path: root/src/services/player.ts

import {VoiceChannel, Snowflake} from 'discord.js';
import {Readable} from 'stream';
import hasha from 'hasha';
import ytdl from 'ytdl-core';
import {WriteStream} from 'fs-capacitor';
import ffmpeg from 'fluent-ffmpeg';
import shuffle from 'array-shuffle';
import {AudioPlayer, AudioPlayerStatus, createAudioPlayer, createAudioResource, joinVoiceChannel, StreamType, VoiceConnection, VoiceConnectionStatus} from '@discordjs/voice';
import FileCacheProvider from './file-cache.js';
import debug from '../utils/debug.js';

export interface QueuedPlaylist {
  title: string;
  source: string;
}

export interface QueuedSong {
  title: string;
  artist: string;
  url: string;
  length: number;
  playlist: QueuedPlaylist | null;
  isLive: boolean;
  addedInChannelId: Snowflake;
  thumbnailUrl: string | null;
  requestedBy: string;
}

export enum STATUS {
  PLAYING,
  PAUSED,
}

export interface PlayerEvents {
  statusChange: (oldStatus: STATUS, newStatus: STATUS) => void;
}

export default class {
  public voiceConnection: VoiceConnection | null = null;
  public status = STATUS.PAUSED;
  public guildId: string;

  private queue: QueuedSong[] = [];
  private queuePosition = 0;
  private audioPlayer: AudioPlayer | null = null;
  private nowPlaying: QueuedSong | null = null;
  private playPositionInterval: NodeJS.Timeout | undefined;
  private lastSongURL = '';

  private positionInSeconds = 0;

  private readonly fileCache: FileCacheProvider;

  constructor(fileCache: FileCacheProvider, guildId: string) {
    this.fileCache = fileCache;
    this.guildId = guildId;
  }

  async connect(channel: VoiceChannel): Promise<void> {
    this.voiceConnection = joinVoiceChannel({
      channelId: channel.id,
      guildId: channel.guild.id,
      adapterCreator: channel.guild.voiceAdapterCreator,
    });
  }

  disconnect(): void {
    if (this.voiceConnection) {
      if (this.status === STATUS.PLAYING) {
        this.pause();
      }

      this.voiceConnection.destroy();
      this.audioPlayer?.stop();

      this.voiceConnection = null;
      this.audioPlayer = null;
    }
  }

  async seek(positionSeconds: number): Promise<void> {
    this.status = STATUS.PAUSED;

    if (this.voiceConnection === null) {
      throw new Error('Not connected to a voice channel.');
    }

    const currentSong = this.getCurrent();

    if (!currentSong) {
      throw new Error('No song currently playing');
    }

    if (positionSeconds > currentSong.length) {
      throw new Error('Seek position is outside the range of the song.');
    }

    const stream = await this.getStream(currentSong.url, {seek: positionSeconds});
    this.audioPlayer = createAudioPlayer({
      behaviors: {
        // Needs to be somewhat high for livestreams
        maxMissedFrames: 50,
      },
    });
    this.voiceConnection.subscribe(this.audioPlayer);
    this.audioPlayer.play(createAudioResource(stream, {
      inputType: StreamType.WebmOpus,
    }));
    this.attachListeners();
    this.startTrackingPosition(positionSeconds);

    this.status = STATUS.PLAYING;
  }

  async forwardSeek(positionSeconds: number): Promise<void> {
    return this.seek(this.positionInSeconds + positionSeconds);
  }

  getPosition(): number {
    return this.positionInSeconds;
  }

  async play(): Promise<void> {
    if (this.voiceConnection === null) {
      throw new Error('Not connected to a voice channel.');
    }

    const currentSong = this.getCurrent();

    if (!currentSong) {
      throw new Error('Queue empty.');
    }

    // Resume from paused state
    if (this.status === STATUS.PAUSED && currentSong.url === this.nowPlaying?.url) {
      if (this.audioPlayer) {
        this.audioPlayer.unpause();
        this.status = STATUS.PLAYING;
        this.startTrackingPosition();
        return;
      }

