
       Actioner_Connection    conn,
       Actioner_Target        targ,
       Actioner_Aspect        asp,
       String                 action,
       List((String,String))  extra_ops,
       String                 form_name
  )=
  actioner(conn, targ, asp, action_name(action), extra_ops, [], form_name)
.

public define HTML_Off_Form
  table
  (
    List(HTML_Row(HTML_Off_Form)) rows
  )=
  table([], empty, rows,empty)
.

public define HTML_Off_Form
  table
  (
    List(Table_Option) options,
    List(HTML_Row(HTML_Off_Form)) rows
  ) =
  table(options,empty,rows,empty)
.

public define HTML_Off_Form
  table
  (
    Table_Option option,
    HTML_Row(HTML_Off_Form) row
  ) =
  table([option], empty, [row], empty)
.

public define HTML_Off_Form
  table
  (
    HTML_Header_Row(HTML_Off_Form)  h_row,
    List(HTML_Row(HTML_Off_Form))   rows
  ) =
  table([],h_row,rows,empty)
.

public define HTML_Off_Form
  table
  (
    List(Table_Option)              options,
    HTML_Header_Row(HTML_Off_Form)  h_row,
    List(HTML_Row(HTML_Off_Form))   rows
  ) =
  table(options,h_row,rows,empty)
.

public define HTML_Off_Form
  table
  (
    Table_Option                    option,
    HTML_Header_Row(HTML_Off_Form)  h_row,
    List(HTML_Row(HTML_Off_Form))   rows
  ) =
  table([option], h_row, rows,empty)
.

   We add two  convenience functions for 'row'.  The reason why we add  two functions, one
   for  'HTML_In_Form' and  one  for 'HTML_Off_Form',  is  that adding  a  schema with  an
   arbitrary '$T' creates too many ambiguities. This is due to the fact that, if we do so,
   the arguments of the function do not refer to any of the types defined here.

public define HTML_Row(HTML_In_Form)
   row
     (
       HTML_In_Form content
     ) =
   row([],[cell([],content)]).

public define HTML_Row(HTML_Off_Form)
   row
     (
       HTML_Off_Form content
     ) =
   row([],[cell([],content)]).

public define HTML_Cell(HTML_Off_Form)
  cells_to_column_in_cell
  (
    List(HTML_Cell(HTML_Off_Form)) cells
  )=
  cell(
    table(
      map( (HTML_Cell(HTML_Off_Form) current_cell) |-> row(current_cell), cells)
      )).

public define HTML_Off_Form
  cells_to_line
  (
    List(HTML_Off_Form) cells
  )=
  table([row(
      map (((HTML_Off_Form) current_cell) |-> cell(current_cell), cells))])
      .

public define HTML_Off_Form
   private_download
     (
       String        abs_path,
       String        name,
       String        extra_ext
     ) =
   private_download(abs_path,name,extra_ext,failure).


public define HTML_Off_Form
  private_download
  (
    String        abs_path,
    String        name,
    String        extra_ext,
    String        action_name,
    List((String,String))   args
  ) =
  private_download(abs_path,name,extra_ext,success((action_name,args))).

.


public define HTML_In_Form
  hr
  =
  hr([])
.

public define HTML_In_Form
  button
  (
    List(HTML_In_Form)   elements
  )=
  button([], elements)
.

public define HTML_In_Form
  button
  (
    List(CoreAttrs) attrs,
    HTML_In_Form   element
  )=
  button(attrs, [element])
.

public define HTML_In_Form
  button
  (
    HTML_In_Form   element
  )=
  button([], [element])
.
   - Cell a gap between two other cells :

public define HTML_Cell(HTML_Off_Form)
  width_gap
  (
    Int w
  )=
  cell([width(w)], empty).

public define HTML_Cell(HTML_In_Form)
  width_gap
  (
    Int w
  )=
  cell([width(w)],empty)
.
   - Row a gap between two other rows :

public define HTML_Row(HTML_Off_Form)
  height_gap
  (
    Int h
  )=
  row([],[cell([height(h)],empty)]).

public define HTML_Row(HTML_In_Form)
  height_gap
  (
    Int h
  )=
  row([],[cell([height(h)],empty)])
.


   Notice that the two types have alternatives in common (same name, same arguments types,
   up to  the value of the  parameter $T), which correspond  to elements which  may be put
   anywhere in the page.

public define HTML_Partial_Content
  partial_content
  (
    List(HTML_Head_Tag) tags,
    List(HTML_Off_Form) content
  )=
  partial_content(tags, sequence(content)).

public define HTML_Partial_Content
  partial_content
  (
    HTML_Off_Form content
  )=
  partial_content([], content).

public define HTML_Partial_Content
  partial_content
  (
    List(HTML_Off_Form) content
  )=
  partial_content([], sequence(content)).

public define HTML_Partial_Content
  partial_content
  (
    List(HTML_Head_Tag)  tags,
    HTML_Partial_Content p_content
  )=
  if p_content is partial_content(ptags, html) then
  partial_content(tags + ptags, html).

define HTML_Partial_Content
  list_to_pcontent
  (
    List(HTML_Partial_Content) l_p_content,
    List(HTML_Head_Tag)        so_far_tags,
    List(HTML_Off_Form)        so_far_html
  )=
  if l_p_content is
  {
    []      then  partial_content(so_far_tags, sequence(reverse(so_far_html))),
    [h . t] then
      //extract resurgent type and symbols of h
      if h is partial_content(tags, html) then
      list_to_pcontent(t, so_far_tags + tags, [html . so_far_html])
  }.

public define HTML_Partial_Content
  partial_content
  (
    List(HTML_Partial_Content) l_p_content
  )=
  list_to_pcontent(l_p_content, [], []).

public define HTML_Partial_Content
  partial_empty
  =
  partial_content(empty)
.

define String
   format
     (
       List(Text_Option) l
     ).


define Printable_tree
   format_css_styles
     (
       List(CSS_Style)   l
     ) =
   if l is
     {
       [ ] then [ ],
       [h . t] then
         [ if h is
             {
               text_options(tos) then
                 ["   body, span, p { ", format(tos), " }\n" ]
             }
         . format_css_styles(t)]
     }.


   Meta tags are put in the 'head' of the HTML page.

public define HTML_Meta
  refresh
  (
    Actioner_Connection connection,
    Actioner_Target     target,
    String              action,
    Int                 delay
  )=
  refresh(connection, target, action_name(action), delay)
.


public define HTTP_Answer
   html_page
     (
       String             title,
       List(HTML_Meta)    metas,
       HTML_Body          body
     ) =
   html_page(http_ok, title,metas,[],[],[],[],body).

public define HTTP_Answer
   html_page
     (
       String             title,
       List(HTML_Meta)    metas,
       List(CSS_Style)    styles,
       HTML_Body          body
     ) =
   html_page(http_ok, title, metas, styles, [], [], [], body).

public define HTTP_Answer
  web_controller_error_page
  (
    String  name
  )
  =
  html_page
  (
    name+" Controller error",  // title of web site
    [],                       // list of 'META' tags (empty for this site)
    body                      // body of page
    (
      // list of body options
      [
        background_color(rgb(255,200,200))
        // add more body options here
      ],

      // content of page
      text(name+" Controller error")
    )
  )
.


   'HTTP_Answer' represents the final product of the construction of a web page.


      *** (3.2) ``in form'' versus ``off form''.

   There is a variety of HTML  elements: texts, buttons, links, forms, inputs, etc... Some
   of them may have  a content, which is yet another HTML  element (or several). Hence, it
   is meaningful to say that an element  is 'within' another one. Now, putting any element
   within any  other one may be  meaningless.  For example,  an input element must  be put
   within a form (otherwise, it is useless), and a from within another form has no precise
   meaning (and is forbidden by the HTML specification).

   Actually, the  main criterium  is ``within  a form or  not within  a form''.   So, HTML
   elements in  a given page  are separated  into two categories:  those who are  within a
   form,  and the  others.  Nevertheless,  there  are elements  which may  belong to  both
   categories, like images and texts. We want to make use of the strong typing mecanism of
   Anubis in order to forbid non meaningful placement of elements.

   The  type  'HTML_In_Form'  defines  elements   to  be  put  within  forms.   Similarly,
   'HTML_Off_Form' defines elements not to be  put within forms. Both types are recursive,
   and 'HTML_Off_Form' refers  to 'HTML_In_Form' (via the 'form'  alternative, of course),
   but the two types  are not cross recursive. This is the reason  why it is impossible to
   put a  form within a form.  In order to construct  a web page, you  essentially have to
   produce a datum of type 'HTML_Off_Form' (maybe containing data of type 'HTML_In_Form').

   In practice, you  don't have to worry  so much about these two  types, because elements
   which may  be put anywhere are  constructed for both  types by functions with  the same
   name and the same arguments. Hence, for  both types, you just write the same thing. You
   are warned by  the compiler only when  you try to put an  element at a place  it is not
   allowed.


      *** (3.3) Defining your own style.

   We provide generic tools for constructing  HTML elements.  However, your web site needs
   to have a ``style''.

   To that  end, you need to  write down a set  of ``styling functions'',  using the tools
   defined here. These  styling functions allow the introduction of  your colors and other
   visual characteristics into the constructed elements once and for all. For example, you
   may want all your texts to be rendered  in the ``Helvetica'' font, in size 14 and using
   some 'text_color'. You may write something like this:

   define RGB    text_color = rgb(10,40,40).

   define HTML_Off_Form
     text
       (
         String the_text
       ) =
     text([font("helvetica"),size(14),color(text_color)],
          the_text).

   (and the same one for type 'HTML_In_Form') so that in order to put a piece of text in a
   page, you just write:

                 text("... some text ...")

   and you don't have  to provide the font, size and color for each  text.  If you want to
   have  several  styles  of text  presentation,  you  just  write  several sets  of  such
   convenience functions. This also suggests a  trick.  You may want for example different
   colors for 'in form' texts and 'off form' texts.  This may be achieved automatically by
   defining  two functions  as  above, with  the same  name  and same  argument type,  but
   returning either a 'HTML_In_Form' or a 'HTML_Off_Form'.

   If this  preliminary work is  well done, you  will not waste  your time later  when you
   concentrate on the actual informational content of your pages.

   This general  principle should be applied  to all sorts  of elements. This is  the best
   thing to  do in  order to  separate the functions  defining the  visual style  from the
   functions defining the informational content itself, so that changing the style without
   changing the  content becomes easy. This  is also the best  way for having  a clean and
   easily readable source for your web site.


      *** (3.4) Actioners and forms.

   We have gathered several  notions from HTML into that of an  'actioner'. An actioner is
   an HTML element which opens a connection to our server when clicked upon. Actioners may
   have different  visual aspects.   They may  look like hypertext  links or  like buttons
   (rollovers),  or even  like  selectors (with  immediate  action).  In  any case,  their
   behavior is  the same: they  open a connection  to our server, and  send a set  of 'web
   arguments', i.e.  pairs  'name=value'.  Among these web arguments,  one of them denotes
   the action to  be performed, and the  others should be considered as  operands for this
   action.  Actually, the precise behavior of the actioner has several variants.

   The connection with  the server may be  secured (HTTPS) or non secured  (HTTP). See the
   type 'Actioner_Connection' above.

   You must also choose where the answer must be rendered.  This may be in the same window
   or in another window  (or frame).  If it is in another window,  the name of that window
   must be given. If  the window does not exist, the browser  will create it.  Optionally,
   you may give the  dimensions of the new window and other  characteristics. See the type
   'Actioner_Target' above.

   The actioner  also has a visual aspect.  See the type 'Actioner_Aspect'  above.  In the
   case  of a rollover  button, you  provide the  URLs of  two images  (of the  same size)
   representing the button:

      url_off:    to be used when the mouse is not over the button,
      url_on:     to be used when the mouse is over the button.

   You  can also  create rollover  buttons without  creating images.  Just use  the second
   alternative named 'button'. The server creates the images automatically.

   The purpose of forms is just to  give operands to actioners.  If the actioner is placed
   within a form,  all the input elements  which are within this form  provide operands to
   the actioner (except sometimes  when they are not set by the client).  If it is not put
   within a form, the actioner gets no operand, except if the name of a form is explicitly
   given,  in   which  case  the  actioner  gets   all  the  inputs  from   that  form  as
   operands. Furthermore, you may want to give extra operands to the actioner. This may be
   useful for separating  families of actioners with the same  action name. Extra operands
   'name=value' must be given in the form of pairs '(name,value)'.

   Notice that the name of a form may be  used by an actioner which is off the form, so as
   to get the operands provided by this form. Also notice that several actioners may refer
   to  the same  form,  being either  in  the form,  or  referring to  the  form from  the
   outside. These actioners  simply get the same set of operands,  even if they correspond
   to distinct actions.

   Input elements may be put only within a form.


      *** (3.5) Local popup.

   This element looks like a link or  a rollover button. When this button is clicked upon,
   a 'popup window' appears.  Actually, this popup window is just a layer in the same HTML
   page,  which becomes suddenly  visible.  It  is realized  with a  '<div>' HTML  tag. In
   particular, clicking  on the button does  not open any  connection.  This is why  it is
   called 'local'. The arguments have the following roles:

      Actioner_Aspect         aspect of the button (same semantics as for actioners)
      content                 content of the popup window
      x, y,                   position of the popup window on the HTML page (not relative
                                to the button but to the page itself)
      title                   title of the popup window
      color                   color of the title bar and close button in the popup window.
                                A lightened version of this color is used for the background
                                of the popup window.
      width                   width of the title bar


   --- That's all for the public part ! --------------------------------------------------


   ----------------------------------- Table of Contents ---------------------------------

   *** [1] States.
      *** [1.1] Saving and retrieving states.
      *** [1.2] Deleting out of date states.

   *** [2] Sessions.
      *** [2.1] Saving and retrieving sessions.
      *** [2.2] Deleting out of date sessions.

   *** [3] Tools.
      *** [3.1] Directories.
      *** [3.2] Secondary documents.

   *** [4] Managing web arguments.
      *** [3.1] Prefixing web arguments names.
      *** [3.2] Separating web arguments.
      *** [3.3] Applying an action.

   *** [5] Web site descriptions and the 'awp handlers'.
      *** [4.1] The type 'Web_Site'.
      *** [4.2] Making a web site description.
      *** [4.3] Starting the servers.

   *** [6] HTML Formating.
      *** [5.1] The type 'HTML_Any($T)'.
      *** [5.2] Formating a color.
      *** [5.3] Creating buttons.
      *** [5.4] Formating an actioner.
      *** [5.5] Formating a private download link.
      *** [5.6] Formating rows and cells in a table.
      *** [5.7] Formating elements which may be put anywhere.
      *** [5.8] Formating 'in form' elements.
      *** [5.9] Formating 'off form' elements.
      *** [5.10] Formating meta-tags.

   ---------------------------------------------------------------------------------------
public type CommonInfo:...

define Printable_tree
   format
     (
       CommonInfo               cinfo,
       //String                   sn,               // state_name
       Var(Int)                 ic_v,             // 'idnum' counter variable
       HTML_Off_Form            element,
       Bool                     is_https,
       Var(Int)                 action_count,
       Var(List(HTML_Head_Tag)) head_tags
     ).

public define String
   doctype_w3c_header
     =
   "<!DOCTYPE html>\n". //html 5


   *** [1] States.

   We have  to define functions for  saving a state,  retrieving a state, deleting  out of
   date  states. We  need one  such function  per web  site. The  types of  the  first two
   functions depend on  the parameter $State. This is  not the case of the  third one. The
   fact that the  instance of $State is variable  from one web sites to  the other implies
   rather subtle manipulations using full functionality.


