feat: add audio engine — Opus encoder, play queue with 4 modes, FFmpeg player

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/audio/queue.ts

@@ -0,0 +1,142 @@
+export enum PlayMode {
+  Sequential = "seq",
+  Loop = "loop",
+  Random = "random",
+  RandomLoop = "rloop",
+}
+
+export interface QueuedSong {
+  id: string;
+  name: string;
+  artist: string;
+  album: string;
+  platform: "netease" | "qq";
+  url: string;
+  coverUrl: string;
+  duration: number; // seconds
+}
+
+export class PlayQueue {
+  private songs: QueuedSong[] = [];
+  private currentIndex = -1;
+  private mode: PlayMode = PlayMode.Sequential;
+
+  add(song: QueuedSong): void {
+    this.songs.push(song);
+  }
+
+  addMany(songs: QueuedSong[]): void {
+    this.songs.push(...songs);
+  }
+
+  remove(index: number): QueuedSong | null {
+    if (index < 0 || index >= this.songs.length) return null;
+    const [removed] = this.songs.splice(index, 1);
+
+    if (index < this.currentIndex) {
+      this.currentIndex--;
+    } else if (index === this.currentIndex) {
+      if (this.currentIndex >= this.songs.length) {
+        this.currentIndex = this.songs.length - 1;
+      }
+    }
+
+    return removed;
+  }
+
+  clear(): void {
+    this.songs = [];
+    this.currentIndex = -1;
+  }
+
+  play(): QueuedSong | null {
+    if (this.songs.length === 0) return null;
+    this.currentIndex = 0;
+    return this.songs[0];
+  }
+
+  playAt(index: number): QueuedSong | null {
+    if (index < 0 || index >= this.songs.length) return null;
+    this.currentIndex = index;
+    return this.songs[index];
+  }
+
+  next(): QueuedSong | null {
+    if (this.songs.length === 0) return null;
+
+    switch (this.mode) {
+      case PlayMode.Sequential: {
+        const nextIndex = this.currentIndex + 1;
+        if (nextIndex >= this.songs.length) return null;
+        this.currentIndex = nextIndex;
+        return this.songs[nextIndex];
+      }
+      case PlayMode.Loop: {
+        this.currentIndex = (this.currentIndex + 1) % this.songs.length;
+        return this.songs[this.currentIndex];
+      }
+      case PlayMode.Random: {
+        if (this.songs.length === 1) return this.songs[0];
+        let nextIndex: number;
+        do {
+          nextIndex = Math.floor(Math.random() * this.songs.length);
+        } while (nextIndex === this.currentIndex && this.songs.length > 1);
+        this.currentIndex = nextIndex;
+        return this.songs[nextIndex];
+      }
+      case PlayMode.RandomLoop: {
+        if (this.songs.length === 1) {
+          this.currentIndex = 0;
+          return this.songs[0];
+        }
+        let idx: number;
+        do {
+          idx = Math.floor(Math.random() * this.songs.length);
+        } while (idx === this.currentIndex);
+        this.currentIndex = idx;
+        return this.songs[idx];
+      }
+    }
+  }
+
+  prev(): QueuedSong | null {
+    if (this.songs.length === 0) return null;
+    const prevIndex = this.currentIndex - 1;
+    if (prevIndex < 0) {
+      this.currentIndex = this.songs.length - 1;
+    } else {
+      this.currentIndex = prevIndex;
+    }
+    return this.songs[this.currentIndex];
+  }
+
+  current(): QueuedSong | null {
+    if (this.currentIndex < 0 || this.currentIndex >= this.songs.length)
+      return null;
+    return this.songs[this.currentIndex];
+  }
+
+  list(): QueuedSong[] {
+    return [...this.songs];
+  }
+
+  size(): number {
+    return this.songs.length;
+  }
+
+  isEmpty(): boolean {
+    return this.songs.length === 0;
+  }
+
+  getMode(): PlayMode {
+    return this.mode;
+  }
+
+  setMode(mode: PlayMode): void {
+    this.mode = mode;
+  }
+
+  getCurrentIndex(): number {
+    return this.currentIndex;
+  }
+}