ep-133-sample-tool-offline/launcher.mjs

import { createReadStream, statSync } from "node:fs";
import { createServer } from "node:http";
import { spawn } from "node:child_process";
import { dirname, extname, join, normalize } from "node:path";
import { fileURLToPath } from "node:url";

const projectRoot = dirname(fileURLToPath(import.meta.url));
const webRoot = join(projectRoot, "web");
const shouldOpenBrowser = !process.argv.includes("--no-open");

const contentTypes = {
  ".css": "text/css; charset=utf-8",
  ".html": "text/html; charset=utf-8",
  ".ico": "image/x-icon",
  ".js": "text/javascript; charset=utf-8",
  ".json": "application/json; charset=utf-8",
  ".pak": "application/octet-stream",
  ".png": "image/png",
  ".wasm": "application/wasm",
  ".woff2": "font/woff2",
};

function localPath(url) {
  const pathname = decodeURIComponent(new URL(url, "http://127.0.0.1").pathname);
  const requested = pathname === "/" ? "/apps/ep-sample-tool/" : pathname;
  const relative = normalize(requested).replace(/^([/\\])+/, "");
  const candidate = join(webRoot, relative);
  if (!candidate.startsWith(webRoot)) return null;

  try {
    return statSync(candidate).isDirectory() ? join(candidate, "index.html") : candidate;
  } catch {
    return candidate;
  }
}

const server = createServer((request, response) => {
  // The upstream app reports errors to /_api/err. Keep that diagnostic local.
  if (request.url?.startsWith("/_api/err")) {
    response.writeHead(204).end();
    return;
  }

  const path = localPath(request.url ?? "/");
  if (!path) {
    response.writeHead(403).end("Forbidden");
    return;
  }

  try {
    const { size } = statSync(path);
    response.writeHead(200, {
      "Cache-Control": "no-store",
      "Content-Length": size,
      "Content-Type": contentTypes[extname(path)] ?? "application/octet-stream",
      "Cross-Origin-Opener-Policy": "same-origin",
      "X-Content-Type-Options": "nosniff",
    });
    createReadStream(path).pipe(response);
  } catch {
    response.writeHead(404, { "Content-Type": "text/plain; charset=utf-8" });
    response.end("Not found");
  }
});

server.listen(0, "127.0.0.1", () => {
  const address = server.address();
  if (!address || typeof address === "string") throw new Error("Could not start local server");

  const url = `http://127.0.0.1:${address.port}/apps/ep-sample-tool/`;
  if (!shouldOpenBrowser) {
    console.log(`READY ${url}`);
    return;
  }

  const candidates = [
    "/Applications/Google Chrome.app/Contents/MacOS/Google Chrome",
    "/Applications/Chromium.app/Contents/MacOS/Chromium",
    "/Applications/Microsoft Edge.app/Contents/MacOS/Microsoft Edge",
  ];
  const browser = candidates.find((candidate) => {
    try {
      return statSync(candidate).isFile();
    } catch {
      return false;
    }
  });

  if (!browser) {
    console.error("Google Chrome, Chromium, or Microsoft Edge is required for Web MIDI.");
    console.error(`Open this URL in a Web MIDI browser: ${url}`);
    return;
  }

  spawn(browser, [`--app=${url}`, "--new-window"], {
    detached: true,
    stdio: "ignore",
  }).unref();

  console.log("EP sample tool is running fully locally.");
  console.log(`Local address: ${url}`);
  console.log("Keep this window open while using the tool. Press Control-C to stop.");
});

for (const signal of ["SIGINT", "SIGTERM"]) {
  process.on(signal, () => server.close(() => process.exit(0)));
}