------------------------------------------------------------------------------
--                             G N A T C O L L                              --
--                                                                          --
--                     Copyright (C) 2006-2013, AdaCore                     --
--                                                                          --
-- This library 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. This library 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.                            --
--                                                                          --
-- 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/>.                                          --
--                                                                          --
------------------------------------------------------------------------------

with Ada.Calendar;            use Ada.Calendar;
with Ada.Calendar.Time_Zones; use Ada.Calendar.Time_Zones;
with Ada.Calendar.Formatting; use Ada.Calendar.Formatting;
with Ada.Characters.Handling; use Ada.Characters.Handling;
with Ada.Strings.Hash_Case_Insensitive;
with GNATCOLL.Utils;          use GNATCOLL.Utils;
with Interfaces;              use Interfaces;

package body GNATCOLL.Email.Utils is

   procedure Read_Integer
     (S : String; Index : in out Integer; Value : out Integer);
   --  return the integer starting at Index, and moves Index after the integer

   procedure Skip_Comment (S : String; Index : in out Integer);
   --  Skip the comment, if any, that starts at Index.
   --  In RFC 2822, comments are between parenthesis, and can be nested

   procedure Skip_Quoted_String (S : String; Index : in out Integer);
   --  Skip a quoted string, taking properly into account the backslashes
   --  Index should point after the opening quote.

   procedure Parse_And_Skip_Address
     (From_C : in out Charset_String_List.Cursor;
      From   : in out Integer;
      Address : out Email_Address);
   --  Parse the first email address at (From_C, From), and leaves them after
   --  it, so that if there are more addresses in From_C they can all be parsed
   --  easily.

   procedure Parse_And_Skip_Address
     (Str           : String;
      From          : in out Integer;
      Buffer        : in out Unbounded_String;
      Buffer_Has_At : in out Boolean;
      In_Quote      : in out Boolean;
      Comment       : in out Unbounded_String;
      Address       : in out Email_Address;
      Found         : out Boolean);
   --  Internal version of Parse_And_Skip_Address, which applies to a
   --  us-ascii string. It maintains internal data.
   --  In_Quote indicates whether we are initially within an open quote ("),
   --  and on exit whether we are still processing a quoted string.

   procedure Post_Process_Address
     (Address         : in out Email_Address;
      Buffer, Comment : Unbounded_String;
      Buffer_Has_At   : Boolean);
   --  Complete the data in Address, given Buffer and Comment that were
   --  generated by Parse_And_Skip_Address. This procedure should be called
   --  after Parse_And_Skip_Address, before returning an address to the user.

   Special_Chars : constant array (Character) of Boolean :=
     ('[' | ']' | '\' | '(' | ')' | '<' | '>' | '@' | ',' => True,
      ':' | ';' | '"' | '.' => True,
      others => False);

   Quoted_Chars : constant array (Character) of Boolean :=
     ('[' | ']' | '\' | '(' | ')' | '"' => True,
      others => False);

   Qp_Convert : constant array (Character) of Short_Integer :=
     ('0' => 0,  '1' => 1,  '2' => 2,  '3' => 3,  '4' => 4,
      '5' => 5,  '6' => 6,  '7' => 7,  '8' => 8,  '9' => 9,
      'A' => 10, 'B' => 11, 'C' => 12, 'D' => 13, 'E' => 14, 'F' => 15,
      'a' => 10, 'b' => 11, 'c' => 12, 'd' => 13, 'e' => 14, 'f' => 15,
      others => -1);

   type Byte is mod 256;
   Base64_Convert : constant array (Character) of Byte :=
     ('+' => 62, '/' => 63, '0' => 52, '1' => 53, '2' => 54, '3' => 55,
      '4' => 56, '5' => 57, '6' => 58, '7' => 59, '8' => 60, '9' => 61,
      'A' => 0,  'B' => 1,  'C' => 2,  'D' => 3,  'E' => 4,  'F' => 5,
      'G' => 6,  'H' => 7,  'I' => 8,  'J' => 9,  'K' => 10, 'L' => 11,
      'M' => 12, 'N' => 13, 'O' => 14, 'P' => 15, 'Q' => 16, 'R' => 17,
      'S' => 18, 'T' => 19, 'U' => 20, 'V' => 21, 'W' => 22, 'X' => 23,
      'Y' => 24, 'Z' => 25, 'a' => 26, 'b' => 27, 'c' => 28, 'd' => 29,
      'e' => 30, 'f' => 31, 'g' => 32, 'h' => 33, 'i' => 34, 'j' => 35,
      'k' => 36, 'l' => 37, 'm' => 38, 'n' => 39, 'o' => 40, 'p' => 41,
      'q' => 42, 'r' => 43, 's' => 44, 't' => 45, 'u' => 46, 'v' => 47,
      'w' => 48, 'x' => 49, 'y' => 50, 'z' => 51, others => -1);

   type Mod64 is mod 2 ** 6;
   To_Base64 : constant array (Mod64) of Character :=
     (00 => 'A',  1 => 'B',  2 => 'C',  3 => 'D',  4 => 'E',  5 => 'F',
       6 => 'G',  7 => 'H',  8 => 'I',  9 => 'J', 10 => 'K', 11 => 'L',
      12 => 'M', 13 => 'N', 14 => 'O', 15 => 'P', 16 => 'Q', 17 => 'R',
      18 => 'S', 19 => 'T', 20 => 'U', 21 => 'V', 22 => 'W', 23 => 'X',
      24 => 'Y', 25 => 'Z', 26 => 'a', 27 => 'b', 28 => 'c', 29 => 'd',
      30 => 'e', 31 => 'f', 32 => 'g', 33 => 'h', 34 => 'i', 35 => 'j',
      36 => 'k', 37 => 'l', 38 => 'm', 39 => 'n', 40 => 'o', 41 => 'p',
      42 => 'q', 43 => 'r', 44 => 's', 45 => 't', 46 => 'u', 47 => 'v',
      48 => 'w', 49 => 'x', 50 => 'y', 51 => 'z', 52 => '0', 53 => '1',
      54 => '2', 55 => '3', 56 => '4', 57 => '5', 58 => '6', 59 => '7',
      60 => '8', 61 => '9', 62 => '+', 63 => '/');

   Hex_Chars : constant array (0 .. 15) of Character := "0123456789ABCDEF";

