#!/bin/bash
#
# firma v0.2: simple encrypted mailing list aliases
# feedback: rhatto@riseup.net | GPL
#
# list configuration is passed through a config file,
# where you put PARAMETER=value (whithout spaces)
#
# MAIL= path for mail program
# GPG= path for gnupg binary
# TMP= where you want the temp files
# LISTNAME= list email
# GPGDIR= gpg dir for the lists' keyring
# PASSWD= passwd for the lists' keyring
# FOOTER= message footer
# ALLOWSENDKEY = set to 1 if you want people automatically receive the list
#                key requesting through listname-request@example.tld
#                with subject: key
#
# design / todo:
#
# - list-request:
#     - key (allow send key)
#     - help
#     - subscribe: exchange pubkey
#     - unsubscribe
# - strings
# - check signatures
# - create list
# - archive (optional)
# - logfile (optional)
# - gpg --no-tty --display-charset --utf8-strings ?
#
# sintax: firma -c || firma config-file
#         -c: create a new list
#         config-file: parse the email from stdin
#         with the parameters specified in the
#         config-file 
#
# fix:
# 
# - special chars
# - id's recipient selection
# 

fuction _refresh_cache { 
  rm $1 $1.gpg
  touch $1; chmod 600 $1;
  touch $1.gpg; chmod 600 $TMP.gpg;
}

function _process_message {
  # get the headers
  FROM=$(grep -m 1 ^From: $1 | cut -f 2 -d :)
  DATE=$(grep -m 1 ^Date: $1)
  SUBJECT=$(grep -m 1 ^Subject: $1)

  # detect the encrypted message
  sed -n '/-----BEGIN PGP MESSAGE-----/,/-----END PGP MESSAGE-----/p' $1 >> $1.gpg

  # encrypting and sending for each recipient on the list
  for EMAIL in $($GPGLIST | grep pub | cut -d "<" -f 2 | sed -e 's/>//' | grep @ | grep -v $LISTNAME); do 

    echo "$PASSWD
    Message from: $FROM
    $SUBJECT
    $DATE

    $(echo "$PASSWD" | $GPGDECRYPT $1.gpg)

    ---
    $FOOTER 
    " | sed -e 's/=20$//' | $GPGENCRYPT $EMAIL | $MAIL -r $LISTNAME $EMAIL 
  done
}

function _process_request {

  # todo: support subjects like "key   ", etc
  FROM=$(grep -m 1 ^From: $1 | cut -f 2 -d :)
  REQUEST=$(grep -m 1 ^Subject: $1)
  if [[ $REQUEST == "key" ]]; then
    if [[ $ALLOWSENDKEY == 1 ]]; then  
      # send key to From: recipient
    else
      # dont send the key; return error message
    fi
  else if [[ $REQUEST == "subscribe" ]]; then
    # check if user put its pubkey and
    # ask the list for subscribe From: recipient
  else if [[ $REQUEST == "unsubscribe" ]]; then
    # unsubscribe and advise the list
  else
    # error message
  fi 

}

function _process {

  # eval the config file
  source $1

  GPGCOMMAND="$GPG -q --homedir $GPGDIR"
  GPGLIST="$GPGCOMMAND --list-keys" 
  GPGDECRYPT="$GPGCOMMAND --decrypt"
  GPGENCRYPT="$GPGCOMMAND --always-trust --hidden-recipient --textmode -e -s -a -r" 

  # clear the cache before read the message
  _refresh_cache $TMP

  # todo: use an array
  while read STDIN; do
    echo $STDIN >> $TMP
  done 

  # check with action is requested depending on the To: field
  TO=$(grep -m 1 ^To: $)
  if [[ $TO == $LISTNAME ]]; then _process_message $TMP;
  else _process_request $TMP;
  fi

  # clear after process
  _refresh_cache $TMP

}

function newlist {

  LISTHOME = 
  LISTNANE = 
  ...

  $GPGCOMMAND --gen-key

}

# check sintax
if [[ $1 = "-c" ]]; then
  _newlist;
else if [ -f $1 ];
  then _process $1;
else
  echo sintax: $0 [-c] [config-file];
fi

rm $TMP $TMP.gpg