#!/usr/bin/env python
"""
Example IRC Server

.. note:: This is an example only and is feature incomplete.

Implements commands::

    USER NICK JOIN PART NICK WHO QUIT
"""

import logging
from argparse import ArgumentDefaultsHelpFormatter, ArgumentParser
from collections import defaultdict
from itertools import chain
from logging import getLogger
from operator import attrgetter
from sys import stderr
from time import time

from circuits import Component, Debugger, handler
from circuits.net.events import close, write
from circuits.net.sockets import TCPServer
from circuits.protocols.irc import IRC, Message, joinprefix, reply, response
from circuits.protocols.irc.replies import (
    ERR_NICKNAMEINUSE,
    ERR_NOMOTD,
    ERR_NOSUCHCHANNEL,
    ERR_NOSUCHNICK,
    ERR_UNKNOWNCOMMAND,
    RPL_CHANNELMODEIS,
    RPL_ENDOFNAMES,
    RPL_ENDOFWHO,
    RPL_LIST,
    RPL_LISTEND,
    RPL_LISTSTART,
    RPL_NAMEREPLY,
    RPL_NOTOPIC,
    RPL_TOPIC,
    RPL_WELCOME,
    RPL_WHOREPLY,
    RPL_YOURHOST,
)


__version__ = '0.0.1'


def parse_args():
    parser = ArgumentParser(
        description=__doc__,
        formatter_class=ArgumentDefaultsHelpFormatter,
    )

    parser.add_argument(
        '-v',
        '--version',
        action='version',
        version=f'%(prog)s {__version__}',
    )

    parser.add_argument(
        '-b',
        '--bind',
        action='store',
        type=str,
        default='0.0.0.0:6667',
        dest='bind',
        help='Bind to address:[port]',
    )

    parser.add_argument(
        '--debug',
        action='store_true',
        default=False,
        dest='debug',
        help='Enable debug mode',
    )

    return parser.parse_args()


class Channel:
    def __init__(self, name):
        self.name = name
        self.topic = None
        self.mode = '+n'

        self.users = []


class User:
    def __init__(self, sock, host, port):
        self.sock = sock
        self.host = host
        self.port = port

        self.nick = None
        self.mode = ''
        self.away = False
        self.channels = []
        self.signon = None
        self.registered = False
        self.userinfo = UserInfo()

    @property
    def prefix(self):
        userinfo = self.userinfo
        return joinprefix(self.nick, userinfo.user, userinfo.host)


class UserInfo:
    def __init__(self, user=None, host=None, name=None):
        self.user = user
        self.host = host
        self.name = name


class Server(Component):
    channel = 'server'

    network = 'Test'
    host = 'localhost'
    version = f'ircd v{__version__:s}'

    def init(self, args, logger=None):
        self.args = args
        self.logger = logger or getLogger(__name__)

        self.buffers = defaultdict(bytes)

        self.nicks = {}
        self.users = {}
        self.channels = {}

        Debugger(events=args.debug, logger=self.logger).register(self)

        if ':' in args.bind:
            address, port = args.bind.split(':')
            port = int(port)
        else:
            address, port = args.bind, 6667

        bind = (address, port)

        self.transport = TCPServer(
            bind,
            channel=self.channel,
        ).register(self)

        self.protocol = IRC(
            channel=self.channel,
            getBuffer=self.buffers.__getitem__,
            updateBuffer=self.buffers.__setitem__,
        ).register(self)

    def _notify(self, users, message, exclude=None):
        for user in users:
            if exclude is not None and user is exclude:
                continue
            self.fire(reply(user.sock, message))

    def read(self, sock, data):
        user = self.users[sock]
        host, port = user.host, user.port

        self.logger.info(
            f'I: [{host:s}:{port:d}] {data!r:s}',
        )

    def write(self, sock, data):
        user = self.users[sock]
        host, port = user.host, user.port

        self.logger.info(
            f'O: [{host:s}:{port:d}] {data!r:s}',
        )

    def ready(self, server, bind):
        stderr.write(
            'ircd v{:s} ready! Listening on: {:s}\n'.format(
                __version__,
                '{:s}:{:d}'.format(*bind),
            ),
        )

    def connect(self, sock, host, port):
        self.users[sock] = User(sock, host, port)

        self.logger.info(f'C: [{host:s}:{port:d}]')

    def disconnect(self, sock):
        if sock not in self.users:
            return

        user = self.users[sock]

        self.logger.info(f'D: [{user.host:s}:{user.port:d}]')

        nick = user.nick
        user, host = user.userinfo.user, user.userinfo.host

        yield self.call(
            response.create('quit', sock, (nick, user, host), 'Leaving'),
        )

        del self.users[sock]

        if nick in self.nicks:
            del self.nicks[nick]

    def quit(self, sock, source, reason='Leaving'):
        user = self.users[sock]

        channels = [self.channels[channel] for channel in user.channels]
        for channel in channels:
            channel.users.remove(user)
            if not channel.users:
                del self.channels[channel.name]

        users = chain(*map(attrgetter('users'), channels))

        self.fire(close(sock))

        self._notify(
            users,
            Message('QUIT', reason, prefix=user.prefix),
            user,
        )

    def nick(self, sock, source, nick):
        user = self.users[sock]

        if nick in self.nicks:
            return self.fire(reply(sock, ERR_NICKNAMEINUSE(nick)))

        if not user.registered:
            user.registered = True
            self.fire(response.create('signon', sock, user))

        user.nick = nick
        self.nicks[nick] = user
        return None

    def user(self, sock, source, nick, user, host, name):
        _user = self.users[sock]

