dobroho_vechora/dobroho_vechora.bash

#!/bin/bash
set -e

mode="${1}"
ip="${2}"
port="${3}"
nick="${4}"

print_usage() {
	echo "${1}"
	echo "${0} <MODE> <IP> <PORT> [NICK]"
	echo "Modes: interactive (intr), send, receive (rec)"
	exit
}
[ -z "${ip}" ]   && print_usage 'No IP given.'
[ -z "${port}" ] && print_usage 'No port given.'
[ -z "${5}" ]    || print_usage 'Too many arguments.'

[ -z "${nick}" ] || nick="<${nick}> "

open_socket() {
	exec 3<> "/dev/tcp/${ip}/${port}"
}

close_socket() {
	exec 3>&-
}

send_message() {
	open_socket
	echo "${1}" >&3
	close_socket
}

get_message() {
	open_socket
	echo "${1}" >&3
	cat <&3 || true
	close_socket
}

case "${mode}" in
	intr | interactive)
		;;
	send)
		open_socket
		text="${nick}$(cat)"
		send_message "0${text}"
		close_socket
		exit
		;;
	rec | receive)
		length="$(get_message 1)"
		open_socket
		echo -n 2 >&3
		head -c "${length}" <&3 
		close_socket
		exit
		;;
	*)
		echo Unknown mode
		exit
esac

encrypt() {
	if [ "${enc}" -eq 0 ] || [ -z "${DOBROHO_VECHORA_ENCRYPTION_PASSWORD}" ]; then
		cat
		return 0
	fi
	echo "ENCRYPTED"'!'"<$(openssl enc -pbkdf2 -a -aes256 -pass env:DOBROHO_VECHORA_ENCRYPTION_PASSWORD)>"
}

decrypt() {
	if [ "${enc}" -eq 0 ] || [ -z "${DOBROHO_VECHORA_ENCRYPTION_PASSWORD}" ]; then
		cat
		return 0
	fi
	while IFS="" read -r i || [ -n "${i}" ]
	do
		echo "${i}"
		cipher="$(echo "${i}" | grep -Po 'ENCRYPTED!<\K([a-zA-Z0-9\=\+\/]*)(?=\>)')" || :
		if [ -n "${cipher}" ]; then
			echo -n "Decrypted: "
			echo "${cipher}" | openssl enc -pbkdf2 -d -a -aes256 -pass env:DOBROHO_VECHORA_ENCRYPTION_PASSWORD || :
		fi
	done
}

print_messages() {
	open_socket
	echo -n 2 >&3
	head -c "${1}" <&3 | decrypt | sed -e 's/\x1B/ESC/g' 
	close_socket
}

wait_for_messages() {
	tmp=0
	trap 'tmp=1' INT
	oldlength="${length}"
	while :; do
		length="$(get_message 1)"
		if [ "${oldlength}" -ne "${length}" ]; then
			trap - INT
			return 0
		fi
		if [ "${tmp}" -eq 1 ]; then
			trap - INT
			return 1
		fi
		echo -n .
		sleep 1
	done
}

length=0
enc=0
while :; do
	read cmd
	case "${cmd}" in
		I)
			tmp="$(mktemp)"
			"${VISUAL:-"${EDITOR:-"$(which vi)"}"}" "${tmp}"
			[ -s "${tmp}" ] && send_message 0"${nick}$(cat "${tmp}" | encrypt)"
			rm "${tmp}"
			;;
		i)
			read a
			send_message 0"${nick}$(echo "${a}" | encrypt)"
			;;
		L)
			length="$(get_message 1)"
			;;
		l)
			echo "${length}"
			;;
		w)
			wait_for_messages &&
			{
				echo
				print_messages "${length}"
				if [ -n "${DOBROHO_VECHORA_ON_WAIT}" ]; then
					${DOBROHO_VECHORA_ON_WAIT}
				fi
			}
			;;
		p)
			length="$(get_message 1)"
			print_messages "${length}"
			;;
		q)
			exit
			;;
		E)
			read -s DOBROHO_VECHORA_ENCRYPTION_PASSWORD
			export DOBROHO_VECHORA_ENCRYPTION_PASSWORD
			;;
		e)
			if [ "${enc}" -eq 0 ]; then
				enc=1
				echo 1
			else
				enc=0
				echo 0
			fi
			;;
		*)
			echo '?'
			;;
	esac
done