-----------------------------------------------------------------------
--          GtkAda - Ada95 binding for the Gimp Toolkit              --
--                                                                   --
--   Copyright (C) 1999-2000 E. Briot, J. Brobecker and A. Charlet   --
--                Copyright (C) 2000-2013, AdaCore                   --
--                                                                   --
-- This library is free software; you can redistribute it and/or     --
-- modify it under the terms of the GNU General Public               --
-- License as published by the Free Software Foundation; either      --
-- version 2 of the License, or (at your option) any later version.  --
--                                                                   --
-- This library 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.  See the GNU --
-- General Public License for more details.                          --
--                                                                   --
-- You should have received a copy of the GNU General Public         --
-- License along with this library; if not, write to the             --
-- Free Software Foundation, Inc., 59 Temple Place - Suite 330,      --
-- Boston, MA 02111-1307, USA.                                       --
--                                                                   --
-----------------------------------------------------------------------

with Ada.Strings.Fixed; use Ada.Strings.Fixed;
with Glib.Convert;  use Glib.Convert;
with Glib.Error;    use Glib.Error;
with Glib.Unicode;  use Glib.Unicode;
with Glib.Messages; use Glib.Messages;

package body Glib.XML is

   function File_Length (FD : Integer) return Long_Integer;
   pragma Import (C, File_Length, "__gnat_file_length");
   --  Get length of file from file descriptor FD

   function Open_Read
     (Name  : String;
      Fmode : Integer := 0) return Integer;
   pragma Import (C, Open_Read, "__gnat_open_read");
   --  Open file Name and return a file descriptor

   function Create_File
     (Name  : String;
      Fmode : Integer := 0) return Integer;
   pragma Import (C, Create_File, "__gnat_open_create");
   --  Creates new file with given name for writing, returning file descriptor
   --  for subsequent use in Write calls. File descriptor returned is
   --  negative if file cannot be successfully created.

   function Read
     (FD   : Integer;
      A    : System.Address;
      N    : Integer) return Integer;
   pragma Import (C, read, "read");
   --  Read N bytes to address A from file referenced by FD. Returned value is
   --  count of bytes actually read, which can be less than N at EOF.

   procedure Write
     (FD   : Integer;
      S    : String;
      N    : Integer);
   pragma Import (C, write, "write");
   --  Write N bytes from address A to file referenced by FD. The returned
   --  value is the number of bytes written, which can be less than N if a
   --  disk full condition was detected.

   procedure Close (FD : Integer);
   pragma Import (C, Close, "close");
   --  Close file referenced by FD

   procedure Skip_Blanks (Buf : String; Index : in out Natural);
   --  Skip blanks, LF and CR, starting at Index. Index is updated to the
   --  new position (first non blank or EOF)

   function Get_Node (Buf : String; Index : access Natural) return Node_Ptr;
   --  The main parse routine. Starting at Index.all, Index.all is updated
   --  on return. Return the node starting at Buf (Index.all) which will
   --  also contain all the children and subchildren.

   procedure Get_Buf
     (Buf        : String;
      Index      : in out Natural;
      Terminator : Character;
      S          : out String_Ptr);
   --  On return, S will contain the String starting at Buf (Index) and
   --  terminating before the first 'Terminator' character. Index will also
   --  point to the next non blank character.
   --  The special XML '&' characters are translated appropriately in S.
   --  S is set to null if Terminator wasn't found in Buf.

   procedure Extract_Attrib
     (Tag        : in out String_Ptr;
      Attributes : out String_Ptr;
      Empty_Node : out Boolean);
   --  Extract the attributes as a string, if the tag contains blanks ' '
   --  On return, Tag is unchanged and Attributes contains the string
   --  If the last character in Tag is '/' then the node is empty and
   --  Empty_Node is set to True.

   procedure Get_Next_Word
     (Buf     : String;
      Index   : in out Natural;
      Word    : out String_Ptr);
   --  extract the next textual word from Buf and return it.
   --  return null if no word left.
   --  The special XML '&' characters are translated appropriately in S.