      *** [1.1] Saving and retrieving states.

   Each state is saved  into a file on the server's disk  (in the directory represented by
   the symbol 'state_directory',  which is 'my_anubis/web_sites/common_name/states').  The
   state is saved together with a time stamp whose value is obtained by adding the current
   time to  the given timeout for  states. The state  receives a name obtained  by hashing
   (using  sha1)  the  content of  the  file  itself,  and  then  encoding the  hash  with
   'web_arg_encode'.  The  name  of  the  file  into  which the  state  is  saved  is  the
   concatenation of "s" and the name of the state.

read web_arg_encode.anubis

   The tool below  constructs the function which is  able to save a state  on the server's
   disk.


define ($State s) -> String    // the function constructed returns the name of the state
  make_save_state_function
  (
    Int                       timeout,
    String                    state_directory,
    (LogLevel, String) -> One logger
  )=
  ($State s) |->
         with    time_stamp = now+timeout,
                to_be_saved = (time_stamp,s),
                 state_name = to_ascii(sha1(s)),
           //println("make_save_state_function " + state_directory+"/s"+state_name);
           if save(to_be_saved,state_directory+"/s"+state_name) is ok then
            state_name
           else
            logger(logError, "Cannot create state file in '"+state_directory+"'.\n");
            ""
.


   When  a request  arrives, we  need to  retrieve the  previous state  from  the server's
   disk. We receive the name of that state. If the state is out of date, the state file is
   kept 3 days, and then deleted.

type PreviousState($State):
   not_found,                    // cannot retrieve the previous state
   out_of_date($State),          // the previous state is out of date
   still_valid($State).          // the previous state is still valid

define (String state_name) -> PreviousState($State)
   make_retrieve_state_function
     (
       String   state_directory
     ) =
   (String state_name) |->
   with file_path = state_directory+"/s"+state_name,
   if (RetrieveResult((Int,$State)))retrieve(file_path) is ok(d)
   then (
        if d is (time_stamp,s) then
        if time_stamp < now
        then (
             forget(remove(file_path));
             out_of_date(s)
             )
        else still_valid(s)        // state has been successfully retrieved
        )
   else
    forget(remove(file_path));
    not_found.


      *** [1.2] Deleting out of date states.

   We also need to delete states which are  out of date and which will never be deleted by
   the above method. This may be performed  by a machine doing this periodically (say once
   per states life time period).

define (List(String) file_names) -> One
   make_delete_out_of_date_states_function
     (
       Maybe($State)    dummy,
       String           state_directory
     ) =
   (List(String) file_names) |-df->
   if file_names is
     {
       [ ]      then unique,
       [h . t]  then
         with file_path = state_directory+"/"+h,
         if (RetrieveResult((Int,$State)))retrieve(file_path) is ok(d)
         then (
                if d is (time_stamp,data) then
                if time_stamp < now
                then (forget(remove(file_path)); df(t))
                else df(t)
              )
         else (forget(remove(file_path)); df(t))
     }.


   The 'labelled arrow' |-df-> is documented in 'documentation/en/anubis_doc.txt'.

   Note: The  argument 'dummy'  (of type  Maybe($State)) is not  used in  the body  of the
   function (hence  its name). Nevertheless, it  is required. Indeed,  the Anubis compiler
   does not accept a  parameter in the body of a function  (here the parameter is required
   by  the use  of 'retrieve')  if  this parameter  does not  appear  in the  type of  the
   function. This  is because this  would create ambiguities  that no explicit  typing may
   ever resolve. If you  put a double slash in front of  the declaration of 'dummy' above,
   and if you compile this file, you will get a message like this one:

    Error in 'making_a_web_site.anubis', line 1300, column 7:
       A definition may not contain parameters which are not present
       in the declaration part (hidden parameters):
          $State

   The type  of the  function constructed by  'make_delete_out_of_date_states_function' is
   independant of  the parameter $State. This  is important because this  allows to create
   the list of  such functions for all web  sites. From this list, it is  possible to call
   the  functions one  after  the  other, so  deleting  out of  date  states  for all  web
   sites. Actually, the next function receives a list of pairs (state_directory,function),
   one for each web site.

define One
   delete_out_of_date_states          // for all web sites
     (
       List((String, List(String) -> One))   directories_and_functions
     ) =
   if directories_and_functions is
     {
       [ ] then unique,
       [h . t] then if h is (state_directory,function) then
         function(directory_list(state_directory,"*"));
         delete_out_of_date_states(t)
     }.


   The  above function  must be  called periodically  in a  separate virtual  machine. The
   period we have choosen  is (rather logically) the life time of  states itself. This may
   be achieved by an 'infinite' loop, using a 'sleep(timeout)'. However, the loop must not
   be really  infinite, because the  servers may be  shutdown.  Hence, our loop  must test
   (rather frequently; say  every second) if the  servers are down. If they  are, the loop
   must be exited.

define One
   delete_states_loop
     (
       List((String,List(String) -> One))    directories_and_functions,
       Int                                 timeout,
       Int                                 next_time,
       Server                                http_server,
       Server                                https_server,
       (One) -> Bool                        shutdown_required
     ) =
   if shutdown_required(unique)
     then (shutdown(http_server); shutdown(https_server))
     else unique;
   if (is_down(http_server) & is_down(https_server))
   then unique
   else if now > next_time
        then
          (
            delete_out_of_date_states(directories_and_functions);
            delete_states_loop(directories_and_functions,
                               timeout,
                               now+timeout,
                               http_server,
                               https_server,
                               shutdown_required)
          )
        else
          (
            sleep(1000);    // sleep just one second and try again
            delete_states_loop(directories_and_functions,
                               timeout,
                               next_time,
                               http_server,
                               https_server,
                               shutdown_required)
          ).

   The above loop must be run in a  separate virtual machine. This will be done just after
   the two servers are started.


   *** [2] Tools.

      *** [2.1] Directories.

   We need a tool for creating directories (if needed).

   (This tool has been moved to 'tools/basis.anubis').


      *** [2.2] Secondary documents.

   Some HTML elements  (like '<object>', '<frame>') cannot receive  their content directly
   from the current  document, but only through  an URL.  For this reason,  we implement a
   mecanism for creating secondary  documents on the fly. To that end  we use the 'private
   download' mecanism.

   A secondary document is formated by the same functions as the main document itself. The
   next function  takes an 'off form'  element, creates the file  containing the secondary
   document in HTML format, and returns the URL at which the document will be available.

define String
   create_secondary_document
     (
       String                  sd,            // site directory
       String                  as,            // authorization_secret
       $T -> Printable_tree    format_element,
       $T                      content,
       HTML_Size               width
     ) =
   with  private_download_directory = sd+"/private_download",
                               hash = web_arg_encode(sha1(content)),
                       file_content = (Printable_tree)
         [doctype_w3c_header,
          "<html><body><table ",
                  if width is
                    {
                      absolute(w)      then ["width=\"",w-25],
                      percentage(w)    then ["width=\"95%\""]
                    },"\"><tbody><tr><td align=right>",
             format_element(content),
          "</td></tr></tbody></table></body></html>"
         ],
                          file_name = "sd"+hash+".html",
                          file_path = private_download_directory+"/"+file_name,
      if write_to_file(file_path,file_content) is
        {
          cannot_open_file then print("Cannot open file '"+file_path+"'.\n"); "",
          write_error(n)   then print("Error writing file '"+file_path+"'.\n"); "",
          ok               then file_name+"?zauth="+
                             make_authorization(sd,as,private_download_directory+"/"+file_name)
        }.


      *** [2.3] Generating unique ids.

   In order to uniquely name object for JavaScript we generate unique ids from a counter.

define Int
   new_idnum
     (
       Var(Int)  ic_v      // 'idnum' counter variable
     ) =
   protect
   with result = *ic_v+1,
   ic_v <- result;
   result.


   *** [3] Managing web arguments.

   Web  arguments are  those pairs  'name=value' which  are transmitted  through  the HTTP
   protocol. We need precise naming conventions for these web arguments.


      *** [3.2] Separating web arguments.

   When a new request arrives, we need to separate the web arguments, that is to say:

     - find the value of "s", and recover the corresponding state,
     - find the value of "a", which is the name of the action to be performed,
     - get the list of all the remaining web arguments (operands of the action).

   We must also  determine if the previous state  may be recovered. If it is  not the case
   (either because  the previous state name  is invalid, or  the previous state is  out of
   date), we must check if there is an action name. Indeed, the presence of an action name
   indicates that the user has clicked on one  of our buttons or links. If on the contrary
   there is no action  name the user has just entered our address  in his browser. In this
   last case, we must send the first page of our site (maybe a 'login' page), but if there
   is an action, we  must send a page just saying that the  session ticket has expired. If
   the previous state  is recovered and there is  no action, the new state is  the same as
   the previous state.

   The result of the separation of the web arguments is of type:

type Separated_Web_Args($State):
   swa(PreviousState($State)     previous_state,
       Maybe(String)             action_name,
       List(Web_arg)             operands).


   The next function constructs the function which separates the web arguments.

define (List(Web_arg) lwa, HTTP_Info info) -> Separated_Web_Args($State)
   make_separate_web_args_function
     (
       String                             state_directory,
       String -> PreviousState($State)    retrieve_state,
       String                             website_name
     ) =
   (List(Web_arg) lwa, HTTP_Info info) |-swaf->
  if lwa is
  {
    [ ] then
         //
         // no web arg found => no previous state and no action
         //
         //println("find_cookie(\"state_"+website_name+"\", ...");
         if find_cookie("state_"+website_name, server_get_cookies(http_headers(info))) is
         {
            failure         then
              //println("find_cookie(\"state_"+website_name+"\" failure");
              swa(not_found,failure,[]),

            success(cookie) then
              //println("find_cookie(\"state_"+website_name+"\" success");
              swa(retrieve_state(value(cookie)),failure,[])
         },

         //swa(failure,failure,[]),

    [wa_1 . wa_others] then
         //
         // at least one web arg =>
         //    separate other web args, and insert the first one as needed
         //
      if (Separated_Web_Args($State))swaf(wa_others, info) is
      {
        swa(ps1, // possible previous state
            an1, // maybe an action name
            op1) // operands so far
        then
          if wa_1 is
          {
            web_arg(n, value)    then
                      with name = if substr(n,0,4) = "amp;" then substr(n, 4, length(n) - 4) else n,
                       if name = "a" then
                         swa(ps1,success(value),op1)
                       else if name = "aws_action" | name = "aws_a" then
                         swa(ps1,success(value),op1)
                       //else if name = "t" then
                       //  swa(ps1,an1,[web_arg("target",value) . op1])
                       else
                        swa(ps1,an1,[web_arg(name,value) . op1]),

            upload(n,v,t)   then
                     swa(ps1,an1,[wa_1 . op1])
          }
      }
  }.


      *** [3.3] Applying an action.

   When the web arguments are separated (and their names cleaned up from prefixes), we may
   apply the action to the operands and the  current state. We search for the action to be
   applied in the  list of actions.  If no action  is found, the new state  is the same as
   the previous  state. Also, we  deny the  application of an  HTTP action if  the request
   arrives through the HTTPS channel and conversely.


define ($State          previous,
        String          action_name,
        HTTP_Info       http_info,
        List(Web_arg)   lwa,
        Bool            is_https) -> $State
  make_apply_action_function
  (
    List(Web_Action($State))  actions_list,
    (LogLevel, String) -> One logger                //logger
  )=
  with f =
     ($State                    previous,
      String                    action_name,
      HTTP_Info                 http_info,
      List(Web_arg)             lwa,
      Bool                      is_https,
      List(Web_Action($State))  actions) |-f->
        //println("Looking for action ["+action_name+"]");
        if actions is
          {
            [ ]             then
              logger(logError, "action '"+action_name+"' not found.\n"); previous,
            [ac1 . others]  then if ac1 is
              {
                //check for http action
                http_action(an, allow, do_it) then

                  //Action name found
                  if an = action_name then
                    if is_https then
                      (logger(logError, "HTTP action '"+an+"' called through HTTPS (denied).\n"); previous)
                    else
                      if allow(previous) then
                        do_it(http_info,lwa,previous)
                      else
                        previous
                  else
                    f(previous,action_name,http_info,lwa,is_https,others),
                //check https action
                https_action(an,allow,do_it) then
                  if an = action_name
                  then if is_https
                       then if allow(previous)
                            then do_it(http_info,lwa,previous)
                            else previous
                       else (logger(logError, "HTTPS action '"+an+"' called through HTTP (denied).\n");
                             previous)
                  else f(previous,action_name,http_info,lwa,is_https,others),

                http_https_action(an,allow,do_it) then
                  if an = action_name then
                    println("Action ["+action_name+"] found");
                    if allow(previous)
                            then do_it(http_info,lwa,previous)
                            else
                              println("user not allowed to execute that Action ["+action_name+"]");
                              previous
                  else f(previous,action_name,http_info,lwa,is_https,others),

              }
          },
   ($State                      previous,
    String                      action_name,
    HTTP_Info                   http_info,
    List(Web_arg)               lwa,
    Bool                        is_https) |->
      f(previous, action_name, http_info, lwa, is_https, actions_list).


   *** [4] Web site descriptions and the 'awp handlers'.

      *** [4.1] The type 'Web_Site'.

   The  type 'Web_Site_Description' is  defined in  'web/multihost_http_server.anubis'. We
   need another one, because, we have some extra informations to record for each site.

public type Web_Site:
   web_site((Word32,Word32) -> Web_Site_Description     description,
            List(String) -> One                       delete_out_of_date).


      *** [4.2] Making a web site description.

   Below  is the  function which  creates a  web site  description. It  first  creates (if
   needed) the directories for the site,  then constructs the tool functions for the site,
   and the site handler. Finally, it constructs the web site description.

   We gather common (constant) informations in the following type:

public type CommonInfo:
   info(String      common_name,
        Word32       http_port,
        Word32       https_port,
        String      site_directory,
        String      authorization_secret
        ).