      // Was disconnected, need to recreate stream
      if (!currentSong.isLive) {
        return this.seek(this.getPosition());
      }
    }

    try {
      const stream = await this.getStream(currentSong.url);
      this.audioPlayer = createAudioPlayer({
        behaviors: {
          // Needs to be somewhat high for livestreams
          maxMissedFrames: 50,
        },
      });
      this.voiceConnection.subscribe(this.audioPlayer);
      const resource = createAudioResource(stream, {
        inputType: StreamType.WebmOpus,
      });

      this.audioPlayer.play(resource);

      this.attachListeners();

      this.status = STATUS.PLAYING;
      this.nowPlaying = currentSong;

      if (currentSong.url === this.lastSongURL) {
        this.startTrackingPosition();
      } else {
        // Reset position counter
        this.startTrackingPosition(0);
        this.lastSongURL = currentSong.url;
      }
    } catch (error: unknown) {
      await this.forward(1);

      if ((error as {statusCode: number}).statusCode === 410 && currentSong) {
        const channelId = currentSong.addedInChannelId;

        if (channelId) {
          debug(`${currentSong.title} is unavailable`);
          return;
        }
      }

      throw error;
    }
  }

  pause(): void {
    if (this.status !== STATUS.PLAYING) {
      throw new Error('Not currently playing.');
    }

    this.status = STATUS.PAUSED;

    if (this.audioPlayer) {
      this.audioPlayer.pause();
    }

    this.stopTrackingPosition();
  }

  async forward(skip: number): Promise<void> {
    this.manualForward(skip);

    try {
      if (this.getCurrent() && this.status !== STATUS.PAUSED) {
        await this.play();
      } else {
        this.status = STATUS.PAUSED;
        this.disconnect();
      }
    } catch (error: unknown) {
      this.queuePosition--;
      throw error;
    }
  }

  canGoForward(skip: number) {
    return (this.queuePosition + skip - 1) < this.queue.length;
  }

  manualForward(skip: number): void {
    if (this.canGoForward(skip)) {
      this.queuePosition += skip;
      this.positionInSeconds = 0;
      this.stopTrackingPosition();
    } else {
      throw new Error('No songs in queue to forward to.');
    }
  }

  canGoBack() {
    return this.queuePosition - 1 >= 0;
  }

  async back(): Promise<void> {
    if (this.canGoBack()) {
      this.queuePosition--;
      this.positionInSeconds = 0;
      this.stopTrackingPosition();

      if (this.status !== STATUS.PAUSED) {
        await this.play();
      }
    } else {
      throw new Error('No songs in queue to go back to.');
    }
  }

  getCurrent(): QueuedSong | null {
    if (this.queue[this.queuePosition]) {
      return this.queue[this.queuePosition];
    }

    return null;
  }

  /**
   * Returns queue, not including the current song.
   * @returns {QueuedSong[]}
   */
  getQueue(): QueuedSong[] {
    return this.queue.slice(this.queuePosition + 1);
  }

  add(song: QueuedSong, {immediate = false} = {}): void {
    if (song.playlist || !immediate) {
      // Add to end of queue
      this.queue.push(song);
    } else {
      // Add as the next song to be played
      const insertAt = this.queuePosition + 1;
      this.queue = [...this.queue.slice(0, insertAt), song, ...this.queue.slice(insertAt)];
    }
  }

  shuffle(): void {
    const shuffledSongs = shuffle(this.queue.slice(this.queuePosition + 1));

    this.queue = [...this.queue.slice(0, this.queuePosition + 1), ...shuffledSongs];
  }

  clear(): void {
    const newQueue = [];

    // Don't clear curently playing song
    const current = this.getCurrent();

    if (current) {
      newQueue.push(current);
    }

    this.queuePosition = 0;
    this.queue = newQueue;
  }

  removeFromQueue(index: number, amount = 1): void {
    this.queue.splice(this.queuePosition + index, amount);
  }

  removeCurrent(): void {
    this.queue = [...this.queue.slice(0, this.queuePosition), ...this.queue.slice(this.queuePosition + 1)];
  }

  queueSize(): number {
    return this.getQueue().length;
  }

  isQueueEmpty(): boolean {
    return this.queueSize() === 0;
  }

  private getHashForCache(url: string): string {
    return hasha(url);
  }

  private async getStream(url: string, options: {seek?: number} = {}): Promise<Readable> {
    let ffmpegInput = '';
    const ffmpegInputOptions: string[] = [];
    let shouldCacheVideo = false;

    let format: ytdl.videoFormat | undefined;

    try {
      ffmpegInput = await this.fileCache.getPathFor(this.getHashForCache(url));

