#!/usr/bin/env python3
libexec_dir = __LIBEXECDIR__

import select
import socket
import subprocess
import sys
import threading
import time

class Channel:
	"""An asynchronic communication channel that can be used to send python object and can be poll()ed."""

	def __init__(self):
		# We use a socket to enable polling and blocking reads
		self.write_socket, self.read_socket = socket.socketpair()
		self.poll = select.poll()
		self.poll.register(self.read_socket, select.POLLIN)

		# Store messages in a list
		self.messages = []
		self.messages_lock = threading.Lock()

	def send(self, message):
		# Add message to the list of messages and write to the write socket to signal there's data to read
		with self.messages_lock:
			self.write_socket.sendall(b'!')
			self.messages.append(message)

	def recv(self, blocking = True):
		# Timeout of -1 will make poll wait until data is available
		# Timeout of 0 will make poll exit immediately if there's no data
		if blocking:
			timeout = -1
		else:
			timeout = 0

		# See if there is data to read / wait until there is
		results = self.poll.poll(timeout)

		# None of the sockets were ready. This can only happen if we weren't blocking
		# Return None to signal lack of data
		if len(results) == 0:
			assert not blocking
			return None

		# Remove first message from the list (FIFO principle), and read one byte from the socket
		# This keeps the number of available messages and the number of bytes readable in the socket in sync
		with self.messages_lock:
			message = self.messages.pop(0)
			self.read_socket.recv(1)

		return message

	def fileno(self):
		# Allows for a Channel object to be passed directly to poll()
		return self.read_socket.fileno()

	def close(self):
		# Close the file descriptors, so that we aren't leaking them
		self.write_socket.close()
		self.read_socket.close()

	# Support with-statements
	def __enter__(self):
		return self

	def __exit__(self, exception_type, exception_value, traceback):
		self.close()

def writeall(f, b):
	written = 0
	while written < len(b):
		written += f.write(b[written:])

def parse_mac(text):
	parts = text.split(':')
	if len(parts) != 6:
		raise ValueError('Invalid MAC format: %s' % text)

	try:
		parsed = bytes(int(field, 16) for field in parts)
	except ValueError:
		raise ValueError('Invalid MAC format %s' % text)

	return parsed

class PollBasedThread(threading.Thread):
	def run(self):
		poll = select.poll()
		for f in self.pollin:
			poll.register(f, select.POLLIN)

		self.initialize()

		running = True
		while running:
			for fd, event in poll.poll():
				if self.poll_loop(fd, event) != None:
					running = False

		self.finalize()

	def initialize(self):
		...

	def poll_loop(self, fd, event):
		...

	def finalize(self):
		...

class Backend(PollBasedThread):
	def __init__(self, writes_channel, control_channel):
		self.writes_channel = writes_channel
		self.control_channel = control_channel
		self.pollin = [self.writes_channel, self.control_channel]
		super().__init__()

	def initialize(self):
		self.proc = subprocess.Popen(['sudo', libexec_dir + '/ethermess-backend', *sys.argv[1:]], stdin = subprocess.PIPE, stdout = sys.stdout, stderr = sys.stderr, bufsize = 0)

	def poll_loop(self, fd, event):
		if fd == self.writes_channel.fileno() and event & select.POLLIN:
			data = self.writes_channel.recv()
			writeall(self.proc.stdin, data)

		elif fd == self.control_channel.fileno() and event & select.POLLIN:
			command = self.control_channel.recv()
			if command == 'quit':
				return 'quit'

			else:
				raise Exception('Unreachable')

		else:
			raise Exception('Unreachable')

	def finalize(self):
		self.proc.wait()

class Input(threading.Thread):
	def __init__(self, writes_channel, control_channel):
		self.writes_channel = writes_channel
		self.control_channel = control_channel
		super().__init__()

	def run(self):
		print('s - request status, i - request msgid, m - send message, ^D - quit')

		while True:
			try:
				try:
					command = input('')

					if command == 's':
						mac = parse_mac(input('mac> '))
						self.writes_channel.send(b's' + mac)

					elif command == 'i':
						mac = parse_mac(input('mac> '))
						self.writes_channel.send(b'i' + mac)

					elif command == 'm':
						mac = parse_mac(input('mac> '))
						message = input('message> ').encode('utf-8')
						self.writes_channel.send(b'm' + mac + bytes([len(message) >> 8, len(message) & 0xff]) + message)

					else:
						print('s - request status, i - request msgid, m - send message, ^D - quit')

				except EOFError:
					self.writes_channel.send(b'q')
					self.control_channel.send('quit')
					break

			except Exception as err:
				print(err)

writes_channel = Channel()
control_channel = Channel()

nick = input('nick> ').encode('utf-8')
writes_channel.send((bytes([0, len(nick)]) + nick))

Backend(writes_channel, control_channel).start()
Input(writes_channel, control_channel).start()