        _user.userinfo.user = user
        _user.userinfo.host = host
        _user.userinfo.name = name

        if _user.nick is not None:
            _user.registered = True
            self.fire(response.create('signon', sock, source))

    def signon(self, sock, source):
        user = self.users[sock]
        if user.signon:
            return

        user.signon = time()

        self.fire(reply(sock, RPL_WELCOME(self.network)))
        self.fire(reply(sock, RPL_YOURHOST(self.host, self.version)))
        self.fire(reply(sock, ERR_NOMOTD()))

        # Force users to join #circuits
        self.fire(response.create('join', sock, source, '#circuits'))

    def join(self, sock, source, name):
        user = self.users[sock]

        if name not in self.channels:
            channel = self.channels[name] = Channel(name)
        else:
            channel = self.channels[name]

        if user in channel.users:
            return

        user.channels.append(name)
        channel.users.append(user)

        self._notify(
            channel.users,
            Message('JOIN', name, prefix=user.prefix),
        )

        if channel.topic:
            self.fire(reply(sock, RPL_TOPIC(channel.topic)))
        else:
            self.fire(reply(sock, RPL_NOTOPIC(channel.name)))
        self.fire(reply(sock, RPL_NAMEREPLY(channel.name, [u.prefix for u in channel.users])))
        self.fire(reply(sock, RPL_ENDOFNAMES(channel.name)))

    def part(self, sock, source, name, reason='Leaving'):
        user = self.users[sock]

        channel = self.channels[name]

        self._notify(
            channel.users,
            Message('PART', name, reason, prefix=user.prefix),
        )

        user.channels.remove(name)
        channel.users.remove(user)

        if not channel.users:
            del self.channels[name]

    def privmsg(self, sock, source, target, message):
        user = self.users[sock]

        if target.startswith('#'):
            if target not in self.channels:
                return self.fire(reply(sock, ERR_NOSUCHCHANNEL(target)))

            channel = self.channels[target]

            self._notify(
                channel.users,
                Message('PRIVMSG', target, message, prefix=user.prefix),
                user,
            )
            return None
        if target not in self.nicks:
            return self.fire(reply(sock, ERR_NOSUCHNICK(target)))

        self.fire(
            reply(
                self.nicks[target].sock,
                Message('PRIVMSG', target, message, prefix=user.prefix),
            ),
        )
        return None

    def who(self, sock, source, mask):
        if mask.startswith('#'):
            if mask not in self.channels:
                return self.fire(reply(sock, ERR_NOSUCHCHANNEL(mask)))

            channel = self.channels[mask]

            for user in channel.users:
                self.fire(reply(sock, RPL_WHOREPLY(user, mask, self.host)))
            self.fire(reply(sock, RPL_ENDOFWHO(mask)))
            return None
        if mask not in self.nicks:
            return self.fire(reply(sock, ERR_NOSUCHNICK(mask)))

        user = self.nicks[mask]

        self.fire(reply(sock, RPL_WHOREPLY(user, mask, self.host)))
        self.fire(reply(sock, RPL_ENDOFWHO(mask)))
        return None

    def ping(self, event, sock, source, server):
        event.stop()
        self.fire(reply(sock, Message('PONG', server)))

    def reply(self, target, message):
        user = self.users[target]

        if message.add_nick:
            message.args.insert(0, user.nick or '')

        if message.prefix is None:
            message.prefix = self.host

        self.fire(write(target, bytes(message)))

    def mode(self, sock, source, mask, mode=None, params=None):
        if mask.startswith('#'):
            if mask not in self.channels:
                return self.fire(reply(sock, ERR_NOSUCHCHANNEL(mask)))
            channel = self.channels[mask]
            if not params:
                self.fire(reply(sock, RPL_CHANNELMODEIS(channel.name, channel.mode)))
                return None
        elif mask not in self.users:
            return self.fire(reply(sock, ERR_NOSUCHNICK(mask)))
        return None

    def list(self, sock, source):
        self.fire(reply(sock, RPL_LISTSTART()))
        for channel in self.channels.values():
            self.fire(reply(sock, RPL_LIST(channel, str(len(channel.users)), channel.topic or '')))
        self.fire(reply(sock, RPL_LISTEND()))

    @property
    def commands(self):
        exclude = {'ready', 'connect', 'disconnect', 'read', 'write'}
        return list(set(self.events()) - exclude)

    @handler()
    def _on_event(self, event, *args, **kwargs):
        if event.name.endswith('_done'):
            return

        if isinstance(event, response) and event.name not in self.commands:
            event.stop()
            self.fire(reply(args[0], ERR_UNKNOWNCOMMAND(event.name)))


def main():
    args = parse_args()

    logging.basicConfig(
        format='%(asctime)s - %(name)s - %(levelname)s - %(message)s',
        stream=stderr,
        level=logging.DEBUG if args.debug else logging.INFO,
    )

    logger = getLogger(__name__)

    Server(args, logger=logger).run()


if __name__ == '__main__':
    main()