feat: improve error messages (#1006)

lib/utils.ts

@@ -2,32 +2,44 @@ import type { CoreAssistantMessage, CoreToolMessage, UIMessage } from 'ai';
 import { type ClassValue, clsx } from 'clsx';
 import { twMerge } from 'tailwind-merge';
 import type { Document } from '@/lib/db/schema';
+import { ChatSDKError, type ErrorCode } from './errors';
 
 export function cn(...inputs: ClassValue[]) {
   return twMerge(clsx(inputs));
 }
 
-interface ApplicationError extends Error {
-  info: string;
-  status: number;
-}
-
 export const fetcher = async (url: string) => {
-  const res = await fetch(url);
+  const response = await fetch(url);
 
-  if (!res.ok) {
-    const error = new Error(
-      'An error occurred while fetching the data.',
-    ) as ApplicationError;
+  if (!response.ok) {
+    const { code, cause } = await response.json();
+    throw new ChatSDKError(code as ErrorCode, cause);
+  }
 
-    error.info = await res.json();
-    error.status = res.status;
+  return response.json();
+};
+
+export async function fetchWithErrorHandlers(
+  input: RequestInfo | URL,
+  init?: RequestInit,
+) {
+  try {
+    const response = await fetch(input, init);
+
+    if (!response.ok) {
+      const { code, cause } = await response.json();
+      throw new ChatSDKError(code as ErrorCode, cause);
+    }
+
+    return response;
+  } catch (error: unknown) {
+    if (typeof navigator !== 'undefined' && !navigator.onLine) {
+      throw new ChatSDKError('offline:chat');
+    }
 
     throw error;
   }
-
-  return res.json();
-};
+}
 
 export function getLocalStorage(key: string) {
   if (typeof window !== 'undefined') {