/*
 * Created by PyramIDE.
 * User: フランスのトトロ 
 * Date: 01/01/2016
 * Time: 1:34
 * © David RENÉ
 */

                                  The HayamiKi (早見木) project

                          Interfacing, generating and controling a database with Anubis


   Author: David René


   In order to generate such tools, DB_Model needs a formal
   description of the database. 
   
   
   
      *** (1.2) 'MaybeNull'. 
   
   This type scheme is isomorphic to 'Maybe', and is used for representing data which 
   can have the value 'NULL'. We don't use 'Maybe' for this purpose because
   we want to avoid the misleading 'Maybe(Maybe(...))'. Instead, we will have
   sometimes 'Maybe(MaybeNull(...))', so that 'null' means 'NULL', and 'failure'
   means an error. 
      
public type MaybeNull($T):
   null,
   not_null($T value). 

   Conversion tools between date, time and datetime in ISO-8601 format and 'Int' 
   (number of seconds since the epoch) are provided in 'library/tools/ISO-8601.anubis'. 
   
   
      *** (1.3) 'HK_Model_Attr' (attributes of columns).
  
   Possible attributes of columns: (each column has a list of such attributes)

                              


  


  
   Of course, 'NOT NULL' is not an alternative of 'HK_Model_Attr' because it is already coded into the 
   database type itself (type 'HK_Model_Field' above). 





      *** (3.7) 'DB_Model_Table' (describing a table). 

   Description of a table:

             

  





   Description of a whole database:

    
// list of all tables in the database
  
        
//public define Maybe(String)            convert_to_date               (MaybeNull(ByteArray) b). 
//public define MaybeNull(String)        convert_to_date_or_null       (MaybeNull(ByteArray) b). 
      
         *** (8.3.6) Converting 'integer?' and 'integer?_or_null' to and fro.

   The next functions are used for integer16, integer32 and integer. 
     
//public define Maybe(Int)               convert_to_integer            (MaybeNull(ByteArray) b). 
//public define MaybeNull(Int)           convert_to_integer_or_null    (MaybeNull(ByteArray) b). 
     

         *** (8.3.7) Converting 'char/text' and 'char_or_null/text_or_null' to and fro.
      
   The same functions are used for 'text/text_or_null' and 'vartext/vartext_or_null'. 
      
   Litteral texts must be 'prepared' before they can be included into 
   SQL commands (this amounts to doubling the single quotes). 
            
 public define MetaSQL_Prepared         prepare_text                  (String t).
 public define MetaSQL_Prepared         prepare_text_or_null          (MaybeNull(String) t).
   
   Conversely, texts arrive from the database in the form of byte arrays which must be
   converted to strings. The two functions for converting to 'text' and to 'text_or_null'
   are almost the same one. The only difference is that 'null' is interpreted as an error in
   the case of 'text'. 
      
   --- That's all for the public part !----------------------------------------------------------------

read tools/basis.anubis   
read tools/base64.anubis
read system/string.anubis
read tools/ISO-8601.anubis
read xlib/web/widgets/icons_set.anubis
   
   *** [1] Tools. 

      *** [1.1] Concatenating strings which may not exist. 
      
   The concatenation function  '+'  for strings is defined in 'tools/basis.anubis'. Here we define 
   an extension of it to strings which may not exist (i.e. data of type 'Maybe(String)'). Of course, 
   the result is always of type 'Maybe(String)'. 
         
define macro Maybe(String)
   Maybe(String) s + String t
     =
   if s is 
     {
       failure then failure, 
       success(s1) then success(s1+t)
     }.
   
define macro Maybe(String)
   String s + Maybe(String) t
     =
   if t is 
     {
       failure then failure, 
       success(t1) then success(s+t1)
     }.
   
define macro Maybe(String)
   Maybe(String) s + Maybe(String) t
     =
   if s is 
     {
       failure then failure, 
       success(s1) then if t is 
         {
           failure then failure, 
           success(t1) then success(s1+t1)
         }
     }.


     
   *** [2] Verifications concerning the description of the database and queries. 
   

   
 define Bool   
   has_forbidden_references
     (
       String                      table_name,     // the first 3 arguments concern the current table. 
       MetaSQL_PrimKey             pk, 
       List(HK_Model_Column)     columns, 
       List(HK_Model_Column)     forwards,       // subsequent tables
       List(String)                backwards       // list of backwards table names
     ) =
   if columns is 
     {
       [ ]                  then false,   // no forbidden reference found
       [col1 . other_cols]  then 
         if is_forbidden_reference(table_name,col1,forwards,backwards)
         then true
         else has_forbidden_references(table_name,pk,other_cols,forwards,backwards)
     }. 
   
 define Bool     // returns 'true' if there is at least one forbidden cycle. 
   has_forbidden_cycles
     (
       String                     db_name, 
       List(HK_Model_Column)    tables, 
       List(String)               backwards     // names of 'backwards' tables
     ) =
   if tables is
     {
       [ ]                  then false,   // no forbidden cycle found
       [tab1 . other_tabs]  then if tab1 is table(name1,pk1,cols1) then 
         if has_forbidden_references(name1,pk1,cols1,other_tabs,backwards) 
         then true
         else has_forbidden_cycles(db_name,other_tabs,[name1 . backwards])
     }.
   
 define Bool
   is_forbidden_column_name
   (
     String   name
   ) =
   name = "id" | name = "metasqlcheck". 
   
 define Bool
   has_forbidden_column_names
   (
     HK_Model_Column   tab
   ) =
   if tab is table(_,_,cols) then 
   mapor((HK_Model_Column cs) |-> 
            if cs is col(name,_,_) then is_forbidden_column_name(name),
         cols).

 define Bool
   has_forbidden_column_names
   (
     DB_Model_DB   db
   ) =
   if db is database(_,tables) then
   mapor(has_forbidden_column_names,tables).

   *** [3] Generating the target file. 
   
      *** [3.1] Converting a database type into the corresponding Anubis type: