web/task-manager: move workers next to runners

web/src/lib/task-manager/workers/fetch.ts

@@ -0,0 +1,94 @@
+import { OPFSStorage } from "$lib/storage";
+
+let attempts = 0;
+
+const fetchFile = async (url: string) => {
+    const error = async (code: string) => {
+        attempts++;
+
+        if (attempts <= 5) {
+            // try 5 more times before actually failing
+
+            console.log("fetch attempt", attempts);
+            await fetchFile(url);
+        } else {
+            // if it still fails, then throw an error and quit
+            self.postMessage({
+                cobaltFetchWorker: {
+                    // TODO: return proper error code here
+                    // (error.code and not just random shit i typed up)
+                    error: code,
+                }
+            });
+            self.close();
+        }
+    };
+
+    try {
+        const response = await fetch(url);
+
+        if (!response.ok) {
+            return error("file response wasn't ok");
+        }
+
+        const contentType = response.headers.get('Content-Type') || 'application/octet-stream';
+        const contentLength = response.headers.get('Content-Length');
+
+        const totalBytes = contentLength ? parseInt(contentLength, 10) : null;
+        const reader = response.body?.getReader();
+
+        const storage = await OPFSStorage.init();
+
+        if (!reader) {
+            return error("no reader");
+        }
+
+        let receivedBytes = 0;
+
+        while (true) {
+            const { done, value } = await reader.read();
+            if (done) break;
+
+            await storage.write(value, receivedBytes);
+            receivedBytes += value.length;
+
+            if (totalBytes) {
+                self.postMessage({
+                    cobaltFetchWorker: {
+                        progress: Math.round((receivedBytes / totalBytes) * 100),
+                        size: receivedBytes,
+                    }
+                });
+            }
+        }
+
+        if (receivedBytes === 0) {
+            return error("tunnel is broken");
+        }
+
+        const file = await storage.res();
+
+        if (Number(contentLength) !== file.size) {
+            return error("file was not downloaded fully");
+        }
+
+        self.postMessage({
+            cobaltFetchWorker: {
+                result: {
+                    file,
+                    type: contentType,
+                }
+            }
+        });
+    } catch (e) {
+        console.log(e);
+        return error("error when downloading the file");
+    }
+}
+
+self.onmessage = async (event: MessageEvent) => {
+    if (event.data.cobaltFetchWorker) {
+        await fetchFile(event.data.cobaltFetchWorker.url);
+        self.close();
+    }
+}