feat: coordinate media playback state

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/media/mediaController.ts

@@ -0,0 +1,119 @@
+import { AppError } from "../errors";
+import { discordPlayer } from "../player";
+import { MediaQueue } from "./mediaQueue";
+import { resolveMediaSource } from "./mediaResolver";
+import { createMusicPlayer } from "./musicPlayer";
+import type {
+  MediaState,
+  MusicPlayback,
+  MusicPlayer,
+  ResolvedMediaSource,
+} from "./mediaTypes";
+
+export interface MediaControllerDependencies {
+  isVoiceConnected?: () => boolean;
+  isBrowserStreaming?: () => boolean;
+  resolveMediaSource?: (source: string) => Promise<ResolvedMediaSource>;
+  musicPlayer?: MusicPlayer;
+  onStateChange?: (state: MediaState) => void;
+}
+
+export class MediaController {
+  private readonly queueStore = new MediaQueue();
+  private playback: MusicPlayback | null = null;
+  private skipInProgress = false;
+
+  constructor(private readonly dependencies: MediaControllerDependencies = {}) {}
+
+  getState(): MediaState {
+    const snapshot = this.queueStore.snapshot();
+    return {
+      playing: snapshot.current?.status === "playing",
+      ...snapshot,
+    };
+  }
+
+  async queue(source: string): Promise<MediaState> {
+    this.assertCanStart();
+    const resolved = await (this.dependencies.resolveMediaSource ?? resolveMediaSource)(
+      source,
+    );
+    this.queueStore.add(resolved);
+    this.startNextIfIdle();
+    return this.emitState();
+  }
+
+  async skip(): Promise<MediaState> {
+    if (this.skipInProgress) {
+      throw new AppError("Skip already in progress", "MEDIA_SKIP_IN_PROGRESS", 409);
+    }
+
+    this.skipInProgress = true;
+    try {
+      this.playback?.stop();
+      this.playback = null;
+      this.queueStore.completeCurrent();
+      this.startNextIfIdle();
+      return this.emitState();
+    } finally {
+      this.skipInProgress = false;
+    }
+  }
+
+  async stop(): Promise<MediaState> {
+    this.playback?.stop();
+    this.playback = null;
+    this.queueStore.clear();
+    return this.emitState();
+  }
+
+  private assertCanStart(): void {
+    const isVoiceConnected = this.dependencies.isVoiceConnected ??
+      (() => discordPlayer.isConnected());
+    if (!isVoiceConnected()) {
+      throw new AppError(
+        "Connect to a voice channel before playing media",
+        "VOICE_NOT_CONNECTED",
+        409,
+      );
+    }
+
+    if (this.dependencies.isBrowserStreaming?.()) {
+      throw new AppError(
+        "Stop browser microphone streaming before playing media",
+        "BROWSER_STREAM_ACTIVE",
+        409,
+      );
+    }
+  }
+
+  private startNextIfIdle(): void {
+    if (this.playback) return;
+    const item = this.queueStore.startNext();
+    if (!item) return;
+
+    const player = this.dependencies.musicPlayer ?? createMusicPlayer();
+    this.playback = player.play(item);
+    this.playback.done.then(
+      () => this.finishCurrent(false),
+      () => this.finishCurrent(true),
+    );
+  }
+
+  private finishCurrent(failed: boolean): void {
+    this.playback = null;
+    if (failed) {
+      this.queueStore.failCurrent();
+    } else {
+      this.queueStore.completeCurrent();
+    }
+    this.startNextIfIdle();
+    this.emitState();
+  }
+
+  private emitState(): MediaState {
+    const state = this.getState();
+    this.dependencies.onStateChange?.(state);
+    return state;
+  }
+}