------------------------------------------------------------------------------
--                                                                          --
--                         GNAT COMPILER COMPONENTS                         --
--                                                                          --
--                                  S C N                                   --
--                                                                          --
--                                 B o d y                                  --
--                                                                          --
--          Copyright (C) 1992-2008, Free Software Foundation, Inc.         --
--                                                                          --
-- GNAT is free software;  you can  redistribute it  and/or modify it under --
-- terms of the  GNU General Public License as published  by the Free Soft- --
-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License --
-- for  more details.  You should have  received  a copy of the GNU General --
-- Public License  distributed with GNAT; see file COPYING3.  If not, go to --
-- http://www.gnu.org/licenses for a complete copy of the license.          --
--                                                                          --
-- GNAT was originally developed  by the GNAT team at  New York University. --
-- Extensive contributions were provided by Ada Core Technologies Inc.      --
--                                                                          --
------------------------------------------------------------------------------

with Atree;    use Atree;
with Csets;    use Csets;
with Hostparm; use Hostparm;
with Namet;    use Namet;
with Opt;      use Opt;
with Output;   use Output;
with Restrict; use Restrict;
with Rident;   use Rident;
with Scans;    use Scans;
with Sinfo;    use Sinfo;
with Sinput;   use Sinput;
with Uintp;    use Uintp;

with GNAT.Byte_Order_Mark; use GNAT.Byte_Order_Mark;

with System.WCh_Con; use System.WCh_Con;

package body Scn is

   use ASCII;

   Used_As_Identifier : array (Token_Type) of Boolean;
   --  Flags set True if a given keyword is used as an identifier (used to
   --  make sure that we only post an error message for incorrect use of a
   --  keyword as an identifier once for a given keyword).

   procedure Check_End_Of_Line;
   --  Called when end of line encountered. Checks that line is not too long,
   --  and that other style checks for the end of line are met.

   function Determine_License return License_Type;
   --  Scan header of file and check that it has an appropriate GNAT-style
   --  header with a proper license statement. Returns GPL, Unrestricted,
   --  or Modified_GPL depending on header. If none of these, returns Unknown.

   procedure Error_Long_Line;
   --  Signal error of excessively long line

   -----------------------
   -- Check_End_Of_Line --
   -----------------------

   procedure Check_End_Of_Line is
      Len : constant Int := Int (Scan_Ptr) - Int (Current_Line_Start);
   begin
      if Style_Check then
         Style.Check_Line_Terminator (Len);
      elsif Len > Max_Line_Length then
         Error_Long_Line;
      end if;
   end Check_End_Of_Line;

   -----------------------
   -- Determine_License --
   -----------------------

   function Determine_License return License_Type is
      GPL_Found : Boolean := False;
      Result    : License_Type;

      function Contains (S : String) return Boolean;
      --  See if current comment contains successive non-blank characters
      --  matching the contents of S. If so leave Scan_Ptr unchanged and
      --  return True, otherwise leave Scan_Ptr unchanged and return False.

      procedure Skip_EOL;
      --  Skip to line terminator character

      --------------
      -- Contains --
      --------------

      function Contains (S : String) return Boolean is
         CP : Natural;
         SP : Source_Ptr;
         SS : Source_Ptr;

      begin
         --  Loop to check characters. This loop is terminated by end of
         --  line, and also we need to check for the EOF case, to take
         --  care of files containing only comments.

         SP := Scan_Ptr;
         while Source (SP) /= CR and then
               Source (SP) /= LF and then
               Source (SP) /= EOF
         loop
            if Source (SP) = S (S'First) then
               SS := SP;
               CP := S'First;

               loop
                  SS := SS + 1;
                  CP := CP + 1;

                  if CP > S'Last then
                     return True;
                  end if;

                  while Source (SS) = ' ' loop
                     SS := SS + 1;
                  end loop;

                  exit when Source (SS) /= S (CP);
               end loop;
            end if;

            SP := SP + 1;
         end loop;

         return False;
      end Contains;