   function Translate (S : String) return String;
   --  Translate S by replacing the XML '&' special characters by the
   --  actual ASCII character.
   --  This function currently handles:
   --   - &quot;
   --   - &gt;
   --   - &lt;
   --   - &amp;
   --   - &apos;

   -----------------
   -- Skip_Blanks --
   -----------------

   procedure Skip_Blanks (Buf : String; Index : in out Natural) is
   begin
      while Index < Buf'Last and then
        (Buf (Index) = ' '  or else Buf (Index) = ASCII.LF
          or else Buf (Index) = ASCII.HT
          or else Buf (Index) = ASCII.CR)
      loop
         Index := Index + 1;
      end loop;
   end Skip_Blanks;

   -------------
   -- Get_Buf --
   -------------

   procedure Get_Buf
     (Buf        : String;
      Index      : in out Natural;
      Terminator : Character;
      S          : out String_Ptr)
   is
      Start : constant Natural := Index;

   begin
      while Index <= Buf'Last
        and then Buf (Index) /= Terminator
      loop
         Index := Index + 1;
      end loop;

      if Index > Buf'Last then
         S := null;

      else
         S := new String'(Translate (Buf (Start .. Index - 1)));
         Index := Index + 1;

         if Index < Buf'Last then
            Skip_Blanks (Buf, Index);
         end if;
      end if;
   end Get_Buf;

   ------------------------
   -- Extract_Attributes --
   ------------------------

   procedure Extract_Attrib
     (Tag        : in out String_Ptr;
      Attributes : out String_Ptr;
      Empty_Node : out Boolean)
   is
      Index             : Natural := Tag'First;
      Index_Last_Of_Tag : Natural;
      S                 : String_Ptr;

   begin
      --  First decide if the node is empty

      if Tag (Tag'Last) = '/' then
         Empty_Node := True;
      else
         Empty_Node := False;
      end if;

      while Index <= Tag'Last and then
        not
          (Tag (Index) = ' '  or else Tag (Index) = ASCII.LF
           or else Tag (Index) = ASCII.HT
           or else Tag (Index) = ASCII.CR)
      loop
         Index := Index + 1;
      end loop;

      Index_Last_Of_Tag := Index - 1;
      Skip_Blanks (Tag.all, Index);

      if Index <= Tag'Last then
         if Empty_Node then
            Attributes := new String'(Tag (Index .. Tag'Last - 1));
         else
            Attributes := new String'(Tag (Index .. Tag'Last));
         end if;

         S := new String'(Tag (Tag'First .. Index_Last_Of_Tag));
         Free (Tag);
         Tag := S;
      end if;
   end Extract_Attrib;

   -------------------
   -- Get_Next_Word --
   -------------------

   procedure Get_Next_Word
     (Buf     : String;
      Index   : in out Natural;
      Word    : out String_Ptr)
   is
      Terminator : Character;
   begin
      Skip_Blanks (Buf, Index);

      if Buf (Index) = ''' or Buf (Index) = '"' then
         --  If the word starts with a quotation mark, then read until
         --  the closing mark

         Terminator := Buf (Index);
         Index := Index + 1;
         Get_Buf (Buf, Index, Terminator, Word);

      else
         --  For a normal word, scan up to either a blank, or a '='

         declare
            Start_Index : constant Natural := Index;
         begin
            while Index <= Buf'Last
              and then Buf (Index) /= ' '
              and then Buf (Index) /= '='
            loop
               Index := Index + 1;
            end loop;

            Word := new String'(Translate (Buf (Start_Index .. Index - 1)));
         end;
      end if;

      if Index < Buf'Last then
         Skip_Blanks (Buf, Index);
      end if;
   end Get_Next_Word;

