(*  Title:      HOL/Tools/string_code.ML

     Author:     Florian Haftmann, TU Muenchen

 Code generation for character and string literals.

 *)

 signature STRING_CODE =

 sig

   val add_literal_list_string: string -> theory -> theory

   val add_literal_char: string -> theory -> theory

   val add_literal_string: string -> theory -> theory

 end;

 structure String_Code : STRING_CODE =

 struct

 open Basic_Code_Thingol;

 fun decode_char nibbles' tt =

   let

     fun idx c = find_index (curry (op =) c) nibbles';

     fun decode ~1 _ = NONE

       | decode _ ~1 = NONE

       | decode n m = SOME (chr (n * 16 + m));

   in case tt

    of (IConst { name = c1, ... }, IConst { name = c2, ... }) => decode (idx c1) (idx c2)

     | _ => NONE

   end;

 fun implode_string literals char' nibbles' ts =

   let

     fun implode_char (IConst { name = c, ... } `$ t1 `$ t2) =

           if c = char' then decode_char nibbles' (t1, t2) else NONE

       | implode_char _ = NONE;

     val ts' = map_filter implode_char ts;

   in if length ts = length ts'

     then (SOME o Code_Printer.str o Code_Printer.literal_string literals o implode) ts'

     else NONE

   end;

 val cs_nibbles = [@{const_name Nibble0}, @{const_name Nibble1},

   @{const_name Nibble2}, @{const_name Nibble3},

   @{const_name Nibble4}, @{const_name Nibble5},

   @{const_name Nibble6}, @{const_name Nibble7},

   @{const_name Nibble8}, @{const_name Nibble9},

   @{const_name NibbleA}, @{const_name NibbleB},

   @{const_name NibbleC}, @{const_name NibbleD},

   @{const_name NibbleE}, @{const_name NibbleF}];

 val cs_summa = [@{const_name Nil}, @{const_name Cons}, @{const_name Char}] @ cs_nibbles;

 fun add_literal_list_string target =

   let

     fun pretty literals (nil' :: cons' :: char' :: nibbles') pr _ vars fxy [(t1, _), (t2, _)] =

       case Option.map (cons t1) (List_Code.implode_list nil' cons' t2)

        of SOME ts => (case implode_string literals char' nibbles' ts

              of SOME p => p

               | NONE =>

                   Code_Printer.literal_list literals (map (pr vars Code_Printer.NOBR) ts))

         | NONE =>

             List_Code.default_list (Code_Printer.infix_cons literals) (pr vars) fxy t1 t2;

   in

     Code_Target.set_printings (Code_Symbol.Constant (@{const_name Cons},

       [(target, SOME (Code_Printer.complex_const_syntax (2, (cs_summa, pretty))))]))

   end;

 fun add_literal_char target =

   let

     fun pretty literals nibbles' _ thm _ _ [(t1, _), (t2, _)] =

       case decode_char nibbles' (t1, t2)

        of SOME c => (Code_Printer.str o Code_Printer.literal_char literals) c

         | NONE => Code_Printer.eqn_error thm "Illegal character expression";

   in

     Code_Target.set_printings (Code_Symbol.Constant (@{const_name Char},

       [(target, SOME (Code_Printer.complex_const_syntax (2, (cs_nibbles, pretty))))]))

   end;

 fun add_literal_string target =

   let

     fun pretty literals (nil' :: cons' :: char' :: nibbles') _ thm _ _ [(t, _)] =

       case List_Code.implode_list nil' cons' t

        of SOME ts => (case implode_string literals char' nibbles' ts

              of SOME p => p

               | NONE => Code_Printer.eqn_error thm "Illegal message expression")

         | NONE => Code_Printer.eqn_error thm "Illegal message expression";

   in

     Code_Target.set_printings (Code_Symbol.Constant (@{const_name STR},

       [(target, SOME (Code_Printer.complex_const_syntax (1, (cs_summa, pretty))))]))

   end;

 end;