      --------------
      -- Skip_EOL --
      --------------

      procedure Skip_EOL is
      begin
         while Source (Scan_Ptr) /= CR
           and then Source (Scan_Ptr) /= LF
           and then Source (Scan_Ptr) /= EOF
         loop
            Scan_Ptr := Scan_Ptr + 1;
         end loop;
      end Skip_EOL;

   --  Start of processing for Determine_License

   begin
      loop
         if Source (Scan_Ptr) /= '-'
           or else Source (Scan_Ptr + 1) /= '-'
         then
            if GPL_Found then
               Result := GPL;
               exit;
            else
               Result := Unknown;
               exit;
            end if;

         elsif Contains ("Asaspecialexception") then
            if GPL_Found then
               Result := Modified_GPL;
               exit;
            end if;

         elsif Contains ("GNUGeneralPublicLicense") then
            GPL_Found := True;

         elsif
             Contains
               ("ThisspecificationisadaptedfromtheAdaSemanticInterface")
           or else
             Contains
              ("ThisspecificationisderivedfromtheAdaReferenceManual")
         then
            Result := Unrestricted;
            exit;
         end if;

         Skip_EOL;

         Check_End_Of_Line;

         if Source (Scan_Ptr) /= EOF then

            --  We have to take into account a degenerate case when the source
            --  file contains only comments and no Ada code.

            declare
               Physical : Boolean;

            begin
               Skip_Line_Terminators (Scan_Ptr, Physical);

               --  If we are at start of physical line, update scan pointers
               --  to reflect the start of the new line.

               if Physical then
                  Current_Line_Start       := Scan_Ptr;
                  Start_Column             := Scanner.Set_Start_Column;
                  First_Non_Blank_Location := Scan_Ptr;
               end if;
            end;
         end if;
      end loop;

      return Result;
   end Determine_License;

   ----------------------------
   -- Determine_Token_Casing --
   ----------------------------

   function Determine_Token_Casing return Casing_Type is
   begin
      return Scanner.Determine_Token_Casing;
   end Determine_Token_Casing;

   ---------------------
   -- Error_Long_Line --
   ---------------------

   procedure Error_Long_Line is
   begin
      Error_Msg
        ("this line is too long",
         Current_Line_Start + Source_Ptr (Max_Line_Length));
   end Error_Long_Line;

   ------------------------
   -- Initialize_Scanner --
   ------------------------

   procedure Initialize_Scanner
     (Unit  : Unit_Number_Type;
      Index : Source_File_Index)
   is
      GNAT_Hedr : constant Text_Buffer (1 .. 78) := (others => '-');

   begin
      Scanner.Initialize_Scanner (Index);

      if Index /= Internal_Source_File then
         Set_Unit (Index, Unit);
      end if;

      Current_Source_Unit := Unit;

      --  Set default for Comes_From_Source (except if we are going to process
      --  an artificial string internally created within the compiler and
      --  placed into internal source duffer). All nodes built now until we
      --  reenter the analyzer will have Comes_From_Source set to True

      if Index /= Internal_Source_File then
         Set_Comes_From_Source_Default (True);
      end if;

      --  Check license if GNAT type header possibly present

      if Source_Last (Index) - Scan_Ptr > 80
        and then Source (Scan_Ptr .. Scan_Ptr + 77) = GNAT_Hedr
      then
         Set_License (Current_Source_File, Determine_License);
      end if;

      --  Check for BOM

      declare
         BOM : BOM_Kind;
         Len : Natural;
         Tst : String (1 .. 5);

      begin
         for J in 1 .. 5 loop
            Tst (J) := Source (Scan_Ptr + Source_Ptr (J) - 1);
         end loop;

         Read_BOM (Tst, Len, BOM, False);

         case BOM is
            when UTF8_All =>
               Scan_Ptr := Scan_Ptr + Source_Ptr (Len);
               Wide_Character_Encoding_Method := WCEM_UTF8;
               Upper_Half_Encoding := True;

            when UTF16_LE | UTF16_BE =>
               Set_Standard_Error;
               Write_Line ("UTF-16 encoding format not recognized");
               Set_Standard_Output;
               raise Unrecoverable_Error;

            when UTF32_LE | UTF32_BE =>
               Set_Standard_Error;
               Write_Line ("UTF-32 encoding format not recognized");
               Set_Standard_Output;
               raise Unrecoverable_Error;

            when Unknown =>
               null;

            when others =>
               raise Program_Error;
         end case;
      end;

      --  Because of the License stuff above, Scng.Initialize_Scanner cannot
      --  call Scan. Scan initial token (note this initializes Prev_Token,
      --  Prev_Token_Ptr).