   We need a forward declaration.

public define AWP_Handler_Answer
  format
  (
    CommonInfo         cinfo,
    List(HTTP_header)  headers,
    HTTP_Answer        page,
    Bool               is_https,
    String             charset
  ).


define Printable_tree
   format
     (
       HTML_Size   s
     ) =
   if s is
     {
       absolute(x)     then ["\"",x,"\""],
       percentage(x)   then ["\"",x,"%\""]
     }.

define List(HTTP_header)
  make_state_cookie_headers
  (
    String website_name,
    String state_name
  )
  =
    //println("Set-Cookie state_"+website_name+"="+state_name);
    [
      http_header("Set-Cookie", "state_"+website_name+"="+state_name)
    ]
  .


public define Web_Site
  make_web_site_description
  (
    String                      website_name,   // site_UID
    List(String)                common_names,   // for example: ["www.our-business.com"]
    String                      site_directory,
    String                      state_directory,
    One -> One                  init,
    (HTTP_Info,
    List(Web_arg),
    Bool is_https) -> $State   initial_state,
    ($State expired,
    Maybe(String),
    HTTP_Info,
    List(Web_arg),
    Bool is_https) -> $State    ticket_expired_state,
    (Maybe(String),
    HTTP_Info,
    List(Web_arg),
    Bool is_https) -> $State   ticket_lost_state,
    List(Web_Action($State))    actions,
    $State -> HTTP_Answer       compute_page,
    $State -> List(HTTP_header) additional_headers,
    List(HTTP_header)           constant_additional_headers,
    Int                         timeout,
    Redirections                redirections,
    String                      charset,
    List(String)                journal_extensions,
    List(String)                journal_headers,
    (LogLevel, String) -> One   logger,                 //logger
    String                      secret,
    List(MIME)                  known_mime_types,
    (String action_name,
    List(Web_arg) args) -> One before_send_file
  )=
  init(unique);


      //
      // make required directories (if needed)
      //
      with //web_sites_directory = (String) make_directory(my_anubis_directory+"/web_sites"),
                base_directory = (String) make_directory(site_directory),
              // state_directory = make_directory(site_directory+"/states"),
          forget((String)make_directory(site_directory+"/public"));
      //
      // construct tool functions
      // TODO 'make_separate_web_args_function' must retrieve state_cookies before parsing web_args if using_state_cookies is true
   with save_state = make_save_state_function(timeout, state_directory, logger),
    retrieve_state = make_retrieve_state_function(state_directory),
 separate_web_args = make_separate_web_args_function(state_directory, retrieve_state, website_name),
      apply_action = make_apply_action_function(actions, logger),
      //
      // construct the site handler
      //
      site_handler = (Word32 http_port, Word32 https_port) |->
                     ((String         host_name,
                       HTTP_Info      http_info,
                       List(Web_arg)  lwa,
                       Bool           is_https) |->
      //println(dump_web_arg_values(lwa));
      since separate_web_args(lwa, http_info) is swa(mb_previous_state, mb_action_name, operands),
      with new_state = if mb_previous_state is
      {
          not_found               then
            //println("previous state not found");
            if mb_action_name is
              {
                failure           then initial_state(http_info, operands, is_https),
                success(_)        then
                  ticket_lost_state(mb_action_name, http_info,operands,is_https)
              },

          out_of_date(state)      then
            //println("previous out_of_date");
            ticket_expired_state(state, mb_action_name, http_info,operands,is_https),

          still_valid(state)      then
            //println("previous still_valid");
            if mb_action_name is
              {
                failure              then state,
                success(action_name) then
                   apply_action(state,action_name,http_info,operands,is_https)
              }
        },
              //if state_and_headers is (session_ticket, mb_new_state, headers) then
                with state_name = save_state(new_state),
                //println("Cookie new STATE NAME "+state_name);
                with cookie_headers = if mb_action_name is
                        {
                          failure              then
                            make_state_cookie_headers(website_name, state_name),
                          success(action_name) then
                            if action_name = "none" then
                              []
                            else if substr(action_name, 0, 5)="ajax_" then
                              []
                            else
                              make_state_cookie_headers(website_name, state_name)
                        },

                format(info(host_name, http_port, https_port, site_directory, secret),
                       additional_headers(new_state) + cookie_headers,
                       compute_page(new_state),
                       is_https,
                       charset)
          ),
       //
       // make the delete_out_of_date function
       //
       delete_out_of_date =
         make_delete_out_of_date_states_function((Maybe($State))failure,
                                                 site_directory+"/states"),
       //
       // construct the web site description
       //
    web_site((Word32 http_port, Word32 https_port) |->
             web_site_description(common_names,
                                  site_directory,
                                  redirections,
                                  charset,
                                  journal_extensions,
                                  journal_headers,
                                  logger,
                                  secret,
                                  known_mime_types,
                                  site_handler(http_port, https_port),
                                  constant_additional_headers,
                                  (HTTP_Info http_info, List(Web_arg) lwa) |-> if separate_web_args(lwa, http_info ) is
                                     swa(mb_previous_state,mb_action_name,operands) then
                                       if mb_action_name is
                                         {
                                           failure     then unique
                                           success(an) then before_send_file(an,operands)
                                         }
                                  //using_state_cookies
                                 ),
             delete_out_of_date).

 public type WEB_Controller:
  web_controller(
    String            name,     //controller name
    (HTTP_Info                    http_info,
     List(Web_arg)                lwa,
     Bool                         is_https
    ) -> HTTP_Answer  view      //view renderer
  )


public define JsonValue to_html_ajax_content(Printable_tree        content_HTML, String additional_script).
public define JsonValue to_html_ajax_content(HTML_Partial_Content  content_HTML, CommonInfo cinfo, String additional_script).


define String
  get_site_uid
  (
    String site_path,
    (LogLevel, String) -> One   logger                 //logger
  )=
  with file_name = site_path+"/site_UID",
    if read_from_file(file_name)  is
    {
      cannot_find_file then
        logger(logInfo,"site UID doesn't exists. Generating one now");
        with uid = generate_random_string(9),
        if write_to_file(file_name, to_byte_array(uid)) is
        {
          cannot_open_file  then logger(logError, "Can't create site UID here "+file_name);"",
          write_error(_)    then logger(logError, "Can't write site UID here "+file_name);"",
          ok                then uid
        }
      read_error(_)   then
        logger(logError, "cannot read site UID from "+file_name);""
      ok(ba)          then  to_string(ba)
   }
  .

// Compatibility function for older websites
 public define Web_Site
  make_web_site_description
  (
       List(String)                common_names,   // for example: ["www.our-business.com"]
       String                      site_directory,
       String                      state_directory,
       One -> One         init,
       (HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State   initial_state,
       ($State expired,
        Maybe(String),
        HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State    ticket_expired_state,
       (Maybe(String),
        HTTP_Info,
        List(Web_arg),
        Bool is_https) -> $State   ticket_lost_state,
       List(Web_Action($State))    actions,
       $State -> HTTP_Answer         compute_page,
       $State -> List(HTTP_header) additional_headers,
       List(HTTP_header)            constant_additional_headers,
       Int                         timeout,
       Redirections                redirections,
       String                      charset,
       List(String)                journal_extensions,
       List(String)                journal_headers,
    (LogLevel, String) -> One                          logger,                 //logger
       String                      secret,
       List(MIME)                  known_mime_types,
       (String action_name,
        List(Web_arg) args) -> One before_send_file
       //Bool using_state_cookies
  )
  =
    //generate an unique ID if doesn't exist in root of site_directory
    with site_UID = get_site_uid(site_directory, logger),
    make_web_site_description(site_UID, common_names, site_directory, state_directory, init, initial_state, ticket_expired_state, ticket_lost_state, actions, compute_page, additional_headers, constant_additional_headers, timeout, redirections, charset, journal_extensions, journal_headers, logger, secret, known_mime_types, before_send_file)
.


      *** [4.3] Starting the servers.

public define Start_Web_Sites_Result
   start_web_sites
     (
       Word32                        ip_address,    // the IP address shared by the web sites
       Word32                        http_port,     // usually: 80
       Word32                        https_port,    // usually: 443
       String                       ssl_certificate_common_name,
       List(Web_Site)               web_sites,     // web sites to be started
       (One) -> Bool                shutdown_required
     ) =
   with get_description = (Web_Site ws) |-> description(ws)(http_port,https_port),
   with http_server_r  =
     start_http_server(ip_address,http_port,
                       map(get_description,web_sites),
                       //load_denial_of_service_info,
                       shutdown_required),
   with https_server_r =
     start_https_server(ip_address,https_port,
                        ssl_certificate_common_name,
                        map(get_description,web_sites),
                        shutdown_required),
   if http_server_r is ok(http_server)
   then
     (
     if https_server_r is ok(https_server)
     then
       (
         start_http_servers_tasks(map(get_description,web_sites),
                                  [http_server,https_server],
                                  600);  // period of 10 minutes
         delegate
         delete_states_loop(
                            map((Web_Site ws) |->
                                  (site_directory(description(ws)(http_port,https_port))+
                                     "/states",delete_out_of_date(ws)),
                                web_sites),
                            3600*24*3,   // keep out of date states 3 days
                            now,
                            http_server,
                            https_server,
                            shutdown_required),
         ok(http_server,https_server)
       )
     else cannot_bind_to_port(https_port)
     )
   else
     (
     if https_server_r is ok(https_server)
     then cannot_bind_to_port(http_port)
     else cannot_bind_to_port(http_port,https_port)
     ).


public define One
  start_web_sites
  (
    Word32          ip_address,   // the IP address shared by the web sites
    Word32          http_port,    // usually: 80
    Word32          https_port,   // usually: 443
    String          ssl_certificate_common_name,
    List(Web_Site)  web_sites,    // web sites to be started
    (One) -> Bool   shutdown_required,
    (LogLevel, String) -> One     logger           //logger where to report the error
  )=
  if (Start_Web_Sites_Result)start_web_sites(ip_address,
                                              http_port,
                                              https_port,
                                              ssl_certificate_common_name,
                                              web_sites,
                                              shutdown_required) is
     {
       cannot_bind_to_port(n)     then logger(logError, "Cannot bind to port: "+n),
       cannot_bind_to_port(n,m)   then logger(logError, "Cannot bind to ports: "+n+", "+m),
       ok(s1,s2)                  then logger(logInfo, "Servers started on ports "+http_port+" (HTTP) and "+https_port+" (HTTPS).")
     }.


   *** [5] HTML Formating.

   We need to translate HTML elements as defined above into actual HTML text.

   Actioners require  special informations, which must  be transmitted when  needed by the
   'format' functions:

       - the 'common name', which is used for URLs,
       - the HTTP/HTTPS port number,
       - the 'state name', which must be transmitted when the actioner is clicked upon,
       - the 'form name' (if any) to which the actioner refers.

   If the  actioner is off  form, and if  it refers to  a form, the  name of that  form is
   already known by the actioner. On the contrary, if the actioner is 'in form', it refers
   implicitly to  the form containing  it.  The  name of that  form is transmitted  to the
   'format' functions called from within the formating of that form.


      *** [5.1] The type 'HTML_Any($T)'.

   The type  'HTML_Any($T)' gathers elements  which may be  put anywhere in the  page. The
   parameter $T becomes either 'HTML_Off_Form' or 'HTML_In_Form'.

type HTML_Any($T):
   any_text               (List(CoreAttrs), String the_text),
   any_preformated        (List(Text_Option), String),
   any_paragraph          (List(Text_Option), List($T) content),
   any_image              (List(CoreAttrs), String url, String alternate),
   any_image              (List(CoreAttrs), String url, String alternate, Int width, Int height),
   any_table              (List(Table_Option), HTML_Header_Row($T), List(HTML_Row($T)), HTML_Footer_Row($T)),
   any_center             ($T),
   any_mail_to            (String email, $T element),
   any_scroller           (Int width, Int height,
                           Int content_width, Int content_height,
                           $T content),
   any_fixed_size         (HTML_Size width, HTML_Size height, $T content),
   any_fixed_size_2       (HTML_Size width, HTML_Size height, String name_of_HTML_file),
   any_actioner           (Actioner_Connection,
                           Actioner_Target,
                           Actioner_Aspect,
                           WEB_Action_Name action,
                           List((String,String)) extra_ops,
                           List(Actioner_Local_Action),
                           Maybe(String) form_name),
   any_foreign_link_new   (Actioner_Target, Actioner_Aspect, String url),
   any_foreign_link       (List(Text_Option), String url),
   any_foreign_link       (List(Text_Option), String url, String name),
   any_private_download   (String abs_path, String name, String extra_ext,
                             Maybe((String,List((String,String))))),
   any_div                (List(CoreAttrs), List($T) element),
   any_div_empty          (List(CoreAttrs)),
   any_coreattrs          (List(CoreAttrs)),
   any_ol                 (List(CoreAttrs), List($T) content),
   any_ul                 (List(CoreAttrs), List($T) content),
   any_li                 (List(CoreAttrs), List($T) content),
   any_button             (List(CoreAttrs), List($T) element),
   any_i                  (List(CoreAttrs), String text),
   any_span               (List(CoreAttrs), String text),
   any_hr                 (List(CoreAttrs))
.


      *** [5.2] Formating a color.

   RGB  colors  are  formatted as  '#rrggbb'  where  rr,  gg  and  bb are  two  characters
   hexadecimal values.

define String
  html_format
    (
      RGB color
    ) =
  if color is rgb(r,g,b) then
     "#" + to_hexa(r)
         + to_hexa(g)
         + to_hexa(b).


   The following is a very arbitrary definition  of the opposite color. The thing which is
   important is that it  is far from the original, so that  characters in 'opposite' color
   are clearly visible over the original.

define RGB
   opposite
     (
       RGB color
     ) =
   if color is rgb(r,g,b) then
   rgb(255-r,
       255-g,
       255-b).

   Converting RGB to RGBA.

define RGBA
   to_rgba
     (
       RGB color
     ) =
   if color is rgb(r,g,b) then rgba(r,g,b,255).


      *** [5.4] Formating an actioner.

   An actioner works as follows. Assume first that it refers to a form. When it is clicked
   upon, the actioner puts (via 'onMouseDown')  the URL into the 'action' attribute of the
   form, and submits  the form, using the JavaScript  command 'form_name.submit()'. If the
   actioner does  not refer to a  form, it fires the  URL directly via  'href', because in
   that case, the actioner is always an <a> tag.

   The URL itself is composed using the  connection sort (same, http or https), the common
   name  and port  number (if  needed), the  state name,  the action  name, and  the extra
   operands, which are put into a query string. It may look like this:

      http://common_name:port/?s=state_name&a=action_name&oname=value...

   Each extra operand is a pair of strings: (name,value). It is formated as:

                 &oname=value

public define String
  format_attrs
  (
    List(CoreAttrs)  attributs
  ).

//public define String
//  format_extra_operands
//  (
//    List((String,String)) l
//  ) =
//  if l is
//  {
//    [ ]     then "",
//    [h . t] then if h is (n,v) then
//    "&amp;"+n+"="+v+format_extra_operands(t)
//  }
//.


   It seams that the standard requires "&amp;" instead of "&" !

   In case the target is another window, we need to format the options for this window.

define String
  format
  (
    List(Other_Window_Option) l
  ) =
  if l is
  {
    [ ]     then "",
    [h . t] then if h is
    {
      resizable      then "resizable",
      scrollbars     then "scrollbars",
      width(w)       then "width="+w,
      height(h2)      then "height="+h2
    } + if t is [ ] then "" else (","+format(t))
  }
.


   Formating choices for a <select> tag.

public define Printable_tree
  format_choices
    (
      List(String) l
    ) =
  if l is
    {
      [ ] then [ ],
      [h . t] then ["<option>", h, "</option>\n" . format_choices(t)]
    }.


public define Printable_tree
  format_choices
  (
    List(String) l,
    InitialValue selected
  ) =
  if l is
    {
      [ ]     then [ ],
      [h . t] then if h = selected.value
        then ["<option selected=\"selected\">", h, "</option>\n" . format_choices(t)]
        else ["<option>", h, "</option>\n" . format_choices(t,selected)]
    }.


public define Printable_tree
  format_choices
    (
      List((List(CoreAttrs),WebArgValue,String)) l
    ) =
  if l is
    {
      [ ] then [ ],
      [h . t] then
       if h is (attrs,val,item)
        then ["<option value=\""+encode_HTML_entities(val.value)+"\" "+format_attrs(attrs)+">", item, "</option>\n" . format_choices(t)]
    }.

public define Printable_tree
  format_choices
    (
      List((List(CoreAttrs),WebArgValue,String)) l,
      InitialValue          selected
    ) =
  if l is
    {
      [ ] then [ ],
      [h . t] then
       if h is (attrs,val,item) then
       if val.value = selected.value
         then ["<option value=\""+encode_HTML_entities(val.value)+"\" "+format_attrs(attrs)+" selected=\"selected\">", item, "</option>\n" . format_choices(t)]
         else ["<option value=\""+encode_HTML_entities(val.value)+"\" "+format_attrs(attrs)+" >", item, "</option>\n" . format_choices(t,selected)]
    }.


