'use strict';

const EventEmitter = require('node:events');
const process = require('node:process');
const { setImmediate } = require('node:timers');
const { Collection } = require('@discordjs/collection');
const {
  WebSocketManager: WSWebSocketManager,
  WebSocketShardEvents: WSWebSocketShardEvents,
  CompressionMethod,
  CloseCodes,
} = require('@discordjs/ws');
const { GatewayCloseCodes, GatewayDispatchEvents } = require('discord-api-types/v10');
const WebSocketShard = require('./WebSocketShard');
const PacketHandlers = require('./handlers');
const { DiscordjsError, ErrorCodes } = require('../../errors');
const Events = require('../../util/Events');
const Status = require('../../util/Status');
const WebSocketShardEvents = require('../../util/WebSocketShardEvents');

let zlib;
let deprecationEmitted = false;

try {
  zlib = require('zlib-sync');
} catch {} // eslint-disable-line no-empty

const BeforeReadyWhitelist = [
  GatewayDispatchEvents.Ready,
  GatewayDispatchEvents.Resumed,
  GatewayDispatchEvents.GuildCreate,
  GatewayDispatchEvents.GuildDelete,
  GatewayDispatchEvents.GuildMembersChunk,
  GatewayDispatchEvents.GuildMemberAdd,
  GatewayDispatchEvents.GuildMemberRemove,
];

const WaitingForGuildEvents = [GatewayDispatchEvents.GuildCreate, GatewayDispatchEvents.GuildDelete];

const UNRECOVERABLE_CLOSE_CODES = [
  GatewayCloseCodes.AuthenticationFailed,
  GatewayCloseCodes.InvalidShard,
  GatewayCloseCodes.ShardingRequired,
  GatewayCloseCodes.InvalidAPIVersion,
  GatewayCloseCodes.InvalidIntents,
  GatewayCloseCodes.DisallowedIntents,
];

const reasonIsDeprecated = 'the reason property is deprecated, use the code property to determine the reason';
let deprecationEmittedForInvalidSessionEvent = false;
let deprecationEmittedForDestroyedEvent = false;

/**
 * The WebSocket manager for this client.
 * <info>This class forwards raw dispatch events,
 * read more about it here {@link https://discord.com/developers/docs/topics/gateway}</info>
 * @extends {EventEmitter}
 */
class WebSocketManager extends EventEmitter {
  constructor(client) {
    super();

    /**
     * The client that instantiated this WebSocketManager
     * @type {Client}
     * @readonly
     * @name WebSocketManager#client
     */
    Object.defineProperty(this, 'client', { value: client });

    /**
     * The gateway this manager uses
     * @type {?string}
     */
    this.gateway = null;

    /**
     * A collection of all shards this manager handles
     * @type {Collection<number, WebSocketShard>}
     */
    this.shards = new Collection();

    /**
     * An array of queued events before this WebSocketManager became ready
     * @type {Object[]}
     * @private
     * @name WebSocketManager#packetQueue
     */
    Object.defineProperty(this, 'packetQueue', { value: [] });

    /**
     * The current status of this WebSocketManager
     * @type {Status}
     */
    this.status = Status.Idle;

    /**
     * If this manager was destroyed. It will prevent shards from reconnecting
     * @type {boolean}
     * @private
     */
    this.destroyed = false;

    /**
     * The internal WebSocketManager from `@discordjs/ws`.
     * @type {WSWebSocketManager}
     * @private
     */
    this._ws = null;
  }

  /**
   * The average ping of all WebSocketShards
   * @type {number}
   * @readonly
   */
  get ping() {
    const sum = this.shards.reduce((a, b) => a + b.ping, 0);
    return sum / this.shards.size;
  }

  /**
   * Emits a debug message.
   * @param {string[]} messages The debug message
   * @param {?number} [shardId] The id of the shard that emitted this message, if any
   * @private
   */
  debug(messages, shardId) {
    this.client.emit(
      Events.Debug,
      `[WS => ${typeof shardId === 'number' ? `Shard ${shardId}` : 'Manager'}] ${messages.join('\n\t')}`,
    );
  }