   ------------------------
   -- Skip_Quoted_String --
   ------------------------

   procedure Skip_Quoted_String (S : String; Index : in out Integer) is
   begin
      while Index <= S'Last loop
         if S (Index) = '"' then
            Index := Index + 1;
            return;
         elsif S (Index) = '\' then
            Index := Index + 2;
         else
            Index := Index + 1;
         end if;
      end loop;
      --  There is no closing '"'
      Index := S'Last + 1;
   end Skip_Quoted_String;

   ------------------
   -- Skip_Comment --
   ------------------

   procedure Skip_Comment (S : String; Index : in out Integer) is
      Par   : Natural := 1;
   begin
      if S (Index) = '(' then
         Index := Index + 1;

         while Index <= S'Last loop
            if S (Index) = ')' then
               Par := Par - 1;
               if Par = 0 then
                  Index := Index + 1;
                  return;
               else
                  Index := Index + 1;
               end if;
            elsif S (Index) = '(' then
               Par := Par + 1;
               Index := Index + 1;
            elsif S (Index) = '\' then
               Index := Index + 2;
            else
               Index := Index + 1;
            end if;
         end loop;

         --   No closing ')'
         Index := S'Last + 1;
      end if;
   end Skip_Comment;

   ------------------
   -- Read_Integer --
   ------------------

   procedure Read_Integer
     (S : String; Index : in out Integer; Value : out Integer)
   is
      Start : constant Integer := Index;
   begin
      if S (Index) = '-' or else S (Index) = '+' then
         Index := Index + 1;
      end if;

      while Index <= S'Last
        and then S (Index) in '0' .. '9'
      loop
         Index := Index + 1;
      end loop;

      Value := Integer'Value (S (Start .. Index - 1));
   end Read_Integer;

   -------------
   -- To_Time --
   -------------

   function To_Time
     (Date   : String;
      Format : Time_Format := Time_RFC2822) return Ada.Calendar.Time
   is
      Index   : Integer := Date'First;
      Index2  : Integer;
      Year    : Year_Number  := Year_Number'First;
      Month   : Month_Number := Month_Number'First;
      Day     : Day_Number   := Day_Number'First;
      Seconds : Day_Duration := 0.0;
      TZ      : Time_Offset  := 0;

      Time_Error : exception;

      procedure Read_Day;
      procedure Read_Month;
      procedure Read_Year;
      procedure Read_Time;
      --  Read the day of month or the year
      procedure Read_Time_Zone;

      procedure Read_Day is
      begin
         Read_Integer (Date (Index .. Date'Last), Index, Value => Index2);
         Day := Day_Number (Index2);
         Skip_Whitespaces (Date (Index .. Date'Last), Index);
      end Read_Day;

      procedure Read_Month is
         pragma Warnings (Off);
         type Month_Name is
                (Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec);
         pragma Warnings (On);
      begin
         Month :=
           Month_Name'Pos (Month_Name'Value (Date (Index .. Index + 2))) + 1;

         --  Some mailers print the month in full, not just the first three
         --  chars. Although this isn't part of the RFC 2822, we still want to
         --  handle these
         Index := Index + 3;
         while Index <= Date'Last
           and then not Is_Whitespace (Date (Index))
         loop
            Index := Index + 1;
         end loop;
         Skip_Whitespaces (Date (Index .. Date'Last), Index);
      exception
         when others =>
            --  This really means the date format is incorrect!
            null;
      end Read_Month;

      procedure Read_Year is
      begin
         Read_Integer (Date (Index .. Date'Last), Index, Value => Index2);
         if Index2 < 0 then
            raise Time_Error;
         elsif Index2 <= 49 then
            Year := Year_Number (2000 + Index2);
         elsif Index2 <= 99 then
            Year := Year_Number (1900 + Index2);
         else
            Year := Year_Number (Index2);
         end if;
         Skip_Whitespaces (Date (Index .. Date'Last), Index);
      end Read_Year;

      procedure Read_Time is
      begin
         Read_Integer (Date (Index .. Date'Last), Index, Value => Index2);
         Seconds := Seconds + Day_Duration (Index2) * 3600.0;
         if Date (Index) /= ':' then
            raise Time_Error;
         end if;
         Index := Index + 1;
         Read_Integer (Date (Index .. Date'Last), Index, Value => Index2);
         Seconds := Seconds + Day_Duration (Index2) * 60.0;
         if Date (Index) = ':' then
            Index := Index + 1;
            Read_Integer (Date (Index .. Date'Last), Index, Value => Index2);
            Seconds := Seconds + Day_Duration (Index2);
         end if;
         Skip_Whitespaces (Date (Index .. Date'Last), Index);
      end Read_Time;

      procedure Read_Time_Zone is
         TZ_Local : Integer;
         type Named_TZ is (AST, ADT, EST, EDT, CST, CDT, MST, MDT, PST, PDT);
         Named_TZ_Offset : constant array (Named_TZ) of Time_Offset :=
           (AST => -240,
            ADT => -180,
            EST => -300,
            EDT => -240,
            CST => -360,
            CDT => -300,
            MST => -420,
            MDT => -360,
            PST => -480,
            PDT => -420);
      begin
         --  Timezone (we might have none in badly formed dates)
         if Index < Date'Last then
            if Date (Index) = '-' or else Date (Index) = '+' or else
               Date (Index) in '0' .. '9' then
               Read_Integer (Date (Index .. Date'Last), Index,
                             Value => TZ_Local);
               TZ := Time_Offset ((TZ_Local / 100) * 60 + TZ_Local mod 100);
            else

               --  The timezone table does not include the military time zones
               --  defined in RFC822, other than Z. According to RFC1123, the
               --  description in RFC822 gets the signs wrong, so we can't rely
               --  on any such time zones. RFC1123 recommends that numeric
               --  timezone indicators be used instead of timezone names.

               if Date (Index .. Index + 1) = "UT"
                 or else Date (Index .. Index + 2) = "UTC"
                 or else Date (Index) = 'Z'
               then
                  TZ := 0;
               else
                  TZ := Named_TZ_Offset
                    (Named_TZ'Value (Date (Index .. Index + 2)));
               end if;
            end if;
         end if;

      exception
         when Constraint_Error =>
            --  Invalid time zone, just ignore
            null;
      end Read_Time_Zone;

   begin
      --  RFC 2822 format is
      --     [day-of-week] ","] day month-name year FWS time-of-day FWS tz
      --     year  := 4 * DIGIT | 2 * DIGIT
      --     day   := 1*2DIGIT
      --     time-of-day := hour ":" minute [":" second]
      --     tz    := (("+" | "-") 4DIGIT) | "UT" | "GMT" | ...
      --
      --  Envelope format is
      --     Tue Jan 24 14:48:49 2006 +0100

