# -*- coding: utf-8 -*-

"""
The MIT License (MIT)

Copyright (c) 2015-2017 Rapptz

Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and associated documentation files (the "Software"),
to deal in the Software without restriction, including without limitation
the rights to use, copy, modify, merge, publish, distribute, sublicense,
and/or sell copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
"""

import sys
import time
import websockets
import asyncio

from . import utils, compat
from .game import Game
from .errors import ConnectionClosed, InvalidArgument
import logging
import zlib, json
from collections import namedtuple
import threading
import struct

log = logging.getLogger(__name__)

__all__ = [ 'DiscordWebSocket', 'KeepAliveHandler', 'VoiceKeepAliveHandler',
            'DiscordVoiceWebSocket', 'ResumeWebSocket' ]

class ResumeWebSocket(Exception):
    """Signals to initialise via RESUME opcode instead of IDENTIFY."""
    def __init__(self, shard_id):
        self.shard_id = shard_id

EventListener = namedtuple('EventListener', 'predicate event result future')

class KeepAliveHandler(threading.Thread):
    def __init__(self, *args, **kwargs):
        ws = kwargs.pop('ws', None)
        interval = kwargs.pop('interval', None)
        shard_id = kwargs.pop('shard_id', None)
        threading.Thread.__init__(self, *args, **kwargs)
        self.ws = ws
        self.interval = interval
        self.daemon = True
        self.shard_id = shard_id
        self.msg = 'Keeping websocket alive with sequence %s.'
        self._stop_ev = threading.Event()
        self._last_ack = time.monotonic()
        self._last_send = time.monotonic()
        self.heartbeat_timeout = ws._max_heartbeat_timeout

    def run(self):
        while not self._stop_ev.wait(self.interval):
            if self._last_ack + self.heartbeat_timeout < time.monotonic():
                log.warn("Shard ID %s has stopped responding to the gateway. Closing and restarting." % self.shard_id)
                coro = self.ws.close(1006)
                f = compat.run_coroutine_threadsafe(coro, loop=self.ws.loop)

                try:
                    f.result()
                except:
                    pass
                finally:
                    self.stop()
                    return

            data = self.get_payload()
            log.debug(self.msg, data['d'])
            coro = self.ws.send_as_json(data)
            f = compat.run_coroutine_threadsafe(coro, loop=self.ws.loop)
            try:
                # block until sending is complete
                f.result()
            except Exception:
                self.stop()
            else:
                self._last_send = time.monotonic()

    def get_payload(self):
        return {
            'op': self.ws.HEARTBEAT,
            'd': self.ws.sequence
        }

    def stop(self):
        self._stop_ev.set()

    def ack(self):
        self._last_ack = time.monotonic()

class VoiceKeepAliveHandler(KeepAliveHandler):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.msg = 'Keeping voice websocket alive with timestamp %s.'

    def get_payload(self):
        return {
            'op': self.ws.HEARTBEAT,
            'd': int(time.time() * 1000)
        }

class DiscordWebSocket(websockets.client.WebSocketClientProtocol):
    """Implements a WebSocket for Discord's gateway v6.

    This is created through :func:`create_main_websocket`. Library
    users should never create this manually.

    Attributes
    -----------
    DISPATCH
        Receive only. Denotes an event to be sent to Discord, such as READY.
    HEARTBEAT
        When received tells Discord to keep the connection alive.
        When sent asks if your connection is currently alive.
    IDENTIFY
        Send only. Starts a new session.
    PRESENCE
        Send only. Updates your presence.
    VOICE_STATE
        Send only. Starts a new connection to a voice guild.
    VOICE_PING
        Send only. Checks ping time to a voice guild, do not use.
    RESUME
        Send only. Resumes an existing connection.
    RECONNECT
        Receive only. Tells the client to reconnect to a new gateway.
    REQUEST_MEMBERS
        Send only. Asks for the full member list of a guild.
    INVALIDATE_SESSION
        Receive only. Tells the client to optionally invalidate the session
        and IDENTIFY again.
    HELLO
        Receive only. Tells the client the heartbeat interval.
    HEARTBEAT_ACK
        Receive only. Confirms receiving of a heartbeat. Not having it implies
        a connection issue.
    GUILD_SYNC
        Send only. Requests a guild sync.
    gateway
        The gateway we are currently connected to.
    token
        The authentication token for discord.
    """