  /**
   * Connects this manager to the gateway.
   * @private
   */
  async connect() {
    const invalidToken = new DiscordjsError(ErrorCodes.TokenInvalid);
    const { shards, shardCount, intents, ws } = this.client.options;
    if (this._ws && this._ws.options.token !== this.client.token) {
      await this._ws.destroy({ code: CloseCodes.Normal, reason: 'Login with differing token requested' });
      this._ws = null;
    }
    if (!this._ws) {
      const wsOptions = {
        intents: intents.bitfield,
        rest: this.client.rest,
        token: this.client.token,
        largeThreshold: ws.large_threshold,
        version: ws.version,
        shardIds: shards === 'auto' ? null : shards,
        shardCount: shards === 'auto' ? null : shardCount,
        initialPresence: ws.presence,
        retrieveSessionInfo: shardId => this.shards.get(shardId).sessionInfo,
        updateSessionInfo: (shardId, sessionInfo) => {
          this.shards.get(shardId).sessionInfo = sessionInfo;
        },
        compression: zlib ? CompressionMethod.ZlibStream : null,
      };
      if (ws.buildIdentifyThrottler) wsOptions.buildIdentifyThrottler = ws.buildIdentifyThrottler;
      if (ws.buildStrategy) wsOptions.buildStrategy = ws.buildStrategy;
      this._ws = new WSWebSocketManager(wsOptions);
      this.attachEvents();
    }

    const {
      url: gatewayURL,
      shards: recommendedShards,
      session_start_limit: sessionStartLimit,
    } = await this._ws.fetchGatewayInformation().catch(error => {
      throw error.status === 401 ? invalidToken : error;
    });

    const { total, remaining } = sessionStartLimit;
    this.debug(['Fetched Gateway Information', `URL: ${gatewayURL}`, `Recommended Shards: ${recommendedShards}`]);
    this.debug(['Session Limit Information', `Total: ${total}`, `Remaining: ${remaining}`]);
    this.gateway = `${gatewayURL}/`;

    this.client.options.shardCount = await this._ws.getShardCount();
    this.client.options.shards = await this._ws.getShardIds();
    this.totalShards = this.client.options.shards.length;
    for (const id of this.client.options.shards) {
      if (!this.shards.has(id)) {
        const shard = new WebSocketShard(this, id);
        this.shards.set(id, shard);

        shard.on(WebSocketShardEvents.AllReady, unavailableGuilds => {
          /**
           * Emitted when a shard turns ready.
           * @event Client#shardReady
           * @param {number} id The shard id that turned ready
           * @param {?Set<Snowflake>} unavailableGuilds Set of unavailable guild ids, if any
           */
          this.client.emit(Events.ShardReady, shard.id, unavailableGuilds);

          this.checkShardsReady();
        });
        shard.status = Status.Connecting;
      }
    }

    await this._ws.connect();

    this.shards.forEach(shard => {
      if (shard.listenerCount(WebSocketShardEvents.InvalidSession) > 0 && !deprecationEmittedForInvalidSessionEvent) {
        process.emitWarning(
          'The WebSocketShard#invalidSession event is deprecated and will never emit.',
          'DeprecationWarning',
        );

        deprecationEmittedForInvalidSessionEvent = true;
      }
      if (shard.listenerCount(WebSocketShardEvents.Destroyed) > 0 && !deprecationEmittedForDestroyedEvent) {
        process.emitWarning(
          'The WebSocketShard#destroyed event is deprecated and will never emit.',
          'DeprecationWarning',
        );

        deprecationEmittedForDestroyedEvent = true;
      }
    });
  }

  /**
   * Attaches event handlers to the internal WebSocketShardManager from `@discordjs/ws`.
   * @private
   */
  attachEvents() {
    this._ws.on(WSWebSocketShardEvents.Debug, ({ message, shardId }) => this.debug([message], shardId));
    this._ws.on(WSWebSocketShardEvents.Dispatch, ({ data, shardId }) => {
      this.client.emit(Events.Raw, data, shardId);
      this.emit(data.t, data.d, shardId);
      const shard = this.shards.get(shardId);
      this.handlePacket(data, shard);
      if (shard.status === Status.WaitingForGuilds && WaitingForGuildEvents.includes(data.t)) {
        shard.gotGuild(data.d.id);
      }
    });

    this._ws.on(WSWebSocketShardEvents.Ready, ({ data, shardId }) => {
      this.shards.get(shardId).onReadyPacket(data);
    });

    this._ws.on(WSWebSocketShardEvents.Closed, ({ code, shardId }) => {
      const shard = this.shards.get(shardId);
      shard.emit(WebSocketShardEvents.Close, { code, reason: reasonIsDeprecated, wasClean: true });
      if (UNRECOVERABLE_CLOSE_CODES.includes(code)) {
        shard.status = Status.Disconnected;
        /**
         * Emitted when a shard's WebSocket disconnects and will no longer reconnect.
         * @event Client#shardDisconnect
         * @param {CloseEvent} event The WebSocket close event
         * @param {number} id The shard id that disconnected
         */
        this.client.emit(Events.ShardDisconnect, { code, reason: reasonIsDeprecated, wasClean: true }, shardId);
        this.debug([`Shard not recoverable: ${code} (${GatewayCloseCodes[code] ?? CloseCodes[code]})`], shardId);
        return;
      }

