#!/bin/sh
#
# ack-recipients – require double-checking of some recipients
#
# refuse to send a mail as long as recipients listed in ~/.mutt/ack-recipients
# are not individually "signed-off" by adding their e-mail addresses to the
# X-Acked header. This header is removed from the mail before it is sent.
#
# The file ~/.mutt/ack-recipients stores sha256sums of lower-cased e-mail
# addresses (no newline) instead of the addresses themselves as a measure to
# protect privacy. You can get new lines like this:
#
#   printf my.new@e-mail.addre.ss | tr '[[:upper:]]' '[[:lower:]]' \
#     | sha256sum | sed -e 's, .*,,'
#
# E.g. my address (see below) will become
#   84d5b33c9376f67274c2ec9ce0e03b6973fb8bc943ebd7abb470c903c47e00f4
#
# Copyright © 2010 martin f. krafft <madduck@madduck.net>
# Released under the terms of the Artistic Licence 2.0
#
set -eu

CHECKLIST="$HOME/.mutt/ack-recipients"
HEADER=X-Acked
ACKED_RCPTS=$(formail -czx ${HEADER}: < $1 | tr -d ',' | tr '[[:upper:]]' '[[:lower:]]')
MAILFILE="$1"; shift

ret=0
for r in $@; do
  ack=0
  # check if this recipient is in the list of acked recipients
  rl=$(printf $r | tr '[[:upper:]]' '[[:lower:]]')
  for a in $ACKED_RCPTS; do [ $a = $rl ] && ack=1 && break; done
  rs=$(printf $rl | sha256sum)
  # now check if this unacked recipient needs to be acked
  if [ $ack -eq 0 ] && grep -q "^${rs%% *}$" "$CHECKLIST"; then
    echo >&2 "E: will not send mail until $r has been added to the $HEADER header"
    ret=1
  fi
done

[ $ret -eq 0 ] || exit $ret

# now remove the X-Acked header from the mail
TMPFILE=$(mktemp --tmpdir mutt-sendmail.XXXXXXXXXX.msg)
settrap () { trap "$@" 0 1 2 3 4 5 6 7 8 10 11 12 13 14 15; }
cleanup () { rm -f "$TMPFILE"; settrap -; }
settrap cleanup
formail -I ${HEADER}: < "$MAILFILE" > "$TMPFILE"
mv "$TMPFILE" "$MAILFILE"
settrap -