      Skip_Whitespaces (Date (Index .. Date'Last), Index);

      --  Day of week is optional, skip it

      case Format is
         when Time_RFC2822 =>
            Index2 := Next_Occurrence (Date (Index .. Date'Last), ',');
            if Index2 <= Date'Last then
               Index := Index2 + 1;
               Skip_Whitespaces (Date (Index .. Date'Last), Index);
            end if;

            Read_Day;
            Read_Month;
            Read_Year;
            Read_Time;

         when Time_Envelope =>
            Index := Index + 3;
            Skip_Whitespaces (Date (Index .. Date'Last), Index);

            Read_Month;
            Read_Day;
            Read_Time;
            Read_Year;
      end case;

      Read_Time_Zone;

      return Time_Of (Year, Month, Day, Seconds, Time_Zone => TZ);

   exception
      when Time_Error =>
         return No_Time;
      when Constraint_Error =>
         return No_Time;
   end To_Time;

   -----------------
   -- Format_Time --
   -----------------

   function Format_Time (Date : Ada.Calendar.Time) return String
   is
      Result : Unbounded_String;
      Y      : Year_Number;
      M      : Month_Number;
      D      : Day_Number;
      H      : Hour_Number;
      Min    : Minute_Number;
      S      : Second_Number;
      SS     : Second_Duration;
   begin
      Split (Date, Y, M, D, H, Min, S, SS);

      Result := To_Unbounded_String
        (Image (Integer (H), Min_Width => 2) & ":");
      Append (Result, Image (Integer (Min), Min_Width => 2) & ":");
      Append (Result, Image (Integer (S), Min_Width => 2));
      return To_String (Result);
   end Format_Time;

   -----------------
   -- Format_Date --
   -----------------

   function Format_Date
     (Date         : Ada.Calendar.Time;
      Date_Is_GMT  : Boolean := False;
      Use_GMT      : Boolean := False;
      From_Line    : Boolean := False;
      No_TZ        : Boolean := False;
      Show_Time    : Boolean := True;
      Show_Seconds : Boolean := True;
      Show_Day     : Boolean := True) return String
   is
      Result : Unbounded_String;
      Y      : Year_Number;
      M      : Month_Number;
      D      : Day_Number;
      H      : Hour_Number;
      Min    : Minute_Number;
      S      : Second_Number;
      SS     : Second_Duration;
      TZ     : Integer := 0;
      RFC_TZ : Integer;
      Unknown_TZ : Boolean := False;
      Adjusted_Date : Time := Date;
   begin
      begin
         --  Number of minutes difference for the timezone
         --  We use moment of time in Date to get proper DST state
         TZ := Integer (UTC_Time_Offset (Date));

         if not Date_Is_GMT then
            Adjusted_Date := Date + Duration (TZ) * 60.0;
         end if;

      exception
         when Unknown_Zone_Error =>
            Unknown_TZ := True;
      end;

      --  We cannot use GNAT.Calendar.Time_IO for week days, since we always
      --  want the english names, not the locale's version.

      if Show_Day then
         case  Day_Of_Week (Adjusted_Date) is
         when Monday    => Result := To_Unbounded_String ("Mon");
         when Tuesday   => Result := To_Unbounded_String ("Tue");
         when Wednesday => Result := To_Unbounded_String ("Wed");
         when Thursday  => Result := To_Unbounded_String ("Thu");
         when Friday    => Result := To_Unbounded_String ("Fri");
         when Saturday  => Result := To_Unbounded_String ("Sat");
         when Sunday    => Result := To_Unbounded_String ("Sun");
         end case;

         if From_Line then
            Append (Result, " ");
         else
            Append (Result, ", ");
         end if;
      end if;

      Split (Adjusted_Date, Y, M, D, H, Min, S, SS);
      if not From_Line then
         Append (Result, Image (Integer (D), Min_Width => 2) & " ");
      end if;

      case M is
         when 1         => Append (Result, "Jan ");
         when 2         => Append (Result, "Feb ");
         when 3         => Append (Result, "Mar ");
         when 4         => Append (Result, "Apr ");
         when 5         => Append (Result, "May ");
         when 6         => Append (Result, "Jun ");
         when 7         => Append (Result, "Jul ");
         when 8         => Append (Result, "Aug ");
         when 9         => Append (Result, "Sep ");
         when 10        => Append (Result, "Oct ");
         when 11        => Append (Result, "Nov ");
         when 12        => Append (Result, "Dec ");
      end case;

      if From_Line then
         Append (Result, Image (Integer (D), Min_Width => 2) & " ");
      else
         Append (Result, Image (Integer (Y), Min_Width => 2) & " ");
      end if;

      if Show_Time then
         Append (Result, Image (Integer (H), Min_Width => 2) & ":");
         Append (Result, Image (Integer (Min), Min_Width => 2));
         if Show_Seconds then
            Append (Result, ":" & Image (Integer (S), Min_Width => 2));
         end if;
      end if;

      if From_Line then
         Append (Result, " " & Image (Integer (Y), Min_Width => 2));
      end if;

      if not No_TZ then
         if Use_GMT then
            Append (Result, " GMT");
         elsif Unknown_TZ then
            Append (Result, " -0000");
         else
            RFC_TZ := (TZ / 60) * 100 + TZ mod 60;
            Append (Result, " " & Image (RFC_TZ, Min_Width => 4,
                                         Force_Sign => True));
         end if;
      end if;

      return To_String (Result);
   end Format_Date;

   -------------------
   -- Parse_Address --
   -------------------

   function Parse_Address (Email : String) return Email_Address is
      Index         : Integer := Email'First;
      Result        : Email_Address;
      Buffer        : Unbounded_String;
      Buffer_Has_At : Boolean := False;
      Comment       : Unbounded_String;
      Found         : Boolean;
      In_Quote      : Boolean := False;
   begin
      Parse_And_Skip_Address
        (Str           => Email,
         From          => Index,
         Buffer        => Buffer,
         Buffer_Has_At => Buffer_Has_At,
         In_Quote      => In_Quote,
         Comment       => Comment,
         Address       => Result,
         Found         => Found);
      Post_Process_Address
        (Address         => Result,
         Buffer          => Buffer,
         Comment         => Comment,
         Buffer_Has_At   => Buffer_Has_At);
      return Result;
   end Parse_Address;

