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

"""
The MIT License (MIT)

Copyright (c) 2015-2019 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 asyncio
from collections import namedtuple
import concurrent.futures
import json
import logging
import struct
import sys
import time
import threading
import zlib

import websockets

from . import utils
from .activity import _ActivityTag
from .enums import SpeakingState
from .errors import ConnectionClosed, InvalidArgument

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.block_msg = 'Heartbeat blocked for more than %s seconds.'
        self.behind_msg = 'Can\'t keep up, websocket is %.1fs behind.'
        self._stop_ev = threading.Event()
        self._last_ack = time.perf_counter()
        self._last_send = time.perf_counter()
        self.latency = float('inf')
        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.perf_counter():
                log.warning("Shard ID %s has stopped responding to the gateway. Closing and restarting.", self.shard_id)
                coro = self.ws.close(4000)
                f = asyncio.run_coroutine_threadsafe(coro, loop=self.ws.loop)

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

            data = self.get_payload()
            log.debug(self.msg, data['d'])
            coro = self.ws.send_as_json(data)
            f = asyncio.run_coroutine_threadsafe(coro, loop=self.ws.loop)
            try:
                # block until sending is complete
                total = 0
                while True:
                    try:
                        f.result(5)
                        break
                    except concurrent.futures.TimeoutError:
                        total += 5
                        log.warning(self.block_msg, total)

            except Exception:
                self.stop()
            else:
                self._last_send = time.perf_counter()

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

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

    def ack(self):
        ack_time = time.perf_counter()
        self._last_ack = ack_time
        self.latency = ack_time - self._last_send
        if self.latency > 10:
            log.warning(self.behind_msg, self.latency)

class VoiceKeepAliveHandler(KeepAliveHandler):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.msg = 'Keeping voice websocket alive with timestamp %s.'
        self.block_msg = 'Voice heartbeat blocked for more than %s seconds'
        self.behind_msg = 'Can\'t keep up, voice websocket is %.1fs behind'

    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
    async 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 = await client.http.get_gateway()
        ws = await websockets.connect(gateway, loop=client.loop, klass=cls, compression=None)

        # dynamically add attributes needed
        ws.token = client.http.token
        ws._connection = client._connection
        ws._discord_parsers = client._connection.parsers
        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
        await ws.poll_event()

        if not resume:
            await ws.identify()
            return ws

        await ws.resume()
        try:
            await 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 await 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: :class:`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 = self.loop.create_future()
        entry = EventListener(event=event, predicate=predicate, result=result, future=future)
        self._dispatch_listeners.append(entry)
        return future

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

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

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

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

    async def received_message(self, msg):
        self._dispatch('socket_raw_receive', msg)

        if type(msg) is 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.DISPATCH:
            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.')
                await 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()
                await 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
                await self.send_as_json(self._keep_alive.get_payload())
                self._keep_alive.start()
                return

            if op == self.INVALIDATE_SESSION:
                if data is True:
                    await asyncio.sleep(5.0, loop=self.loop)
                    await 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)
                await self.identify()
                return

            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)

        elif 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))

        try:
            func = self._discord_parsers[event]
        except KeyError:
            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 exc:
                future.set_exception(exc)
                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):
        """:class:`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.latency

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

    async 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 = await self.recv()
            await self.received_message(msg)
        except websockets.exceptions.ConnectionClosed as exc:
            if self._can_handle_close(exc.code):
                log.info('Websocket closed with %s (%s), attempting a reconnect.', exc.code, exc.reason)
                raise ResumeWebSocket(self.shard_id) from exc
            else:
                log.info('Websocket closed with %s (%s), cannot reconnect.', exc.code, exc.reason)
                raise ConnectionClosed(exc, shard_id=self.shard_id) from exc

    async def send(self, data):
        self._dispatch('socket_raw_send', data)
        await super().send(data)

    async def send_as_json(self, data):
        try:
            await self.send(utils.to_json(data))
        except websockets.exceptions.ConnectionClosed as exc:
            if not self._can_handle_close(exc.code):
                raise ConnectionClosed(exc, shard_id=self.shard_id) from exc

    async def change_presence(self, *, activity=None, status=None, afk=False, since=0.0):
        if activity is not None:
            if not isinstance(activity, _ActivityTag):
                raise InvalidArgument('activity must be one of Game, Streaming, or Activity.')
            activity = activity.to_dict()

