#! /bin/sh
#
# ircsink - send stdin to IRC
#
# SYNOPSIS
#   ircsink [--nick=NICK] [--port=PORT] [--secure]
#           --server=SERVER --target=TARGET
#
#   ircsink --help
#
# DESCRIPTION
#   ircsink sends lines from standard input to the specified IRC target.
#
#   --help
#
#   --nick=NICK (default: the system's host name)
#
#   --port=PORT (default: 6667, or 6697 if --secure is specified)
#
#   --secure
#     If specified, then the connection will be made using openssl.
#     Otherwise netcat will be used.
#
#   --server=SERVER
#
#   --target=TARGET
#     The target for receiving PRIVMSGs.
#     Can be either a channel's or a user's name.
#

set -efu

main() {(

  exec 3<&0

  _args=$(getopt -n "$0" -s sh \
      -l help,nick:,port:,secure,server:,target: \
      -- "$0" "$@")
  eval set -- "$_args"
  unset _args

  help=
  nick=
  port=
  secure=
  server=
  target=
  while :; do
    case $1 in
      --help) help=1; shift;;
      --nick) nick=$2; shift 2;;
      --port) port=$2; shift 2;;
      --secure) secure=1; shift;;
      --server) server=$2; shift 2;;
      --target) target=$2; shift 2;;
      --) shift; break;;
    esac
  done
  case $# in
    0) :;;
    1) echo "$0: bad argument: $*" >&2; exit 1;;
    *) echo "$0: bad arguments: $*" >&2; exit 1;;
  esac

  if test "$help" = 1; then
    print_help
    exit
  fi

  if test -t 3; then
    echo "$0: error: ircsink cannot be used interactively" >&2
    exit 1
  fi

  if test -z "$nick"; then
    nick=$(hostname)
  fi

  if test -z "$port"; then
    case $secure in
      '') port=6667;;
      1) port=6697;;
      *)
        echo "$0: missing argument: --port" >&2
        exit 1
        ;;
    esac
  fi

  if test -z "$server"; then
    echo "$0: missing argument: --server" >&2
    exit 1
  fi

  if test -z "$target"; then
    echo "$0: missing argument: --target" >&2
    exit 1
  fi

  is_channel() {
    case $1 in
      \#*) :;;
      *) ! :;;
    esac
  }

  # echo2 and cat2 are used output to both, stdout and stderr
  # This is used to see what we send to the irc server. (debug output)
  echo2() { echo "$*"; echo "$*" >&2; }
  cat2() {
    awk '{
      print $0
      print $0 > "/dev/stderr"
    }'
  }

  # privmsg_cat transforms stdin to a privmsg
  privmsg_cat() {
    awk -v target="$target" '{ print "PRIVMSG "target" :"$0 }'
  }

  ircat() {
    if test "$secure" = 1; then
      openssl s_client -connect "$server:$port"
    else
      nc "$server" "$port"
    fi
  }

  # ircin is used to feed the output of netcat back to the "irc client"
  # so we can implement expect-like behavior with sed^_^
  # XXX mkselfdestructingtmpfifo would be nice instead of this cruft
  tmpdir=$(mktemp --tmpdir -d ircsink_XXXXXXXX)
  cd "$tmpdir"
  mkfifo ircin
  trap cleanup EXIT
  cleanup() {
    trap - EXIT
    rm ircin
    cd "$OLDPWD"
    rmdir "$tmpdir"
  }

  {
    echo2 "USER $LOGNAME 0 * :$LOGNAME@$(hostname)"
    echo2 "NICK $nick"

    sed -nru '
      # wait for MODE message
      /^:[^ ]* MODE /q

      # answer any PING messages while waiting
      s/^PING (:.*)/PONG \1/p
    '

    if is_channel "$target"; then
      echo2 "JOIN $target"
    fi

    privmsg_cat <&3 \
      | cat2

    if is_channel "$target"; then
      echo2 "PART $target"

      # wait for PART confirmation
      sed -n '/:'"$nick"'![^ ]* PART /q'
    fi

    echo2 'QUIT :Gone to have lunch'
  } < ircin \
    | ircat | tee -a ircin
)}

print_help() {
  sed -nr '
    0,/^$/{
      /^#!/d
      s/^#($| )//p
    }
  ' "$0"
}

main "$@"