-------------------------------------------------------------------------------
--                                                                           --
--            XPATH IN ADA Copyright (C) 2003, McKae Technologies            --
--     XPATH IN ADA Copyright (C) 2021, Simon Wright <simon@pushface.org>    --
--                                                                           --
--  XPath in  Ada (XIA) is  free software;  you can redistribute  it and/or  --
--  modify it under terms of the GNU General Public License as published by  --
--  the Free Software Foundation; either version 3, or (at your option) any  --
--  later version.  GNAT is distributed in the hope that it will be useful,  --
--  but  WITHOUT  ANY  WARRANTY;  without  even  the  implied  warranty  of  --
--  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.                     --
--                                                                           --
--  As  a special  exception under  Section  7 of  GPL version  3, you  are  --
--  granted  additional permissions  described in  the GCC  Runtime Library  --
--  Exception, version 3.1, as published by the Free Software Foundation.    --
--                                                                           --
--  You should have received a copy of the GNU General Public License and a  --
--  copy of the GCC Runtime Library  Exception along with this program; see  --
--  the  files  COPYING3 and  COPYING.RUNTIME  respectively.   If not,  see  --
--  <http://www.gnu.org/licenses/>.                                          --
--                                                                           --
--  XIA is maintained at https://github.com/simonjwright/xia                 --
--                                                                           --
-------------------------------------------------------------------------------

with Mckae.XML.XPath.DFS_Processing;
with Mckae.XML.XPath.Locations;
with Ada.Directories;
with Ada.Environment_Variables;
with Ada.IO_Exceptions;
with Ada.Text_IO;
with Xpath_Model;
with Xpath_Parser;

package body Mckae.XML.XPath.Query_Handling is

   Visitor : aliased DFS_Processing.DFS;

   --  Decode the string representation of the location path into its
   --  components parts
   function Pathify (Xpath_Query : Locations.Xpath_String)
                    return Locations.Location_Paths is

      Path : Locations.Location_Paths;

      --  The generated parser expects the input line in a file.
      Tmp_Dir : constant String :=
        (if Ada.Environment_Variables.Exists ("TMPDIR")
         then Ada.Environment_Variables.Value ("TMPDIR")
         elsif Ada.Environment_Variables.Exists ("TMP")
         then Ada.Environment_Variables.Value ("TMP")
         else "/tmp");
      Tmp_File_Name : constant String
        := Ada.Directories.Compose (Containing_Directory => Tmp_Dir,
                                    Name => "xia-tmp");
      Tmp_File : Ada.Text_IO.File_Type;

   begin

      --  Create the temp file if needed
      begin
         Ada.Text_IO.Create (Tmp_File,
                             Mode => Ada.Text_IO.Out_File,
                             Name => Tmp_File_Name);
         Ada.Text_IO.Close (Tmp_File);
      exception
         when Ada.IO_Exceptions.Name_Error => null;  -- already exists
         when others => null;
      end;

      --  Write the query to the temp file
      Ada.Text_IO.Open (Tmp_File,
                        Mode => Ada.Text_IO.Out_File,
                        Name => Tmp_File_Name);
      Ada.Text_IO.Put (Tmp_File, Xpath_Query);
      Ada.Text_IO.Close (Tmp_File);

      Xpath_Parser.Run (Tmp_File_Name);
      Parse_Tree := Xpath_Parser.Get_Parse_Tree;

      Locations.Reset_For_Parsing;

      Parse_Tree.Acceptor (Visitor'Access);

      Path := Locations.Get_Path;

      Path.Absolute := Xpath_Query (Xpath_Query'First) = '/';
      Path.Path (Positive (Path.Path.Length)).Output_Step := True;

      return Path;

   exception
      when Xpath_Parser.Syntax_Error =>
        raise Malformed_Query;
   end Pathify;

   -- Release the resources used by the construction of a location path
   procedure Free (Location_Path : in out Locations.Location_Paths) is
   begin
      Locations.Free (Location_Path);
   end Free;

end Mckae.XML.XPath.Query_Handling;