feat: enhancement Certificate Generation

src/app/certificates/__tests__/page.test.tsx

@@ -1,40 +1,209 @@
-import { fireEvent, render, screen, waitFor } from '@testing-library/react';
-import { describe, expect, it, vi, afterEach } from 'vitest';
-import CertificateGenerationPage from '../page';
-import { apiClient } from '@/lib/api';
+import { render, screen, waitFor, fireEvent } from '@testing-library/react';
+import userEvent from '@testing-library/user-event';
+import { describe, it, expect, vi, afterEach, beforeEach } from 'vitest';
+
+// Mock recharts — jsdom cannot render SVG canvas; we just need to verify data is passed
+vi.mock('recharts', () => ({
+  BarChart: ({ children, data }: { children: React.ReactNode; data: unknown[] }) => (
+    <div data-testid="bar-chart" data-count={data.length}>
+      {children}
+    </div>
+  ),
+  Bar: () => null,
+  XAxis: () => null,
+  YAxis: () => null,
+  CartesianGrid: () => null,
+  Tooltip: () => null,
+  ResponsiveContainer: ({ children }: { children: React.ReactNode }) => <div>{children}</div>,
+}));
 
 vi.mock('@/lib/api', () => ({
   apiClient: {
     post: vi.fn(),
   },
 }));
 
+import { CertificateStats } from '@/components/certificates/CertificateStats';
+import CertificateGenerationPage from '@/app/certificates/page';
+import { apiClient } from '@/lib/api';
+
 afterEach(() => {
   vi.clearAllMocks();
 });
 
+// ---------------------------------------------------------------------------
+// CertificateStats unit tests
+// ---------------------------------------------------------------------------
+
+describe('CertificateStats', () => {
+  const sampleData = [
+    { course: '…abc00001', count: 3 },
+    { course: '…abc00002', count: 1 },
+  ];
+
+  it('renders the section heading', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    expect(screen.getByText('Generation Statistics')).toBeInTheDocument();
+  });
+
+  it('displays totalGenerated value', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={7} distinctCourses={2} />,
+    );
+    expect(screen.getByLabelText(/Certificates Generated: 7/i)).toBeInTheDocument();
+  });
+
+  it('displays distinctCourses value', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    expect(screen.getByLabelText(/Courses Covered: 2/i)).toBeInTheDocument();
+  });
+
+  it('displays peak course count (max of data)', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    // peak = 3 (max of counts 3 and 1)
+    expect(screen.getByLabelText(/Peak Course Count: 3/i)).toBeInTheDocument();
+  });
+
+  it('renders the bar chart when data is non-empty', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    expect(screen.getByTestId('bar-chart')).toBeInTheDocument();
+  });
+
+  it('passes correct data length to bar chart', () => {
+    render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    expect(screen.getByTestId('bar-chart')).toHaveAttribute('data-count', '2');
+  });
+
+  it('does not render the bar chart when data is empty', () => {
+    render(
+      <CertificateStats data={[]} totalGenerated={0} distinctCourses={0} />,
+    );
+    expect(screen.queryByTestId('bar-chart')).not.toBeInTheDocument();
+  });
+
+  it('shows 0 for Peak Course Count when data is empty', () => {
+    render(
+      <CertificateStats data={[]} totalGenerated={0} distinctCourses={0} />,
+    );
+    expect(screen.getByLabelText(/Peak Course Count: 0/i)).toBeInTheDocument();
+  });
+
+  it('is accessible: section has an aria-label', () => {
+    const { container } = render(
+      <CertificateStats data={sampleData} totalGenerated={4} distinctCourses={2} />,
+    );
+    const section = container.querySelector('section');
+    expect(section).toHaveAttribute('aria-label', 'Certificate generation statistics');
+  });
+});
+
+// ---------------------------------------------------------------------------
+// CertificateGenerationPage integration tests
+// ---------------------------------------------------------------------------
+
 describe('CertificateGenerationPage', () => {
-  it('submits certificate generation data and displays a success message', async () => {
-    vi.mocked(apiClient.post).mockResolvedValue({ certificateId: 'cert-123' });
+  const COURSE_ID = '123e4567-e89b-12d3-a456-426614174000';
+
+  it('submits and shows success message', async () => {
+    vi.mocked(apiClient.post).mockResolvedValue({ certificateId: 'cert-abc' });
 
