jamcp/src/http.ts at main · CopilotKit/jamcp · GitHub

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/**
 * HTTP server — handles:
 *   GET  /          → health check
 *   GET  /auth      → kick off Spotify OAuth
 *   GET  /auth/callback → Spotify redirects here with the code
 *   POST /mcp       → MCP StreamableHTTP endpoint
 *   GET  /mcp       → MCP SSE stream (older clients)
 *   DELETE /mcp     → MCP session teardown
 */

import express from "express";
import { randomBytes, createHash } from "crypto";
import { StreamableHTTPServerTransport } from "@modelcontextprotocol/sdk/server/streamableHttp.js";
import { SpotifyClient } from "./spotify.js";
import { createMcpServer } from "./mcp.js";

const SCOPES = [
  "streaming",
  "user-read-playback-state",
  "user-modify-playback-state",
  "user-read-currently-playing",
  "playlist-read-private",
  "playlist-modify-public",
  "playlist-modify-private",
  "user-library-read",
  "user-read-private",
].join(" ");

// In-flight PKCE state (single-user server — one pending auth at a time is fine)
let pendingAuth: { codeVerifier: string; state: string } | null = null;

// SDK browser device registry — sdk-frame tab communicates with player via server
let _sdkDeviceId: string | null = null;
let _sdkSseClients: express.Response[] = [];

export function createApp(spotify: SpotifyClient): express.Express {
  const app = express();
  app.use(express.json());

  // Allow cross-origin requests from the CopilotKit host (e.g. localhost:3000)
  // The iframe's origin differs from the MCP server's origin (127.0.0.1:3124),
  // so without this header the browser blocks fetch() calls from the iframe.
  app.use((_req, res, next) => {
    res.setHeader("Access-Control-Allow-Origin", "*");
    res.setHeader("Access-Control-Allow-Methods", "GET, POST, DELETE, OPTIONS");
    res.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization, mcp-session-id");
    if (_req.method === "OPTIONS") { res.sendStatus(204); return; }
    next();
  });

  const CLIENT_ID = process.env.SPOTIFY_CLIENT_ID!;
  const CLIENT_SECRET = process.env.SPOTIFY_CLIENT_SECRET!;
  const REDIRECT_URI = process.env.SPOTIFY_REDIRECT_URI!;
  // Base URL of this server — used so the iframe knows where to send the user for auth
  const BASE_URL = REDIRECT_URI.replace(/\/auth\/callback$/, "");

  // ── Login page ───────────────────────────────────────────────────────────────
  app.get("/", (_req, res) => {
    const authed = spotify.isAuthenticated();
    res.send(`<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8" />
  <meta name="viewport" content="width=device-width, initial-scale=1.0" />
  <title>spotify-mcp</title>
  <style>
    * { box-sizing: border-box; margin: 0; padding: 0; }
    body {
      font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;
      background: #121212;
      color: #fff;
      height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
    }
    .card {
      text-align: center;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 20px;
    }
    .logo { font-size: 48px; }
    h1 { font-size: 22px; font-weight: 700; }
    p { color: #a7a7a7; font-size: 14px; }
    .btn {
      display: inline-block;
      background: #1DB954;
      color: #000;
      font-weight: 700;
      font-size: 15px;
      padding: 14px 40px;
      border-radius: 50px;
      text-decoration: none;
      letter-spacing: 0.05em;
      transition: background 0.15s;
    }
    .btn:hover { background: #1ed760; }
    .status {
      font-size: 13px;
      color: ${authed ? "#1DB954" : "#a7a7a7"};
    }
  </style>
</head>
<body>
  <div class="card">
    <div class="logo">🎵</div>
    <h1>spotify-mcp</h1>
    <p>Connect your Spotify account to use the MCP player.</p>
    ${authed
      ? `<div class="status">✅ Connected — <a href="/auth" style="color:#1DB954">re-authenticate</a></div>`
      : `<a href="/auth" class="btn">Connect Spotify</a>`
    }
  </div>
</body>
</html>`);
  });

  // ── Spotify OAuth — step 1: redirect to Spotify ────────────────────────────
  app.get("/auth", (_req, res) => {
    const codeVerifier = randomBytes(32).toString("base64url");
    const codeChallenge = createHash("sha256").update(codeVerifier).digest("base64url");
    const state = randomBytes(16).toString("hex");

    pendingAuth = { codeVerifier, state };

    const url = new URL("https://accounts.spotify.com/authorize");
    url.searchParams.set("client_id", CLIENT_ID);
    url.searchParams.set("response_type", "code");
    url.searchParams.set("redirect_uri", REDIRECT_URI);
    url.searchParams.set("state", state);
    url.searchParams.set("scope", SCOPES);
    url.searchParams.set("code_challenge_method", "S256");
    url.searchParams.set("code_challenge", codeChallenge);

    res.redirect(url.toString());
  });

  // ── Spotify OAuth — step 2: handle callback ────────────────────────────────
  app.get("/auth/callback", async (req, res) => {
    try {
      const { code, state, error } = req.query as Record<string, string>;

      if (error) {
        res.status(400).send(`Auth error: ${error}`);
        return;
      }

      if (!pendingAuth || state !== pendingAuth.state || !code) {
        res.status(400).send("Invalid state or missing code. Try /auth again.");
        return;
      }

      const { codeVerifier } = pendingAuth;
      pendingAuth = null;

      const tokenRes = await fetch("https://accounts.spotify.com/api/token", {
        method: "POST",
        headers: { "Content-Type": "application/x-www-form-urlencoded" },
        body: new URLSearchParams({
          grant_type: "authorization_code",
          code,
          redirect_uri: REDIRECT_URI,
          client_id: CLIENT_ID,
          code_verifier: codeVerifier,
        }),
      });

      if (!tokenRes.ok) {
        const err = await tokenRes.text();
        res.status(500).send(`Token exchange failed: ${err}`);
        return;
      }

      const tokens = await tokenRes.json() as {
        access_token: string;
        refresh_token: string;
        expires_in: number;
      };

      spotify.saveTokens({
        access_token: tokens.access_token,
        refresh_token: tokens.refresh_token,
        expires_at: Date.now() + tokens.expires_in * 1000,
      });

      res.send(`
        <html>
          <body style="font-family:sans-serif;text-align:center;padding:60px;background:#121212;color:#1DB954;">
            <h1>✅ Authenticated!</h1>
            <p style="color:#fff;margin-top:12px">Spotify is connected. You can close this tab.</p>
            <script>
              // Try to close the tab automatically; works if opened via window.open or ui/open-link
              setTimeout(() => window.close(), 1500);
            </script>
          </body>
        </html>
      `);
    } catch (err) {
      console.error("Auth callback error:", err);
      if (!res.headersSent) {
        res.status(500).send("Authentication failed. Please try again via /auth");
      }
    }
  });

  // ── Auth status — polled by the iframe after triggering ui/open-link ─────────
  app.get("/auth/status", (_req, res) => {
    res.json({ authenticated: spotify.isAuthenticated() });
  });

  // ── Auth token — used by the Web Playback SDK in the iframe ──────────────────
  app.get("/auth/token", async (_req, res) => {
    if (!spotify.isAuthenticated()) {
      res.status(401).json({ error: "Not authenticated" });
      return;
    }
    try {
      const access_token = await spotify.getFreshAccessToken();
      res.json({ access_token });
    } catch (err: any) {
      res.status(500).json({ error: err.message });
    }
  });

  // ── SDK device registry ───────────────────────────────────────────────────────
  // sdk-frame runs as a standalone top-level tab (opened via ui/open-link) so it
  // has full Permissions Policy including encrypted-media. It communicates with
  // the player UI via these server endpoints instead of postMessage.