      --  There are two reasons not to do the Scan step in case if we
      --  initialize the scanner for the internal source buffer:

      --  - The artificial string may not be created by the compiler in this
      --    buffer when we call Initialize_Scanner

      --  - For these artificial strings a special way of scanning is used, so
      --    the standard step of the scanner may just break the algorithm of
      --    processing these strings.

      if Index /= Internal_Source_File then
         Scan;
      end if;

      --  Clear flags for reserved words used as identifiers

      for J in Token_Type loop
         Used_As_Identifier (J) := False;
      end loop;
   end Initialize_Scanner;

   -----------------------
   -- Obsolescent_Check --
   -----------------------

   procedure Obsolescent_Check (S : Source_Ptr) is
   begin
      --  This is a pain in the neck case, since we normally need a node to
      --  call Check_Restrictions, and all we have is a source pointer. The
      --  easiest thing is to construct a dummy node. A bit kludgy, but this
      --  is a marginal case. It's not worth trying to do things more cleanly.

      Check_Restriction (No_Obsolescent_Features, New_Node (N_Empty, S));
   end Obsolescent_Check;

   ---------------
   -- Post_Scan --
   ---------------

   procedure Post_Scan is
   begin
      case Token is
         when Tok_Char_Literal =>
            Token_Node := New_Node (N_Character_Literal, Token_Ptr);
            Set_Char_Literal_Value (Token_Node, UI_From_CC (Character_Code));
            Set_Chars (Token_Node, Token_Name);

         when Tok_Identifier =>
            Token_Node := New_Node (N_Identifier, Token_Ptr);
            Set_Chars (Token_Node, Token_Name);

         when Tok_Real_Literal =>
            Token_Node := New_Node (N_Real_Literal, Token_Ptr);
            Set_Realval (Token_Node, Real_Literal_Value);

         when Tok_Integer_Literal =>
            Token_Node := New_Node (N_Integer_Literal, Token_Ptr);
            Set_Intval (Token_Node, Int_Literal_Value);

         when Tok_String_Literal =>
            Token_Node := New_Node (N_String_Literal, Token_Ptr);
            Set_Has_Wide_Character (Token_Node, Wide_Character_Found);
            Set_Strval (Token_Node, String_Literal_Id);

         when Tok_Operator_Symbol =>
            Token_Node := New_Node (N_Operator_Symbol, Token_Ptr);
            Set_Chars (Token_Node, Token_Name);
            Set_Strval (Token_Node, String_Literal_Id);

         when others =>
            null;
      end case;
   end Post_Scan;

   ------------------------------
   -- Scan_Reserved_Identifier --
   ------------------------------

   procedure Scan_Reserved_Identifier (Force_Msg : Boolean) is
      Token_Chars : constant String := Token_Type'Image (Token);

   begin
      --  We have in Token_Chars the image of the Token name, i.e. Tok_xxx.
      --  This code extracts the xxx and makes an identifier out of it.

      Name_Len := 0;

      for J in 5 .. Token_Chars'Length loop
         Name_Len := Name_Len + 1;
         Name_Buffer (Name_Len) := Fold_Lower (Token_Chars (J));
      end loop;

      Token_Name := Name_Find;

      if not Used_As_Identifier (Token) or else Force_Msg then
         Error_Msg_Name_1 := Token_Name;
         Error_Msg_SC ("reserved word* cannot be used as identifier!");
         Used_As_Identifier (Token) := True;
      end if;

      Token := Tok_Identifier;
      Token_Node := New_Node (N_Identifier, Token_Ptr);
      Set_Chars (Token_Node, Token_Name);
   end Scan_Reserved_Identifier;

end Scn;