   ---------------
   -- Translate --
   ---------------

   function Translate (S : String) return String is
      Str       : String (1 .. S'Length);
      Start, J  : Positive;
      Index     : Positive := S'First;
      In_String : Boolean  := False;

   begin
      if S'Length = 0 then
         return S;
      else
         J := Str'First;

         loop
            if In_String or else S (Index) /= '&' then
               Str (J) := S (Index);
            else
               Index := Index + 1;
               Start := Index;

               while S (Index) /= ';' loop
                  Index := Index + 1;
                  pragma Assert (Index <= S'Last);
               end loop;

               if S (Start .. Index - 1) = "quot" then
                  Str (J) := '"';
               elsif S (Start .. Index - 1) = "gt" then
                  Str (J) := '>';
               elsif S (Start .. Index - 1) = "lt" then
                  Str (J) := '<';
               elsif S (Start .. Index - 1) = "amp" then
                  Str (J) := '&';
               elsif S (Start .. Index - 1) = "apos" then
                  Str (J) := ''';
               end if;
            end if;

            exit when Index = S'Last;

            if S (Index) = '"' then
               In_String := not In_String;
            end if;

            Index := Index + 1;
            J     := J + 1;
         end loop;

         return Str (1 .. J);
      end if;
   end Translate;

   -------------------
   -- Get_Attribute --
   -------------------

   function Get_Attribute
     (N              : Node_Ptr;
      Attribute_Name : UTF8_String;
      Default        : UTF8_String := "") return UTF8_String
   is
      Index      : Natural;
      Key, Value : String_Ptr;

   begin
      if N = null or else N.Attributes = null then
         return Default;
      end if;

      Index := N.Attributes'First;
      while Index < N.Attributes'Last loop
         Get_Next_Word (N.Attributes.all, Index, Key);
         Get_Buf (N.Attributes.all, Index, '=', Value);
         Free (Value);
         Get_Next_Word (N.Attributes.all, Index, Value);

         if Attribute_Name = Key.all then
            exit;
         else
            Free (Key);
            Free (Value);
         end if;
      end loop;

      Free (Key);

      if Value = null then
         return Default;
      else
         declare
            V : constant String := Value.all;
         begin
            Free (Value);
            return V;
         end;
      end if;
   end Get_Attribute;

   -------------------
   -- Set_Attribute --
   -------------------

   procedure Set_Attribute
     (N : Node_Ptr; Attribute_Name, Attribute_Value : UTF8_String)
   is
      Index, Tmp : Natural;
      Key, Value : String_Ptr;
      Atts       : String_Ptr;
      Str        : constant String :=
        Attribute_Name & "=""" & Protect (Attribute_Value) & """ ";

   begin
      if N.Attributes /= null then
         Index := N.Attributes'First;
         --  First remove any definition of the attribute in the current list
         while Index < N.Attributes'Last loop
            Tmp := Index;
            Get_Next_Word (N.Attributes.all, Index, Key);
            Get_Buf (N.Attributes.all, Index, '=', Value);
            Free (Value);

            Get_Next_Word (N.Attributes.all, Index, Value);
            Free (Value);

            if Attribute_Name = Key.all then
               Atts := new String'
                 (Str
                  & N.Attributes (N.Attributes'First .. Tmp - 1)
                  & N.Attributes (Index .. N.Attributes'Last));
               Free (N.Attributes);
               N.Attributes := Atts;
               Free (Key);
               return;
            end if;

            Free (Key);
         end loop;

         Atts := new String'(Str & N.Attributes.all);
         Free (N.Attributes);
         N.Attributes := Atts;

      else
         N.Attributes := new String'(Str);
      end if;
   end Set_Attribute;

   ---------------
   -- Add_Child --
   ---------------

   procedure Add_Child
     (N : Node_Ptr; Child : Node_Ptr; Append : Boolean := False)
   is
      Tmp : Node_Ptr;
   begin
      if Append then
         if N.Child = null then
            N.Child := Child;
         else
            Tmp := N.Child;
            while Tmp.Next /= null loop
               Tmp := Tmp.Next;
            end loop;
            Tmp.Next := Child;
         end if;
      else
         Child.Next := N.Child;
         N.Child := Child;
      end if;
      Child.Parent := N;
   end Add_Child;

