import aiohttp
import aiohttp.web
import asyncio
import base64
import collections
import concurrent.futures
import logging
import os.path
import signal
import ssl
import string
import sys
import toml


SSL_CONTEXTS = {'yes': True, 'no': False, 'insecure': ssl.SSLContext()}


class InvalidConfig(Exception):
	'''Error in configuration file'''


def is_valid_pem(path, withCert):
	'''Very basic check whether something looks like a valid PEM certificate'''
	try:
		with open(path, 'rb') as fp:
			contents = fp.read()

		# All of these raise exceptions if something's wrong...
		if withCert:
			assert contents.startswith(b'-----BEGIN CERTIFICATE-----\n')
			endCertPos = contents.index(b'-----END CERTIFICATE-----\n')
			base64.b64decode(contents[28:endCertPos].replace(b'\n', b''), validate = True)
			assert contents[endCertPos + 26:].startswith(b'-----BEGIN PRIVATE KEY-----\n')
		else:
			assert contents.startswith(b'-----BEGIN PRIVATE KEY-----\n')
			endCertPos = -26 # Please shoot me.
		endKeyPos = contents.index(b'-----END PRIVATE KEY-----\n')
		base64.b64decode(contents[endCertPos + 26 + 28: endKeyPos].replace(b'\n', b''), validate = True)
		assert contents[endKeyPos + 26:] == b''
		return True
	except: # Yes, really
		return False


class Config(dict):
	def __init__(self, filename):
		super().__init__()
		self._filename = filename

		with open(self._filename, 'r') as fp:
			obj = toml.load(fp)

		logging.info(repr(obj))

		# Sanity checks
		if any(x not in ('logging', 'irc', 'web', 'maps') for x in obj.keys()):
			raise InvalidConfig('Unknown sections found in base object')
		if any(not isinstance(x, collections.abc.Mapping) for x in obj.values()):
			raise InvalidConfig('Invalid section type(s), expected objects/dicts')
		if 'logging' in obj:
			if any(x not in ('level', 'format') for x in obj['logging']):
				raise InvalidConfig('Unknown key found in log section')
			if 'level' in obj['logging'] and obj['logging']['level'] not in ('DEBUG', 'INFO', 'WARNING', 'ERROR'):
				raise InvalidConfig('Invalid log level')
			if 'format' in obj['logging']:
				if not isinstance(obj['logging']['format'], str):
					raise InvalidConfig('Invalid log format')
				try:
					#TODO: Replace with logging.Formatter's validate option (3.8+); this test does not cover everything that could be wrong (e.g. invalid format spec or conversion)
					# This counts the number of replacement fields. Formatter.parse yields tuples whose second value is the field name; if it's None, there is no field (e.g. literal text).
					assert sum(1 for x in string.Formatter().parse(obj['logging']['format']) if x[1] is not None) > 0
				except (ValueError, AssertionError) as e:
					raise InvalidConfig('Invalid log format: parsing failed') from e
		if 'irc' in obj:
			if any(x not in ('host', 'port', 'ssl', 'nick', 'real', 'certfile', 'certkeyfile') for x in obj['irc']):
				raise InvalidConfig('Unknown key found in irc section')
			if 'host' in obj['irc'] and not isinstance(obj['irc']['host'], str): #TODO: Check whether it's a valid hostname
				raise InvalidConfig('Invalid IRC host')
			if 'port' in obj['irc'] and (not isinstance(obj['irc']['port'], int) or not 1 <= obj['irc']['port'] <= 65535):
				raise InvalidConfig('Invalid IRC port')
			if 'ssl' in obj['irc'] and obj['irc']['ssl'] not in ('yes', 'no', 'insecure'):
				raise InvalidConfig(f'Invalid IRC SSL setting: {obj["irc"]["ssl"]!r}')
			if 'nick' in obj['irc'] and not isinstance(obj['irc']['nick'], str): #TODO: Check whether it's a valid nickname
				raise InvalidConfig('Invalid IRC nick')
			if 'real' in obj['irc'] and not isinstance(obj['irc']['real'], str):
				raise InvalidConfig('Invalid IRC realname')
			if ('certfile' in obj['irc']) != ('certkeyfile' in obj['irc']):
				raise InvalidConfig('Invalid IRC cert config: needs both certfile and certkeyfile')
			if 'certfile' in obj['irc']:
				if not isinstance(obj['irc']['certfile'], str):
					raise InvalidConfig('Invalid certificate file: not a string')
				if not os.path.isfile(obj['irc']['certfile']):
					raise InvalidConfig('Invalid certificate file: not a regular file')
				if not is_valid_pem(obj['irc']['certfile'], True):
					raise InvalidConfig('Invalid certificate file: not a valid PEM cert')
			if 'certkeyfile' in obj['irc']:
				if not isinstance(obj['irc']['certkeyfile'], str):
					raise InvalidConfig('Invalid certificate key file: not a string')
				if not os.path.isfile(obj['irc']['certkeyfile']):
					raise InvalidConfig('Invalid certificate key file: not a regular file')
				if not is_valid_pem(obj['irc']['certkeyfile'], False):
					raise InvalidConfig('Invalid certificate key file: not a valid PEM key')
		if 'web' in obj:
			if any(x not in ('host', 'port') for x in obj['web']):
				raise InvalidConfig('Unknown key found in web section')
			if 'host' in obj['web'] and not isinstance(obj['web']['host'], str): #TODO: Check whether it's a valid hostname (must resolve I guess?)
				raise InvalidConfig('Invalid web hostname')
			if 'port' in obj['web'] and (not isinstance(obj['web']['port'], int) or not 1 <= obj['web']['port'] <= 65535):
				raise InvalidConfig('Invalid web port')
		if 'maps' in obj:
			for key, map_ in obj['maps'].items():
				if not isinstance(key, str) or not key:
					raise InvalidConfig(f'Invalid map key {key!r}')
				if not isinstance(map_, collections.abc.Mapping):
					raise InvalidConfig(f'Invalid map for {key!r}')
				if any(x not in ('webpath', 'ircchannel', 'auth') for x in map_):
					raise InvalidConfig(f'Unknown key(s) found in map {key!r}')
				#TODO: Check values

