sync: phase 1 backend + frontend from server

web/src/lib/api.ts

@@ -1,12 +1,17 @@
 const API_BASE = '/api/v1';
 
+export interface ApiError extends Error {
+  status?: number;
+  retryAfter?: number;
+}
+
 async function request<T>(method: string, path: string, body?: unknown): Promise<T> {
   const headers: Record<string, string> = {};
   if (body !== undefined) {
     headers['Content-Type'] = 'application/json';
   }
 
-  const response = await fetch(`${API_BASE}${path}`, {
+  const response = await fetch(API_BASE + path, {
     method,
     headers,
     credentials: 'include',
@@ -14,7 +19,8 @@ async function request<T>(method: string, path: string, body?: unknown): Promise
   });
 
   if (!response.ok) {
-    let errorMessage = `Request failed: ${response.status}`;
+    let errorMessage = 'Request failed: ' + response.status;
+    let retryAfter: number | undefined;
     try {
       const errorData = await response.json();
       if (typeof errorData?.message === 'string') {
@@ -22,10 +28,19 @@ async function request<T>(method: string, path: string, body?: unknown): Promise
       } else if (typeof errorData?.error === 'string') {
         errorMessage = errorData.error;
       }
+      if (response.status === 429 && typeof errorData?.retry_after === 'number') {
+        retryAfter = errorData.retry_after;
+      }
     } catch {
       // ignore parse error
     }
-    throw new Error(errorMessage);
+    const err = new Error(errorMessage) as ApiError;
+    err.status = response.status;
+    if (response.status === 429) {
+      const ra = response.headers.get('Retry-After');
+      err.retryAfter = retryAfter ?? (ra ? parseInt(ra, 10) : undefined);
+    }
+    throw err;
   }
 
   if (response.status === 204) {