  // sdk-frame POSTs its device_id here when the SDK player is ready
  app.post("/sdk-device", (req, res) => {
    _sdkDeviceId = req.body?.device_id ?? null;
    res.json({ ok: true });
  });

  // Player polls this to get the browser device_id
  app.get("/sdk-device", (_req, res) => {
    res.json({ device_id: _sdkDeviceId });
  });

  // sdk-frame subscribes here (SSE) to receive instant playback commands from the player
  app.get("/sdk-events", (req, res) => {
    res.setHeader("Content-Type", "text/event-stream");
    res.setHeader("Cache-Control", "no-cache");
    res.setHeader("Connection", "keep-alive");
    res.write(`data: ${JSON.stringify({ type: "connected" })}\n\n`);
    _sdkSseClients.push(res);
    req.on("close", () => {
      _sdkSseClients = _sdkSseClients.filter(c => c !== res);
      if (_sdkSseClients.length === 0) _sdkDeviceId = null;
    });
  });

  // Player POSTs playback commands here; forwarded instantly to sdk-frame via SSE
  app.post("/sdk-command", (req, res) => {
    const cmd = req.body;
    _sdkSseClients.forEach(c => c.write(`data: ${JSON.stringify(cmd)}\n\n`));
    res.json({ ok: true });
  });

  // ── SDK frame ─────────────────────────────────────────────────────────────────
  // Served as a real top-level page (opened via ui/open-link) so the Spotify Web
  // Playback SDK has full Permissions Policy access including encrypted-media.
  app.get("/sdk-frame", (_req, res) => {
    res.setHeader("Content-Type", "text/html");
    res.send(`<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Claude Spotify Player</title>
<script src="https://sdk.scdn.co/spotify-player.js"></script>
<style>
  * { box-sizing: border-box; margin: 0; padding: 0; }
  body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    background: #0a0a0a;
    color: #fff;
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
  }
  .card {
    background: #181818;
    border-radius: 16px;
    padding: 40px 48px;
    text-align: center;
    max-width: 380px;
    width: 100%;
    box-shadow: 0 8px 32px rgba(0,0,0,0.5);
  }
  .logo { font-size: 40px; margin-bottom: 16px; }
  h2 { font-size: 18px; font-weight: 600; margin-bottom: 6px; }
  .subtitle { font-size: 13px; color: #a7a7a7; margin-bottom: 32px; }
  .status-row {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    font-size: 13px;
    padding: 12px 20px;
    border-radius: 999px;
    background: #232323;
    margin-bottom: 16px;
  }
  .dot {
    width: 8px; height: 8px; border-radius: 50%;
    background: #535353;
    transition: background 0.3s;
    flex-shrink: 0;
  }
  .dot.ready { background: #1db954; box-shadow: 0 0 6px #1db954; }
  .dot.error { background: #e22134; }
  .hint { font-size: 12px; color: #535353; margin-top: 24px; line-height: 1.5; }
</style>
</head>
<body>
<div class="card">
  <div class="logo">🎵</div>
  <h2>Claude Spotify Player</h2>
  <p class="subtitle">Browser audio device</p>
  <div class="status-row">
    <span class="dot" id="dot"></span>
    <span id="status-text">Connecting to Spotify…</span>
  </div>
  <p class="hint">This tab provides audio output for the Spotify player.<br>You can minimize it — don't close it.</p>
</div>
<script>
const SERVER = ${JSON.stringify(BASE_URL)};

function setStatus(msg, state) {
  document.getElementById('status-text').textContent = msg;
  const dot = document.getElementById('dot');
  dot.className = 'dot' + (state ? ' ' + state : '');
}

window.onSpotifyWebPlaybackSDKReady = () => {
  const player = new Spotify.Player({
    name: 'Claude Spotify Player',
    getOAuthToken: async (cb) => {
      try {
        const r = await fetch(SERVER + '/auth/token');
        const d = await r.json();
        cb(d.access_token);
      } catch(e) {
        setStatus('Failed to get token', 'error');
        console.error('[sdk-frame] token fetch failed', e);
      }
    },
    volume: 0.8,
  });