		# Default values
		finalObj = {'logging': {'level': 'INFO', 'format': '{asctime} {levelname} {message}'}, 'irc': {'host': 'irc.hackint.org', 'port': 6697, 'ssl': 'yes', 'nick': 'h2ibot', 'real': 'I am an http2irc bot.', 'certfile': None, 'certkeyfile': None}, 'web': {'host': '127.0.0.1', 'port': 8080}, 'maps': {}}

		# Fill in default values for the maps
		for key, map_ in obj['maps'].items():
			if 'webpath' not in map_:
				map_['webpath'] = f'/{key}'
			if 'ircchannel' not in map_:
				map_['ircchannel'] = f'#{key}'
			if 'auth' not in map_:
				map_['auth'] = False

		# Merge in what was read from the config file and set keys on self
		for key in ('logging', 'irc', 'web', 'maps'):
			if key in obj:
				finalObj[key].update(obj[key])
			self[key] = finalObj[key]

	def __repr__(self):
		return f'<Config(logging={self["logging"]!r}, irc={self["irc"]!r}, web={self["web"]!r}, maps={self["maps"]!r})>'

	def reread(self):
		return Config(self._filename)


class MessageQueue:
	# An object holding onto the messages received from nodeping
	# This is effectively a reimplementation of parts of asyncio.Queue with some specific additional code.
	# Unfortunately, asyncio.Queue's extensibility (_init, _put, and _get methods) is undocumented, so I don't want to rely on that.
	# Differences to asyncio.Queue include:
	#  - No maxsize
	#  - No put coroutine (not necessary since the queue can never be full)
	#  - Only one concurrent getter
	#  - putleft_nowait to put to the front of the queue (so that the IRC client can put a message back when delivery fails)

	def __init__(self):
		self._getter = None  # None | asyncio.Future
		self._queue = collections.deque()