   --------------
   -- Get_Node --
   --------------

   function Get_Node (Buf : String; Index : access Natural) return Node_Ptr is
      N : constant Node_Ptr := new Node;
      Q : Node_Ptr;
      S : String_Ptr;
      Empty_Node : Boolean;
      Last_Child : Node_Ptr;

   begin
      pragma Assert (Buf (Index.all) = '<');

      Index.all := Index.all + 1;
      Get_Buf (Buf, Index.all, '>', N.Tag);

      --  Check to see whether it is a comment, !DOCTYPE, or the like:

      if N.Tag (N.Tag'First) = '!' then
         return Get_Node (Buf, Index);
      else
         --  Here we have to deal with the attributes of the form
         --  <tag attrib='xyyzy'>

         Extract_Attrib (N.Tag, N.Attributes, Empty_Node);

         --  it is possible to have a child-less node that has the form
         --  <tag /> or <tag attrib='xyyzy'/>

         if Empty_Node then
            N.Value := new String'("");
         else
            if Buf (Index.all) = '<' then
               if Buf (Index.all + 1) = '/' then
                  --  No value contained on this node

                  N.Value := new String'("");
                  Index.all := Index.all + 1;

               else
                  --  Parse the children

                  Add_Child (N, Get_Node (Buf, Index));
                  Last_Child := N.Child;
                  pragma Assert (Buf (Index.all) = '<');

                  while Buf (Index.all + 1) /= '/' loop
                     Q := Last_Child;
                     Q.Next := Get_Node (Buf, Index);
                     Q.Next.Parent := N;
                     Last_Child := Q.Next;
                     pragma Assert (Buf (Index.all) = '<');
                  end loop;

                  Index.all := Index.all + 1;
               end if;

            else
               --  Get the value of this node

               Get_Buf (Buf, Index.all, '<', N.Value);
            end if;

            pragma Assert (Buf (Index.all) = '/');
            Index.all := Index.all + 1;
            Get_Buf (Buf, Index.all, '>', S);
            pragma Assert (N.Tag.all = S.all);
            Free (S);
         end if;

         return N;
      end if;
   exception
      when others =>
         return null;
   end Get_Node;

   -------------
   -- Protect --
   -------------

   function Protect (S : String) return String is
      Length      : Natural := 0;
      Valid_Utf8  : Boolean;
      Invalid_Pos : Natural;
      Pos         : Natural;

      procedure Update_Length (Idx : Natural);
      --  Update the final length of the result string

      procedure Translate
        (Idx : Natural; Res : in out String; Res_Idx : in out Natural);
      --  Protect an xml-reserved character into its entities equivalence

      -------------------
      -- Update_Length --
      -------------------

      procedure Update_Length (Idx : Natural) is
      begin
         case S (Idx) is
            when '<' => Length := Length + 4;
            when '>' => Length := Length + 4;
            when '&' => Length := Length + 5;
            when ''' => Length := Length + 6;
            when '"' => Length := Length + 6;
            when others =>
               --  Single case for ascii/utf8: ascii control characters will
               --  also match.
               if Unichar_Type (UTF8_Get_Char (S (Idx .. S'Last))) =
                 Unicode_Control
               then
                  declare
                     Str : constant String :=
                             Glib.Gunichar'Image
                               (UTF8_Get_Char (S (Idx .. S'Last)));
                  begin
                     --  Add 2: -1 for the starting space, and +3 for leading
                     --  &# and trailing ;
                     Length := Length + Str'Length + 2;
                  end;
               elsif Valid_Utf8 then
                  Length := Length + UTF8_Next_Char (S, Idx) - Idx;
               else
                  Length := Length + 1;
               end if;
         end case;
      end Update_Length;