   Note: this  counter is private to  the virtual machine,  hence there is one  counter by
   client and by page : it seems that a new VM (simply a delegate) is started for each request.

define Int
   new_count
   (
    Var(Int) count
   )
   =
   count <- *count+1;
   *count.


   The next function composes  the URL. It is a JavaScript URL  when the target is another
   window.

//public define String
//  format_web_action_name
//  (
//    WEB_Action_Name           action
//  )=
//  if action is
//  {
//    no_action                                   then "",
//    controller_action(controller, action_name)  then "?aws_controller="+controller+"&amp;aws_action="+action_name,
//    action_name(action_name)                    then "?aws_action="+action_name,
//    url(url)                                    then url
//  }  
//.
//
//public define String
//  format_web_action_name
//  (
//    WEB_Action_Name           action,
//    List((String,String))     extra_ops,        
//  )=
//  format_web_action_name(action)
//  +
//  format_extra_operands(extra_ops)
//.

define String 
  make_actioner_url
  (
    CommonInfo                cinfo, 
    Actioner_Connection       connection, 
    Actioner_Target           target, 
    WEB_Action_Name           action, 
    List((String,String))     extra_ops,
    Bool                      is_https
  ) =
   if cinfo is info(common_name,http_port,https_port,site_directory,secret) then 
   with strict_url = 
     if connection is 
       {
         same      then "/",
         http      then
          if http_port = 80 then
            "http://"+common_name+"/"
          else
            "http://"+common_name+":"+http_port+"/",
         https     then
          if https_port = 443 then
            "https://"+common_name+"/"
          else
            "https://"+common_name+":"+https_port+"/",
       } +
     //with action_string =
   format_web_action_name(action, extra_ops),
   if target is
     {
       same            then strict_url,
       same(label)     then strict_url+"#"+label,
       other(wn,ops)   then

         "javascript:void window.open('"+strict_url+"&amp;t="+wn+"','"+
                "w"+to_ascii(sha1(wn))+"','"+format(ops)+"')"
     }.

define String
   make_foreign_link_url
     (
       Actioner_Target  target,
       String           url
     ) =
   if target is
     {
       same            then "/",
       same(label)     then "/#"+label,
       other(wn,ops)   then

         "javascript:void window.open('"+url+"','"+
                "w"+to_ascii(sha1(wn))+"','"+format(ops)+"')"
     }.


   Depending on the fact that the actioner refers to a form or not, the URL is used in two
   different ways.  If  the actioner does not refer  to a form, it is realized  by a '<a>'
   tag, with a 'href'  attribute. If it refers to a form, it is  still realized by a '<a>'
   tag, but with no href attribute.  In  this case, we use the 'onMouseDown' or 'onChange'
   event handler. The handler calls a JavaScript  function which puts the URL as the value
   of the 'action' attribute of the form, and submits the form.

type URL_or_JavaScript:
   url          (String),
   javascript   (Printable_tree script, Printable_tree handler).


   It was as  shown below, in order to  allow submission of a form from  outside the form,
   but this makes problems:

define URL_or_JavaScript
   format_action
     (
       String                 the_url,
       Actioner_Aspect        aspect,
       Maybe(String)          mb_id,
       Maybe(String)          mb_form_name,
       Var(Int)               action_count
     ) =
   if mb_form_name is
     {
       failure then
         url(the_url),
       success(form_name) then
       with n = new_count(action_count),
             fn_name = "pfu_" + if mb_id is
                                {
                                  failure then form_name + "_" + n,
                                  success(id) then id,
                                },
         javascript(
           [
             "<script type=\"text/javascript\" language =\"JavaScript\">\n", 
               "function ", fn_name, "() {\n",
               "  var fa = document.forms.",form_name,";\n", 
               "  var u = \"",the_url,"\";\n",
               "  fa.action = u;",
               if aspect is submit(_, _) then " }\n"
                                         else "\n  fa.submit(); }\n",
             "</script>\n"
           ],
           [fn_name,"();"]
         )
     }.

   Now, we format the actioner according to its aspect.

define List(Text_Option)
  get_text_options
  (
     List(Text_Option) l
  )
  =
  if l is
  {
    []        then [],
    [h . t ]  then
      if h is class(_) then
        get_text_options(t)
      else if h is id(_) then
        get_text_options(t)
      else if h is style(_) then
        get_text_options(t)
      else if h is title(_) then
        get_text_options(t)
      else if h is core_attrs(_) then
        get_text_options(t)
      else
      [  h .  get_text_options(t) ]

  }.

  /**
   * Extract the CSS class list from the list of Text_Option
   */
define List(CoreAttrs)
  get_css_class
  (
     List(Text_Option) l
  )
  =
  if l is
  {
    []        then [],
    [h . t ]  then


      if h is class(name) then
       [ class(name) .  get_css_class(t) ]
      else if h is id(name) then
       [ id(name) .  get_css_class(t) ]
      else if h is style(the_style) then
       [ style(the_style) .  get_css_class(t) ]
      else if h is title(name) then
       [ tooltip(name) .  get_css_class(t) ]
      else if h is attr(name, value) then
       [ attr(name, value) .  get_css_class(t) ]
      else
        get_css_class(t)
  }
  .


define List(CoreAttrs)
  get_core_attrs
  (
     List(Text_Option) l
  )
  =
  if l is
  {
    []        then [],
    [h . t ]  then
      if h is core_attrs(attrs) then
       attrs + get_core_attrs(t)
      else
        get_core_attrs(t)
  }
  .

define Printable_tree
  format
  (
    List(Actioner_Local_Action)   l
  ) =
   if l is
     {
       [ ] then [ ],
       [h . t] then [if h is
         {
           close_window then [" window.close(); "]
         }
         . format(t)]
     }.


define String
  format_attrs
  (
    List(InputAttrs)  attributs,
    List(String)      classes,
    List(String)      styles
  )=
  if attributs is
  {
    []      then
      if length(classes) = 0 then "" else " class=\""+join(" ",classes)+"\""+
      if length(styles) = 0 then "" else " style=\""+join(";",styles)+"\"",
    [h . t] then
      with new_classes = if h is class(class_name) then [class_name. classes] else classes,
           new_styles  = if h is style(style_string) then [style_string . styles] else styles,
           current = if h is
      {
        id(id_name)          then
           " id=\"" + id_name + "\"",
        class(class_name)    then "",
        style(style_string)  then "",
        title(title_string)  then
           " title=\"" + title_string + "\"",

        lang(lang) then
           " xml:lang=" + lang,
        dir(reading_Way)  then
          if reading_Way is
          {
            ltr then  " dir=ltr",
            rtl then  " dir=rtl"
          },

        accesskey(key) then
          " accesskey=\"" + key + "\"",
        tabindex(index) then
          " tabindex=\"" + index + "\"",

        attr(name, value) then
           " " + name + "=\"" + value + "\"",

        event(e, value) then
           " " + event_name(e) + "=\"" + value + "\"",
        data(name, value) then
          " data-" + to_lower(name) + "=\"" + value + "\"",
      },
      current + format_attrs(t, classes, styles)
  }.

public define List(CoreAttrs) extract_attributes(HTML_tooltip htt).

define String
  format_attrs
  (
    List(CoreAttrs)  attributs,
    List(String)     classes,
    List(String)     styles
  )=
  if attributs is
  {
    []      then
      (if length(classes) = 0 then "" else " class=\""+join(" ",classes)+"\"")+
      if length(styles) = 0   then "" else " style=\""+join(";",styles)+"\"",
    [h . t] then
      with new_classes  = if h is class(class_name)   then [class_name. classes]    else classes,
           new_styles   = if h is style(style_string) then [style_string . styles]  else styles,
           new_attrs    = if h is tooltip(tt)         then extract_attributes(tt)   else [],

           current      = if h is
                          {
                            empty                 then "",
                            id(id_name)           then
                               " id=\"" + id_name + "\"",
                            class(class_name)     then "",   //do nothing here, because we accumulate the class until we have some other attributes
                            style(style_string)   then "",   //do nothing here, because we accumulate the style until we have some other attributes
                            title(title_string)   then
                               " title=\"" + title_string + "\"",

                            lang(lang)            then
                               " xml:lang=" + lang,
                            dir(reading_Way)      then
                              if reading_Way is
                              {
                                ltr then  " dir=ltr",
                                rtl then  " dir=rtl"
                              },

                            accesskey(key)        then
                              " accesskey=\"" + key + "\"",
                            tabindex(index)       then
                              " tabindex=\"" + index + "\"",
                            attr(name, value)     then
                               " " + name + "=\"" + value + "\"",
                            bool_attr(bool, value)then
                              if bool then " "+value+" " else "",
                            event(e, value)       then
                               " " + event_name(e) + "=\"" + value + "\"",
                            tooltip(_)            then  "",   //do nothing here, because we extract attributes at first in new_attrs
                            data(name, value)     then
                              " data-" + to_lower(name) + "=\"" + value + "\"",

                            contenteditable(value)then  //boolean value
                              " contenteditable=\""+ to_String(value)+ "\""

                            contextmenu(id_name)  then  //ID value
                              " contextmenu=\"" + id_name + "\"",

                            draggable(value)      then  //boolean value
                              " draggable=\""+ to_String(value)+ "\""

                            hidden(value)         then  //boolean value
                              " hidden=\""+ (if value then "hidden" else "") + "\""

                            spellcheck(value)     then  //boolean value
                              " spellcheck=\""+ to_String(value)+ "\""

                          },
      current + format_attrs(t + new_attrs, new_classes, new_styles)
  }.

define String
  format_attrs
  (
    List(InputAttrs)  attributs
  )=
  format_attrs(attributs, [], []).

public define String
  format_attrs
  (
    List(CoreAttrs) attributs
  )=
  format_attrs(attributs, [], []).

define String
  format_text_options
  (
     List(Text_Option) l
  )
  =
  with text_options = get_text_options(l),
         core_attrs = get_css_class(l) + get_core_attrs(l),
  (if length(text_options)= 0 then "" else " style=\"" + format(text_options) + "\" ")
  +
  (if length(core_attrs) = 0 then "" else format_attrs(core_attrs))
  .

define Printable_tree
  format_div_option
  (
    List(CoreAttrs) options
  )=
  ["<div" + format_attrs(options) + ">"]
.

define Maybe(String)
  extract_id
  (
    List(CoreAttrs) attrbs
  ) =
  if attrbs is
  {
    []      then failure,
    [h . t] then
      if h is id(value) then success(value)
                        else extract_id(t)
  }
.

define Maybe(String)
  extract_id
  (
    Actioner_Aspect aspect
  ) =
  if aspect is
  {
    link(_,_,_)                 then failure,
    img_link(_,_,_)               then failure,
    push_button(opts,_)         then extract_id(opts),
    button(_,_)                 then failure,
    button(_,_,_,_)             then failure,
    submit(opts,_)              then extract_id(opts),
    //immediate_selector(_,_,_,_)   then failure,
    immediate_selector(_,_,_,_,_,_) then failure,
    html(_, _)                      then failure,
  }.

to do Complete format_foreign_link
//TODO Complete format_foreign_link

       CommonInfo                     cinfo,
       String                         state_name,
       Var(Int)                       action_count,
       Var(Int)                       ic_v             // 'idnum' counter variable

define Printable_tree
   format_foreign_link
     (
//       CommonInfo                     cinfo,
       Actioner_Target                target,
       Actioner_Aspect                aspect,
       String                         url,
       Bool                           is_https,
       CommonInfo                     cinfo,
//       String                         state_name,
       Var(Int)                       action_count,
       Var(Int)                       ic_v,             // 'idnum' counter variable
       Var(List(HTML_Head_Tag))       head_tags
   ) =
   //if cinfo is info(common_name,http_port,https_port,site_dir,secret) then
   with full_url = make_foreign_link_url(target,url),
//   with action = format_action(full_url, aspect, extract_id(aspect), mb_form_name),
   if aspect is
     {

       link(opt, text, mb_name) then
                        with name_tag = if mb_name is success(n) then " name=\"" + n + "\"" else "",
                        [
                          "<a href=\"", full_url, "\"", format_text_options(opt), name_tag, ">",
                          text,
                          "</a>"
                        ],
       img_link(opt, img, alt_text)       then
                        [
                          "<a href=\"", full_url ,"\"", format_attrs(opt),"><img src=\"", img,
                          "\" alt=\"" + alt_text + "\" border=\"0\"></a>"
                        ],
       push_button(options, text) then
            ["<a href=\"",full_url,"\"", format_attrs(options), ">",
                                        text, "</a>"
            ],
       button(url_off,url_on) then
         [ ],

       button(url_off,url_on,w,h) then
         [ ],

       submit(options, text) then
         [ ],

       //immediate_selector(opt,name,size,choices) then
       //  [ ],
       immediate_selector(opt,name,size,choices,selected,function) then
         [ ],
       html(options, html_off_form)  then
         [
          "<a href=\"", full_url,"\"", format_attrs(options), ">",
             format(cinfo, ic_v, html_off_form, is_https, action_count, head_tags),
          "</a>"
         ]
     }.

define Printable_tree
   format_actioner
     (
       CommonInfo                     cinfo,
       Actioner_Connection            connection,
       Actioner_Target                target,
       Actioner_Aspect                aspect,
       WEB_Action_Name                action,
       List((String,String))          extra_ops,
       List(Actioner_Local_Action)    local_actions,
       Maybe(String)                  mb_form_name,
       Bool                           is_https,
       Var(Int)                       action_count,
       Var(Int)                       ic_v,            // 'idnum' counter variable
       Var(List(HTML_Head_Tag))       head_tags

     ) =

   if cinfo is info(common_name,http_port,https_port,site_dir,secret) then
   with url = make_actioner_url(cinfo,connection,target,
                                action,extra_ops,is_https),
   with formatted_action = format_action(url, aspect, extract_id(aspect), mb_form_name, action_count),
   if aspect is
     {

       link(opt, text, mb_name) then
                        with name_tag = if mb_name is success(n) then " name=\"" + n + "\"" else "",
                        with action_name = if action is {
                                             no_action                then ""
                                             controller_action(_, an) then an,
                                             action_name(an)          then an,
                                             url(_)                   then ""
                        },
                        if action_name = ""  then
                          ["<a ", format_text_options(opt), name_tag, ">", text, "</a>" ]
                        else
                          ["<a href=\"",url,"\"",
                           format_text_options(opt), name_tag, ">",
                            text,
                            "</a>"
                          ],
       img_link(options, img, alt_text)       then
                        //if action name is empty, format options on image because maybe there onclick action
                        with action_name = if action is {
                                             no_action                then ""
                                             controller_action(_, an) then an,
                                             action_name(an)          then an,
                                             url(_)                   then ""
                        },
                        if action_name ="" then
                          [
                            "<img src=\"", img,"\"",
                            format_attrs(options)," alt=\"" + alt_text + "\" border=\"0\">"
                          ]
                        else
                          [
                            "<a href=\"", url,"\"", format_attrs(options),"><img src=\"", img,
                            "\" alt=\"" + alt_text + "\" border=\"0\"></a>"
                          ],
       push_button(options, text) then
         [
           if formatted_action is
           {
              url(u)          then    ["<a href=\"",u,"\"", format_attrs(options), ">",
                                        text, "</a>"
                                      ],
              javascript(s,h) then
                          with action_name =
                            if action is
                            {
                              no_action                 then  "",
                              controller_action(_, an)  then an,
                              action_name(an)           then an,
                              url(_)                    then ""
                            },
                            if action_name = "" then
                              ["<input type=\"button\" value=\"",encode_HTML_entities(text),"\"", format_attrs(options), " />"]
                            else
                              [s,"<input type=\"button\" value=\"",encode_HTML_entities(text),"\"", format_attrs(options), " onclick=\"",h,"\" />"]
           }
         ],
       button(url_off,url_on) then
         [ if formatted_action is
             {
               url(u)           then ["<a href=\"",u],
               javascript(s,h)  then [s,"<a onMouseDown=\"",h]
             },
             "\" style=\"text-decoration:none\">",
             "<img alt=\"",url_off,"\" src=\"",url_off,"\" border=0",
               " onMouseOver=\"this.src='",url_on,"'\" ",
                " onMouseOut=\"this.src='",url_off,"'\">",
           "</a>"
         ],

       button(url_off,url_on,w,h) then
         [ if formatted_action is
             {
               url(u)           then ["<a href=\"",u],
               javascript(s,h2)  then [s,"<a onMouseDown=\"",h2]
             },
             "\" style=\"text-decoration:none\">",
             "<img width=",w," height=",h," alt=\"",url_off,"\" src=\"",url_off,"\" border=0",
               " onMouseOver=\"this.src='",url_on,"'\" ",
                " onMouseOut=\"this.src='",url_off,"'\">",
           "</a>"
         ],

       submit(options, text) then
         [
           if formatted_action is
           {
              url(u)          then    ["<a href=\"",u,"\"", format_attrs(options), ">",
                                        text, "</a>"
                                      ],
              javascript(s,h) then
                with action_name = if action is {
                                            no_action                 then "",
                                             controller_action(_, an) then an,
                                             action_name(an)          then an,
                                             url(_)                   then ""
                        },
                          if action_name = "" then  // special case where URL (so the action_name) is provided by the form itself
                                                    // so javascript isn't needed. This is the standard HMTL way.
                              ["<input type=\"submit\" value=\"",text,"\"", format_attrs(options), " />"]
                          else
                              [s,"<input type=\"submit\" value=\"",text,"\"", format_attrs(options), " onclick=\"",h,"\" />"]
           }
         ],