	async def get(self):
		if self._getter is not None:
			raise RuntimeError('Cannot get concurrently')
		if len(self._queue) == 0:
			self._getter = asyncio.get_running_loop().create_future()
			logging.debug('Awaiting getter')
			try:
				await self._getter
			except asyncio.CancelledError:
				logging.debug('Cancelled getter')
				self._getter = None
				raise
			logging.debug('Awaited getter')
			self._getter = None
		# For testing the cancellation/putting back onto the queue
		#logging.debug('Delaying message queue get')
		#await asyncio.sleep(3)
		#logging.debug('Done delaying')
		return self.get_nowait()

	def get_nowait(self):
		if len(self._queue) == 0:
			raise asyncio.QueueEmpty
		return self._queue.popleft()

	def put_nowait(self, item):
		self._queue.append(item)
		if self._getter is not None and not self._getter.cancelled():
			self._getter.set_result(None)

	def putleft_nowait(self, *item):
		self._queue.extendleft(reversed(item))
		if self._getter is not None and not self._getter.cancelled():
			self._getter.set_result(None)

	def qsize(self):
		return len(self._queue)


class IRCClientProtocol(asyncio.Protocol):
	def __init__(self, messageQueue, connectionClosedEvent, loop, config, channels):
		logging.debug(f'Protocol init {id(self)}: {messageQueue} {id(messageQueue)}, {connectionClosedEvent}, {loop}')
		self.messageQueue = messageQueue
		self.connectionClosedEvent = connectionClosedEvent
		self.loop = loop
		self.config = config
		self.buffer = b''
		self.connected = False
		self.channels = channels # Currently joined/supposed-to-be-joined channels; set(str)
		self.unconfirmedMessages = []
		self.pongReceivedEvent = asyncio.Event()

	def connection_made(self, transport):
		logging.info('Connected')
		self.transport = transport
		self.connected = True
		nickb = self.config['irc']['nick'].encode('utf-8')
		self.send(b'NICK ' + nickb)
		self.send(b'USER ' + nickb + b' ' + nickb + b' ' + nickb + b' :' + self.config['irc']['real'].encode('utf-8'))

	def update_channels(self, channels: set):
		channelsToPart = self.channels - channels
		channelsToJoin = channels - self.channels
		self.channels = channels

		if self.connected:
			if channelsToPart:
				#TODO: Split if too long
				self.send(b'PART ' + ','.join(channelsToPart).encode('utf-8'))
			if channelsToJoin:
				self.send(b'JOIN ' + ','.join(channelsToJoin).encode('utf-8'))

	def send(self, data):
		logging.info(f'Send: {data!r}')
		self.transport.write(data + b'\r\n')

	async def _get_message(self):
		logging.debug(f'Message queue {id(self.messageQueue)} length: {self.messageQueue.qsize()}')
		messageFuture = asyncio.create_task(self.messageQueue.get())
		done, pending = await asyncio.wait((messageFuture, self.connectionClosedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
		if self.connectionClosedEvent.is_set():
			if messageFuture in pending:
				logging.debug('Cancelling messageFuture')
				messageFuture.cancel()
				try:
					await messageFuture
				except asyncio.CancelledError:
					logging.debug('Cancelled messageFuture')
					pass
			else:
				# messageFuture is already done but we're stopping, so put the result back onto the queue
				self.messageQueue.putleft_nowait(messageFuture.result())
			return None, None
		assert messageFuture in done, 'Invalid state: messageFuture not in done futures'
		return messageFuture.result()

	async def send_messages(self):
		while self.connected:
			logging.debug(f'{id(self)}: trying to get a message')
			channel, message = await self._get_message()
			logging.debug(f'{id(self)}: got message: {message!r}')
			if message is None:
				break
			#TODO Split if the message is too long.
			self.unconfirmedMessages.append((channel, message))
			self.send(b'PRIVMSG ' + channel.encode('utf-8') + b' :' + message.encode('utf-8'))
			await asyncio.sleep(1) # Rate limit