   ----------------------------
   -- Parse_And_Skip_Address --
   ----------------------------

   procedure Parse_And_Skip_Address
     (Str           : String;
      From          : in out Integer;
      Buffer        : in out Unbounded_String;
      Buffer_Has_At : in out Boolean;
      In_Quote      : in out Boolean;
      Comment       : in out Unbounded_String;
      Address       : in out Email_Address;
      Found         : out Boolean)
   is
      Index   : Integer;
   begin
      if In_Quote then
         Index := From;
         Skip_Quoted_String (Str (Index .. Str'Last), Index);
         Address.Real_Name := Trim
           (To_Unbounded_String
              (Str (From + 1 .. Index - 2)), Ada.Strings.Both);
         From := Index + 1;
         In_Quote := False;
      end if;

      --  Skip spaces

      while From <= Str'Last
        and then (Str (From) = ASCII.LF
                  or else Str (From) = ASCII.CR
                  or else Str (From) = ASCII.HT
                  or else Str (From) = ' ')
      loop
         From := From + 1;
      end loop;

      --  Only parse the contents of us-ascii strings. The rest cannot
      --  contain email addresses nor comments anyway.

      while From <= Str'Last loop
         if From <= Str'Last then
            if Str (From) = '(' then
               --  A comment. Ignored in general, but if we do not have a
               --  real name, it is likely to be contained in this
               --  comment, which is what some old mailers used to do:
               --     report@gnat.com (Report)

               Index := From;
               Skip_Comment (Str (From .. Str'Last), Index);
               Append (Comment, Str (From + 1 .. Index - 2));
               From := Index;

            elsif Str (From) = '<' then
               --  The email address

               Index := From;
               while Index <= Str'Last
                 and then Str (Index) /= '>'
               loop
                  Index := Index + 1;
               end loop;

               Address.Address := To_Unbounded_String
                 (Str (From + 1 .. Index - 1));
               From := Index + 1;

            --  ',' is the standard separator in mail messages, but ';' is
            --  often used by users when manually typing a list of addresses
            elsif Str (From) = ','
              or else Str (From) = ';'
              or else Str (From) = ASCII.LF
              or else Str (From) = ASCII.CR
              or else Str (From) = ASCII.HT
              or else (Buffer_Has_At and then Str (From) = ' ')
            then
               --  End of current address
               From := From + 1;
               Found := True;
               return;

            elsif Str (From) = '"' then
               Index := From + 1;
               Skip_Quoted_String (Str (Index .. Str'Last), Index);

               if Index > Str'Last then
                  In_Quote := True;
               end if;

               Address.Real_Name := Trim
                 (To_Unbounded_String
                    (Str (From + 1 .. Index - 2)), Ada.Strings.Both);

               if Index <= Str'Last and then Str (Index) = ' ' then
                  From := Index + 1;
               else
                  From := Index;
               end if;

            else
               if Str (From) = '@' then
                  Buffer_Has_At := True;
               end if;

               Append (Buffer, Str (From));
               From := From + 1;
            end if;
         end if;
      end loop;

      Found := False;
   end Parse_And_Skip_Address;

   ----------------------------
   -- Parse_And_Skip_Address --
   ----------------------------

   procedure Parse_And_Skip_Address
     (From_C  : in out Charset_String_List.Cursor;
      From    : in out Integer;
      Address : out Email_Address)
   is
      use Charset_String_List;
      Buffer  : Unbounded_String;
      Comment : Unbounded_String;
      Buffer_Has_At : Boolean := False;

      In_Quote : Boolean := False;
      --  Quotes are not necessarily encoded, and we could have for instance:
      --     " =?iso-2022-jp?b?...?= " <foo@nowhere.jp>
      --  which is made of several strings: one for the opening quote, one for
      --  the encoded name, and a last one that includes the quote and the
      --  email address.

      Continue : Boolean;

      procedure Analyze (CS : Charset_String);
      --  Analyze a given element of the list. Done in nested procedure to
      --  avoid a copy of each element of Email

      procedure Analyze (CS : Charset_String) is
         Tmp     : Unbounded_String;
         Found   : Boolean := False;
      begin
         --  Only parse the contents of us-ascii strings. The rest cannot
         --  contain email addresses nor comments anyway

         if CS.Charset = Charset_US_ASCII then
            Parse_And_Skip_Address
              (Str           => To_String (CS.Contents),
               From          => From,
               Buffer        => Buffer,
               Buffer_Has_At => Buffer_Has_At,
               In_Quote      => In_Quote,
               Comment       => Comment,
               Address       => Address,
               Found         => Found);
         else
            --  Reencode, to preserve names in international charsets
            Encode (Str     => To_String (CS.Contents),
                    Charset => To_String (CS.Charset),
                    Header  => True,
                    Result  => Tmp);
            Append (Buffer, Tmp);
         end if;

         Continue := not Found;
      end Analyze;

   begin
      Address := Null_Address;
      while Has_Element (From_C) loop
         Query_Element (From_C, Analyze'Unrestricted_Access);
         exit when not Continue;
         Next (From_C);
         From := 1;
      end loop;

      Post_Process_Address (Address, Buffer, Comment, Buffer_Has_At);
   end Parse_And_Skip_Address;

   --------------------------
   -- Post_Process_Address --
   --------------------------

   procedure Post_Process_Address
     (Address         : in out Email_Address;
      Buffer, Comment : Unbounded_String;
      Buffer_Has_At   : Boolean)
   is
      pragma Unreferenced (Buffer_Has_At);
   begin
      if Address.Address = Null_Unbounded_String then
         --  Ideally, we should test whether Buffer contains a @ string. But
         --  there are degenerate cases where we have an email address on its
         --  own with no @ sign, and we want to handle them for backward
         --  compatibility...
         Address.Address := Trim (Buffer, Ada.Strings.Both);

      else
         if Address.Real_Name = Null_Unbounded_String then
            if Buffer = Null_Unbounded_String then
               Address.Real_Name := Trim (Comment, Ada.Strings.Both);
            else
               Address.Real_Name := Trim (Buffer, Ada.Strings.Both);
            end if;
         end if;
      end if;
   end Post_Process_Address;

   -------------------
   -- Get_Addresses --
   -------------------

   function Get_Addresses (Str : String) return Address_Set.Set is
      use Charset_String_List;
      L : Charset_String_List.List;
   begin
      Append (L, (Contents => To_Unbounded_String (Str),
                  Charset  => To_Unbounded_String (Charset_US_ASCII)));
      return Get_Addresses (L);
   end Get_Addresses;

