feat(server/workers): serve b2 assets

Author: PoiScript

web/workers/main.ts

@@ -1,3 +1,6 @@
+// environment variables
+declare const B2_URL: string;
+
 import { getAssetFromKV } from "@cloudflare/kv-asset-handler";
 
 addEventListener("fetch", (event) => {
@@ -9,10 +12,19 @@ addEventListener("fetch", (event) => {
 });
 
 async function handleEvent(event: FetchEvent): Promise<Response> {
-  const url = new URL(event.request.url);
+  const request = event.request;
+  const url = new URL(request.url);
 
   if (url.pathname.startsWith("/api")) {
-    return fetch(event.request);
+    const response = await fetch(request);
+
+    return hanldeEtag(request, response);
+  }
+
+  if (url.pathname.startsWith("/thumbnail")) {
+    const response = await getAssetFromB2(url.pathname.slice(10));
+
+    return hanldeEtag(request, response);
   }
 
   return getAssetFromKV(event).catch(() =>
@@ -21,3 +33,48 @@ async function handleEvent(event: FetchEvent): Promise<Response> {
     })
   );
 }
+
+async function getAssetFromB2(key: string): Promise<Response> {
+  const response = await fetch(`${B2_URL}${key}`, {
+    cf: { cacheEverything: true, cacheTtl: 60 },
+  });
+
+  const headers = new Headers(response.headers);
+
+  if (!response.ok) {
+    headers.set("cache-control", "max-age=0, no-cache, no-store");
+
+    return new Response(null, {
+      status: 404,
+      headers,
+      statusText: "Not Found",
+    });
+  }
+
+  headers.set("cache-control", "public, max-age=3600");
+  if (headers.has("x-bz-upload-timestamp")) {
+    headers.set("etag", headers.get("x-bz-upload-timestamp") as string);
+  }
+  headers.delete("x-bz-content-sha1");
+  headers.delete("x-bz-file-id");
+  headers.delete("x-bz-file-name");
+  headers.delete("x-bz-upload-timestamp");
+
+  return new Response(response.body, { headers });
+}
+
+function hanldeEtag(request: Request, response: Response): Response {
+  if (
+    response.headers.has("etag") &&
+    request.headers.has("if-none-match") &&
+    request.headers.get("if-none-match") === response.headers.get("etag")
+  ) {
+    return new Response(null, {
+      status: 304,
+      headers: response.headers,
+      statusText: "Not Modified",
+    });
+  }
+
+  return response;
+}