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

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

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

    async def request_sync(self, guild_ids):
        payload = {
            'op': self.GUILD_SYNC,
            'd': list(guild_ids)
        }
        await self.send_as_json(payload)

    async 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)
        await self.send_as_json(payload)

    async def close(self, code=1000, reason=''):
        if self._keep_alive:
            self._keep_alive.stop()

        await super().close(code, reason)

    async def close_connection(self, *args, **kwargs):
        if self._keep_alive:
            self._keep_alive.stop()

        await super().close_connection(*args, **kwargs)

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.
    CLIENT_CONNECT
        Indicates a user has connected to voice.
    CLIENT_DISCONNECT
        Receive only.  Indicates a user has disconnected from voice.
    """

    IDENTIFY            = 0
    SELECT_PROTOCOL     = 1
    READY               = 2
    HEARTBEAT           = 3
    SESSION_DESCRIPTION = 4
    SPEAKING            = 5
    HEARTBEAT_ACK       = 6
    RESUME              = 7
    HELLO               = 8
    INVALIDATE_SESSION  = 9
    CLIENT_CONNECT      = 12
    CLIENT_DISCONNECT   = 13

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

    async def send_as_json(self, data):
        log.debug('Sending voice websocket frame: %s.', data)
        await self.send(utils.to_json(data))

    async 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
            }
        }
        await self.send_as_json(payload)

    async 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
            }
        }
        await self.send_as_json(payload)

    @classmethod
    async def from_client(cls, client, *, resume=False):
        """Creates a voice websocket for the :class:`VoiceClient`."""
        gateway = 'wss://' + client.endpoint + '/?v=4'
        ws = await websockets.connect(gateway, loop=client.loop, klass=cls, compression=None)
        ws.gateway = gateway
        ws._connection = client
        ws._max_heartbeat_timeout = 60.0

        if resume:
            await ws.resume()
        else:
            await ws.identify()

        return ws

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

        await self.send_as_json(payload)

    async def client_connect(self):
        payload = {
            'op': self.CLIENT_CONNECT,
            'd': {
                'audio_ssrc': self._connection.ssrc
            }
        }

        await self.send_as_json(payload)

    async def speak(self, state=SpeakingState.voice):
        payload = {
            'op': self.SPEAKING,
            'd': {
                'speaking': int(state),
                'delay': 0
            }
        }

        await self.send_as_json(payload)

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

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

    async def initial_connection(self, data):
        state = self._connection
        state.ssrc = data['ssrc']
        state.voice_port = data['port']
        state.endpoint_ip = data['ip']

        packet = bytearray(70)
        struct.pack_into('>I', packet, 0, state.ssrc)
        state.socket.sendto(packet, (state.endpoint_ip, state.voice_port))
        recv = await 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)

        # there *should* always be at least one supported mode (xsalsa20_poly1305)
        modes = [mode for mode in data['modes'] if mode in self._connection.supported_modes]
        log.debug('received supported encryption modes: %s', ", ".join(modes))

        mode = modes[0]
        await self.select_protocol(state.ip, state.port, mode)
        log.info('selected the voice protocol for use (%s)', mode)

        await self.client_connect()

    async def load_secret_key(self, data):
        log.info('received secret key for voice connection')
        self._connection.secret_key = data.get('secret_key')
        await self.speak()
        await self.speak(False)

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

    async def close_connection(self, *args, **kwargs):
        if self._keep_alive:
            self._keep_alive.stop()

        await super().close_connection(*args, **kwargs)