      this.shards.get(shardId).status = Status.Connecting;
      /**
       * Emitted when a shard is attempting to reconnect or re-identify.
       * @event Client#shardReconnecting
       * @param {number} id The shard id that is attempting to reconnect
       */
      this.client.emit(Events.ShardReconnecting, shardId);
    });
    this._ws.on(WSWebSocketShardEvents.Hello, ({ shardId }) => {
      const shard = this.shards.get(shardId);
      if (shard.sessionInfo) {
        shard.closeSequence = shard.sessionInfo.sequence;
        shard.status = Status.Resuming;
      } else {
        shard.status = Status.Identifying;
      }
    });

    this._ws.on(WSWebSocketShardEvents.Resumed, ({ shardId }) => {
      const shard = this.shards.get(shardId);
      shard.status = Status.Ready;
      /**
       * Emitted when the shard resumes successfully
       * @event WebSocketShard#resumed
       */
      shard.emit(WebSocketShardEvents.Resumed);
    });

    this._ws.on(WSWebSocketShardEvents.HeartbeatComplete, ({ heartbeatAt, latency, shardId }) => {
      this.debug([`Heartbeat acknowledged, latency of ${latency}ms.`], shardId);
      const shard = this.shards.get(shardId);
      shard.lastPingTimestamp = heartbeatAt;
      shard.ping = latency;
    });

    this._ws.on(WSWebSocketShardEvents.Error, ({ error, shardId }) => {
      /**
       * Emitted whenever a shard's WebSocket encounters a connection error.
       * @event Client#shardError
       * @param {Error} error The encountered error
       * @param {number} shardId The shard that encountered this error
       */
      this.client.emit(Events.ShardError, error, shardId);
    });
  }

  /**
   * Broadcasts a packet to every shard this manager handles.
   * @param {Object} packet The packet to send
   * @private
   */
  broadcast(packet) {
    for (const shardId of this.shards.keys()) this._ws.send(shardId, packet);
  }

  /**
   * Destroys this manager and all its shards.
   * @private
   */
  async destroy() {
    if (this.destroyed) return;
    // TODO: Make a util for getting a stack
    this.debug([Object.assign(new Error(), { name: 'Manager was destroyed:' }).stack]);
    this.destroyed = true;
    await this._ws?.destroy({ code: CloseCodes.Normal, reason: 'Manager was destroyed' });
  }

  /**
   * Processes a packet and queues it if this WebSocketManager is not ready.
   * @param {Object} [packet] The packet to be handled
   * @param {WebSocketShard} [shard] The shard that will handle this packet
   * @returns {boolean}
   * @private
   */
  handlePacket(packet, shard) {
    if (packet && this.status !== Status.Ready) {
      if (!BeforeReadyWhitelist.includes(packet.t)) {
        this.packetQueue.push({ packet, shard });
        return false;
      }
    }

    if (this.packetQueue.length) {
      const item = this.packetQueue.shift();
      setImmediate(() => {
        this.handlePacket(item.packet, item.shard);
      }).unref();
    }

    if (packet && PacketHandlers[packet.t]) {
      PacketHandlers[packet.t](this.client, packet, shard);
    }

    return true;
  }

  /**
   * Checks whether the client is ready to be marked as ready.
   * @private
   */
  checkShardsReady() {
    if (this.status === Status.Ready) return;
    if (this.shards.size !== this.totalShards || this.shards.some(shard => shard.status !== Status.Ready)) {
      return;
    }

    this.triggerClientReady();
  }

  /**
   * Causes the client to be marked as ready and emits the ready event.
   * @private
   */
  triggerClientReady() {
    this.status = Status.Ready;

    this.client.readyTimestamp = Date.now();

    /**
     * Emitted when the client becomes ready to start working.
     * @event Client#ready
     * @deprecated Use {@link Client#event:clientReady} instead.
     * @param {Client} client The client
     */
    if (this.client.emit('ready', this.client) && !deprecationEmitted) {
      deprecationEmitted = true;

      process.emitWarning(
        // eslint-disable-next-line max-len
        'The ready event has been renamed to clientReady to distinguish it from the gateway READY event and will only emit under that name in v15. Please use clientReady instead.',
        'DeprecationWarning',
      );
    }

    /**
     * Emitted when the client becomes ready to start working.
     * @event Client#clientReady
     * @param {Client} client The client
     */
    this.client.emit(Events.ClientReady, this.client);

    this.handlePacket();
  }
}

module.exports = WebSocketManager;