      ---------------
      -- Translate --
      ---------------

      procedure Translate
        (Idx : Natural; Res : in out String; Res_Idx : in out Natural) is
      begin
         case S (Idx) is
            when '<' =>
               Res (Res_Idx .. Res_Idx + 3) := "&lt;";
               Res_Idx := Res_Idx + 4;
            when '>' =>
               Res (Res_Idx .. Res_Idx + 3) := "&gt;";
               Res_Idx := Res_Idx + 4;
            when '&' =>
               Res (Res_Idx .. Res_Idx + 4) := "&amp;";
               Res_Idx := Res_Idx + 5;
            when ''' =>
               Res (Res_Idx .. Res_Idx + 5) := "&apos;";
               Res_Idx := Res_Idx + 6;
            when '"' =>
               Res (Res_Idx .. Res_Idx + 5) := "&quot;";
               Res_Idx := Res_Idx + 6;
            when others =>
               declare
                  Char : constant Glib.Gunichar :=
                           UTF8_Get_Char (S (Idx .. S'Last));
                  Next : Natural;
               begin
                  if Unichar_Type (Char) = Unicode_Control then
                     declare
                        Str : constant String := Glib.Gunichar'Image (Char);
                     begin
                        Res (Res_Idx .. Res_Idx + Str'Length + 1) :=
                          "&#" & Str (Str'First + 1 .. Str'Last) & ";";
                        Res_Idx := Res_Idx + Str'Length + 2;
                     end;

                  elsif Valid_Utf8 then
                     Next := UTF8_Next_Char (S, Idx);
                     Res (Res_Idx .. Res_Idx + Next - Idx - 1) :=
                       S (Idx .. Next - 1);
                     Res_Idx := Res_Idx + Next - Idx;

                  else
                     Res (Res_Idx) := S (Idx);
                     Res_Idx := Res_Idx + 1;
                  end if;
               end;
         end case;
      end Translate;

   begin
      UTF8_Validate (S, Valid_Utf8, Invalid_Pos);

      if Valid_Utf8 then
         Pos := S'First;

         while Pos <= S'Last loop
            Update_Length (Pos);
            Pos := UTF8_Next_Char (S, Pos);
         end loop;

      else
         for J in S'Range loop
            Update_Length (J);
         end loop;
      end if;

      declare
         Result : String (1 .. Length);
         Index : Integer := 1;

      begin
         if Valid_Utf8 then
            Pos := S'First;

            while Pos <= S'Last loop
               Translate (Pos, Result, Index);
               Pos := UTF8_Next_Char (S, Pos);
            end loop;

         else
            for J in S'Range loop
               Translate (J, Result, Index);
            end loop;
         end if;

         return Result;
      end;
   end Protect;

   -----------
   -- Print --
   -----------

   procedure Print (N : Node_Ptr; File_Name : String := "") is
      Success : Boolean;
      pragma Unreferenced (Success);
   begin
      Print (N, File_Name, Success);
   end Print;

   -----------
   -- Print --
   -----------

   procedure Print
     (N         : Node_Ptr;
      File_Name : String;
      Success   : out Boolean)
   is
      File : Integer := 1;

      procedure Do_Indent (Indent : Natural);
      --  Print a string made of Indent blank characters.

      procedure Print_String (S : String);
      --  Print S to File, after replacing the special '<', '>',
      --  '"', '&' and ''' characters.

      procedure Print_Node (N : Node_Ptr; Indent : Natural);
      --  Write a node and its children to File

      procedure Put (S : String);
      --  Write S to File

      procedure Put_Line (S : String);
      --  Write S & LF to File

      ---------
      -- Put --
      ---------

      procedure Put (S : String) is
      begin
         Write (File, S, S'Length);
      end Put;

      --------------
      -- Put_Line --
      --------------

      procedure Put_Line (S : String) is
      begin
         Put (S & ASCII.LF);
      end Put_Line;

      ---------------
      -- Do_Indent --
      ---------------

      procedure Do_Indent (Indent : Natural) is
      begin
         Put ((1 .. Indent => ' '));
      end Do_Indent;