    DISPATCH           = 0
    HEARTBEAT          = 1
    IDENTIFY           = 2
    PRESENCE           = 3
    VOICE_STATE        = 4
    VOICE_PING         = 5
    RESUME             = 6
    RECONNECT          = 7
    REQUEST_MEMBERS    = 8
    INVALIDATE_SESSION = 9
    HELLO              = 10
    HEARTBEAT_ACK      = 11
    GUILD_SYNC         = 12

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.max_size = None
        # an empty dispatcher to prevent crashes
        self._dispatch = lambda *args: None
        # generic event listeners
        self._dispatch_listeners = []
        # the keep alive
        self._keep_alive = None

        # ws related stuff
        self.session_id = None
        self.sequence = None
        self._zlib = zlib.decompressobj()
        self._buffer = bytearray()

    @classmethod
    @asyncio.coroutine
    def from_client(cls, client, *, shard_id=None, session=None, sequence=None, resume=False):
        """Creates a main websocket for Discord from a :class:`Client`.

        This is for internal use only.
        """
        gateway = yield from client.http.get_gateway()
        ws = yield from websockets.connect(gateway, loop=client.loop, klass=cls)

        # dynamically add attributes needed
        ws.token = client.http.token
        ws._connection = client._connection
        ws._dispatch = client.dispatch
        ws.gateway = gateway
        ws.shard_id = shard_id
        ws.shard_count = client._connection.shard_count
        ws.session_id = session
        ws.sequence = sequence
        ws._max_heartbeat_timeout = client._connection.heartbeat_timeout

        client._connection._update_references(ws)

        log.info('Created websocket connected to %s', gateway)

        # poll event for OP Hello
        yield from ws.poll_event()

        if not resume:
            yield from ws.identify()
            return ws

        yield from ws.resume()
        try:
            yield from ws.ensure_open()
        except websockets.exceptions.ConnectionClosed:
            # ws got closed so let's just do a regular IDENTIFY connect.
            log.info('RESUME failed (the websocket decided to close) for Shard ID %s. Retrying.', shard_id)
            return (yield from cls.from_client(client, shard_id=shard_id))
        else:
            return ws

    def wait_for(self, event, predicate, result=None):
        """Waits for a DISPATCH'd event that meets the predicate.

        Parameters
        -----------
        event : str
            The event name in all upper case to wait for.
        predicate
            A function that takes a data parameter to check for event
            properties. The data parameter is the 'd' key in the JSON message.
        result
            A function that takes the same data parameter and executes to send
            the result to the future. If None, returns the data.

        Returns
        --------
        asyncio.Future
            A future to wait for.
        """

        future = compat.create_future(self.loop)
        entry = EventListener(event=event, predicate=predicate, result=result, future=future)
        self._dispatch_listeners.append(entry)
        return future

    @asyncio.coroutine
    def identify(self):
        """Sends the IDENTIFY packet."""
        payload = {
            'op': self.IDENTIFY,
            'd': {
                'token': self.token,
                'properties': {
                    '$os': sys.platform,
                    '$browser': 'discord.py',
                    '$device': 'discord.py',
                    '$referrer': '',
                    '$referring_domain': ''
                },
                'compress': True,
                'large_threshold': 250,
                'v': 3
            }
        }

        if not self._connection.is_bot:
            payload['d']['synced_guilds'] = []

        if self.shard_id is not None and self.shard_count is not None:
            payload['d']['shard'] = [self.shard_id, self.shard_count]

        state = self._connection
        if state._game is not None or state._status is not None:
            payload['d']['presence'] = {
                'status': state._status,
                'game': state._game,
                'since': 0,
                'afk': False
            }

        yield from self.send_as_json(payload)
        log.info('Shard ID %s has sent the IDENTIFY payload.', self.shard_id)

