/* -*- buffer-read-only: t -*- vi: set ro:
   THIS FILE IS GENERATED AUTOMATICALLY.  PLEASE DO NOT EDIT.
*/
#line 1 "header_rename.mf4"
/* Header rename functions                              -*- mfl -*-
   Copyright (C) 2010-2020 Sergey Poznyakoff

   This program 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 3, or (at your option)
   any later version.

   This program 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 program.  If not, see <http://www.gnu.org/licenses/>. */

module 'header_rename'.
require status

func header_rename(string name, string newname; number idx)
do
  if not $#>@idx
    set idx 1
  fi
  number msg current_message()
  try
  do
    string value message_find_header(msg, name, idx)
    header_delete(name, idx)
    header_add(newname, value)
  done
  catch e_range
  do
    pass
  done
done

/*
 * Prefixes all headers with the given NAME with PREFIX.
 * If PREFIX is not supplied, removes the matching headers.
 */
func header_prefix_all(string name; string prefix)
do
  number msg current_message()
  loop for number i message_header_count(msg, name),
       while i >= 1,
       set i i - 1
  do
    if $#>@prefix
      header_rename(name, prefix . name, i)
    else
      header_delete(name, i)
    fi
  done
done

/*
 * header_prefix_pattern(string pattern; string prefix)
 * ----------------------------------------------------
 * Prefixes all headers that match PATTERN with PREFIX
 *
 * Implementing such functionality faces considerable difficulties because
 * the milter API doesn't provide calls for iterating over all message
 * headers.
 * The basic algorithm is:
 *   1. get the list of available messages from the captured message
 *   2. for each header that matches pattern
 *   2.1.  save its value
 *   2.2.  delete that header
 *   2.3.  insert new header with the name constructed as concatenation
 *         or the prefix and original header name and value saved in 2.1
 *
 * The 2.3 should ideally preserve locations of the renamed headers.
 * However, that is impossible using the Milter API.  It was consented then
 * that it should preserve relative ordering of the renamed headers.
 *
 * The initial approach was to use header_add function.  Unfortunately, it
 * follows whimsical rules when selecting the position where to insert the
 * header.  Normally, headers are added to the end of the list.  However, if
 * a header with such name already exists, the new one is added before it.
 * The flags assigned to the header (H_USER and H_TRACE, in Sendmail) alter
 * that decision.  Consequently, using header_add produces unjustifiably
 * complex code.
 *
 * Then, there is header_insert.  Formally, it inserts the header at the given
 * index in the header list.  However, the header list it operates on is not
 * the list of headers as present in the message, but an opaque internal list
 * maintained in MTA, whose contents is unknown to the filter and is updated
 * after the filter finishes its job.  The only more or less reliable way of
 * using this call is with index 0, which is supposed to add the header at
 * the beginning of that internal list.  At least, this ensures that the
 * relative ordering of the renamed headers is preserved.
 * Obviously the renamed headers must be inserted in the reverse order.
 *
 * So, the modified algorithm is:
 *   1. Build a temporary list of headers that match the pattern.  Each
 *      element of the list contains the header name and its instance number.
 *      The list is sorted in reverse order: the last header in the message
 *      appears at the start of the list.
 *      Here, the difficulty is the lack of dictionary data type in MFL, so
 *      the list is built as colon-delimited list of header specifications.
 *      Each specification is HDR/N, where HDR is the header name and N is
 *      its instance number.
 *   2. Iterate over that list using the `string_list_iterate' macro.  For
 *      each element in the list
 *   2.1.  save the header value
 *   2.2.  delete that header
 *   2.3.  insert the renamed header in position 0.
 */
#pragma regex push +extended
func header_prefix_pattern(string pattern; string prefix)
do
  number msg current_message()
  number count message_header_count(msg)
  string h_list ':'

  loop for number i 1,
       while i <= count,
       set i i + 1
  do
    string name message_nth_header_name(msg, i)
    if name fnmatches pattern
      if h_list matches ".*:%name/([[:digit:]]+):.*"
	set h_list ":%name/" . (\1 + 1) . h_list
      else
        set h_list ":%name/1" . h_list 
      fi
    fi
  done

  if h_list matches '^:(.+):$'
    set h_list \1
  fi

  
#line 135
  if h_list != ""
#line 135
    
#line 135
    
#line 135
    loop for string __h_list_itr h_list . ":"
#line 135
              number __h_list_pos index(__h_list_itr, ":"),
#line 135
         while __h_list_pos != -1,
#line 135
         set __h_list_itr substr(__h_list_itr, __h_list_pos + 1)
#line 135
         set __h_list_pos index(__h_list_itr, ":")
#line 135
    do
#line 135
      set h_spec substr(__h_list_itr, 0, __h_list_pos)
#line 135
      
#line 135
  if h_spec matches "^(.+)/([[:digit:]]+)$"
#line 135
    string value message_find_header(msg, \1, \2)
#line 135
    header_delete(\1, \2)
#line 135
    if $#>@prefix
#line 135
      header_add(prefix . \1, value, 0)
#line 135
    fi
#line 135
  fi
#line 135
    done
#line 135
    
#line 135
    
#line 135
  fi
#line 143
done
  
#pragma regex pop