      ------------------
      -- Print_String --
      ------------------

      procedure Print_String (S : String) is
      begin
         for J in S'Range loop
            case S (J) is
               when '<' => Put ("&lt;");
               when '>' => Put ("&gt;");
               when '&' => Put ("&amp;");
               when ''' => Put ("&apos;");
               when '"' => Put ("&quot;");
               when ASCII.NUL .. Character'Val (9)
                  | Character'Val (11) .. Character'Val (31) =>
                  declare
                     Img : constant String :=
                       Integer'Image (Character'Pos (S (J)));
                  begin
                     Put ("&#" & Img (Img'First + 1 .. Img'Last) & ";");
                  end;
               when others => Put ((1 => S (J)));
            end case;
         end loop;
      end Print_String;

      ----------------
      -- Print_Node --
      ----------------

      procedure Print_Node (N : Node_Ptr; Indent : Natural) is
         P : Node_Ptr;
      begin
         Do_Indent (Indent);
         Put ("<" & N.Tag.all);

         if N.Attributes /= null then
            Put (" " & N.Attributes.all);
         end if;

         if N.Child /= null then
            Put_Line (">");
            P := N.Child;
            while P /= null loop
               Print_Node (P, Indent + 2);
               P := P.Next;
            end loop;

            Do_Indent (Indent);
            Put_Line ("</" & N.Tag.all & ">");

         elsif N.Value = null
           or else N.Value.all = ""
         then
            --  The following handles the difference between what you got
            --  when you parsed <tag/> vs. <tag />.
            if N.Tag (N.Tag'Last) = '/' then
               Put_Line (">");
            else
               Put_Line (" />");
            end if;
         else
            Put (">");
            Print_String (N.Value.all);
            Put_Line ("</" & N.Tag.all & ">");
         end if;
      end Print_Node;

   begin
      if File_Name /= "" then
         File := Create_File (File_Name & ASCII.NUL);

         if File < 0 then
            Success := False;
            return;
         end if;
      end if;

      Put_Line ("<?xml version=""1.0""?>");
      Print_Node (N, 0);

      if File_Name /= "" then
         Close (File);
      end if;

      Success := True;
   end Print;

   -----------
   -- Parse --
   -----------

   function Parse (File : String) return Node_Ptr is

      function Read_File (The_File : String) return String_Ptr;
      --  Return the contents of an entire file.
      --  If the file cannot be found, return null.
      --  The caller is responsible for freeing the returned memory.

      ---------------
      -- Read_File --
      ---------------

      function Read_File (The_File : String) return String_Ptr is
         FD     : Integer;
         Buffer : String_Ptr;
         Length : Integer;
         pragma Warnings (Off, Length);

      begin
         FD := Open_Read (The_File & ASCII.NUL);

         if FD < 0 then
            return null;
         end if;

         Length := Integer (File_Length (FD));
         Buffer := new String (1 .. Length);
         Length := Read (FD, Buffer.all'Address, Length);
         Close (FD);
         return Buffer;
      end Read_File;

      Buf    : String_Ptr;
      Result : Node_Ptr;

   begin
      Buf := Read_File (File);

      if Buf = null then
         return null;
      end if;

      Result := Parse_Buffer (Buf.all);
      Free (Buf);
      return Result;
   end Parse;

   ------------------
   -- Parse_Buffer --
   ------------------

   function Parse_Buffer (Buffer : UTF8_String) return Node_Ptr is
      Index       : aliased Natural := 2;
      XML_Version : String_Ptr;
      Encoding    : Integer;
      Encoding_Last : Integer;
      Result        : Node_Ptr;
   begin
      Get_Buf (Buffer, Index, '>', XML_Version);
      if XML_Version = null then
         return null;
      else
         --  Check the encoding specified for that file
         Encoding := Ada.Strings.Fixed.Index (XML_Version.all, "encoding");

         if Encoding /= 0 then
            while Encoding <= XML_Version'Last
              and then XML_Version (Encoding) /= '"'
            loop
               Encoding := Encoding + 1;
            end loop;

