fix: validate ActivityFeed API response schema

Author: Tanayajadhav1

src/components/ActivityFeed.tsx

@@ -9,9 +9,58 @@ interface EventType {
   };
 }
 
+interface FetchError {
+  message: string;
+  isRateLimited: boolean;
+  statusCode?: number;
+}
+
+// Custom error class for ActivityFeed errors
+class ActivityFeedError extends Error {
+  constructor(
+    message: string,
+    public isRateLimited = false,
+    public statusCode?: number
+  ) {
+    super(message);
+    this.name = "ActivityFeedError";
+  }
+}
+
+// Type guard to validate if data is EventType[]
+const isEventTypeArray = (data: unknown): data is EventType[] => {
+  if (!Array.isArray(data)) return false;
+  return data.every((item) => {
+    if (typeof item !== "object" || item === null) return false;
+
+    // Validate required fields
+    if (
+      typeof item.id !== "string" ||
+      typeof item.type !== "string" ||
+      typeof item.created_at !== "string"
+    ) {
+      return false;
+    }
+
+    // Validate optional repo field
+    if (item.repo !== undefined) {
+      if (
+        typeof item.repo !== "object" ||
+        item.repo === null ||
+        typeof item.repo.name !== "string"
+      ) {
+        return false;
+      }
+    }
+
+    return true;
+  });
+};
+
 export default function ActivityFeed({ username }: { username: string }) {
   const [events, setEvents] = useState<EventType[]>([]);
   const [loading, setLoading] = useState(true);
+  const [error, setError] = useState<FetchError | null>(null);
 
   // 🕒 time ago function
   const getTimeAgo = (dateString: string) => {
@@ -29,16 +78,65 @@ export default function ActivityFeed({ username }: { username: string }) {
     const fetchEvents = async () => {
       try {
         setLoading(true);
+        setError(null);
 
         const res = await fetch(
           `https://api.github.com/users/${username}/events`
         );
+
+        // ✅ Check HTTP response success
+        if (!res.ok) {
+          const isRateLimited = res.status === 403;
+          const errorData = await res.json().catch(() => ({}));
+          const errorMessage =
+            typeof errorData === "object" &&
+            errorData !== null &&
+            "message" in errorData &&
+            typeof errorData.message === "string"
+              ? errorData.message
+              : `HTTP ${res.status}: Failed to fetch events`;
+
+          throw new ActivityFeedError(
+            isRateLimited
+              ? "GitHub API rate limit exceeded. Try again later."
+              : errorMessage,
+            isRateLimited,
+            res.status
+          );
+        }
+
         const data = await res.json();
 
+        // ✅ Validate response structure matches EventType[]
+        if (!isEventTypeArray(data)) {
+          throw new ActivityFeedError(
+            "Invalid API response structure. Expected array of events.",
+            false,
+            200
+          );
+        }
+
         setEvents(data);
-        setLoading(false);
       } catch (err) {
-        console.error(err);
+        const fetchError: FetchError = {
+          message: "Failed to fetch activity. Please try again.",
+          isRateLimited: false,
+        };
+
+        // Handle ActivityFeedError instances
+        if (err instanceof ActivityFeedError) {
+          fetchError.message = err.message;
+          fetchError.isRateLimited = err.isRateLimited;
+          fetchError.statusCode = err.statusCode;
+        } else if (err instanceof Error) {
+          // Handle generic errors
+          fetchError.message = err.message || fetchError.message;
+        }
+
+        setError(fetchError);
+        console.error("ActivityFeed fetch error:", fetchError);
+        setEvents([]);
+      } finally {
         setLoading(false);
       }
     };
@@ -56,9 +154,25 @@ export default function ActivityFeed({ username }: { username: string }) {
       </h2>
 
       {loading ? (
-        <p className="text-center">Loading...</p>
+        <p className="text-center text-gray-500">Loading activity...</p>
+      ) : error ? (
+        <div className="border border-red-300 rounded-lg p-4 mb-3 bg-red-50 dark:bg-red-900/20">
+          <p className="text-sm font-semibold text-red-700 dark:text-red-300">
+            ⚠️ {error.message}
+          </p>
+          {error.isRateLimited && (
+            <p className="text-xs text-red-600 dark:text-red-400 mt-2">
+              You've hit GitHub's API rate limit. The limit resets in 1 hour.
+            </p>
+          )}
+          {error.statusCode === 404 && (
+            <p className="text-xs text-red-600 dark:text-red-400 mt-2">
+              User not found. Please check the username.
+            </p>
+          )}
+        </div>
       ) : events.length === 0 ? (
-        <p className="text-center">No activity found</p>
+        <p className="text-center text-gray-500">No activity found</p>
       ) : (
         events.slice(0, 10).map((event) => (
           <div