useful utility for debugging raw LLM response (#181)

src/ipc/utils/debug_fetch.ts

+import log from "electron-log";
+
+const logger = log.scope("debug-fetch");
+
+interface DebugFetchOptions extends RequestInit {
+  debugTag?: string;
+  logResponse?: boolean;
+  logStream?: boolean;
+  includeUsageInStream?: boolean;
+}
+
+/**
+ * A debug-friendly fetch wrapper that logs requests and responses
+ * Particularly useful for debugging SSE streams
+ */
+export async function debugFetch(
+  url: RequestInfo | URL,
+  options: DebugFetchOptions = {},
+): Promise<Response> {
+  const {
+    debugTag = "fetch",
+    logResponse = true,
+    logStream = true,
+    ...fetchOptions
+  } = options;
+
+  // Log the request
+  logger.info(`[${debugTag}] Request:`, {
+    url,
+    method: fetchOptions.method || "GET",
+    headers: fetchOptions.headers,
+  });
+
+  if (fetchOptions.body && options.includeUsageInStream) {
+    fetchOptions.body = JSON.stringify({
+      ...JSON.parse(fetchOptions.body as string),
+      stream_options: { include_usage: true },
+    });
+  }
+
+  const response = await fetch(url, fetchOptions);
+
+  // Log the initial response
+  logger.info(`[${debugTag}] Response:`, {
+    status: response.status,
+    statusText: response.statusText,
+    headers: Object.fromEntries(response.headers.entries()),
+  });
+
+  // If it's not a stream or we don't want to log it, return as is
+  if (!logResponse || !response.body) {
+    return response;
+  }
+
+  // Clone the response so we can read it multiple times
+  const clonedResponse = response.clone();
+
+  // If it's a stream and we want to log it
+  if (logStream && isEventStream(response)) {
+    // Create a new ReadableStream that will log chunks as they come in
+    const loggedBody = new ReadableStream({
+      async start(controller) {
+        const reader = clonedResponse.body!.getReader();
+        const decoder = new TextDecoder();
+
+        try {
+          while (true) {
+            const { done, value } = await reader.read();
+            if (done) break;
+
+            const chunk = decoder.decode(value, { stream: true });
+            logger.info(`[${debugTag}] Stream chunk:`, chunk);
+            controller.enqueue(value);
+          }
+          controller.close();
+        } catch (error) {
+          logger.error(`[${debugTag}] Stream error:`, error);
+          controller.error(error);
+        }
+      },
+    });
+
+    // Return a new response with our logged body
+    return new Response(loggedBody, {
+      headers: response.headers,
+      status: response.status,
+      statusText: response.statusText,
+    });
+  }
+
+  // For non-stream responses, log the body if requested
+  if (logResponse) {
+    try {
+      const bodyText = await clonedResponse.text();
+      logger.info(`[${debugTag}] Response body:`, bodyText);
+    } catch (error) {
+      logger.error(`[${debugTag}] Error reading response body:`, error);
+    }
+  }
+
+  return response;
+}
+
+function isEventStream(response: Response): boolean {
+  const contentType = response.headers.get("content-type");
+  return contentType?.includes("text/event-stream") || false;
+}