  function dispatch(action, extra = {}) {
    switch (action) {
      case 'pause':    player.pause(); break;
      case 'resume':   player.resume(); break;
      case 'next':     player.nextTrack(); break;
      case 'previous': player.previousTrack(); break;
      case 'seek':     player.seek(extra.position_ms); break;
      case 'volume':   player.setVolume(extra.volume / 100); break;
    }
  }

  player.addListener('ready', ({ device_id }) => {
    setStatus('Ready · browser audio active', 'ready');
    // Notify parent iframe (when embedded)
    try { window.parent.postMessage({ type: 'BROWSER_DEVICE_READY', device_id }, '*'); } catch(_) {}
  });

  player.addListener('not_ready', () => {
    setStatus('Device went offline', 'error');
    try { window.parent.postMessage({ type: 'BROWSER_DEVICE_OFFLINE' }, '*'); } catch(_) {}
  });

  player.addListener('player_state_changed', async (state) => {
    if (!state) return;
    // Unlock AudioContext whenever Spotify signals a non-paused state
    if (!state.paused) await ensureAudioUnlocked();
    const t = state.track_window?.current_track;
    try {
      window.parent.postMessage({ type: 'SDK_STATE', state: {
        paused: state.paused, position: state.position,
        shuffle: state.shuffle, repeat_mode: state.repeat_mode,
        volume: state.playback_volume,
        track: t ? { name: t.name, uri: t.uri, duration_ms: t.duration_ms,
          artists: t.artists, album: t.album } : null,
      }}, '*');
    } catch(_) {}
  });

  player.addListener('account_error', () => {
    setStatus('Spotify Premium required', 'error');
    try { window.parent.postMessage({ type: 'SDK_PREMIUM_REQUIRED' }, '*'); } catch(_) {}
  });
  player.addListener('initialization_error', ({ message }) => setStatus('Error: ' + message, 'error'));
  player.addListener('authentication_error', ({ message }) => setStatus('Auth error — please re-authenticate', 'error'));

  // Unlock the browser AudioContext on first interaction.
  // The SDK uses an internal AudioContext that starts "suspended" when there
  // has been no user gesture directly inside this frame. We work around this
  // by creating a silent AudioContext and calling resume() — Chrome's
  // per-tab sticky activation means this succeeds once the user has clicked
  // anywhere in the tab (e.g. the play button in the parent player frame).
  let _audioUnlocked = false;
  async function ensureAudioUnlocked() {
    if (_audioUnlocked) return;
    try {
      const ctx = new AudioContext();
      await ctx.resume();
      // Play a silent buffer so the browser marks audio as "user-initiated"
      const buf = ctx.createBuffer(1, 1, 22050);
      const src = ctx.createBufferSource();
      src.buffer = buf;
      src.connect(ctx.destination);
      src.start(0);
      _audioUnlocked = true;
    } catch(_) {}
  }

  player.connect();
  window._player = player;

  // Accept commands via postMessage from parent iframe
  window.addEventListener('message', async (e) => {
    const d = e.data;
    if (d?.type === 'SDK_COMMAND') {
      await ensureAudioUnlocked();
      dispatch(d.action, d);
    }
  });

};
</script>
</body>
</html>`);
  });

  // ── MCP endpoint ────────────────────────────────────────────────────────────
  // We create a fresh McpServer + transport per request (stateless mode).
  // This keeps things simple for a single-user server and avoids session
  // management complexity. Each tool call round-trip is self-contained.

  app.all("/mcp", async (req, res) => {
    try {
      const mcpServer = createMcpServer(spotify, BASE_URL);
      const transport = new StreamableHTTPServerTransport({
        sessionIdGenerator: undefined, // stateless — no session IDs needed
      });

      // Clean up after the response is done
      res.on("finish", async () => {
        await transport.close();
        await mcpServer.close();
      });

      await mcpServer.connect(transport);
      await transport.handleRequest(req, res, req.body);
    } catch (err) {
      console.error("MCP request error:", err);
      if (!res.headersSent) {
        res.status(500).json({ error: "Internal server error" });
      }
    }
  });

  return app;
}