   -------------------
   -- Get_Addresses --
   -------------------

   function Get_Addresses
     (Str : Charset_String_List.List) return Address_Set.Set
   is
      use Charset_String_List, Address_Set;
      C    : Charset_String_List.Cursor := First (Str);
      From : Integer := 1;
      Result : Address_Set.Set;
      Addr   : Email_Address;
   begin
      while Has_Element (C) loop
         Parse_And_Skip_Address (C, From, Addr);
         if Addr /= Null_Address then
            Include (Result, Addr);
         end if;
      end loop;
      return Result;
   end Get_Addresses;

   ---------------
   -- To_String --
   ---------------

   function To_String
     (Addresses    : Address_Set.Set;
      Separator    : String := ", ";
      Address_Only : Boolean := False) return String
   is
      use Address_Set;
      Tmp : Unbounded_String;
      C   : Address_Set.Cursor := First (Addresses);
   begin
      while Has_Element (C) loop
         if Tmp /= Null_Unbounded_String then
            Append (Tmp, Separator);
         end if;

         if Address_Only then
            Append (Tmp, Element (C).Address);
         else
            Append (Tmp, Format_Address (Element (C)));
         end if;

         Next (C);
      end loop;
      return To_String (Tmp);
   end To_String;

   --------------------
   -- Format_Address --
   --------------------

   function Format_Address (Addr : Email_Address) return String is
   begin
      return Format_Address
        (To_String (Addr.Real_Name), To_String (Addr.Address));
   end Format_Address;

   --------------------
   -- Format_Address --
   --------------------

   function Format_Address (Real : String; Address : String) return String is
      Has_Special : Boolean := False;
   begin
      if Real = "" then
         return Address;
      else
         for C in Real'Range loop
            if Special_Chars (Real (C)) then
               Has_Special := True;
               exit;
            end if;
         end loop;

         if Has_Special then
            return '"' & Quote (Real) & """ <" & Address & '>';
         else
            return Quote (Real) & " <" & Address & '>';
         end if;
      end if;
   end Format_Address;

   -----------
   -- Quote --
   -----------

   function Quote (Str : String) return String is
      Result : String (Str'First .. Str'Last * 2);
      Index  : Integer := Result'First;
   begin
      for C in Str'Range loop
         if Quoted_Chars (Str (C)) then
            Result (Index) := '\';
            Index := Index + 1;
         end if;
         Result (Index) := Str (C);
         Index := Index + 1;
      end loop;
      return Result (Result'First .. Index - 1);
   end Quote;

   -------------
   -- Unquote --
   -------------

   function Unquote (Str : String) return String is
      Result : String (Str'Range);
      Index  : Integer := Result'First;
      C      : Integer := Str'First;
   begin
      while C <= Str'Last loop
         if Str (C) = '\' and then C < Str'Last then
            Result (Index) := Str (C + 1);
            C := C + 1;
         else
            Result (Index) := Str (C);
         end if;
         C     := C + 1;
         Index := Index + 1;
      end loop;
      return Result (Result'First .. Index - 1);
   end Unquote;

   ---------
   -- "=" --
   ---------

   function "=" (Addr1, Addr2 : Email_Address) return Boolean is
   begin
      return To_Lower (To_String (Addr1.Address))
        = To_Lower (To_String (Addr2.Address));
   end "=";

   ----------
   -- Hash --
   ----------

   function Hash (Addr : Email_Address) return Ada.Containers.Hash_Type is
   begin
      return Ada.Strings.Hash_Case_Insensitive (To_String (Addr.Address));
   end Hash;

   --------------------
   -- Get_Recipients --
   --------------------

   function Get_Recipients
     (Msg          : Message'Class;
      Include_From : Boolean := False)
      return Address_Set.Set
   is
      use Address_Set;
      Iter   : Header_Iterator := Get_Headers (Msg);
      H      : Header;
      Result : Address_Set.Set;
   begin
      loop
         Next (Iter, H => H);
         exit when H = Null_Header;
         if Get_Name (H) = "to"
           or else Get_Name (H) = "cc"
           or else Get_Name (H) = "resent-to"
           or else Get_Name (H) = "resent-cc"
           or else (Include_From and then Get_Name (H) = "from")
         then
            --  ??? Should avoid extra copy here
            Union (Result, Get_Recipients (H));
         end if;
      end loop;
      return Result;
   end Get_Recipients;

   --------------------
   -- Get_Recipients --
   --------------------

   function Get_Recipients (H : Header'Class) return Address_Set.Set is
   begin
      if H.Contents = null then
         return Address_Set.Empty_Set;
      else
         return Get_Addresses (H.Contents.Value);
      end if;
   end Get_Recipients;

   -------------
   -- Flatten --
   -------------

   procedure Flatten
     (List   : Charset_String_List.List;
      Result : out Unbounded_String)
   is
      use Charset_String_List;
      C      : Charset_String_List.Cursor := First (List);
   begin
      Result := Null_Unbounded_String;
      while Has_Element (C) loop
         Append (Result, Element (C).Contents);
         Next (C);
      end loop;
   end Flatten;

   ---------------
   -- To_String --
   ---------------

   procedure To_String
     (List   : Charset_String_List.List;
      Result : out Unbounded_String)
   is
      use Charset_String_List;
      C   : Charset_String_List.Cursor := First (List);
      Tmp : Unbounded_String;
   begin
      Result := Null_Unbounded_String;
      while Has_Element (C) loop
         Encode
           (Str     => To_String (Element (C).Contents),
            Charset => To_String (Element (C).Charset),
            Header  => True,
            Result  => Tmp);

         Append (Result, Tmp);
         Next (C);
      end loop;
   end To_String;

   -------------------------
   -- Domain_From_Address --
   -------------------------

   function Domain_From_Address (Email : String) return String is
   begin
      for E in Email'First .. Email'Last - 1 loop
         if Email (E) = '@' then
            return Email (E + 1 .. Email'Last);
         end if;
      end loop;
      return "";
   end Domain_From_Address;

   function Domain_From_Address (Email : Email_Address) return String is
   begin
      return Domain_From_Address (To_String (Email.Address));
   end Domain_From_Address;

   -----------------------
   -- Login_From_Address --
   ------------------------

   function Login_From_Address (Email : String) return String is
   begin
      for E in Email'First .. Email'Last loop
         if Email (E) = '@' then
            return Email (Email'First .. E - 1);
         end if;
      end loop;
      return Email;
   end Login_From_Address;

   function Login_From_Address (Email : Email_Address) return String is
   begin
      return Login_From_Address (To_String (Email.Address));
   end Login_From_Address;