            Encoding := Encoding + 1;
            Encoding_Last := Encoding + 1;

            while Encoding_Last <= XML_Version'Last
              and then XML_Version (Encoding_Last) /= '"'
            loop
               Encoding_Last := Encoding_Last + 1;
            end loop;

            if Encoding_Last <= XML_Version'Last then
               declare
                  Error       : aliased GError;
                  Utf8_Buffer : constant String := Glib.Convert.Convert
                    (Buffer,
                     To_Codeset => "UTF-8",
                     From_Codeset =>
                       XML_Version (Encoding .. Encoding_Last - 1),
                     Error => Error'Unchecked_Access);
               begin
                  if Utf8_Buffer /= "" then
                     Result := Get_Node (Utf8_Buffer, Index'Unchecked_Access);
                  else
                     Glib.Messages.Log
                       ("Glib", Log_Level_Warning, Get_Message (Error));
                     Error_Free (Error);
                  end if;
               end;
            else
               Result := Get_Node (Buffer, Index'Unchecked_Access);
            end if;
         else
            Result := Get_Node (Buffer, Index'Unchecked_Access);
         end if;

         Free (XML_Version);
         return Result;
      end if;
   end Parse_Buffer;

   --------------
   -- Find_Tag --
   --------------

   function Find_Tag (N : Node_Ptr; Tag : UTF8_String) return Node_Ptr is
      P : Node_Ptr := N;

   begin
      while P /= null loop
         if P.Tag.all = Tag then
            return P;
         end if;

         P := P.Next;
      end loop;

      return null;
   end Find_Tag;

   -----------------------------
   -- Find_Tag_With_Attribute --
   -----------------------------

   function Find_Tag_With_Attribute
     (N : Node_Ptr;
      Tag : UTF8_String;
      Key : UTF8_String;
      Value : UTF8_String := "") return Node_Ptr
   is
      P : Node_Ptr := N;
   begin
      while P /= null loop
         if P.Tag.all = Tag then
            declare
               The_Value : constant String := Get_Attribute (P, Key);
            begin
               if The_Value /= "" then
                  if Value = "" or The_Value = Value then
                     --  if Value is not given when calling the
                     --  the function only the Key need to match
                     return P;
                  end if;
               end if;
            end;
         end if;
         P := P.Next;
      end loop;

      return null;
   end Find_Tag_With_Attribute;

   ---------------
   -- Get_Field --
   ---------------

   function Get_Field (N : Node_Ptr; Field : UTF8_String) return String_Ptr is
      P : constant Node_Ptr := Find_Tag (N.Child, Field);

   begin
      if P /= null then
         return P.Value;
      else
         return null;
      end if;
   end Get_Field;

   ----------
   -- Free --
   ----------

   procedure Free
     (N : in out Node_Ptr; Free_Data : Free_Specific_Data := null)
   is
      procedure Free_Node (N : in out Node_Ptr);
      --  Free the memory for a node, but doesn't remove it from its parent

      procedure Unchecked_Free is new Unchecked_Deallocation (Node, Node_Ptr);

      ---------------
      -- Free_Node --
      ---------------

      procedure Free_Node (N : in out Node_Ptr) is
         Child : Node_Ptr := N.Child;
         Next  : Node_Ptr;

      begin
         Free (N.Tag);
         Free (N.Attributes);
         Free (N.Value);

         if Free_Data /= null then
            Free_Data (N.Specific_Data);
         end if;

         --  Free all the children
         while Child /= null loop
            Next := Child.Next;
            Free_Node (Child);
            Child := Next;
         end loop;

         Unchecked_Free (N);
      end Free_Node;

      Child    : Node_Ptr;
      Previous : Node_Ptr;

   begin
      if N = null then
         return;
      end if;

      if N.Parent /= null then
         Child := N.Parent.Child;

         --  Remove the node from its parent
         while Child /= null and then Child /= N loop
            Previous := Child;
            Child := Child.Next;
         end loop;

         if Child = N then
            if Previous = null then
               N.Parent.Child := N.Next;
            else
               Previous.Next := N.Next;
            end if;
         end if;
      end if;