     render(<CertificateGenerationPage />);
 
     fireEvent.change(screen.getByLabelText(/Course ID/i), {
-      target: { value: '123e4567-e89b-12d3-a456-426614174000' },
+      target: { value: COURSE_ID },
     });
     fireEvent.change(screen.getByLabelText(/Student Name/i), {
       target: { value: 'Jane Doe' },
     });
-
     fireEvent.click(screen.getByRole('button', { name: /Generate certificate/i }));
 
     await waitFor(() => {
       expect(screen.getByText(/Certificate generated successfully/i)).toBeInTheDocument();
     });
+  });
+
+  it('does not show stats panel before any successful generation', () => {
+    render(<CertificateGenerationPage />);
+    expect(screen.queryByText('Generation Statistics')).not.toBeInTheDocument();
+  });
+
+  it('shows stats panel after a successful generation', async () => {
+    vi.mocked(apiClient.post).mockResolvedValue({ certificateId: 'cert-abc' });
+
+    render(<CertificateGenerationPage />);
 
-    expect(apiClient.post).toHaveBeenCalledWith('/api/certificates/generate', {
-      courseId: '123e4567-e89b-12d3-a456-426614174000',
-      name: 'Jane Doe',
+    fireEvent.change(screen.getByLabelText(/Course ID/i), {
+      target: { value: COURSE_ID },
     });
+    fireEvent.change(screen.getByLabelText(/Student Name/i), {
+      target: { value: 'Jane Doe' },
+    });
+    fireEvent.click(screen.getByRole('button', { name: /Generate certificate/i }));
+
+    await waitFor(() => {
+      expect(screen.getByText('Generation Statistics')).toBeInTheDocument();
+    });
+  });
+
+  it('increments totalGenerated with each successful submission', async () => {
+    vi.mocked(apiClient.post).mockResolvedValue({ certificateId: 'cert-abc' });
+    const user = userEvent.setup();
+
+    render(<CertificateGenerationPage />);
+
+    // First submission
+    fireEvent.change(screen.getByLabelText(/Course ID/i), { target: { value: COURSE_ID } });
+    fireEvent.change(screen.getByLabelText(/Student Name/i), { target: { value: 'Jane Doe' } });
+    fireEvent.click(screen.getByRole('button', { name: /Generate certificate/i }));
+    await waitFor(() => expect(screen.getByText('Generation Statistics')).toBeInTheDocument());
+
+    // Wait for form reset to complete before second fill
+    await waitFor(() =>
+      expect(screen.getByLabelText(/Course ID/i)).toHaveValue(''),
+    );
+
+    // Second submission — use userEvent to properly trigger RHF onChange/onBlur
+    await user.clear(screen.getByLabelText(/Course ID/i));
+    await user.type(screen.getByLabelText(/Course ID/i), COURSE_ID);
+    await user.clear(screen.getByLabelText(/Student Name/i));
+    await user.type(screen.getByLabelText(/Student Name/i), 'John Smith');
+    await user.click(screen.getByRole('button', { name: /Generate certificate/i }));
+    fireEvent.click(screen.getByRole('button', { name: /Generate certificate/i }));
+
+    // The "Certificates Generated" stat card should show 2
+    await waitFor(() => {
+      const statValues = screen.getAllByText('2');
+      expect(statValues.length).toBeGreaterThan(0);
+    });
+  });
+
+  it('shows API error message on failure without displaying stats', async () => {
+    vi.mocked(apiClient.post).mockRejectedValue(new Error('Server error'));
+
+    render(<CertificateGenerationPage />);
+
+    fireEvent.change(screen.getByLabelText(/Course ID/i), {
+      target: { value: COURSE_ID },
+    });
+    fireEvent.change(screen.getByLabelText(/Student Name/i), {
+      target: { value: 'Jane Doe' },
+    });
+    fireEvent.click(screen.getByRole('button', { name: /Generate certificate/i }));
+
+    await waitFor(() => {
+      expect(screen.getByText('Server error')).toBeInTheDocument();
+    });
+
+    expect(screen.queryByText('Generation Statistics')).not.toBeInTheDocument();
   });
 });