   -----------------------------
   -- Quoted_Printable_Encode --
   -----------------------------

   procedure Quoted_Printable_Encode
     (Str                : String;
      Block_Prefix       : String  := "";
      Block_Suffix       : String  := "";
      Max_Block_Len      : Integer := 76;
      Quote_White_Spaces : Boolean;
      Header             : Boolean := False;
      Result             : out Unbounded_String)
   is
      function Compute_Block_Sep return String;
      function Compute_Block_Sep return String is
      begin
         if Header then
            return " ";
         else
            --  A soft line-break
            return "=" & ASCII.LF;
         end if;
      end Compute_Block_Sep;

      Block_Separator : constant String := Compute_Block_Sep;
      Start           : Integer := -1;
      Current_Len     : Natural := 0;
      Max             : constant Natural :=
                          Max_Block_Len - Block_Prefix'Length -
                            Block_Suffix'Length;

      function Needs_Quoting
         (Char : Character; Is_EOL : Boolean) return Boolean;
      --  Return True if C needs to be quoted, False otherwise

      function Quote (Char : Character) return String;
      --  Encode a single character

      procedure Append (Substring : String; Splittable : Boolean);
      --  Append Substring to Result, taking into account the max line length.
      --  If Splittable is false, Substring cannot be cut

      -------------------
      -- Needs_Quoting --
      -------------------

      function Needs_Quoting
         (Char : Character; Is_EOL : Boolean) return Boolean
      is
      begin
         if Char = ' ' or else Char = ASCII.HT then
            return Is_EOL or else Quote_White_Spaces;

         elsif Char = '_' then
            return Header;

         else
            return Char = '='
              or else Char = '?'
              or else not (Character'Pos (Char) >= 32
                           and then Character'Pos (Char) <= 126);
         end if;
      end Needs_Quoting;

      -----------
      -- Quote --
      -----------

      function Quote (Char : Character) return String is
         P : Integer;
      begin
         if Header
           and then Quote_White_Spaces
           and then Char = ' '
         then
            return "_";
         end if;

         P := Character'Pos (Char);
         return "=" & Hex_Chars (P / 16) & Hex_Chars (P mod 16);
      end Quote;

      ------------
      -- Append --
      ------------

      procedure Append (Substring : String; Splittable : Boolean) is
         S : Integer := Substring'First;
      begin
         if Splittable then
            while Substring'Last - S + 1 > Max - Current_Len loop
               if Current_Len = 0 then
                  Append (Result, Block_Prefix);
               end if;

               Append
                 (Result,
                  Substring (S .. S + Max - Current_Len - 1));
               Append (Result, Block_Suffix & Block_Separator);

               S           := S + Max - Current_Len;
               Current_Len := 0;  --  We just started a new line
            end loop;

            if Current_Len = 0 then
               Append (Result, Block_Prefix);
            end if;

            Append (Result, Substring (S .. Substring'Last));
            Current_Len := Current_Len + Substring'Last - S + 1;

         else
            if Current_Len + Substring'Length > Max then
               if Current_Len /= 0 then
                  Append (Result, Block_Suffix & Block_Separator);
               end if;
               Current_Len := 0;
               Append (Result, Block_Prefix);
               Append (Result, Substring);
               Current_Len := Substring'Length;
            else
               if Current_Len = 0 then
                  Append (Result, Block_Prefix);
               end if;
               Append (Result, Substring);
               Current_Len := Current_Len + Substring'Length;
            end if;
         end if;
      end Append;

   begin
      Result := Null_Unbounded_String;

      for S in Str'Range loop
         if Needs_Quoting (Str (S), Is_EOL => S = Str'Last) then
            if Start /= -1 then
               Append (Str (Start .. S - 1), Splittable => True);
               Start := -1;
            end if;

            declare
               Q : constant String := Quote (Str (S));
            begin
               Append (Q, Splittable => False);
               Start := S + 1;
            end;

         else
            if Start = -1 then
               Start := S;
            end if;
         end if;
      end loop;

      if Start /= -1 then
         Append (Str (Start .. Str'Last), Splittable => True);
      end if;

      if Current_Len /= 0 then
         Append (Result, Block_Suffix);
      end if;
   end Quoted_Printable_Encode;

   -----------------------------
   -- Quoted_Printable_Decode --
   -----------------------------

   procedure Quoted_Printable_Decode
     (Str    : String;
      Result : out Unbounded_String;
      Header : Boolean := False)
   is
      Start  : Integer := -1;
      S      : Integer;

      function Is_Hex (Char : Character) return Boolean;
      --  Return true if Char is an hexa character

      ------------
      -- Is_Hex --
      ------------

      function Is_Hex (Char : Character) return Boolean is
      begin
         return Qp_Convert (Char) >= 0;
      end Is_Hex;

   begin
      S := Str'First;
      Result := Null_Unbounded_String;

      while S <= Str'Last loop
         if Str (S) = '_' and then Header then
            --  Encoded SPACE
            if Start /= -1 then
               Append (Result, Str (Start .. S - 1));
               Start := -1;
            end if;
            Append (Result, ' ');

         elsif Str (S) /= '=' then
            --  Regular character
            if Start = -1 then
               Start := S;
            end if;

         elsif Str (S) = '='
           and then S + 1 <= Str'Last
           and then Str (S + 1) = ASCII.LF
         then
            --  Soft line break
            if Start /= -1 then
               Append (Result, Str (Start .. S - 1));
               Start := -1;
            end if;
            S := S + 1;

         elsif S + 2 <= Str'Last
           and then Is_Hex (Str (S + 1))
           and then Is_Hex (Str (S + 2))
         then
            --  Valid quote sequence
            if Start /= -1 then
               Append (Result, Str (Start .. S - 1));
               Start := -1;
            end if;
            Append
              (Result,
               Character'Val
                 (Qp_Convert (Str (S + 1)) * 16 + Qp_Convert (Str (S + 2))));
            S := S + 2;

         else
            --  Invalid quote sequence. Leave it as is
            if Start /= -1 then
               Append (Result, Str (Start .. S - 1));
               Start := -1;
            end if;
         end if;

         S := S + 1;
      end loop;

      if Start /= -1 then
         Append (Result, Str (Start .. Str'Last));
      end if;
   end Quoted_Printable_Decode;