      if (options.seek) {
        ffmpegInputOptions.push('-ss', options.seek.toString());
      }
    } catch {
      // Not yet cached, must download
      const info = await ytdl.getInfo(url);

      const {formats} = info;

      const filter = (format: ytdl.videoFormat): boolean => format.codecs === 'opus' && format.container === 'webm' && format.audioSampleRate !== undefined && parseInt(format.audioSampleRate, 10) === 48000;

      format = formats.find(filter);

      const nextBestFormat = (formats: ytdl.videoFormat[]): ytdl.videoFormat | undefined => {
        if (formats[0].isLive) {
          formats = formats.sort((a, b) => (b as unknown as {audioBitrate: number}).audioBitrate - (a as unknown as {audioBitrate: number}).audioBitrate); // Bad typings

          return formats.find(format => [128, 127, 120, 96, 95, 94, 93].includes(parseInt(format.itag as unknown as string, 10))); // Bad typings
        }

        formats = formats
          .filter(format => format.averageBitrate)
          .sort((a, b) => {
            if (a && b) {
              return b.averageBitrate! - a.averageBitrate!;
            }

            return 0;
          });
        return formats.find(format => !format.bitrate) ?? formats[0];
      };

      if (!format) {
        format = nextBestFormat(info.formats);

        if (!format) {
          // If still no format is found, throw
          throw new Error('Can\'t find suitable format.');
        }
      }

      ffmpegInput = format.url;

      // Don't cache livestreams or long videos
      const MAX_CACHE_LENGTH_SECONDS = 30 * 60; // 30 minutes
      shouldCacheVideo = !info.player_response.videoDetails.isLiveContent && parseInt(info.videoDetails.lengthSeconds, 10) < MAX_CACHE_LENGTH_SECONDS && !options.seek;

      ffmpegInputOptions.push(...[
        '-reconnect',
        '1',
        '-reconnect_streamed',
        '1',
        '-reconnect_delay_max',
        '5',
      ]);

      if (options.seek) {
        // Fudge seek position since FFMPEG doesn't do a great job
        ffmpegInputOptions.push('-ss', (options.seek + 7).toString());
      }
    }

    // Create stream and pipe to capacitor
    return new Promise((resolve, reject) => {
      const capacitor = new WriteStream();

      // Cache video if necessary
      if (shouldCacheVideo) {
        const cacheStream = this.fileCache.createWriteStream(this.getHashForCache(url));

        capacitor.createReadStream().pipe(cacheStream);
      } else {
        ffmpegInputOptions.push('-re');
      }

      const youtubeStream = ffmpeg(ffmpegInput)
        .inputOptions(ffmpegInputOptions)
        .noVideo()
        .audioCodec('libopus')
        .outputFormat('webm')
        .on('error', error => {
          console.error(error);
          reject(error);
        })
        .on('start', command => {
          debug(`Spawned ffmpeg with ${command as string}`);
        });

      youtubeStream.pipe(capacitor);

      resolve(capacitor.createReadStream());
    });
  }

  private startTrackingPosition(initalPosition?: number): void {
    if (initalPosition !== undefined) {
      this.positionInSeconds = initalPosition;
    }

    if (this.playPositionInterval) {
      clearInterval(this.playPositionInterval);
    }

    this.playPositionInterval = setInterval(() => {
      this.positionInSeconds++;
    }, 1000);
  }

  private stopTrackingPosition(): void {
    if (this.playPositionInterval) {
      clearInterval(this.playPositionInterval);
    }
  }

  private attachListeners(): void {
    if (!this.voiceConnection) {
      return;
    }

    if (this.voiceConnection.listeners(VoiceConnectionStatus.Disconnected).length === 0) {
      this.voiceConnection.on(VoiceConnectionStatus.Disconnected, this.onVoiceConnectionDisconnect.bind(this));
    }

    if (!this.audioPlayer) {
      return;
    }

    if (this.audioPlayer.listeners('stateChange').length === 0) {
      this.audioPlayer.on('stateChange', this.onAudioPlayerStateChange.bind(this));
    }
  }

  private onVoiceConnectionDisconnect(): void {
    this.disconnect();
  }

  private async onAudioPlayerStateChange(_oldState: {status: AudioPlayerStatus}, newState: {status: AudioPlayerStatus}): Promise<void> {
    // Automatically advance queued song at end
    if (newState.status === AudioPlayerStatus.Idle && this.status === STATUS.PLAYING) {
      await this.forward(1);
    }
  }
}