      --  Free the memory occupied by the node
      Free_Node (N);
   end Free;

   ---------------
   -- Deep_Copy --
   ---------------

   function Deep_Copy (N : Node_Ptr) return Node_Ptr is
      function Deep_Copy_Internal
        (N : Node_Ptr; Parent : Node_Ptr := null) return Node_Ptr;
      --  Internal version of Deep_Copy. Returns a deep copy of N, whose
      --  parent should be Parent.

      function Deep_Copy_Internal
        (N : Node_Ptr; Parent : Node_Ptr := null) return Node_Ptr
      is
         Attr  : String_Ptr;
         Value : String_Ptr;

         New_N : Node_Ptr;
         Child : Node_Ptr;
         N_Child : Node_Ptr;
      begin
         if N = null then
            return null;
         else
            if N.Attributes /= null then
               Attr := new String'(N.Attributes.all);
            end if;

            if N.Value /= null then
               Value := new String'(N.Value.all);
            end if;

            --  Do not clone Next: For the initial node, we should not clone
            --  the next nodes, only its children. And for children this is
            --  done by Deep_Copy_Internal on the parent

            New_N := new Node'
              (Tag => new String'(N.Tag.all),
               Attributes => Attr,
               Value => Value,
               Parent => Parent,
               Child => null,
               Next => null,
               Specific_Data => N.Specific_Data);

            --  Clone each child

            Child := N.Child;
            while Child /= null loop
               if N_Child = null then
                  New_N.Child := Deep_Copy_Internal (Child, Parent => New_N);
                  N_Child := New_N.Child;
               else
                  N_Child.Next := Deep_Copy_Internal (Child, Parent => New_N);
                  N_Child := N_Child.Next;
               end if;
               Child := Child.Next;
            end loop;

            return New_N;
         end if;
      end Deep_Copy_Internal;

   begin
      return Deep_Copy_Internal (N);
   end Deep_Copy;

   --------------
   -- Is_Equal --
   --------------

   function Is_Equal (Node1, Node2 : Node_Ptr) return Boolean is
   begin
      if Node1 = null then
         if Node2 /= null then
            return False;
         else
            return True;
         end if;
      elsif Node2 = null then
         return False;
      end if;

      if Node1.Tag = null then
         if Node2.Tag /= null then
            return False;
         end if;
      elsif Node2.Tag = null then
         return False;
      elsif Node1.Tag.all /= Node2.Tag.all then
         return False;
      end if;

      if Node1.Attributes = null then
         if Node2.Attributes /= null then
            return False;
         end if;
      elsif Node2.Attributes = null then
         return False;
      elsif Node1.Attributes.all /= Node2.Attributes.all then
         return False;
      end if;

      if Node1.Value = null then
         if Node2.Value /= null then
            return False;
         end if;
      elsif Node2.Value = null then
         return False;
      elsif Node1.Value.all /= Node2.Value.all then
         return False;
      end if;

      if Node1.Child = null then
         if Node2.Child /= null then
            return False;
         end if;
      elsif Node2.Child = null then
         return False;
      elsif not Is_Equal (Node1.Child, Node2.Child) then
         return False;
      end if;

      if Node1.Next = null then
         if Node2.Next /= null then
            return False;
         end if;
      elsif Node2.Next = null then
         return False;
      elsif not Is_Equal (Node1.Next, Node2.Next) then
         return False;
      end if;
      return True;
   end Is_Equal;

   --------------------
   -- Children_Count --
   --------------------

   function Children_Count (N : Node_Ptr) return Natural is
      Tmp : Node_Ptr;
      Count : Natural := 0;
   begin
      if N /= null then
         Tmp := N.Child;
         while Tmp /= null loop
            Count := Count + 1;
            Tmp := Tmp.Next;
         end loop;
      end if;
      return Count;
   end Children_Count;

end Glib.XML;