   -------------------
   -- Base64_Encode --
   -------------------

   procedure Base64_Encode
     (Str             : String;
      Block_Prefix    : String := "";
      Block_Suffix    : String := "";
      Block_Separator : String := "" & ASCII.LF;
      Max_Block_Len   : Integer := Integer'Last;
      Separate_Blocks : Boolean := False;
      Result          : out Unbounded_String)
   is
      function Get_Line_Length return Integer;
      --  Get the line length for the encoded string

      function Get_Line_Length return Integer is
         Len : Integer := Integer'Min (76, Max_Block_Len);
      begin
         --  Do not cound prefix and suffix in line length
         Len := Len - Block_Prefix'Length - Block_Suffix'Length;

         --  Check that the line length is a multiple of 4 and make a shorter
         --  line if necessary
         if Separate_Blocks and then Len mod 4 /= 0 then
            Len := Len - Len mod 4;
         end if;

         --  At least 1 character in word, otherwise there's no point
         return Integer'Max (Len, 1);
      end Get_Line_Length;

      Line_Len : constant Integer := Get_Line_Length;

      --  Characters are grouped by 6 bits.
      --     4/3+1 => 8 bits represented by groups of 6 bits
      Bytes    : constant Integer := Str'Length * 4 / 3 + 1;

      --  A newline occurs every Line_Len char, and we have at least one
      Lines    : constant Integer := Bytes / Line_Len + 1;

      --  For each line, we have a Block_Separator, the prefix and a suffix
      --  Leave space for trailing == if needed
      --  For instance, 'b' gets encoded as 'Yg=='
      Len      : constant Integer :=
        Bytes
        + Lines * (Block_Separator'Length
                  + Block_Prefix'Length
                  + Block_Suffix'Length)
        + 2;

      --  Do not allocate on stack, since when using tasking this will often
      --  be too small.
      Output   : Ada.Strings.Unbounded.String_Access := new String (1 .. Len);
      Index    : Integer := Output'First;
      Left     : Unsigned_16 := 0;
      Leftbits : Natural := 0;
      Ch       : Mod64;
      Current  : Integer := 0;

      procedure Append (Ch : Character);
      --  Append a new character in the output, splitting lines as necessary

      procedure Append (Ch : Character) is
      begin
         if Current = 0 then
            Output (Index .. Index + Block_Prefix'Length - 1) :=
              Block_Prefix;
            Index := Index + Block_Prefix'Length;
         end if;

         Output (Index) := Ch;
         Index          := Index + 1;
         Current        := Current + 1;

         if Current = Line_Len then
            --  Suffix
            Output (Index .. Index + Block_Suffix'Length - 1) := Block_Suffix;
            Index := Index + Block_Suffix'Length;

            --  Separator
            Output (Index .. Index + Block_Separator'Length - 1) :=
              Block_Separator;
            Index := Index + Block_Separator'Length;

            Current := 0;
         end if;
      end Append;

   begin
      for S in Str'Range loop
         Left     := Shift_Left (Left, 8) or Character'Pos (Str (S));
         Leftbits := Leftbits + 8;

         while Leftbits >= 6 loop
            Ch        := Mod64 ((Shift_Right (Left, Leftbits - 6)) and 16#3F#);
            Leftbits  := Leftbits - 6;
            Append (To_Base64 (Ch));
         end loop;
      end loop;

      if Leftbits = 2 then
         Ch := Mod64 (Shift_Left (Left and 3, 4));
         Append (To_Base64 (Ch));
         Append ('=');
         Append ('=');

      elsif Leftbits = 4 then
         Ch := Mod64 (Shift_Left (Left and 16#F#, 2));
         Append (To_Base64 (Ch));
         Append ('=');
      end if;

      if Current = 0 then
         --  Remove last separator
         Index := Index - Block_Separator'Length;
      elsif Current > 0 then
         Output (Index .. Index + Block_Suffix'Length - 1) :=
           Block_Suffix;
         Index := Index + Block_Suffix'Length;
      end if;

      if Output'Last /= Index - 1 then
         Set_Unbounded_String (Result, Output (1 .. Index - 1));
      else
         Set_Unbounded_String (Result, Output.all);
      end if;

      Free (Output);
   end Base64_Encode;

   -------------------
   -- Base64_Decode --
   -------------------

   procedure Base64_Decode
     (Str    : String;
      Result : out Unbounded_String)
   is
      type Phase_Type is mod 4;
      --  We must use the heap rather than the stack here. In some
      --  cases, we'll be able to avoid a copy of the string anyway,
      --  and in case where this code is run in a multi-threaded
      --  application, the stack size is generally too small anyway
      Output   : Ada.Strings.Unbounded.String_Access :=
         new String (1 .. Str'Length * 6 / 8);
      Index    : Integer := Output'First;

      Phase    : Phase_Type := 0;
      D, Dlast : Byte := 0;
   begin
      for S in Str'First .. Str'Last loop
         if Str (S) = ASCII.LF
           or else Str (S) = ASCII.CR
         then
            Phase := 0;
            Dlast := 0;

         else
            D := Base64_Convert (Str (S));
            if D /= -1 then
               case Phase is
                  when 0 =>
                     Phase := Phase + 1;
                  when 1 =>
                     Output (Index) := Character'Val
                       (Dlast * 4 or ((D and 16#30#) / 16));
                     Index := Index + 1;
                     Phase := Phase + 1;
                  when 2 =>
                     Output (Index) := Character'Val
                       (((Dlast and 16#F#) * 16) or ((D and 16#3C#) / 4));
                     Index := Index + 1;
                     Phase := Phase + 1;
                  when 3 =>
                     Output (Index) := Character'Val
                       (((Dlast and 16#3#) * 64) or D);
                     Index := Index + 1;
                     Phase := 0;
               end case;

               Dlast := D;
            end if;
         end if;
      end loop;

      if Index - 1 = Output'Last then
         Set_Unbounded_String (Result, Output.all);
      else
         Set_Unbounded_String (Result, Output (Output'First .. Index - 1));
      end if;

      Free (Output);
   end Base64_Decode;