    @asyncio.coroutine
    def resume(self):
        """Sends the RESUME packet."""
        payload = {
            'op': self.RESUME,
            'd': {
                'seq': self.sequence,
                'session_id': self.session_id,
                'token': self.token
            }
        }

        yield from self.send_as_json(payload)
        log.info('Shard ID %s has sent the RESUME payload.', self.shard_id)

    @asyncio.coroutine
    def received_message(self, msg):
        self._dispatch('socket_raw_receive', msg)

        if isinstance(msg, bytes):
            self._buffer.extend(msg)

            if len(msg) >= 4:
                if msg[-4:] == b'\x00\x00\xff\xff':
                    msg = self._zlib.decompress(self._buffer)
                    msg = msg.decode('utf-8')
                    self._buffer = bytearray()
                else:
                    return
            else:
                return

        msg = json.loads(msg)

        log.debug('For Shard ID %s: WebSocket Event: %s', self.shard_id, msg)
        self._dispatch('socket_response', msg)

        op = msg.get('op')
        data = msg.get('d')
        seq = msg.get('s')
        if seq is not None:
            self.sequence = seq

        if op == self.RECONNECT:
            # "reconnect" can only be handled by the Client
            # so we terminate our connection and raise an
            # internal exception signalling to reconnect.
            log.info('Received RECONNECT opcode.')
            yield from self.close()
            raise ResumeWebSocket(self.shard_id)

        if op == self.HEARTBEAT_ACK:
            self._keep_alive.ack()
            return

        if op == self.HEARTBEAT:
            beat = self._keep_alive.get_payload()
            yield from self.send_as_json(beat)
            return

        if op == self.HELLO:
            interval = data['heartbeat_interval'] / 1000.0
            self._keep_alive = KeepAliveHandler(ws=self, interval=interval, shard_id=self.shard_id)
            # send a heartbeat immediately
            yield from self.send_as_json(self._keep_alive.get_payload())
            self._keep_alive.start()
            return

        if op == self.INVALIDATE_SESSION:
            if data == True:
                yield from asyncio.sleep(5.0, loop=self.loop)
                yield from self.close()
                raise ResumeWebSocket(self.shard_id)

            self.sequence = None
            self.session_id = None
            log.info('Shard ID %s session has been invalidated.' % self.shard_id)
            yield from self.identify()
            return

        if op != self.DISPATCH:
            log.warning('Unknown OP code %s.', op)
            return

        event = msg.get('t')

        if event == 'READY':
            self._trace = trace = data.get('_trace', [])
            self.sequence = msg['s']
            self.session_id = data['session_id']
            log.info('Shard ID %s has connected to Gateway: %s (Session ID: %s).',
                      self.shard_id, ', '.join(trace), self.session_id)

        if event == 'RESUMED':
            self._trace = trace = data.get('_trace', [])
            log.info('Shard ID %s has successfully RESUMED session %s under trace %s.',
                     self.shard_id, self.session_id, ', '.join(trace))

        parser = 'parse_' + event.lower()

        try:
            func = getattr(self._connection, parser)
        except AttributeError:
            log.warning('Unknown event %s.', event)
        else:
            func(data)

        # remove the dispatched listeners
        removed = []
        for index, entry in enumerate(self._dispatch_listeners):
            if entry.event != event:
                continue

            future = entry.future
            if future.cancelled():
                removed.append(index)
                continue

            try:
                valid = entry.predicate(data)
            except Exception as e:
                future.set_exception(e)
                removed.append(index)
            else:
                if valid:
                    ret = data if entry.result is None else entry.result(data)
                    future.set_result(ret)
                    removed.append(index)

        for index in reversed(removed):
            del self._dispatch_listeners[index]

    @property
    def latency(self):
        """:obj:`float`: Measures latency between a HEARTBEAT and a HEARTBEAT_ACK in seconds."""
        heartbeat = self._keep_alive
        return float('inf') if heartbeat is None else heartbeat._last_ack - heartbeat._last_send

    def _can_handle_close(self, code):
        return code not in (1000, 4004, 4010, 4011)

    @asyncio.coroutine
    def poll_event(self):
        """Polls for a DISPATCH event and handles the general gateway loop.