	async def confirm_messages(self):
		while self.connected:
			await asyncio.wait((asyncio.sleep(60), self.connectionClosedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)  # Confirm once per minute
			if not self.connected: # Disconnected while sleeping, can't confirm unconfirmed messages, requeue them directly
				self.messageQueue.putleft_nowait(*self.unconfirmedMessages)
				self.unconfirmedMessages = []
				break
			if not self.unconfirmedMessages:
				logging.debug(f'{id(self)}: no messages to confirm')
				continue
			logging.debug(f'{id(self)}: trying to confirm message delivery')
			self.pongReceivedEvent.clear()
			self.send(b'PING :42')
			await asyncio.wait((asyncio.sleep(5), self.pongReceivedEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			logging.debug(f'{id(self)}: message delivery success: {self.pongReceivedEvent.is_set()}')
			if not self.pongReceivedEvent.is_set():
				# No PONG received in five seconds, assume connection's dead
				self.messageQueue.putleft_nowait(*self.unconfirmedMessages)
				self.transport.close()
			self.unconfirmedMessages = []

	def data_received(self, data):
		logging.debug(f'Data received: {data!r}')
		# Split received data on CRLF. If there's any data left in the buffer, prepend it to the first message and process that.
		# Then, process all messages except the last one (since data might not end on a CRLF) and keep the remainder in the buffer.
		# If data does end with CRLF, all messages will have been processed and the buffer will be empty again.
		messages = data.split(b'\r\n')
		if self.buffer:
			self.message_received(self.buffer + messages[0])
			messages = messages[1:]
		for message in messages[:-1]:
			self.message_received(message)
		self.buffer = messages[-1]

	def message_received(self, message):
		logging.info(f'Message received: {message!r}')
		if message.startswith(b':'):
			# Prefixed message, extract command + parameters (the prefix cannot contain a space)
			message = message.split(b' ', 1)[1]
		if message.startswith(b'PING '):
			self.send(b'PONG ' + message[5:])
		elif message.startswith(b'PONG '):
			self.pongReceivedEvent.set()
		elif message.startswith(b'001 '):
			# Connection registered
			self.send(b'JOIN ' + ','.join(self.channels).encode('utf-8')) #TODO: Split if too long
			asyncio.create_task(self.send_messages())
			asyncio.create_task(self.confirm_messages())

	def connection_lost(self, exc):
		logging.info('The server closed the connection')
		self.connected = False
		self.connectionClosedEvent.set()


class IRCClient:
	def __init__(self, messageQueue, config):
		self.messageQueue = messageQueue
		self.config = config
		self.channels = {map_['ircchannel'] for map_ in config['maps'].values()}

		self._transport = None
		self._protocol = None

	def update_config(self, config):
		needReconnect = self.config['irc'] != config['irc']
		self.config = config
		if self._transport: # if currently connected:
			if needReconnect:
				self._transport.close()
			else:
				self.channels = {map_['ircchannel'] for map_ in config['maps'].values()}
				self._protocol.update_channels(self.channels)

	def _get_ssl_context(self):
		ctx = SSL_CONTEXTS[self.config['irc']['ssl']]
		if self.config['irc']['certfile'] and self.config['irc']['certkeyfile']:
			if ctx is True:
				ctx = ssl.create_default_context()
			if isinstance(ctx, ssl.SSLContext):
				ctx.load_cert_chain(self.config['irc']['certfile'], keyfile = self.config['irc']['certkeyfile'])
		return ctx

	async def run(self, loop, sigintEvent):
		connectionClosedEvent = asyncio.Event()
		while True:
			connectionClosedEvent.clear()
			try:
				self._transport, self._protocol = await loop.create_connection(lambda: IRCClientProtocol(self.messageQueue, connectionClosedEvent, loop, self.config, self.channels), self.config['irc']['host'], self.config['irc']['port'], ssl = self._get_ssl_context())
				try:
					await asyncio.wait((connectionClosedEvent.wait(), sigintEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
				finally:
					self._transport.close() #TODO BaseTransport.close is asynchronous and then triggers the protocol's connection_lost callback; need to wait for connectionClosedEvent again perhaps to correctly handle ^C?
			except (ConnectionRefusedError, asyncio.TimeoutError) as e:
				logging.error(str(e))
			await asyncio.wait((asyncio.sleep(5), sigintEvent.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			if sigintEvent.is_set():
				break


class WebServer:
	def __init__(self, messageQueue, config):
		self.messageQueue = messageQueue
		self.config = config

		self._paths = {} # '/path' => ('#channel', auth)  where auth is either False (no authentication) or the HTTP header value for basic auth

