feat(github): add exponential backoff retry for GitHub API calls

Wraps all fetch calls to the GitHub GraphQL and REST APIs with an
exponential backoff retry helper. Retries only on network errors,
429 Too Many Requests, and 5xx server errors (up to 3 attempts with
500ms → 1s → 2s delays). All 4xx client errors return immediately
without retrying to avoid duplicate requests on non-transient failures.

Author: Priyanshu-byte-coder

lib/github.ts

@@ -9,6 +9,39 @@ interface GitHubRepo {
   language: string | null;
 }
 
+const MAX_RETRIES = 3;
+const BASE_DELAY_MS = 500;
+
+/**
+ * Wraps fetch with exponential backoff retry logic.
+ * Retries ONLY on network errors, 429 Too Many Requests, and 5xx server errors.
+ * Returns immediately for all other statuses (2xx success, 3xx redirects, 4xx client errors).
+ */
+export async function fetchWithRetry(
+  url: string,
+  options: RequestInit,
+  attempt = 0
+): Promise<Response> {
+  let res: Response | null = null;
+  try {
+    res = await fetch(url, options);
+  } catch (err) {
+    // Network error — retry if attempts remain, otherwise rethrow
+    if (attempt >= MAX_RETRIES) throw err;
+    const delay = BASE_DELAY_MS * Math.pow(2, attempt);
+    await new Promise((resolve) => setTimeout(resolve, delay));
+    return fetchWithRetry(url, options, attempt + 1);
+  }
+
+  // Only retry on 429 or 5xx — all other statuses are returned immediately
+  const shouldRetry = res.status === 429 || res.status >= 500;
+  if (!shouldRetry || attempt >= MAX_RETRIES) return res;
+
+  const delay = BASE_DELAY_MS * Math.pow(2, attempt);
+  await new Promise((resolve) => setTimeout(resolve, delay));
+  return fetchWithRetry(url, options, attempt + 1);
+}
+
 const GITHUB_GRAPHQL_URL = 'https://api.github.com/graphql';
 const GITHUB_REST_URL = 'https://api.github.com';
 
@@ -91,7 +124,7 @@ export async function fetchGitHubContributions(
     }
   `;
 
-  const res = await fetch(GITHUB_GRAPHQL_URL, {
+  const res = await fetchWithRetry(GITHUB_GRAPHQL_URL, {
     method: 'POST',
     headers: getHeaders(),
     body: JSON.stringify({ query, variables: { login: username } }),
@@ -133,7 +166,7 @@ export async function fetchUserProfile(
     if (cached) return cached;
   }
 
-  const res = await fetch(`${GITHUB_REST_URL}/users/${username}`, {
+  const res = await fetchWithRetry(`${GITHUB_REST_URL}/users/${username}`, {
     headers: getHeaders(),
     cache: 'no-store',
   });
@@ -163,10 +196,13 @@ export async function fetchUserRepos(
     if (cached) return cached;
   }
 
-  const res = await fetch(`${GITHUB_REST_URL}/users/${username}/repos?per_page=100&sort=pushed`, {
-    headers: getHeaders(),
-    cache: 'no-store',
-  });
+  const res = await fetchWithRetry(
+    `${GITHUB_REST_URL}/users/${username}/repos?per_page=100&sort=pushed`,
+    {
+      headers: getHeaders(),
+      cache: 'no-store',
+    }
+  );
 
   if (!res.ok) {
     throw new Error(`GitHub REST API error: ${res.status}`);