//       immediate_selector(options,name,size,choices) then
//         [ if action is
//             {
//               url(u)           then ["<select href=\"",u]
//               javascript(s,h)  then [s,"<select onchange=\"",h]
//             },
//             "\" name=\"",name,"\" size=\"",size,"\"", format_attrs(options), ">",
//              format_choices(choices),"</select>"
//         ],
       immediate_selector(options, name, size, choices, mb_selected, custom_function_name) then
         [
          //if custom function name is provided, that name is used instead of autogenerated js function
          if custom_function_name = "" then
            if formatted_action is
             {
               url(u)           then ["<select href=\"",u]
               javascript(s,h)  then [s,"<select onchange=\"",h]
             }
           else
            ["<select onchange=\"",custom_function_name],

             "\" name=\"",name,"\" size=\"",size,"\"", format_attrs(options), ">",
             if mb_selected is success(selected) then format_choices(choices, selected) else format_choices(choices),"</select>"
         ],
       html(options, html_off_form)  then
       [
        "<a href=\"", url,"\"", format_attrs(options), ">",
           format(cinfo, ic_v, html_off_form, is_https, action_count, head_tags),
        "</a>"
       ]
     }.


      *** [5.5] Formating a private download link.

   We get  the absolute path  of the file  to be downloaded, and  the name under  which it
   should  appear  to  the  client.   The function  'format_private_download'  creates  an
   hypertext link  for downloading the file.  The secured mecanism of  private download is
   used. This function is called by the function which formats HTML_Any($T) elements.


define Printable_tree
  format_private_download
  (
    CommonInfo               cinfo,
    String                   abs_path,    // absolute file path on server
    String                   name,        // name of file as it appears in the browser
    String                   extra,       // extra extension
    Maybe((String,List((String,String))))   action
  ) =
  if cinfo is info(common_name,http_port,https_port,site_directory,secret) then
    with private_download_directory = site_directory+"/private_download",
    with auth = make_authorization(site_directory,secret,abs_path),
     [
       "<a href=\"",name,extra,"?zauth=",auth,
           if action is
             {
               failure then [ ]
               success(a) then if a is (an,args) then
                 ["&a=",an,format_extra_operands(args)]
             },
            "\">",
         name,
       "</a>"
     ].

      *** [5.6] Formating rows and cells in a table.

define Int
   percent
     (
       Int p
     ) =
   if p < 0 then 0 else if p > 100 then 100 else p.


   Formating cell options.


define String
   format
     (
       BackgroundOption o
     ) =
   if o is
     {
       repeat             then "",
       repeat_horizontal  then "; background-repeat: repeat-x",
       repeat_vertical    then "; background-repeat: repeat-y",
       no_repeat          then "; background-repeat: no-repeat",
       center             then "; background-position: center top"
     }.

define String
   format
     (
        List(BackgroundOption) l
     ) =
   if l is
     {
       [ ] then "",
       [h . t] then format(h)+format(t)
     }.


define String
   format
     (
       List(Cell_Option)   options
     ) =
   if options is
     {
       [ ] then "",
       [h . t] then
         if h is
            {
              core_attrs(core_attr_list)    then format_attrs(core_attr_list),
              left                          then " align=\"left\"",
              h_center                      then " align=\"center\"",
              right                         then " align=\"right\"",
              top                           then " valign=\"top\"",
              v_center                      then " valign=\"middle\"",
              bottom                        then " valign=\"bottom\"",
              base_line                     then " valign=\"baseline\"",
              background_color(c)           then " bgcolor=\""+html_format(c)+"\"",
              background_image(n,o)         then " style=\"background: url("+n+")"+format(o)+"\"",
              width(w)                      then " width=\""+w+"\"",
              percentage_width(n)           then " width=\""+percent(n)+"%\"",
              height(h2)                    then " height=\""+h2+"\"",
              columns(n)                    then " colspan=\""+n+"\"",
              rows(n)                       then " rowspan=\""+n+"\"",
              nowrap                        then " nowrap",
              style(style_string)           then " style=\"" + style_string + "\"",
              class(class_name)             then " class=\""+class_name+"\""
            }
         + format(t)
     }.


   Normalizing a list of cell options  (horizontal position must be specified; the default
   is 'left').

   Formating cells in a row.

define Printable_tree
   format
     (
       List(HTML_Cell($T))               cells,
       $T -> Printable_tree     format_element
     ) =
   if cells is
     {
       [ ] then [ ],
       [h . t] then if h is cell(options,element) then
         ["<td",format(reverse(options)),">",
            format_element(element),
          "</td>"
          . format(t,format_element)]
     }.

define Printable_tree
   format
     (
       List(HTML_Header_Cell($T)) cells,
       $T -> Printable_tree       format_element
     ) =
   if cells is
     {
       [ ] then [ ],
       [h . t] then if h is header_cell(options,element) then
         ["<th ",format(reverse(options)),">",
            format_element(element),
          "</th>"
          . format(t,format_element)]
     }.

   Formating the rows in a table.

define Printable_tree
  format
  (
    List(HTML_Row($T))    rows,
    $T -> Printable_tree  format_element,
  )=
  if rows is
  {
    [ ]     then [ ],
    [h . t] then
      if h is
      {
        empty               then format(t, format_element),
        row(options, cells) then
          ["<tr",format(reverse(options)),">", format(cells, format_element), "</tr>\n"
           . format(t, format_element)]
     }
  }
.

define Printable_tree
  format
  (
    HTML_Header_Row($T)     row,
    $T -> Printable_tree     format_element
  ) =
  if row is
  {
    empty                     then [ ],
    header_row(options,cells) then
         ["<thead> <tr",format(reverse(options)),">",
          format(cells,format_element),
          "</tr> </thead>\n"
         ]
   }.

define Printable_tree
  format
  (
    HTML_Footer_Row($T)      row,
    $T -> Printable_tree     format_element
  ) =
  if row is
  {
    empty                     then [ ],
    footer_row(options,cells) then
         ["<tfoot> <tr",format(reverse(options)),">",
          format(cells,format_element),
          "</tr> </tfoot>\n"
         ]
   }.

define Printable_tree
   format1
     (
       List(TextAreaOption) l
     ) =
   if l is
     {
       [] then [],
       [h . t] then if h is
         {
           input_attrs(input_attr_list)    then [format_attrs(input_attr_list) . format1(t)],
           disabled    then [" disabled=\"disabled\" " . format1(t)]
           read_only   then [" readonly=\"readonly\" " . format1(t)]
           wrap_lines  then [" wrap=\"wrap\" " . format1(t)]
         }
     }.

define Printable_tree
  format
  (
    List(TextAreaOption) l
  )=
  if member(l, wrap_lines) then
    format1(l)
  else
    [" wrap=\"off\" " . format1(l)]
.


      *** [5.7] Formating elements which may be put anywhere.

   The  function  below  involves  the   parameter  $T  which  is  later  instantiated  as
   'HTML_In_Form' or as 'HTML_Off_Form'. Now,  since there are dictinct 'format' functions
   for these two  types, and because formating of tables requires  recursive calls of such
   functions, it is necessary to provide the 'format' function to be called recursively as
   an argument.   Putting naively a call to  'format' will not work,  because the compiler
   will look for a function able to format data of type $T (which is at that time distinct
   from any other type,  including our two types).  Such a function  does not exist. Hence
   the  function to  be  called for  formating elements  must  be passed  as a  functional
   argument (called 'format_element' below).  Actually,  what we pass is a function taking
   a unique  argument of type  $T.  Other  informations (like the  name of the  state) are
   already in the function by way of full functionality.


   Formating  text  options.  They are  formated  in  CSS  syntax,  to  be used  within  a
   'style=...'.

define String
   format
     (
       List(Text_Option) l
     ) =
   if l is
     {
       [ ] then "",
       [h . t] then if h is
         {
         core_attrs(core_attr_list) then format_attrs(core_attr_list),
         size(n)            then "font-size:"+n+"pt",
         font(fn)           then "font-family:"+fn,
         color(c)         then if c is rgb(r,g,b) then
         "color:rgb("+to_decimal(r)+","+to_decimal(g)+","+to_decimal(b)+")",
         italic           then "font-style:italic",
           oblique          then "font-style:oblique",
           small_capitals   then "font-variant:small-caps",
           bold             then "font-weight:bold",
           underlined       then "text-decoration:underline",
           left_justified   then "text-align:left",
           right_justified  then "text-align:right",
           justified        then "text-align:justify",
           line_through     then "text-decoration:line-through",
           nowrap           then "white-space:nowrap",
           class(class_name)then " class=\"" + class_name +"\"",
           id(id_name)      then " id=\"" + id_name +"\"",
           style(style_string)  then " style=\"" + style_string + "\"",
           title(s)         then " title=\"" + s +"\""
           attr(n,v)        then " " + n + "=\"" + v +"\""
         } + if t is [ ] then "" else ("; "+format(t))
     }.


   Formating table options.

define String
   format
     (
       List(Table_Option)    l,
       Bool                  border_seen
     ) =
   if l is
     {
       [ ] then if border_seen then "" else " border=\"0\" cellspacing=\"0\" cellpadding=\"0\"",
       [h . t] then if h is
         {
           core_attrs(core_attr_list) then format_attrs(core_attr_list),
           background_color(c)        then " bgcolor=\""+html_format(c)+"\""+format(t,border_seen),
           background_image(url)      then " background="+url+format(t,border_seen),
           border(o,top,i,c)          then " border=\""+o+"\" cellspacing=\""+top+"\" cellpadding=\""+i+"\""+
                                         //" bordercolor="+format(c)+
                                         format(t,true),
           width(w)                   then " width=\""+w+"\""+format(t,border_seen),
           percentage_width(p)        then " width=\""+percent(p)+"%\""+format(t,border_seen),
           attr(name, value)          then " " + name + "=\"" + value + "\"" +format(t,border_seen),
           class(name)                then " class=\""+name+"\""
         }
     }.


define Printable_tree
   format_scroller
     (
       Int                        width,
       Int                        height,
       Int                        content_width,
       Int                        content_height,
       Int                        idnum,       // identifying the scroller
       $T                           content,
       $T -> Printable_tree         format_element
     ) =
   [
     "<script type = \"text/javascript\" language=\"JavaScript\">",
       "function doscroll_",idnum,"(dx,dy) {\n", 
       "  if (document.layers) { var c_",idnum," = eval(document.cs_",idnum,"); } else\n",
       "  if (document.getElementById) {var c_",idnum," = eval(\"document.getElementById('cs_",
                                                            idnum,"').style\"); } else\n",
       "  if (document.all) { var c_",idnum," = eval(document.all.cs_",idnum,".style); };\n",
       "  var x_",idnum," = parseInt(c_",idnum,".left);\n",
       "  var y_",idnum," = parseInt(c_",idnum,".top);\n",
       "  if ((x_",idnum,"+dx <= 0) && (x_",idnum,"+dx > ",width-content_width,"))\n",
       "    { x_",idnum," += dx; }\n",
       "  if ((y_",idnum,"+dy <= 0) && (y_",idnum,"+dy > ",height-content_height,"))\n",
       "    { y_",idnum," += dy; }\n",
       "  c_",idnum,".left = x_",idnum,";\n",
       "  c_",idnum,".top = y_",idnum,";\n",
       "   }\n",
     "</script>\n",
     "<table>",
      "<tbody>",
       "<tr>",
         "<td align=left valign=top",
            " width=",width,
            " height=",height,
            ">",
            "<div id=\"ws_",idnum,"\" style=\"position:absolute; width:",width,"px; height:",height,"px;",
                                       " clip:rect(0px ",width,"px ",height,"px 0px)\">",
              "<div id=\"cs_",idnum,"\" style=\"position:absolute; left:0px; top:0px\">",
                 format_element(content),
              "</div>",
            "</div>",
         "</td>",
         "<td valign=bottom>",
           "<table>",
            "<tbody>",
             "<tr><td><img alt=\"sroll up\" src=\"scrollup.gif\"   onmousedown=\"doscroll_", idnum,"(0,20);\"></td></tr>",
             "<tr><td><img alt=\"scroll down\" src=\"scrolldown.gif\" onmousedown=\"doscroll_", idnum,"(0,-20);\"></td></tr>",
            "</tbody>",
           "</table>",
         "</td>",
       "</tr>",
       (if content_width > width then
        [
        "<tr>",
          "<td align=right>",
             "<table>",
              "<tbody>",
               "<tr>",
                 "<td><img alt=\"scroll left\" src=\"scrollleft.gif\" onmousedown=\"doscroll_", idnum,"(20,0);\"></td>",
                 "<td><img alt=\"scroll right\" src=\"scrollright.gif\" onmousedown=\"doscroll_", idnum,"(-20,0);\"></td>",
               "</tr>",
              "</tbody>",
             "</table>",
           "</td>",
         "</tr>",
        ] else [ ]),
      "</tbody>",
     "</table>"
   ].


define Printable_tree
  format
    (
      Body_Option o
    ) =
  if o is
    {
      core_attrs(core_attr_list)         then [" " + format_attrs(core_attr_list)],
      background_color(c)                then [" bgcolor=\"" , (String)html_format(c), "\""],
      background_image(n)                then [" background=", n],
      background_image(n,o2)             then [" style=\"background: url(",n,")",format(o2),"\""]

    }.


define Printable_tree
   format
     (
       List(Body_Option) l
     ) =
   if l is
     {
       [ ]     then [ ],
       [h . t] then [format(h) . format(t)]
     }.

define Printable_tree
  add_css_files
  (
    List(CSS_File)   l
  ) =
  if l is
  {
    [ ]     then [ ],
    [h . t] then
      since h is css_file(file_name, media),
       [ ["<link rel=\"stylesheet\" type=\"text/css\" href=\"" + file_name + "\" media=\""+to_String(media)+"\"/>\n" ]
         . add_css_files(t)]
  }.

define Printable_tree
   add_js_files_attributes
     (
       List(JS_Attribute)   l
     ) =
   if l is
     {
       [ ] then [ ],
       [h . t] then
         if h is attr(name, value) then
         [ " " + name + "=\"" + value + "\""
           . add_js_files_attributes(t)]
     }.


define Printable_tree
  add_js_files
  (
    List(JS_File)   l
  ) =
  if l is
  {
    [ ]     then [ ],
    [h . t] then
      [ ["<script src=\""+ file_name(h) +"\" type=\"text/javascript\""
            . add_js_files_attributes(attributes(h)) ]
           . ["></script>\n"
             . add_js_files(t)] ]
  }
.

define Printable_tree
  add_script
  (
    List(Script)   l
  ) =
  if l is
  {
    [ ]     then [ ],
    [h . t] then [ "<script type=\""+ script_type(h) +"\">\n"+ content(h) + "\n</script>\n" . add_script(t) ]
  }.

define Printable_tree
  add_css_styles
  (
    List(CSS_Style) css_styles
  ) =

  if css_styles is
  {
    []      then [],
    [_ . _] then [ "<style type=\"text/css\"><!--\n",
                  format_css_styles(css_styles),
                 "  --></style>\n"
               ]
  }.