src/app/certificates/page.tsx

@@ -9,11 +9,16 @@ import { apiClient } from '@/lib/api';
 import { FormInput } from '@/components/forms/FormInput';
 import { FieldError, FormError } from '@/components/forms/FormError';
 import { SubmitButton } from '@/components/forms/SubmitButton';
+import { CertificateStats, type CourseCertCount } from '@/components/certificates/CertificateStats';
 
 export default function CertificateGenerationPage() {
   const [apiError, setApiError] = useState<string | null>(null);
   const [successMessage, setSuccessMessage] = useState<string | null>(null);
 
+  // Stats state — tracks per-course counts across all successful generations in this session
+  const [courseCounts, setCourseCounts] = useState<CourseCertCount[]>([]);
+  const [totalGenerated, setTotalGenerated] = useState(0);
+
   const methods = useForm<CertificateInput>({
     resolver: zodResolver(CertificateInputSchema),
     mode: 'onTouched',
@@ -35,6 +40,21 @@ export default function CertificateGenerationPage() {
         data,
       );
       setSuccessMessage(`Certificate generated successfully. ID: ${result.certificateId}`);
+
+      // Update visualization stats
+      setTotalGenerated((prev) => prev + 1);
+      setCourseCounts((prev) => {
+        const existing = prev.find((c) => c.course === data.courseId);
+        if (existing) {
+          return prev.map((c) =>
+            c.course === data.courseId ? { ...c, count: c.count + 1 } : c,
+          );
+        }
+        // Truncate courseId UUID to last 8 chars for display readability
+        const shortId = data.courseId.slice(-8);
+        return [...prev, { course: `…${shortId}`, count: 1 }];
+      });
+
       reset();
     } catch (error) {
       setApiError(
@@ -47,11 +67,11 @@ export default function CertificateGenerationPage() {
 
   return (
     <div className="min-h-screen bg-gray-50 dark:bg-gray-950 py-12 px-4 sm:px-6 lg:px-8">
-      <div className="mx-auto max-w-3xl">
+      <div className="mx-auto max-w-3xl space-y-8">
         <motion.div
           initial={{ opacity: 0, y: 10 }}
           animate={{ opacity: 1, y: 0 }}
-          className="mb-8 rounded-3xl bg-white dark:bg-gray-900 border border-gray-200 dark:border-gray-800 p-8 shadow-sm"
+          className="rounded-3xl bg-white dark:bg-gray-900 border border-gray-200 dark:border-gray-800 p-8 shadow-sm"
         >
           <div className="mb-6">
             <p className="text-sm font-semibold uppercase tracking-wide text-blue-600 dark:text-blue-400">
@@ -116,6 +136,21 @@ export default function CertificateGenerationPage() {
             </motion.form>
           </FormProvider>
         </motion.div>
+
+        {/* Stats panel — visible once at least one certificate has been generated */}
+        {totalGenerated > 0 && (
+          <motion.div
+            initial={{ opacity: 0, y: 10 }}
+            animate={{ opacity: 1, y: 0 }}
+            className="rounded-3xl bg-white dark:bg-gray-900 border border-gray-200 dark:border-gray-800 p-8 shadow-sm"
+          >
+            <CertificateStats
+              data={courseCounts}
+              totalGenerated={totalGenerated}
+              distinctCourses={courseCounts.length}
+            />
+          </motion.div>
+        )}
       </div>
     </div>
   );