Fix video playback from R2 with proper range request handling

Critical fixes for video streaming:

- Fix range request handling by using HEAD request first
  - Get total file size before processing range requests
  - Properly calculate Content-Range header with accurate boundaries
  - Prevent issues where object.size wasn't available on range requests

- Add proper CORS headers for video streaming
  - Expose Content-Length, Content-Range, Accept-Ranges headers
  - Allow Range header in requests
  - Enables video seeking and progressive loading in browsers

- Improve range request logic
  - Ensure end byte doesn't exceed file size
  - Calculate correct Content-Length for partial responses
  - Always return accurate byte ranges in 206 responses

These fixes resolve issues where videos wouldn't play or seek properly
due to incorrect Content-Range headers and missing CORS headers.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

worker/video-server-enhanced.js

@@ -139,7 +139,8 @@ export default {
     const corsHeaders = {
       'Access-Control-Allow-Origin': '*',
       'Access-Control-Allow-Methods': 'GET, HEAD, POST, DELETE, OPTIONS',
-      'Access-Control-Allow-Headers': '*',
+      'Access-Control-Allow-Headers': 'Range, Content-Type, Accept',
+      'Access-Control-Expose-Headers': 'Content-Length, Content-Range, Accept-Ranges',
     };
 
     if (request.method === 'OPTIONS') {
@@ -450,15 +451,32 @@ async function handleClip(request, env, path, corsHeaders) {
 async function serveVideo(request, bucket, filename, corsHeaders) {
   const range = request.headers.get('Range');
 
+  // First, get the file metadata to know the total size
+  const objectHead = await bucket.head(filename);
+  if (!objectHead) {
+    return new Response('Video not found', { status: 404, headers: corsHeaders });
+  }
+
+  const totalSize = objectHead.size;
+  const contentType = getContentType(filename);
+
   let object;
+  let start = 0;
+  let end = totalSize - 1;
+
   if (range) {
     const rangeMatch = range.match(/bytes=(\d+)-(\d*)/);
     if (rangeMatch) {
-      const start = parseInt(rangeMatch[1]);
+      start = parseInt(rangeMatch[1]);
-      const end = rangeMatch[2] ? parseInt(rangeMatch[2]) : undefined;
+      end = rangeMatch[2] ? parseInt(rangeMatch[2]) : totalSize - 1;
+
+      // Ensure end doesn't exceed file size
+      if (end >= totalSize) {
+        end = totalSize - 1;
+      }
 
       object = await bucket.get(filename, {
-        range: { offset: start, length: end ? end - start + 1 : undefined }
+        range: { offset: start, length: end - start + 1 }
       });
     } else {
       object = await bucket.get(filename);
@@ -471,7 +489,6 @@ async function serveVideo(request, bucket, filename, corsHeaders) {
     return new Response('Video not found', { status: 404, headers: corsHeaders });
   }
 
-  const contentType = getContentType(filename);
   const headers = {
     'Content-Type': contentType,
     'Cache-Control': 'public, max-age=31536000',
@@ -479,13 +496,13 @@ async function serveVideo(request, bucket, filename, corsHeaders) {
     ...corsHeaders,
   };
 
-  if (range && object.range) {
+  if (range) {
-    headers['Content-Range'] = `bytes ${object.range.offset}-${object.range.offset + object.range.length - 1}/${object.size}`;
+    headers['Content-Range'] = `bytes ${start}-${end}/${totalSize}`;
-    headers['Content-Length'] = object.range.length;
+    headers['Content-Length'] = end - start + 1;
 
     return new Response(object.body, { status: 206, headers });
   } else {
-    headers['Content-Length'] = object.size;
+    headers['Content-Length'] = totalSize;
     return new Response(object.body, { status: 200, headers });
   }
 }