   // The function below formats a datum of type 'HTML_Any($T)'.

define Printable_tree
  format
  (
    CommonInfo                 cinfo,
    Var(Int)                   ic_v,
    HTML_Any($T)               element,
    $T -> Printable_tree       format_element,  // able to format a datum of type $T
    Bool                       is_https,
    Var(Int)                   action_count,
    Var(List(HTML_Head_Tag))   head_tags
  ) =
  if cinfo is info(common_name,http_port,https_port,site_directory,secret) then
  if element is
  {
    any_text(opts , t)            then
      if opts is
      {
        []      then [t],
        [_ . _] then ["<span", format_attrs(opts), ">",t,"</span>"]
      },
    any_preformated(opts,s)       then
     ["<span", format_text_options(opts), "><pre>",s,"</pre></span>"],
     //["<pre>",s,"</pre>"],
    any_paragraph(opts,l)         then
     ["<p", format_text_options(opts), ">", flat(map(($T e) |-> format_element(e), l)),"</p>\n"],
    any_image(opts, url, _alt)                then
      with alt = if _alt = "" then "" else "alt=\""+_alt+"\"",
     ["<img ",alt," src=\"",url,"\" ", format_attrs(opts)," />"],
    any_image(opts, url, alt, w, h)            then
     ["<img alt=\"",alt,"\" src=\"",url,"\" width=\"",w,"\" height=\"",h,"\" ", format_attrs(opts)," />"],
    any_table(opts,h_row, rows, f_row) then
     ["<table",format(reverse(opts),false),">",
        format(h_row, format_element),
        "<tbody>",format(rows,format_element),"</tbody>",
        format(f_row, format_element),
        "</table>\n"],
    any_center(e)                 then
     ["<center>",format_element(e),"</center>"],
    any_mail_to(email,elem)       then
     ["<a href=\"mailto:",email,"\">",format_element(elem),"</a>"],
    any_scroller(w,h,cw,ch,c)     then
     format_scroller(w,h,cw,ch,new_idnum(ic_v),c,format_element),
    any_fixed_size(w,h,c)         then
     with url = create_secondary_document(site_directory,secret,format_element,c,w),
     ["<object data=\"",url,"\" type=\"text/html\" width=\"",format(w),"\" height=\"",format(h),"\" >",
         "secondary document",
      "</object>"],
    any_fixed_size_2(w,h,fn)        then
     with url = fn+"?zauth="+make_authorization(site_directory,secret,
             fn),
     ["<object data=\"",url,"\" type=\"text/html\" width=\"",format(w),"\" height=\"",format(h),"\" >",
         "secondary document",
      "</object>"],
    any_actioner(c,t,a,an,eo,ja,fn)  then
     format_actioner(cinfo,c,t,a,an,eo,ja,fn,is_https, action_count, ic_v, head_tags),

    any_foreign_link_new(target, aspect, url)    then
     format_foreign_link(target, aspect, url, is_https, cinfo, action_count, ic_v, head_tags),

    any_foreign_link(options,url)    then
     ["<a href=\"",url,"\" ", format_text_options(options), "></a>"],  // IE7 doesn't support the form <a href="..." />
    any_foreign_link(options,url,name)    then
     ["<a href=\"",url,"\"><span ", format_text_options(options), ">",name,"</span></a>"],
    any_private_download(url,name,extra_ext,action)  then
     format_private_download(cinfo,url,name,extra_ext,action),
    any_div(options, l)                   then
     [format_div_option(options), flat(map(($T e) |-> format_element(e), l)),"</div>\n"],
    any_div_empty(options)                then
     [format_div_option(options), "</div>\n"],
    any_coreattrs(attributs)              then
     [format_attrs(attributs)],
    any_ol(opts, l)         then
     ["<ol", format_attrs(opts), ">", flat(map(($T e) |-> format_element(e), l)),"</ol>\n"],
    any_ul(opts, l)         then
     ["<ul", format_attrs(opts), ">", flat(map(($T e) |-> format_element(e), l)),"</ul>\n"],
    any_li(opts, l)         then
     ["<li", format_attrs(opts), ">", flat(map(($T e) |-> format_element(e), l)),"</li>\n"],
    any_button(options, l)  then
     [["<button" + format_attrs(options) + ">"], flat(map(($T e) |-> format_element(e), l)),"</button>\n"],
    any_i(opts,t)           then
      if t = "" then
        ["<i", format_attrs(opts), "></i>\n"]
      else
        ["<i", format_attrs(opts), ">",t,"</i>\n"],
    any_span(opts , t)            then
       ["<span", format_attrs(opts), ">",t,"</span>"]
    any_hr(opts)            then
      ["<hr", format_attrs(opts),">"]
    }
.


  //    *** [5.8] Formating 'in form' elements.


//public define Printable_tree
//  format
//  (
//    HTML_tooltip  tooltip
//  )=
//  if tooltip is
//  {
//    html_tooltip(title, keyword, width)                           then
//      ["<a id=\"help_",keyword,"\" class=\"jTipu jTip_help\" name=\"",title,"\" href=\"/?a=ajax_show_tooltip&amp;tooltip_id=",keyword,(if width > 0 then ["&width=",width,"\""] else ["\""]), "></a>"],
//
//    html_tooltip_ext(title, extend_type, class_suffix, ext_args)  then
//      with extra_args = format_extra_operands(ext_args),
//      ["<a id=\"jTip\" class=\"jTipu jTip_",class_suffix,"\" name=\"",title,"\" href=\"/?a=ajax_show_tooltip&amp;tooltip_ext=",extend_type+extra_args,"\"></a>"]
//  }.

public define List(CoreAttrs)
  extract_attributes
  (
    HTML_tooltip  tooltip
  )=
  if tooltip is
  {
    html_tooltip(title, keyword, width)                           then  //TODO
      []
      //["<a id=\"help_",keyword,"\" class=\"jTipu \" name=\"",title,"\" href=\"/?a=ajax_show_tooltip&tooltip_id=",keyword,(if width > 0 then ["&width=",width,"\""] else ["\""]), "><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],

    html_tooltip_ext(title, extend_type, class_suffix, ext_args)  then  //TODO
      //[]
      with extra_args = format_extra_operands(ext_args),
      [id("jTip"), class("jTipu jTip_"+class_suffix), data("name",title), data("href", "/?a=ajax_show_tooltip&tooltip_ext="+extend_type+extra_args)]

    html_tooltip_ext(title, extend_type, ext_args)  then  //TODO
      with extra_args = format_extra_operands(ext_args),
      [id("jTip"), class("jTipu"), data("name",title), data("href", "/?a=ajax_show_tooltip&tooltip_ext="+extend_type+extra_args)]
//      []
      //with extra_args = format_extra_operands(ext_args),
      //["<a id=\"jTip\" class=\"jTipu \" name=\"",title,"\" href=\"/?a=ajax_show_tooltip&tooltip_ext=",extend_type+extra_args,"\"><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],

    html_tooltip(title, web_action, extra_args)     then
      [ id("jTip"), class("jTipu"), data("name", title), data("href", "/"+format_web_action_name(web_action, extra_args))
      ]

      //["<a id=\"jTip\" class=\"jTipu \" name=\"",title,"\" href=\"/", format_web_action_name(web_action, extra_args) ,"\"><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],

  }
.

    literal_pt(["<span id=\"jTip\" class=\"jTipu\" data-name=\"",title,"\" data-href=\"/", format_web_action_name(web_action, extra_args) ,"\">"]),


public define Printable_tree
  format
  (
    HTML_tooltip  tooltip
  )=
  if tooltip is
  {
    html_tooltip(title, keyword, width)                           then
      ["<a id=\"help_",keyword,"\" class=\"jTipu \" data-name=\"",title,"\" data-href=\"/?a=ajax_show_tooltip&tooltip_id=",keyword,(if width > 0 then ["&width=",width,"\""] else ["\""]), "><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],

    html_tooltip_ext(title, extend_type, class_suffix, ext_args)  then
      with extra_args = format_extra_operands(ext_args),
      ["<a id=\"jTip\" class=\"jTipu jTip_",class_suffix,"\" data-name=\"",title,"\" data-href=\"/?a=ajax_show_tooltip&tooltip_ext=",extend_type+extra_args,"\"></a>"]

    html_tooltip_ext(title, extend_type, ext_args)  then
      with extra_args = format_extra_operands(ext_args),
      ["<a id=\"jTip\" class=\"jTipu \" data-name=\"",title,"\" data-href=\"/?a=ajax_show_tooltip&tooltip_ext=",extend_type+extra_args,"\"><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],
    html_tooltip(title, web_action, extra_args)     then
      ["<a id=\"jTip\" class=\"jTipu \" data-name=\"",title,"\" data-href=\"/", format_web_action_name(web_action, extra_args) ,"\"><i class=\"fa fa-info\" aria-hidden=\"true\" style=\"color:#2e6da4\"></i></a>"],

  }
.

public define HTML_Off_Form
  html_tooltip
  (
    String                title,
    WEB_Action_Name       web_action,
    List((String,String)) extra_args,
    HTML_Off_Form         html_element,
  )=
  sequence([
    literal_pt(["<span id=\"jTip\" class=\"jTipu\" data-name=\"",title,"\" data-href=\"/", format_web_action_name(web_action, extra_args) ,"\">"]),
    html_element,
    literal_pt(["</span>"])
  ])
.

public define HTML_Off_Form
  html_tooltip
  (
    String title,
    String keyword,
  ) =
  literal_pt(format(html_tooltip(title, keyword, 0))).

public define HTML_In_Form
  html_tooltip
  (
    String title,
    String keyword,
  ) =
  literal_pt(format(html_tooltip(title, keyword, 0))).

public define HTML_Off_Form
  html_tooltip
  (
    String  keyword,
    Int     size,
  ) =
  literal_pt(format(html_tooltip("", keyword, size))).

public define HTML_In_Form
  html_tooltip
  (
    String  keyword,
    Int     size,
  ) =
  literal_pt(format(html_tooltip("", keyword, size))).

public define Printable_tree
  format_help
  (
    Printable_tree  label,
    HTML_Help       _help
  ) =
  if _help is
  {
    no_help                     then label,
    tooltip(html_tooltip, position)  then
      if position is
      {
        left  then pt_pt(format(html_tooltip),label),
        right then pt_pt(label, format(html_tooltip))
      }
  }.


public define HTML_Label
  label
  (
    String  text
  )=
  label(text, no_help).


public define Printable_tree
  format_label
  (
    HTML_Label  _label,
    HTML_Id     _id
  ) =
  if _label is
  {
    no_label              then [],
    label(text, help) then
      format_help(
        ["<label"+(if _id.id ="" then "" else " for=\""+_id.id+"\"")+">",text,"</label>"],
        help
      )
  }.


define Printable_tree
  format
  (
     CommonInfo               cinfo,
     String                   fn,      // form_name
     Var(Int)                 ic_v,    // idnum counter variable
     HTML_In_Form             element,
     Bool                     is_https,
     Var(Int)                 action_count,
     Var(List(HTML_Head_Tag))   head_tags
  ) =
   if cinfo is info(common_name,http_port,https_port,site_directory,secret) then
   with format_element = (HTML_In_Form e) |-> format(cinfo, fn, ic_v, e, is_https, action_count, head_tags),
   if element is
     {
       empty                       then [],
       literal_pt(t)               then t,
       literal(t)                  then [t],
       sequence(l)                 then flat(map(format_element,l))
       text(opts,t)                then
         format(cinfo,ic_v,any_text(opts,t),format_element,is_https, action_count, head_tags),
       preformated(o,s)            then
         format(cinfo,ic_v,any_preformated(o,s),format_element,is_https, action_count, head_tags),
       paragraph(opts,t)           then
         format(cinfo,ic_v,any_paragraph(opts,t),format_element,is_https, action_count, head_tags),
       image(opts, url, alt)       then
         format(cinfo,ic_v,any_image(opts, url, alt),format_element,is_https, action_count, head_tags),
       image(opts, url, alt, w, h) then
         format(cinfo,ic_v,any_image(opts, url, alt, w, h),format_element,is_https, action_count, head_tags),
       table(opts,header_row,rows,footer_row)            then
         format(cinfo,ic_v,any_table(opts, header_row, rows, footer_row),format_element,is_https, action_count, head_tags),
       center(e)                   then
         format(cinfo,ic_v,any_center(e),format_element,is_https, action_count, head_tags),
       mail_to(a,e)                then
         format(cinfo,ic_v,any_mail_to(a,e),format_element,is_https, action_count, head_tags),
       scroller(w,h,cw,ch,c)       then
         format(cinfo,ic_v,any_scroller(w,h,cw,ch,c),format_element,is_https, action_count, head_tags),
       actioner(c,t,a,an,eo,ja)    then
         format(cinfo,ic_v,any_actioner(c,t,a,an,eo,ja,success(fn)),format_element,is_https, action_count, head_tags),

       foreign_link_new(target, aspect, url)  then
         format(cinfo,ic_v,any_foreign_link_new(target,aspect,url),format_element,is_https, action_count, head_tags),

