Merging Resources and Responding in Streaming Mode

async function sequentialCombine(urls, destination) {
  try {
    // Process each URL in order
    for (let i = 0; i < urls.length; i++) {
      const url = urls[i];

      // Get the current clip
      const response = await fetch(url);

      if (!response.ok) {
        console.error(`Failed to obtain video clip: ${url}, Error code: ${response.status}`);
        continue;
      }

      // Get a readable stream
      const readable = response.body;

      // Execute pipeTo immediately to write the current clip to the target stream
      try {
        await readable.pipeTo(destination, {
          preventClose: true // Keep the stream open for subsequent writing
        });
      } catch (e) {
        console.error(`Stream processing errors (${url}): ${e.message}`);
      }
    }
  } catch (err) {
    console.error(`Merging video streams error: ${err.message}`);
  } finally {
    // Close the stream after all fragments are processed
    const writer = destination.getWriter();
    writer.close();
    writer.releaseLock();
  }
}

async function handleRequest(request) {
  // The URLs of the video clips.
  const urls = [
    'https://vod.example.com/stream-01.mov',
    'https://vod.example.comm/stream-02.mov',
    'https://vod.example.com/stream-03.mov',
  ];

  // Creating a Transformation Flow
  const { readable, writable } = new TransformStream();

  // Get and merge video clips in sequence
  sequentialCombine(urls, writable);

  // Returns the merged video stream response
  return new Response(readable, {
    headers: {
      'content-type': 'video/mp4',
    }
  });
}

// Listening for fetch events
addEventListener('fetch', event => {
  event.respondWith(handleRequest(event.request));
});