feat(api): add GitHub health check to health endpoint

app/api/health/route.test.ts

@@ -0,0 +1,102 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest';
+import { GET } from './route';
+
+vi.mock('@/lib/github', () => ({
+  checkGitHubHealth: vi.fn(),
+  getCircuitTelemetry: vi.fn(),
+}));
+
+vi.mock('@/services/github/quota-monitor', () => ({
+  quotaMonitor: {
+    getAggregateQuota: vi.fn(),
+  },
+}));
+
+import { checkGitHubHealth, getCircuitTelemetry } from '@/lib/github';
+import { quotaMonitor } from '@/services/github/quota-monitor';
+
+describe('GET /api/health', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+
+    vi.mocked(checkGitHubHealth).mockResolvedValue(undefined);
+
+    vi.mocked(getCircuitTelemetry).mockReturnValue({
+      isOpen: false,
+      resetInMs: 0,
+    });
+
+    vi.mocked(quotaMonitor.getAggregateQuota).mockReturnValue({
+      totalTokens: 1,
+      activeTokens: 1,
+      aggregateLimit: 5000,
+      aggregateRemaining: 4500,
+      lowestRemainingPercent: 90,
+      totalRefreshes: 0,
+    });
+  });
+
+  it('returns 200 when GitHub health check succeeds', async () => {
+    const response = await GET();
+
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+
+    expect(body.status).toBe('healthy');
+    expect(body.githubApi).toBe('ok');
+    expect(body.quota).toBeDefined();
+    expect(body.circuitBreaker).toBeDefined();
+    expect(body.timestamp).toBeDefined();
+  });
+
+  it('returns 503 when GitHub health check fails', async () => {
+    vi.mocked(checkGitHubHealth).mockRejectedValue(new Error('Bad credentials'));
+
+    const response = await GET();
+
+    expect(response.status).toBe(503);
+
+    const body = await response.json();
+
+    expect(body.status).toBe('degraded');
+    expect(body.githubApi).toBe('error');
+    expect(body.message).toContain('Bad credentials');
+  });
+
+  it('returns exhausted when the circuit breaker is open', async () => {
+    vi.mocked(getCircuitTelemetry).mockReturnValue({
+      isOpen: true,
+      resetInMs: 1000,
+    });
+
+    const response = await GET();
+
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+
+    expect(body.status).toBe('exhausted');
+    expect(body.githubApi).toBe('ok');
+  });
+
+  it('returns degraded when quota is low', async () => {
+    vi.mocked(quotaMonitor.getAggregateQuota).mockReturnValue({
+      totalTokens: 1,
+      activeTokens: 1,
+      aggregateLimit: 5000,
+      aggregateRemaining: 200,
+      lowestRemainingPercent: 5,
+      totalRefreshes: 0,
+    });
+
+    const response = await GET();
+
+    expect(response.status).toBe(200);
+
+    const body = await response.json();
+
+    expect(body.status).toBe('degraded');
+    expect(body.githubApi).toBe('ok');
+  });
+});

app/api/health/route.ts

@@ -1,10 +1,22 @@
 import { NextResponse } from 'next/server';
-import { getCircuitTelemetry } from '@/lib/github';
+import { checkGitHubHealth, getCircuitTelemetry } from '@/lib/github';
 import { quotaMonitor } from '@/services/github/quota-monitor';
 
 export const dynamic = 'force-dynamic';
 
 export async function GET() {
+  try {
+    await checkGitHubHealth();
+  } catch (error) {
+    return NextResponse.json(
+      {
+        status: 'degraded',
+        githubApi: 'error',
+        message: error instanceof Error ? error.message : 'Unknown GitHub API error',
+      },
+      { status: 503 }
+    );
+  }
   const aggregate = quotaMonitor.getAggregateQuota();
   const circuit = getCircuitTelemetry();
 
@@ -16,6 +28,7 @@ export async function GET() {
 
   return NextResponse.json({
     status,
+    githubApi: 'ok',
     quota: {
       totalTokens: aggregate.totalTokens,
       activeTokens: aggregate.activeTokens,

lib/github.ts

@@ -791,7 +791,7 @@ export async function handleTokenExpiration(token: string): Promise<void> {
   }
 }
 
-const getHeaders = (userToken?: string) => ({
+export const getHeaders = (userToken?: string) => ({
   Authorization: `bearer ${userToken || getGitHubToken()}`,
   'Content-Type': 'application/json',
 });
@@ -2884,3 +2884,30 @@ function getMockRepo(repoName: string): GitHubRepo {
     participation: [],
   };
 }
+
+export async function checkGitHubHealth(): Promise<void> {
+  const query = `
+    query {
+      viewer {
+        login
+      }
+    }
+  `;
+
+  const response = await fetchWithRetry(GITHUB_GRAPHQL_URL, {
+    method: 'POST',
+    headers: getHeaders(),
+    body: JSON.stringify({ query }),
+    cache: 'no-store',
+  });
+
+  if (!response.ok) {
+    throw new Error(`GitHub API returned ${response.status}`);
+  }
+
+  const data = await response.json();
+
+  if (data.errors) {
+    throw new Error(getGraphQLErrorMessage(data.errors));
+  }
+}