       foreign_link(options,url)  then
         format(cinfo,ic_v,any_foreign_link(options,url),format_element,is_https, action_count, head_tags),
       foreign_link(options,url,name)  then
         format(cinfo,ic_v,any_foreign_link(options,url,name),format_element,is_https, action_count, head_tags),
       private_download(url,name,extra,action)    then
         format(cinfo,ic_v,any_private_download(url,name,extra,action),format_element,is_https, action_count, head_tags),
       text_input(options, label_text, id, name, init, w)           then
         [ format_label(label_text, id),
           "<input type=\"text\" name=\"",name,"\" id=\"",id,"\" size=\"",w,"\" value=\"",encode_HTML_entities(init.value),"\"",format_attrs([class("in") . options])," />"],
       text_input_ro(options, label_text, id, name, init, w)           then
         [ format_label(label_text, id),
           "<input readonly=\"readonly\" type=\"text\" name=\"",name,"\" id=\"",id,"\" size=\"",w,"\" value=\"",encode_HTML_entities(init.value),"\"",format_attrs([class("in") . options])," />"],
       password_input(options, label_text, id, name, init, w)         then
         [ format_label(label_text, id),
           "<input type=\"password\" name=\"",name,"\" id=\"",id,"\" size=\"",w,"\" value=\"",encode_HTML_entities(init.value),"\"",format_attrs([class("in") . options])," />"],
       text_area(options,label_text, id, n, init, w, h)          then
         [ format_label(label_text, id), "<textarea ",format(options)," id=\"",id,"\" name=\"",n,"\" cols=\"",w,"\" rows=\"",h,"\">",encode_HTML_entities(init.value),"</textarea>"],
       file_upload(options, label, id, n, w)            then
         [ format_label(label, id),
           "<input type=\"file\" id=\"",id,"\" size=\"",w,"\" name=\"",n,"\"",format_attrs([class("in") . options])," />"],
       selector(options, label, id, n,s,cs)            then
         [ format_label(label, id),
          "<select id=\"",id,"\" name=\"",n,"\" size=\"",s,"\" ",format_attrs([class("in") . options]),">",format_choices(cs),"</select>"],
       selector(options, label, id, n,s,cs,sd)         then
         [ format_label(label, id),
          "<select id=\"",id,"\" name=\"",n,"\" size=\"",s,"\" ",format_attrs([class("in") . options]),">",format_choices(cs,sd),"</select>"],
       selector_c(options, label, id, n,s,cs)            then
         [ format_label(label, id),
          "<select id=\"",id,"\" name=\"",n,"\" size=\"",s,"\" ",format_attrs([class("in") . options]),">",format_choices(cs),"</select>"],
       selector_c(options, label, id, n,s,cs,sd)         then
         [ format_label(label, id),
          "<select id=\"",id,"\" name=\"",n,"\" size=\"",s,"\" ",format_attrs([class("in") . options]),">",format_choices(cs,sd),"</select>"],

       radio_button(options, label, id, n, value, c)         then
         [ format_label(label, id),
           "<input type=\"radio\" name=\"",n,"\" id=\"",id,"\" value=\"",value,"\"",(if c then " checked=\"checked\"" else ""),format_attrs([class("in") . options])," />"],
       radio_button_r(options, label, id, n, value, c)         then
         [ "<input type=\"radio\" name=\"",n,"\" id=\"",id,"\" value=\"",value,"\"",(if c then " checked=\"checked\"" else ""),format_attrs([class("in") . options])," />",
           format_label(label, id)],
       check_box(options, label, id, n, c)              then
         [ format_label(label, id),
           "<input type=\"hidden\" name=\"~",n,"\" value=\"~true\" /><input type=\"checkbox\" name=\"",n,"\" id=\"",id,"\" value=\"true\"",(if c then " checked=\"checked\" " else ""),format_attrs([class("in") . options])," />"]
       check_box_r(options, label, id, n, c)              then
         [ "<input type=\"hidden\" name=\"~",n,"\" value=\"~true\" /><input type=\"checkbox\" name=\"",n,"\" id=\"",id,"\" value=\"true\"",(if c then " checked=\"checked\" " else ""),format_attrs([class("in") . options])," />",
           format_label(label, id)]
       div(options, e)                  then
        format(cinfo,ic_v,any_div(options, e),format_element,is_https, action_count, head_tags),
       div_empty(options)               then
        format(cinfo,ic_v,any_div_empty(options),format_element,is_https, action_count, head_tags),
      hidden(_id, name, init)          then
        since _id is html_Id(id),
         ["<input type=\"hidden\"",(if id = "" then "" else " id=\""+id+"\"")," name=\"",name,"\" value=\"",encode_HTML_entities(init.value),"\" />"],
       partial(p_content)               then
        if p_content is partial_content(tags, html_elements) then
          head_tags <- *head_tags + tags;

          format(cinfo, ic_v, html_elements, is_https, action_count, head_tags),
       br                               then ["<br>"],
       progress(options, value, max)    then ["<progress max=\"",value,"\" value=\"",max,"\"",format_attrs(options),"></progress>"],
       ol(opts, t)            then
         format(cinfo,ic_v,any_ol(opts,t),format_element,is_https, action_count, head_tags),
       ul(opts, t)            then
         format(cinfo,ic_v,any_ul(opts,t),format_element,is_https, action_count, head_tags),
       li(opts, t)            then
         format(cinfo,ic_v,any_li(opts,t),format_element,is_https, action_count, head_tags),
       button(options, e)     then
        format(cinfo,ic_v,any_button(options, e),format_element,is_https, action_count, head_tags),
       i(opts, t)             then
         format(cinfo,ic_v,any_i(opts,t),format_element,is_https, action_count, head_tags),
       span(opts,t)           then
         format(cinfo,ic_v,any_span(opts,t),format_element,is_https, action_count, head_tags)
       hr(opts)           then
         format(cinfo,ic_v,any_hr(opts),format_element,is_https, action_count, head_tags)
     }.


      *** [5.9] Formating 'off form' elements.

   The encryption type 'multipart/form-data' is required for a form containing an upload.


define Bool
  contains_an_upload
  (
    HTML_In_Form form_content
  ).

define Bool
  contains_an_upload
  (
    HTML_Row(HTML_In_Form) row
  ) =
  if row is
  {
    empty         then false,
    row(_, cells) then
      mapor(contains_an_upload,
         map(content, cells))
  }
.

define Bool
  contains_an_upload
  (
    HTML_Footer_Row(HTML_In_Form) row
  )=
  if row is
  {
    empty                 then false,
    footer_row(_, cells)  then
      mapor(contains_an_upload,
            map(content,cells))
  }.

define Bool
   contains_an_upload
    (
      HTML_In_Form form_content
    ) =
   if form_content is
     {
   empty                      then false,
   literal_pt(t)              then false,
   literal(t)                 then false,
   sequence(l)                then mapor(contains_an_upload,l),
   text(o,t)                  then false,
   preformated(o,s)           then false,
   paragraph(o,l)             then mapor(contains_an_upload,l),
   image(o,u,a)               then false,
   image(o,u,a,w,h)           then false,
   table(o,_,rows,f_row)      then if mapor(contains_an_upload,rows) then true
                                                                     else contains_an_upload(f_row),
   center(e)                  then contains_an_upload(e),
   mail_to(m,e)               then false, // 'e' may but should not contain an upload
   scroller(w,h,cw,ch,e)      then contains_an_upload(e),
   actioner(c,t,a,an,eo,ja)   then false,
   foreign_link_new(_,_,_)    then false,
   foreign_link(o,u)          then false,
   foreign_link(o,u,n)        then false,
   private_download(p,n,e,a)  then false,
   text_input(o,lt,l,n,i,w)     then false,
   text_input_ro(o,lt,l,n,i,w)  then false,
   password_input(o,lt,l,n,i,w) then false,
   text_area(o,lt,id,n,i,w,h)   then false,
   file_upload(o,l,i,n,w)     then true,
   selector(o,l,i,n,s,c)      then false,
   selector(o,l,i,n,s,c,p)    then false,
   selector_c(o,l,i,n,s,c)    then false,
   selector_c(o,l,i,n,s,c,p)  then false,
   radio_button(o,_,_,n,v,c)  then false,
   radio_button_r(o,_,_,n,v,c)  then false,
   check_box(o,_,_,n,c)       then false,
   check_box_r(o,_,_,n,c)     then false,
   div(o,l)                   then mapor(contains_an_upload,l), //contains_an_upload(c),
   div_empty(o)               then false,
   hidden(_,_,_)              then false,
   partial(_)                 then false,
   br                         then false,
   progress(_,_,_)            then false,
   ol(_,l)                    then mapor(contains_an_upload,l),
   ul(_,l)                    then mapor(contains_an_upload,l),
   li(_,l)                    then mapor(contains_an_upload,l),
   button(_,_)                then false,
   i(_,_)                     then false,
   span(_,_)                  then false,
   hr(_)                      then false
  }
.

define String
  enctype
  (
      List(HTML_In_Form) form_contents
  )=
  if mapor(contains_an_upload, form_contents) then
    " enctype=\"multipart/form-data\""
  else
    ""
.

define Printable_tree
  format_href
  (
    A_href _href
  )=
  if _href is
  {
    href(str)           then if str = "" then [] else [" href=\"", str, "\""],
    href(action, extra) then [" href=\"",format_web_action_name(action, extra), "\""]
  }
.

define Printable_tree
  format_target
  (
    A_target  _target
  )=
  [" target=\"",
    if _target is
    {
      _blank  then  "_blank",
      _self   then  "_self",
      _parent then  "_parent",
      _top    then  "_top",
      framename(name) then  name
    },
  "\""]
.

define Printable_tree
  format
  (
    CommonInfo               cinfo,
    Var(Int)                 ic_v,             // 'idnum' counter variable
    HTML_Off_Form            element,
    Bool                     is_https,
    Var(Int)                 action_count,
    Var(List(HTML_Head_Tag)) head_tags
  ) =
   if cinfo is info(common_name,http_port,https_port,site_directory,secret) then
   with format_element = (HTML_Off_Form e) |-> format(cinfo, ic_v, e, is_https, action_count, head_tags),
  if element is
  {
    a(opts, _href, _target, l)      then ["<a ", format_attrs(opts), format_href(_href), format_target(_target), ">",flat(map(format_element,l)),"</a>\n"],
    empty                           then [],
       literal_pt(t)                then t,
       literal(t)                   then [t],
       sequence(l)                  then flat(map(format_element,l)),
       text(opts,t)                 then
         format(cinfo,ic_v,any_text(opts,t),format_element,is_https, action_count, head_tags),
//       preformated(o,s)             then
//         format(cinfo,ic_v,any_preformated(o,s),format_element,is_https, action_count, head_tags),
//       paragraph(opts,t)            then
//         format(cinfo,ic_v,any_paragraph(opts,t),format_element,is_https, action_count, head_tags),
//       image(opts,url,alt)          then
//         format(cinfo,ic_v,any_image(opts,url,alt),format_element,is_https, action_count, head_tags),
//       image(opts,url,alt,w,h)      then
//         format(cinfo,ic_v,any_image(opts,url,alt,w,h),format_element,is_https, action_count, head_tags),
       table(opts,header_row, rows, footer_row) then
         format(cinfo,ic_v,any_table(opts,header_row, rows, footer_row),format_element,is_https, action_count, head_tags),
//       center(e)                    then
//         format(cinfo,ic_v,any_center(e),format_element,is_https, action_count, head_tags),
//       mail_to(a,e)                 then
//         format(cinfo,ic_v,any_mail_to(a,e),format_element,is_https, action_count, head_tags),
//       scroller(w,h,cw,ch,c)        then
//         format(cinfo,ic_v,any_scroller(w,h,cw,ch,c),format_element,is_https, action_count, head_tags),
//       fixed_size(w,h,c)            then
//         format(cinfo,ic_v,any_fixed_size(w,h,c),format_element,is_https, action_count, head_tags),
//       fixed_size_2(w,h,fn)           then
//         format(cinfo,ic_v,any_fixed_size_2(w,h,fn),format_element,is_https, action_count, head_tags),
       actioner(c,t,a,an,eo,ja)     then
         format(cinfo,ic_v,any_actioner(c,t,a,an,eo,ja,failure),format_element,is_https, action_count, head_tags),
       actioner(c,t,a,an,eo,ja,fn)  then
         format(cinfo,ic_v,any_actioner(c,t,a,an,eo,ja,success(fn)),format_element,is_https, action_count, head_tags),
       foreign_link_new(target, aspect, url)  then
         format(cinfo,ic_v,any_foreign_link_new(target,aspect,url),format_element,is_https, action_count, head_tags),
       foreign_link(options,url)       then
         format(cinfo,ic_v,any_foreign_link(options,url),format_element,is_https, action_count, head_tags),
       foreign_link(options,url,name)       then
         format(cinfo,ic_v,any_foreign_link(options,url,name),format_element,is_https, action_count, head_tags),
       private_download(url,name,extra,action)     then
         format(cinfo,ic_v,any_private_download(url,name,extra,action),format_element,is_https, action_count, head_tags),
//       label(n)                     then ["<a name=\"",n,"\">"],
       form(fn,attributs, l)        then
         [
           "<form id=\"",fn,"\"",
           format(cinfo,ic_v,any_coreattrs(attributs),format_element,is_https, action_count, head_tags),
           " method=\"post\"",
              enctype(l),
              " action=\"http",
                         if is_https then "s" else "",
                         "://",common_name,":",to_decimal(http_port),"/\">",
                                      // action is set dynamically by
                                      // the actioner using JavaScript
              if fn is html_Id(id) then
              flat(map((HTML_In_Form e) |-> format(cinfo,id,ic_v,e,is_https, action_count, head_tags), l)),
           "</form>"
         ]
       form(fn,attributs, action, extra_ops, l)        then
         with url = make_actioner_url(cinfo, same, same,
                                      action, extra_ops, is_https),
         [
           "<form id=\"",fn,"\"",
           format(cinfo,ic_v,any_coreattrs(attributs),format_element,is_https, action_count, head_tags),
           " method=\"post\"",
              enctype(l),
              " action=\"" + url + "\">",
//              " action=\"http",
//                         if is_https then "s" else "",
//                         "://",common_name,":",http_port,"/\">",
                                      // action is set dynamically by
                                      // the actioner using JavaScript
              if fn is html_Id(id) then
              flat(map((HTML_In_Form e) |-> format(cinfo,id,ic_v,e,is_https, action_count, head_tags),l)),
           "</form>"
         ],
       in_form(fn, content)             then
          if fn is html_Id(id) then
            format(cinfo,id,ic_v, content,is_https, action_count, head_tags),
//       div(options, e)              then
//          format(cinfo, ic_v, any_div(options, e), format_element, is_https, action_count, head_tags),
       div(options, p_content)      then
        with html_elements = map((HTML_Partial_Content pc) |-> since pc is partial_content(tags, html_elem), head_tags <- *head_tags +tags; html_elem, p_content),

          format(cinfo, ic_v, any_div(options, html_elements), format_element, is_https, action_count, head_tags),
//       div_empty(options)           then
//          format(cinfo, ic_v, any_div_empty(options), format_element, is_https, action_count, head_tags),
       iframe(options, css_styles, css_files, js_files, body) then
          println("formating iframe");
          if body is body(body_options,elem) then
          [ "<iframe", format_attrs(options), " srcdoc=\"\n",

            encode_HTML_quote(to_String([
            "<html style=\"margin: 0pt; padding: 0pt;\">\n",
            "<head>\n",
            add_css_styles(css_styles),
            add_css_files(css_files),
            add_js_files(js_files),
            "</head>\n",
            "<body ", format(body_options), ">\n",                       // format body options
            format(cinfo,ic_v,elem,is_https, action_count, head_tags),
            "</body>\n",
            "</html>\n",])),

            "\"></iframe>\n",
          ],
       partial(p_content)           then
        if p_content is partial_content(tags, html_elements) then
          head_tags <- *head_tags + tags;
          format(cinfo, ic_v, html_elements, is_https, action_count, head_tags),
//       br                               then ["<br>"],
//       progress(options, value, max)    then ["<progress max=\"",max,"\" value=\"",value,"\"",format_attrs(options),"></progress>"],
//       ol(opts, t)            then
//         format(cinfo,ic_v,any_ol(opts,t),format_element,is_https, action_count, head_tags),
//       ul(opts, t)            then
//         format(cinfo,ic_v,any_ul(opts,t),format_element,is_https, action_count, head_tags),
//       li(opts, t)            then
//         format(cinfo,ic_v,any_li(opts,t),format_element,is_https, action_count, head_tags),
//       button(options, e)     then
//          format(cinfo, ic_v, any_button(options, e), format_element, is_https, action_count, head_tags),
       i(opts, t)             then
         format(cinfo,ic_v,any_i(opts,t),format_element,is_https, action_count, head_tags),
//       span(opts,t)           then
//         format(cinfo,ic_v,any_span(opts,t),format_element,is_https, action_count, head_tags),


//       hr(opts)               then
//         format(cinfo,ic_v,any_hr(opts),format_element,is_https, action_count, head_tags),
//       nav(opts, l)          then ["<nav", format_attrs(opts), ">",flat(map(format_element,l)),"</nav>\n"],
       html_tag(tag_name, opts, l)    then ["<",tag_name, format_attrs(opts), ">",flat(map(format_element,l)),"</",tag_name,">\n"],
       html_void_tag(tag_name, opts)  then ["<",tag_name, format_attrs(opts), ">"],
     }.