        Raises
        ------
        ConnectionClosed
            The websocket connection was terminated for unhandled reasons.
        """
        try:
            msg = yield from self.recv()
            yield from self.received_message(msg)
        except websockets.exceptions.ConnectionClosed as e:
            if self._can_handle_close(e.code):
                log.info('Websocket closed with %s (%s), attempting a reconnect.', e.code, e.reason)
                raise ResumeWebSocket(self.shard_id) from e
            else:
                log.info('Websocket closed with %s (%s), cannot reconnect.', e.code, e.reason)
                raise ConnectionClosed(e, shard_id=self.shard_id) from e

    @asyncio.coroutine
    def send(self, data):
        self._dispatch('socket_raw_send', data)
        yield from super().send(data)

    @asyncio.coroutine
    def send_as_json(self, data):
        try:
            yield from super().send(utils.to_json(data))
        except websockets.exceptions.ConnectionClosed as e:
            if not self._can_handle_close(e.code):
                raise ConnectionClosed(e, shard_id=self.shard_id) from e

    @asyncio.coroutine
    def change_presence(self, *, game=None, status=None, afk=False, since=0.0):
        if game is not None and not isinstance(game, Game):
            raise InvalidArgument('game must be of type Game or None')

        if status == 'idle':
            since = int(time.time() * 1000)

        sent_game = dict(game) if game else None

        payload = {
            'op': self.PRESENCE,
            'd': {
                'game': sent_game,
                'afk': afk,
                'since': since,
                'status': status
            }
        }

        sent = utils.to_json(payload)
        log.debug('Sending "%s" to change status', sent)
        yield from self.send(sent)

    @asyncio.coroutine
    def request_sync(self, guild_ids):
        payload = {
            'op': self.GUILD_SYNC,
            'd': list(guild_ids)
        }
        yield from self.send_as_json(payload)

    @asyncio.coroutine
    def voice_state(self, guild_id, channel_id, self_mute=False, self_deaf=False):
        payload = {
            'op': self.VOICE_STATE,
            'd': {
                'guild_id': guild_id,
                'channel_id': channel_id,
                'self_mute': self_mute,
                'self_deaf': self_deaf
            }
        }

        log.debug('Updating our voice state to %s.', payload)
        yield from self.send_as_json(payload)

    @asyncio.coroutine
    def close_connection(self, force=False):
        if self._keep_alive:
            self._keep_alive.stop()

        yield from super().close_connection(force=force)

class DiscordVoiceWebSocket(websockets.client.WebSocketClientProtocol):
    """Implements the websocket protocol for handling voice connections.

    Attributes
    -----------
    IDENTIFY
        Send only. Starts a new voice session.
    SELECT_PROTOCOL
        Send only. Tells discord what encryption mode and how to connect for voice.
    READY
        Receive only. Tells the websocket that the initial connection has completed.
    HEARTBEAT
        Send only. Keeps your websocket connection alive.
    SESSION_DESCRIPTION
        Receive only. Gives you the secret key required for voice.
    SPEAKING
        Send only. Notifies the client if you are currently speaking.
    HEARTBEAT_ACK
        Receive only. Tells you your heartbeat has been acknowledged.
    RESUME
        Sent only. Tells the client to resume its session.
    HELLO
        Receive only. Tells you that your websocket connection was acknowledged.
    INVALIDATE_SESSION
        Sent only. Tells you that your RESUME request has failed and to re-IDENTIFY.
    """

    IDENTIFY            = 0
    SELECT_PROTOCOL     = 1
    READY               = 2
    HEARTBEAT           = 3
    SESSION_DESCRIPTION = 4
    SPEAKING            = 5
    HEARTBEAT_ACK       = 6
    RESUME              = 7
    HELLO               = 8
    INVALIDATE_SESSION  = 9

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.max_size = None
        self._keep_alive = None

    @asyncio.coroutine
    def send_as_json(self, data):
        log.debug('Sending voice websocket frame: %s.', data)
        yield from self.send(utils.to_json(data))

