Add better caching, seek command

src/services/player.ts

@@ -1,8 +1,14 @@
 import {inject, injectable} from 'inversify';
 import {VoiceConnection, VoiceChannel} from 'discord.js';
+import {promises as fs, createWriteStream} from 'fs';
+import {Readable} from 'stream';
+import path from 'path';
+import hasha from 'hasha';
+import ytdl from 'ytdl-core';
+import {WriteStream} from 'fs-capacitor';
+import prism from 'prism-media';
 import {TYPES} from '../types';
-import Queue from './queue';
-import getYouTubeStream from '../utils/get-youtube-stream';
+import Queue, {QueuedSong} from './queue';
 
 export enum Status {
   Playing,
@@ -19,9 +25,11 @@ export interface GuildPlayer {
 export default class {
   private readonly guildPlayers = new Map<string, GuildPlayer>();
   private readonly queue: Queue;
+  private readonly cacheDir: string;
 
-  constructor(@inject(TYPES.Services.Queue) queue: Queue) {
+  constructor(@inject(TYPES.Services.Queue) queue: Queue, @inject(TYPES.Config.CACHE_DIR) cacheDir: string) {
     this.queue = queue;
+    this.cacheDir = cacheDir;
   }
 
   async connect(guildId: string, channel: VoiceChannel): Promise<void> {
@@ -46,6 +54,23 @@ export default class {
     }
   }
 
+  async seek(guildId: string, positionSeconds: number): Promise<void> {
+    const guildPlayer = this.get(guildId);
+    if (guildPlayer.voiceConnection === null) {
+      throw new Error('Not connected to a voice channel.');
+    }
+
+    const currentSong = this.getCurrentSong(guildId);
+
+    if (!currentSong) {
+      throw new Error('No song currently playing');
+    }
+
+    await this.waitForCache(currentSong.url);
+
+    guildPlayer.voiceConnection.play(this.getCachedPath(currentSong.url), {seek: positionSeconds});
+  }
+
   async play(guildId: string): Promise<void> {
     const guildPlayer = this.get(guildId);
     if (guildPlayer.voiceConnection === null) {
@@ -57,17 +82,18 @@ export default class {
       return;
     }
 
-    const songs = this.queue.get(guildId);
+    const currentSong = this.getCurrentSong(guildId);
 
-    if (songs.length === 0) {
+    if (!currentSong) {
       throw new Error('Queue empty.');
     }
 
-    const song = songs[0];
-
-    const stream = await getYouTubeStream(song.url);
-
-    this.get(guildId).voiceConnection!.play(stream, {type: 'webm/opus'});
+    if (await this.isCached(currentSong.url)) {
+      this.get(guildId).voiceConnection!.play(this.getCachedPath(currentSong.url));
+    } else {
+      const stream = await this.getStream(currentSong.url);
+      this.get(guildId).voiceConnection!.play(stream, {type: 'webm/opus'});
+    }
 
     guildPlayer.status = Status.Playing;
 
@@ -80,9 +106,136 @@ export default class {
     return this.guildPlayers.get(guildId) as GuildPlayer;
   }
 
+  private getCurrentSong(guildId: string): QueuedSong|null {
+    const songs = this.queue.get(guildId);
+
+    if (songs.length === 0) {
+      return null;
+    }
+
+    return songs[0];
+  }
+
   private initGuild(guildId: string): void {
     if (!this.guildPlayers.get(guildId)) {
       this.guildPlayers.set(guildId, {status: Status.Disconnected, voiceConnection: null});
     }
   }
+
+  private getCachedPath(url: string): string {
+    const hash = hasha(url);
+    return path.join(this.cacheDir, `${hash}.webm`);
+  }
+
+  private getCachedPathTemp(url: string): string {
+    const hash = hasha(url);
+
+    return path.join('/tmp', `${hash}.webm`);
+  }
+
+  private async isCached(url: string): Promise<boolean> {
+    try {
+      await fs.access(this.getCachedPath(url));
+
+      return true;
+    } catch (_) {
+      return false;
+    }
+  }
+
+  private async waitForCache(url: string, maxRetries = 50, retryDelay = 500): Promise<void> {
+    // eslint-disable-next-line no-async-promise-executor
+    return new Promise(async (resolve, reject) => {
+      if (await this.isCached(url)) {
+        resolve();
+      } else {
+        let nOfChecks = 0;
+
+        const cachedCheck = setInterval(async () => {
+          if (await this.isCached(url)) {
+            clearInterval(cachedCheck);
+            resolve();
+          } else {
+            nOfChecks++;
+
+            if (nOfChecks > maxRetries) {
+              clearInterval(cachedCheck);
+              reject(new Error('Timed out waiting for file to become cached.'));
+            }
+          }
+        }, retryDelay);
+      }
+    });
+  }
+
+  private async getStream(url: string): Promise<Readable|string> {
+    const cachedPath = this.getCachedPath(url);
+
+    if (await this.isCached(url)) {
+      return cachedPath;
+    }
+
+    // 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;
+
+    let format = formats.find(filter);
+    let canDirectPlay = true;
+
+    const nextBestFormat = (formats: ytdl.videoFormat[]): ytdl.videoFormat => {
+      formats = formats
+        .filter(format => format.averageBitrate)
+        .sort((a, b) => b.averageBitrate - a.averageBitrate);
+      return formats.find(format => !format.bitrate) ?? formats[0];
+    };
+
+    if (!format) {
+      format = nextBestFormat(info.formats);
+      canDirectPlay = false;
+    }
+
+    const cacheTempPath = this.getCachedPathTemp(url);
+    const cacheStream = createWriteStream(cacheTempPath);
+
+    cacheStream.on('finish', async () => {
+      await fs.rename(cacheTempPath, cachedPath);
+    });
+
+    let youtubeStream: Readable;
+
+    if (canDirectPlay) {
+      youtubeStream = ytdl.downloadFromInfo(info, {format});
+    } else {
+      youtubeStream = new prism.FFmpeg({
+        args: [
+          '-reconnect',
+          '1',
+          '-reconnect_streamed',
+          '1',
+          '-reconnect_delay_max',
+          '5',
+          '-i',
+          format.url,
+          '-loglevel',
+          'verbose',
+          '-vn',
+          '-acodec',
+          'libopus',
+          '-f',
+          'webm'
+        ]
+      });
+    }
+
+    const capacitor = new WriteStream();
+
+    youtubeStream.pipe(capacitor);
+
+    capacitor.createReadStream().pipe(cacheStream);
+
+    return capacitor.createReadStream();
+  }
 }