		self._app = aiohttp.web.Application()
		self._app.add_routes([aiohttp.web.post('/{path:.+}', self.post)])

		self.update_config(config)
		self._configChanged = asyncio.Event()

	def update_config(self, config):
		self._paths = {map_['webpath']: (map_['ircchannel'], f'Basic {base64.b64encode(map_["auth"].encode("utf-8")).decode("utf-8")}' if map_['auth'] else False) for map_ in config['maps'].values()}
		needRebind = self.config['web'] != config['web']
		self.config = config
		if needRebind:
			self._configChanged.set()

	async def run(self, stopEvent):
		while True:
			runner = aiohttp.web.AppRunner(self._app)
			await runner.setup()
			site = aiohttp.web.TCPSite(runner, self.config['web']['host'], self.config['web']['port'])
			await site.start()
			await asyncio.wait((stopEvent.wait(), self._configChanged.wait()), return_when = concurrent.futures.FIRST_COMPLETED)
			await runner.cleanup()
			if stopEvent.is_set():
				break
			self._configChanged.clear()

	async def post(self, request):
		logging.info(f'Received request for {request.path!r}')
		try:
			channel, auth = self._paths[request.path]
		except KeyError:
			logging.info(f'Bad request: no path {request.path!r}')
			raise aiohttp.web.HTTPNotFound()
		if auth:
			authHeader = request.headers.get('Authorization')
			if not authHeader or authHeader != auth:
				logging.info(f'Bad request: authentication failed: {authHeader!r} != {auth}')
				raise aiohttp.web.HTTPForbidden()
		try:
			message = await request.text()
		except Exception as e:
			logging.info(f'Bad request: exception while reading request data: {e!s}')
			raise aiohttp.web.HTTPBadRequest() # Yes, it's always the client's fault. :-)
		logging.debug(f'Request payload: {message!r}')
		# Strip optional [CR] LF at the end of the payload
		if message.endswith('\r\n'):
			message = message[:-2]
		elif message.endswith('\n'):
			message = message[:-1]
		if '\r' in message or '\n' in message:
			logging.info('Bad request: linebreaks in message')
			raise aiohttp.web.HTTPBadRequest()
		logging.debug(f'Putting message {message!r} for {channel} into message queue')
		self.messageQueue.put_nowait((channel, message))
		raise aiohttp.web.HTTPOk()


def configure_logging(config):
	#TODO: Replace with logging.basicConfig(..., force = True) (Py 3.8+)
	root = logging.getLogger()
	root.setLevel(getattr(logging, config['logging']['level']))
	root.handlers = [] #FIXME: Undocumented attribute of logging.Logger
	formatter = logging.Formatter(config['logging']['format'], style = '{')
	stderrHandler = logging.StreamHandler()
	stderrHandler.setFormatter(formatter)
	root.addHandler(stderrHandler)


async def main():
	if len(sys.argv) != 2:
		print('Usage: http2irc.py CONFIGFILE', file = sys.stderr)
		sys.exit(1)
	configFile = sys.argv[1]
	config = Config(configFile)
	configure_logging(config)

	loop = asyncio.get_running_loop()

	messageQueue = MessageQueue()

	irc = IRCClient(messageQueue, config)
	webserver = WebServer(messageQueue, config)

	sigintEvent = asyncio.Event()
	def sigint_callback():
		logging.info('Got SIGINT')
		nonlocal sigintEvent
		sigintEvent.set()
	loop.add_signal_handler(signal.SIGINT, sigint_callback)

	def sigusr1_callback():
		logging.info('Got SIGUSR1, reloading config')
		nonlocal config, irc, webserver
		try:
			newConfig = config.reread()
		except InvalidConfig as e:
			logging.error(f'Config reload failed: {e!s}')
			return
		config = newConfig
		configure_logging(config)
		irc.update_config(config)
		webserver.update_config(config)
	loop.add_signal_handler(signal.SIGUSR1, sigusr1_callback)

	await asyncio.gather(irc.run(loop, sigintEvent), webserver.run(sigintEvent))


if __name__ == '__main__':
	asyncio.run(main())