feat: add ffmpeg music player

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

src/media/musicPlayer.ts

@@ -0,0 +1,70 @@
+import { spawn as nodeSpawn } from "node:child_process";
+import type { ChildProcessWithoutNullStreams } from "node:child_process";
+import { discordPlayer } from "../player";
+import type {
+  DiscordAudioPlayer,
+  MusicPlayback,
+  MusicPlayer,
+  ResolvedMediaSource,
+} from "./mediaTypes";
+
+export interface MusicPlayerDependencies {
+  spawn?: typeof nodeSpawn;
+  discordPlayer?: DiscordAudioPlayer;
+}
+
+export function createMusicPlayer(
+  dependencies: MusicPlayerDependencies = {},
+): MusicPlayer {
+  const spawn = dependencies.spawn ?? nodeSpawn;
+  const audioPlayer = dependencies.discordPlayer ?? discordPlayer;
+
+  return {
+    play(source: ResolvedMediaSource): MusicPlayback {
+      const proc = spawn("ffmpeg", buildFfmpegArgs(source.source), {
+        stdio: ["ignore", "pipe", "pipe"],
+      }) as unknown as ChildProcessWithoutNullStreams;
+
+      audioPlayer.playStream(proc.stdout);
+
+      const done = new Promise<void>((resolve, reject) => {
+        proc.on("error", reject);
+        proc.on("close", (code) => {
+          if (code === 0) {
+            resolve();
+            return;
+          }
+          reject(new Error(`ffmpeg exited with code ${code}`));
+        });
+      });
+
+      return {
+        done,
+        stop() {
+          proc.kill("SIGTERM");
+          audioPlayer.stop();
+        },
+      };
+    },
+  };
+}
+
+export function buildFfmpegArgs(source: string): string[] {
+  return [
+    "-hide_banner",
+    "-loglevel",
+    "warning",
+    "-i",
+    source,
+    "-vn",
+    "-acodec",
+    "libopus",
+    "-ar",
+    "48000",
+    "-ac",
+    "2",
+    "-f",
+    "ogg",
+    "pipe:1",
+  ];
+}