------------------------------------------------------------------------------
--                                  G P S                                   --
--                                                                          --
--                     Copyright (C) 2001-2018, AdaCore                     --
--                                                                          --
-- This 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.  This software is distributed in the hope  that it will be useful, --
-- but WITHOUT ANY WARRANTY;  without even the implied warranty of MERCHAN- --
-- TABILITY 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  this  software;   see  file --
-- COPYING3.  If not, go to http://www.gnu.org/licenses for a complete copy --
-- of the license.                                                          --
------------------------------------------------------------------------------

with System;

separate (Help_Module)
procedure Display_Help
  (Kernel    : access Kernel_Handle_Record'Class;
   URL       : String)
is
   File_Protocol : constant String := "file://";

   function Shell_Open (File : String) return Boolean;
   --  Open file with the associated command registered under Windows.
   --  Return True in case of success.

   ----------------
   -- Shell_Open --
   ----------------

   function Shell_Open (File : String) return Boolean is

      SW_SHOW : constant := 5;  --  winuser.h:206

      function ShellExecute
        (Hwnd         : System.Address;
         Lpoperation  : String;
         Lpfile       : String;
         Lpparameters : System.Address := System.Null_Address;
         Lpdirectory  : System.Address := System.Null_Address;
         Nshowcmd     : Integer := SW_SHOW) return Long_Integer;
      pragma Import (Stdcall, ShellExecute, "ShellExecuteA");

      Result : Long_Integer;
   begin
      Result := ShellExecute
        (System.Null_Address, "open" & ASCII.NUL, File & ASCII.NUL);

      if Result <= 32 then
         Trace (Me, "ShellExecute failed:" & Long_Integer'Image (Result));
         return False;
      else
         return True;
      end if;
   end Shell_Open;

   Stripped : constant String :=
     (if URL'Length > File_Protocol'Length
      and then URL
        (URL'First .. URL'First + File_Protocol'Length - 1) = File_Protocol
      then URL (URL'First + File_Protocol'Length .. URL'Last)
      else URL);
   --  Strip file:// part, since it causes troubles on some configurations

begin
   if Shell_Open (Stripped) then
      Insert
        (Kernel, -"Using default browser to view " & URL, Mode => Info);
   else
      Insert
        (Kernel, -"Could not display help file " & URL, Mode => Error);
   end if;
end Display_Help;