    @asyncio.coroutine
    def resume(self):
        state = self._connection
        payload = {
            'op': self.RESUME,
            'd': {
                'token': state.token,
                'server_id': str(state.server_id),
                'session_id': state.session_id
            }
        }
        yield from self.send_as_json(payload)

    @asyncio.coroutine
    def identify(self):
        state = self._connection
        payload = {
            'op': self.IDENTIFY,
            'd': {
                'server_id': str(state.server_id),
                'user_id': str(state.user.id),
                'session_id': state.session_id,
                'token': state.token
            }
        }
        yield from self.send_as_json(payload)

    @classmethod
    @asyncio.coroutine
    def from_client(cls, client, *, resume=False):
        """Creates a voice websocket for the :class:`VoiceClient`."""
        gateway = 'wss://' + client.endpoint + '/?v=3'
        ws = yield from websockets.connect(gateway, loop=client.loop, klass=cls)
        ws.gateway = gateway
        ws._connection = client
        ws._max_heartbeat_timeout = 60.0

        if resume:
            yield from ws.resume()
        else:
            yield from ws.identify()

        return ws

    @asyncio.coroutine
    def select_protocol(self, ip, port):
        payload = {
            'op': self.SELECT_PROTOCOL,
            'd': {
                'protocol': 'udp',
                'data': {
                    'address': ip,
                    'port': port,
                    'mode': 'xsalsa20_poly1305'
                }
            }
        }

        yield from self.send_as_json(payload)

    @asyncio.coroutine
    def speak(self, is_speaking=True):
        payload = {
            'op': self.SPEAKING,
            'd': {
                'speaking': is_speaking,
                'delay': 0
            }
        }

        yield from self.send_as_json(payload)

    @asyncio.coroutine
    def received_message(self, msg):
        log.debug('Voice websocket frame received: %s', msg)
        op = msg['op']
        data = msg.get('d')

        if op == self.READY:
            interval = data['heartbeat_interval'] / 1000.0
            self._keep_alive = VoiceKeepAliveHandler(ws=self, interval=interval)
            self._keep_alive.start()
            yield from self.initial_connection(data)
        elif op == self.HEARTBEAT_ACK:
            self._keep_alive.ack()
        elif op == self.INVALIDATE_SESSION:
            log.info('Voice RESUME failed.')
            yield from self.identify()
        elif op == self.SESSION_DESCRIPTION:
            yield from self.load_secret_key(data)

    @asyncio.coroutine
    def initial_connection(self, data):
        state = self._connection
        state.ssrc = data['ssrc']
        state.voice_port = data['port']

        packet = bytearray(70)
        struct.pack_into('>I', packet, 0, state.ssrc)
        state.socket.sendto(packet, (state.endpoint_ip, state.voice_port))
        recv = yield from self.loop.sock_recv(state.socket, 70)
        log.debug('received packet in initial_connection: %s', recv)

        # the ip is ascii starting at the 4th byte and ending at the first null
        ip_start = 4
        ip_end = recv.index(0, ip_start)
        state.ip = recv[ip_start:ip_end].decode('ascii')

        # the port is a little endian unsigned short in the last two bytes
        # yes, this is different endianness from everything else
        state.port = struct.unpack_from('<H', recv, len(recv) - 2)[0]

        log.debug('detected ip: %s port: %s', state.ip, state.port)
        yield from self.select_protocol(state.ip, state.port)
        log.info('selected the voice protocol for use')

    @asyncio.coroutine
    def load_secret_key(self, data):
        log.info('received secret key for voice connection')
        self._connection.secret_key = data.get('secret_key')
        yield from self.speak()

    @asyncio.coroutine
    def poll_event(self):
        try:
            msg = yield from asyncio.wait_for(self.recv(), timeout=30.0, loop=self.loop)
            yield from self.received_message(json.loads(msg))
        except websockets.exceptions.ConnectionClosed as e:
            raise ConnectionClosed(e, shard_id=None) from e

    @asyncio.coroutine
    def close_connection(self, force=False):
        if self._keep_alive:
            self._keep_alive.stop()

        yield from super().close_connection(force=force)