      *** [5.10] Formating meta-tags.

define Printable_tree
   format_keywords
     (
       List(String) l
     ) =
   if l is
     {
       []      then [ ],
       [h . t] then if t is []
         then [h]
         else [h , ", " . format_keywords(t)]
     }.


define Printable_tree
  format
  (
    CommonInfo        cinfo,
    HTML_Meta         m,
    Bool              is_https
  ) =
  if m is
  {
    keywords(l)        then ["<meta name=\"keywords\" content=\"",format_keywords(l),"\" />\n"],
    refresh(co,ta,an,delay)  then
                               ["<meta http-equiv=\"Refresh\" content=\"",delay,"; URL=",
                                    make_actioner_url(cinfo,co,ta,an,[],is_https),"\" />\n"],
    refresh(url,delay) then
                               ["<meta http-equiv=\"Refresh\" content=\"",delay,"; URL=",url,"\" />\n"],
     meta(n,c)          then ["<meta name=\"",n,"\" content=\"",c,"\" />\n"],
     http_equiv(n,c)    then ["<meta http-equiv=\"",n,"\" content=\"",c,"\" />\n"],
     generic_meta(l)    then ["<meta ",
                                  flat(map(((String,String) p) |-> if p is (n,v) then [n,"=\"",v,"\" "],
                                      l)),
                                 " />\n"],
     literal(s)         then [s]
  }
.

define Printable_tree // c'est le nôtre et c'est meilleur
   format
     (
       HTML_Meta         m,
     ) =
   if m is
     {
       keywords(l)        then ["<meta name=\"keywords\" content=\"",format_keywords(l),"\" />\n"],
       refresh(co,ta,an,delay)  then
                               ["<!-- TODO refresh(co,ta,an,delay) --> "], // TODO
       refresh(url,delay) then
                               ["<meta http-equiv=\"Refresh\" content=\"",delay,"; URL=",url,"\" />\n"],
       meta(n,c)          then ["<meta name=\"",n,"\" content=\"",c,"\" />\n"],
       http_equiv(n,c)    then ["<meta http-equiv=\"",n,"\" content=\"",c,"\" />\n"],
       generic_meta(l)    then ["<meta ",
                                  flat(map(((String,String) p) |-> if p is (n,v) then [n,"=\"",v,"\" "],
                                      l)),
                                 " />\n"],
       literal(s)         then [s]
     }.


define Printable_tree
   format
     (
       CommonInfo         cinfo,
       List(HTML_Meta)    metas,
       Bool               is_https,
       String             charset
     ) =
   if metas is
     {
       []      then [format(cinfo,http_equiv("content-type",
                                                        "text/html; charset="+charset),is_https)],
       [h . t] then [format(cinfo,h,is_https)
                     . format(cinfo,t,is_https,charset)]
     }.

 define List(HTML_Head_Tag)
  rebuild_html_head_tags
  (
    List(HTML_Head_Tag) lwf,
    List(HTML_Head_Tag) so_far
  ) =
  if lwf is
  {
    [] then so_far,
    [h . t] then
      rebuild_html_head_tags(t, append_once(so_far, h))
  }.

define Printable_tree
  _format_html_head
  (
    List(HTML_Head_Tag) lwf,
    Printable_tree so_far,
    Dictionary(String, Word32) js_dict
  )
  =
    //with lwf_ = rebuild_html_head_tags(lwf, []),
    if lwf is
    {
      []        then reverse(so_far),
      [ h . t]  then
        if h is
        {
          meta(meta)        then
            [format(meta) . _format_html_head(t, so_far, js_dict)],
          title(title)      then
            ["<title>"+title+"</title>\n" . _format_html_head(t, so_far, js_dict)],
          js(jsf)           then
            since jsf is js_file(filename, _),
            if js_dict.get(filename) is
            {
              failure then
                forget(js_dict.insert(filename, 0));
                [add_js_files([jsf]) . _format_html_head(t, so_far, js_dict)],

              success(_) then
                _format_html_head(t, so_far, js_dict),
            }
          js_inline(jsi)    then
            if jsi is
            {
                script(type, _) then
                  ["<script type=\"" + type + "\">"+content(jsi)+"</script>\n" . _format_html_head(t, so_far, js_dict)],
            }
          css(cssf)         then
            since cssf is css_file(file_name, media),
            ["<link rel=\"stylesheet\" type=\"text/css\" href=\""+file_name+"\" media=\""+to_String(media)+"\" />\n" . _format_html_head(t, so_far, js_dict)],
          css_inline(cssi)  then
            ["<style>"+cssi+"</style>\n" . _format_html_head(t, so_far, js_dict)]
        }
    }
  .

public define Printable_tree
  format_html_head
  (
    List(HTML_Head_Tag) lwf,
    String              charset
  )
  =
  _format_html_head((List(HTML_Head_Tag))[ meta(http_equiv("content-type", "text/html; charset="+charset)) . lwf], [], make_dictionary((Word32)0, dictionaryComparerString)).

public define Printable_tree
  format_html_head
  (
    List(HTML_Head_Tag) lwf
  )
  =
  _format_html_head(lwf, [], make_dictionary((Word32)0, dictionaryComparerString)).


public type HTML_ajax_content:
  html_ajax_content( String html_body, String script, List(String) js_file, List(String) css_file).

public define HTML_ajax_content
  sort_head_tag
  (
    List(HTML_Head_Tag) lwf,
    String              script,
    List(String)        js_file,
    List(String)        css_file
  )=
  if lwf is
  {
    []        then  html_ajax_content("", script, reverse(js_file), reverse(css_file)),
    [ h . t ] then
        if h is
        {
          meta(meta)        then sort_head_tag(t, script, js_file, css_file),
          title(title)      then sort_head_tag(t, script, js_file, css_file),
          js(jsf)           then /*println("sort_head_tag jsf["+jsf.file_name+"]");*/sort_head_tag(t, script, [file_name(jsf) . js_file], css_file),
          js_inline(jsi)    then /*println("sort_head_tag jsi["+jsi.content+"]");*/sort_head_tag(t, script + content(jsi), js_file, css_file),
          css(cssf)         then sort_head_tag(t, script, js_file, [file_name(cssf) . css_file]),
          css_inline(cssi)  then sort_head_tag(t, script, js_file, css_file)
        }
  }.

public define HTML_ajax_content
  to_html_ajax_content
  (
    HTML_Off_Form content_HTML,
    CommonInfo    cinfo
  )=
  //println("to_html_ajax_content(content_HTML, cinfo)");
  with p_content_head_tags = var((List(HTML_Head_Tag))[]),
  with content = format(cinfo, var((Int)0), content_HTML, false, var(0), p_content_head_tags),
  if sort_head_tag(*p_content_head_tags, "", [], []) is html_ajax_content(_, script, js_file, css_file) then
    html_ajax_content(to_String(content), script, js_file, css_file).

public define String
  to_String
  (
    HTML_Off_Form content_HTML,
    CommonInfo    cinfo
  )=
  //println("to_html_ajax_content(content_HTML, cinfo)");
  with p_content_head_tags = var((List(HTML_Head_Tag))[]),
  with content = format(cinfo, var((Int)0), content_HTML, false, var(0), p_content_head_tags),
  to_String(content)
.


public define JsonValue
  to_html_ajax_content
  (
    HTML_Partial_Content  content_HTML,
    CommonInfo            cinfo,
    String                additional_script
  )=
  //println("to_html_ajax_content(content_HTML, cinfo, additional_script)");
  //println("additional_script"+additional_script);
  since to_html_ajax_content(partial(content_HTML), cinfo) is html_ajax_content(html, script, js_files, css_files),
  json_object([
    json_member("html",      json_string(html)),
    json_member("js_files",  to_json_array(js_files)),
    json_member("css_files", to_json_array(css_files)),
    json_member("script",    json_string(additional_script+script)),
  ])
.

public define JsonValue
  to_html_ajax_content
  (
    HTML_Partial_Content  content_HTML,
    CommonInfo            cinfo
  )= to_html_ajax_content(content_HTML, cinfo, "").

public define JsonValue
  to_html_ajax_content
  (
    Printable_tree  content_HTML,
    String          additional_script
  )=
  //since to_html_ajax_content(partial(content_HTML), cinfo) is html_ajax_content(html, script, js_files, css_files),
  json_object([
    json_member("html",      json_string(to_String(content_HTML))),
    json_member("js_files",  to_json_array([])),
    json_member("css_files", to_json_array([])),
    json_member("script",    json_string(additional_script)),
  ])
.

public define AWP_Handler_Answer //Printable_tree
  format
  (
    CommonInfo               cinfo,
    List(HTTP_header)        additional_headers,
    HTTP_Answer              page,
    Bool                     is_https,
    String                   charset
  )=
  if cinfo is info(common_name,http_port,https_port,site_directory,secret) then
    with ic_v = var((Int)0),
      p_content_head_tags = var((List(HTML_Head_Tag))[]), //list of heat_tags extracted from partial_content during format of body content
    if page is
    {
       html_page(status, head_tags, body) then
         if body is body(options,element) then
         if format(status) is (status_string, status_headers) then
          with
           answer_body_body = (Printable_tree)
           [  "<body ", format(options), ">",                       // format body options
              format(cinfo,ic_v,element,is_https, var(0), p_content_head_tags),
              "</body>\n",

              "</html>"],
           answer_body_header =
            [doctype_w3c_header,
             // html_header,

              "<head>\n", format_html_head(head_tags + *p_content_head_tags, charset),"</head>\n",
            ],
          printable_tree([
            "HTTP/1.1 " + status_string, crlf,
            format_headers(standard_headers),
             format_headers(standard_headers_for("text/html", length(answer_body_header) + length(answer_body_body), success(charset))),
             format_headers(status_headers),
             format_headers(additional_headers),
             crlf,
             answer_body_header .
             answer_body_body
           ]),

       html_page(status, title, metas, css_styles, css_files, js_files, script, body) then
         if body is body(options,element) then
         if format(status) is (status_string, status_headers) then
          with
            answer_body_body = (Printable_tree)
            [  "<body ", format(options), ">",                       // format body options
              format(cinfo,ic_v,element,is_https, var(0), p_content_head_tags),
              "</body>\n",
              "</html>"
            ],
            answer_body_header =
            [ doctype_w3c_header,
              //html_header,
              "<head>\n",
              add_css_styles(css_styles),
              add_css_files(css_files),
              add_js_files(js_files),
              add_script(script),
              "<link rel=\"shortcut icon\" href=\"favicon.ico\" />\n",
              "<script type = \"text/javascript\" language=\"JavaScript\">",
              "  function show_local_popup(divname,stvname) {",
              "  if (document.layers) { var d = eval(document.divname); } else\n",
              "  if (document.getElementById) { var d = eval(\"document.getElementById(divname)\"); } else\n",
              "  if (document.all) { var d = eval(document.all.divname.style)};\n",
              // " alert(typeof(eval(stvname))); ",
              " var s = eval(stvname); ",
              "  if (s[0]==0) ",
              "   { s[0]=1; d.style.visibility = 'visible'; d.zIndex = 100; } else\n",
              "   { s[0]=0; d.style.visibility = 'hidden'; }; }",
              "</script>\n",
              "<title>",title,"</title>\n",                         // put title
              format(cinfo,metas,is_https,charset),      // format the metas
              format_html_head(*p_content_head_tags, charset),
              "</head>\n"
           ],
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
          format_headers(standard_headers),
          format_headers(standard_headers_for("text/html", length(answer_body_header) + length(answer_body_body), success(charset))),
          format_headers(status_headers),
          format_headers(additional_headers),
          crlf,
             answer_body_header .
             answer_body_body
        ]),

       plain_text (HTTP_Status status, String text) then
          if format(status) is (status_string, status_headers) then
        printable_tree([
           "HTTP/1.1 " + status_string, crlf,
            format_headers(standard_headers),
            format_headers(standard_headers_for("text/plain", length(text), success(charset))),
            format_headers(status_headers),
            format_headers(additional_headers),
            crlf,
            text . (Printable_tree)[]
        ]),

       custom_text(HTTP_Status status, mime_type, String content) then
          if format(status) is (status_string, status_headers) then
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
            format_headers(standard_headers),
            format_headers(standard_headers_for(to_String(mime_type), length(content), success(charset))),
            format_headers(status_headers),
            format_headers(additional_headers),
            crlf,
            content . (Printable_tree)[]
          ]),

       custom_binary(HTTP_Status status, mime_type, ByteArray content, List(HTTP_header) other_headers) then
          if format(status) is (status_string, status_headers) then
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
            format_headers(status_headers),
            format_headers(standard_headers_for(to_String(mime_type), length(content), failure)),
            format_headers(status_headers),
            format_headers(other_headers),
            format_headers(additional_headers),
            crlf,
            content . (Printable_tree)[]
        ]),

       custom_tree(HTTP_Status status, mime_type, Printable_tree content) then
        if format(status) is (status_string, status_headers) then
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
            format_headers(standard_headers),
            format_headers(standard_headers_for(to_String(mime_type), length(content), success(charset))),
            format_headers(status_headers),
            format_headers(additional_headers),
            crlf .
            content
        ]),

       json(HTTP_Status status, JsonValue json_content) then
          //with          start = unow,
          with content = (Printable_tree)format_json(json_content),
          //println(show_duration_string("HTTP json format json object ", start));
          if format(status) is (status_string, status_headers) then
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
          format_headers(standard_headers),
            format_headers(standard_headers_for(to_String(mime_application_json), length(content), success(charset))),
            format_headers(status_headers),
            format_headers(additional_headers),
            crlf .
            content
        ])
        ,
       send_file(file_path, c_disposition) then
        send_file(file_path, c_disposition),

       http_raw(Printable_tree content) then
        printable_tree(content),

       html_content(HTTP_Status status, HTML_Off_Form content_HTML) then
          if format(status) is (status_string, status_headers) then
          with content = format(cinfo, ic_v, content_HTML, is_https, var(0), p_content_head_tags),
        printable_tree([
           "HTTP/1.1 " + status_string, crlf,
            format_headers(standard_headers),
            format_headers(standard_headers_for("text/html", length(content), success(charset))),
            format_headers(status_headers),
            format_headers(additional_headers),
            crlf .
            content
          ]),
       //HMTL content with some header
      html_partial_content(HTTP_Status status, HTML_Partial_Content p_content) then

        since p_content      is partial_content(head_tags, html_content),
        since format(status) is (status_string, status_headers),
          with
            answer_body = (Printable_tree)
            [
              format(cinfo, ic_v, html_content, is_https, var(0), p_content_head_tags),
            ],
            answer_header = (Printable_tree)
            [
             // html_header,
             format_html_head(head_tags + *p_content_head_tags),
            ],
        printable_tree([
          "HTTP/1.1 " + status_string, crlf,
             format_headers(standard_headers),
             format_headers(standard_headers_for("text/html", length(answer_header) + length(answer_body), success(charset))),
             format_headers(status_headers),
             format_headers(additional_headers),
             crlf,
             answer_header .
             answer_body
           ]),
     }.