   ------------
   -- Encode --
   ------------

   procedure Encode
     (Str     : String;
      Charset : String := Charset_US_ASCII;
      Header  : Boolean := False;
      Result  : out Unbounded_String)
   is
      Encoding : Encoding_Type;
      Set      : constant String := To_Lower (Charset);
   begin
      --  Preferred encoding are the same as in Python
      if Set = Charset_US_ASCII then
         Encoding := Encoding_7bit;
      elsif Set = Charset_ISO_8859_1
        or else Set = "latin_1" or else Set = "latin-1"
        or else Set = Charset_ISO_8859_2
        or else Set = "latin_2" or else Set = "latin-2"
        or else Set = Charset_ISO_8859_3
        or else Set = "latin_3" or else Set = "latin-3"
        or else Set = Charset_ISO_8859_4
        or else Set = "latin_4" or else Set = "latin-4"
        or else Set = Charset_ISO_8859_9
        or else Set = "latin_5" or else Set = "latin-5"
        or else Set = Charset_ISO_8859_10
        or else Set = "latin_6" or else Set = "latin-6"
        or else Set = Charset_ISO_8859_13
        or else Set = "latin_7" or else Set = "latin-7"
        or else Set = Charset_ISO_8859_14
        or else Set = "latin_8" or else Set = "latin-8"
        or else Set = Charset_ISO_8859_15
        or else Set = "latin_9" or else Set = "latin-9"
        or else Set = Charset_Windows_1252
        or else Set = "viscii"
        or else Set = Charset_UTF_8 or else Set = "utf8"
      then
         Encoding := Encoding_QP;
      else
         Encoding := Encoding_Base64;
      end if;

      case Encoding is
         when Encoding_Base64 =>
            if Header then
               --  The encoded word payload should have a multiple of 4
               --  characters (see base64 spec), or else the encoded words will
               --  need to be concatenated before being base64 decoded,  and no
               --  parser will be able to handler that. This is why
               --  Separate_Blocks is True.
               Base64_Encode
                 (Str,
                  Block_Prefix    => "=?" & Set & "?b?",
                  Block_Suffix    => "?=",
                  Block_Separator => " ",
                  Max_Block_Len   => 75,
                  Separate_Blocks => True,
                  Result          => Result);
            else
               Base64_Encode (Str, Result => Result);
            end if;
         when Encoding_QP =>
            if Header then
               Quoted_Printable_Encode
                 (Str,
                  Block_Prefix       => "=?" & Set & "?q?",
                  Block_Suffix       => "?=",
                  Max_Block_Len      => 75,
                  Quote_White_Spaces => True,
                  Header             => Header,
                  Result             => Result);
            else
               Quoted_Printable_Encode
                 (Str,
                  Quote_White_Spaces => False,
                  Header             => Header,
                  Result             => Result);
            end if;
         when others =>
            Result := To_Unbounded_String (Str);
      end case;
   end Encode;

   -------------------
   -- Decode_Header --
   -------------------

   procedure Decode_Header
     (Str             : String;
      Default_Charset : String := Charset_US_ASCII;
      Result          : out Charset_String_List.List)
   is
      use Charset_String_List;
      Start    : Integer;
      Index    : Integer;
      Index2   : Integer;
      Section  : Charset_String;
      Encoding : Encoding_Type;
      S        : Integer;

      procedure Append (Section : Charset_String);
      --  Add Section to the result, merging with previous section if needed

      procedure Append (Section : Charset_String) is
      begin
         if Is_Empty (Result) then
            Append (Result, Section);
         else

            --  An empty section between two encoded ones must be
            --  ignored
            if Section.Charset /= Default_Charset
              and then Element (Last (Result)).Charset = Default_Charset
            then
               declare
                  Previous : constant Unbounded_String :=
                    Element (Last (Result)).Contents;
               begin
                  if Index_Non_Blank (Previous) < 1 then
                     Delete_Last (Result);
                  end if;
               end;
            end if;

            if not Is_Empty (Result)
              and then Section.Charset = Element (Last (Result)).Charset
            then
               Replace_Element
                 (Result,
                  Last (Result),
                  (Contents =>
                     Element (Last (Result)).Contents & Section.Contents,
                   Charset  => Section.Charset));
            else
               Append (Result, Section);
            end if;
         end if;
      end Append;

   begin
      Result := Charset_String_List.Empty_List;
      S     := Str'First;
      Start := Str'First;
      while S < Str'Last loop
         if Str (S) = '='
           and then S < Str'Last
           and then Str (S + 1) = '?'
         then
            Index := Next_Occurrence (Str (S + 2 .. Str'Last), '?');
            if Index < Str'Last then
               Section.Charset :=
                 To_Unbounded_String (To_Lower (Str (S + 2 .. Index - 1)));

               case To_Lower (Str (Index + 1)) is
                  when 'q'    => Encoding := Encoding_QP;
                  when 'b'    => Encoding := Encoding_Base64;
                  when others => Encoding := Encoding_7bit;
               end case;

               if Encoding /= Encoding_7bit
                 and then Index + 2 < Str'Last
               then
                  if Str (Index + 2) = '?' then
                     --  So far we have the prefix =?iso-8859-1?
                     Index2 := Index + 3;
                     Index := Next_Occurrence (Str (Index2 .. Str'Last), '?');
                     if Index < Str'Last and then Str (Index + 1) = '=' then
                        case Encoding is
                           when Encoding_QP   =>
                              Quoted_Printable_Decode
                                (Str (Index2 .. Index - 1),
                                 Header => True,
                                 Result => Section.Contents);
                           when Encoding_Base64 =>
                              Base64_Decode
                                (Str (Index2 .. Index - 1),
                                 Result => Section.Contents);
                           when others => null;
                        end case;

                        if Start <= S - 1 then
                           Append
                             ((Contents => To_Unbounded_String
                                 (Str (Start .. S - 1)),
                               Charset  =>
                                 To_Unbounded_String (Default_Charset)));
                        end if;

                        Append (Section);
                        S := Index + 2;
                        Start := S;
                     else
                        S := Index2;
                     end if;
                  else
                     S := Index + 1;
                  end if;
               else
                  S := Index + 1;
               end if;
            end if;
         end if;
         S := S + 1;
      end loop;

      if Start <= Str'Last then
         Append
           ((Contents => To_Unbounded_String (Str (Start .. Str'Last)),
             Charset  => To_Unbounded_String (Default_Charset)));
      end if;
   end Decode_Header;

   -------------------
   -- Get_Main_Type --
   -------------------

   function Get_Main_Type (MIME_Type : String) return String is
   begin
      for M in MIME_Type'Range loop
         if MIME_Type (M) = '/' then
            return MIME_Type (MIME_Type'First .. M - 1);
         end if;
      end loop;
      return MIME_Type;
   end Get_Main_Type;

   ------------------
   -- Get_Sub_Type --
   ------------------

   function Get_Sub_Type (MIME_Type : String) return String is
   begin
      for M in MIME_Type'Range loop
         if MIME_Type (M) = '/' then
            if M + 1 <= MIME_Type'Last then
               return MIME_Type (M + 1 .. MIME_Type'Last);
            else
               return "";
            end if;
         end if;
      end loop;
      return MIME_Type;
   end Get_Sub_Type;

end GNATCOLL.Email.Utils;
