writeStream

web/apps/photos/src/utils/native-stream.ts

@@ -0,0 +1,39 @@
+/**
+ * @file Streaming IPC communication with the Node.js layer of our desktop app.
+ *
+ * NOTE: These functions only work when we're running in our desktop app.
+ */
+
+/**
+ * Write the given stream to a file on the local machine.
+ *
+ * **This only works when we're running in our desktop app**. It uses the
+ * "stream://" protocol handler exposed by our custom code in the Node.js layer.
+ * See: [Note: IPC streams].
+ *
+ * @param path The path on the local machine where to write the file to.
+ * @param stream The stream which should be written into the file.
+ *  */
+export const writeStream = async (path: string, stream: ReadableStream) => {
+    // The duplex parameter needs to be set to 'half' when streaming requests.
+    //
+    // Currently browsers, and specifically in our case, since this code runs
+    // only within our desktop (Electron) app, Chromium, don't support 'full'
+    // duplex mode (i.e. streaming both the request and the response).
+    // https://developer.chrome.com/docs/capabilities/web-apis/fetch-streaming-requests
+    //
+    // In another twist, the TypeScript libdom.d.ts does not include the
+    // "duplex" parameter, so we need to cast to get TypeScript to let this code
+    // through. e.g. see https://github.com/node-fetch/node-fetch/issues/1769
+    const req = new Request(`stream://write/${path}`, {
+        // GET can't have a body
+        method: "POST",
+        body: stream,
+        duplex: "half",
+    } as unknown as RequestInit);
+    const res = await fetch(req);
+    if (!res.ok)
+        throw new Error(
+            `Failed to write stream to ${path}: HTTP ${res.status}`,
+        );
+};