feat: add GET /api/nfc/payload endpoint for NFC tag payload generation

apps/backend/src/__tests__/nfc.test.ts

@@ -0,0 +1,73 @@
+import { describe, it, expect, vi, beforeAll, afterAll } from 'vitest';
+import Fastify from 'fastify';
+import { nfcRoutes } from '../routes/nfc.js';
+
+const TEST_APP_URL = 'https://test.devcard.dev';
+
+beforeAll(() => { process.env.PUBLIC_APP_URL = TEST_APP_URL; });
+afterAll(() => { delete process.env.PUBLIC_APP_URL; });
+
+function buildApp(prismaOverrides: Record<string, any> = {}, authenticateReject = false) {
+  const app = Fastify();
+
+  (app as any).prisma = {
+    user: {
+      findUnique: prismaOverrides.findUser ?? vi.fn(async () => ({ username: 'testuser' })),
+    },
+    card: {
+      findFirst: prismaOverrides.findCard ?? vi.fn(async () => ({ id: 'card-1' })),
+    },
+  };
+
+  (app as any).authenticate = async (request: any, reply: any) => {
+    if (authenticateReject) return reply.status(401).send({ error: 'Unauthorized' });
+    request.user = { id: 'user-1' };
+  };
+
+  app.register(nfcRoutes, { prefix: '/api/nfc' });
+  return app;
+}
+
+describe('GET /api/nfc/payload', () => {
+  it('returns 401 when unauthenticated', async () => {
+    const app = buildApp({}, true);
+    await app.ready();
+    const res = await app.inject({ method: 'GET', url: '/api/nfc/payload' });
+    expect(res.statusCode).toBe(401);
+  });
+
+  it('returns full profile URI payload when no cardId given', async () => {
+    const app = buildApp();
+    await app.ready();
+    const res = await app.inject({ method: 'GET', url: '/api/nfc/payload' });
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.type).toBe('URI');
+    expect(body.payload).toBe(`${TEST_APP_URL}/u/testuser`);
+  });
+
+  it('does not call user lookup when cardId is provided', async () => {
+    const findUser = vi.fn(async () => ({ username: 'testuser' }));
+    const app = buildApp({ findUser });
+    await app.ready();
+    await app.inject({ method: 'GET', url: '/api/nfc/payload?card=card-1' });
+    expect(findUser).not.toHaveBeenCalled();
+  });
+
+  it('returns full card URI payload when cardId is provided and owned', async () => {
+    const app = buildApp();
+    await app.ready();
+    const res = await app.inject({ method: 'GET', url: '/api/nfc/payload?card=card-1' });
+    expect(res.statusCode).toBe(200);
+    const body = JSON.parse(res.body);
+    expect(body.type).toBe('URI');
+    expect(body.payload).toBe(`${TEST_APP_URL}/devcard/card-1`);
+  });
+
+  it('returns 403 when cardId does not belong to the user', async () => {
+    const app = buildApp({ findCard: vi.fn(async () => null) });
+    await app.ready();
+    const res = await app.inject({ method: 'GET', url: '/api/nfc/payload?card=other-card' });
+    expect(res.statusCode).toBe(403);
+  });
+});

apps/backend/src/app.ts

@@ -17,6 +17,7 @@ import { publicRoutes } from './routes/public.js';
 import { followRoutes } from './routes/follow.js';
 import { connectRoutes } from './routes/connect.js';
 import { analyticsRoutes } from './routes/analytics.js';
+import { nfcRoutes } from './routes/nfc.js';
 
 const __dirname = path.dirname(fileURLToPath(import.meta.url));
 
@@ -74,6 +75,7 @@ export async function buildApp() {
   await app.register(followRoutes, { prefix: '/api/follow' });
   await app.register(connectRoutes, { prefix: '/api/connect' });
   await app.register(analyticsRoutes, { prefix: '/api/analytics' });
+  await app.register(nfcRoutes, { prefix: '/api/nfc' });
 
   // ─── Health Check ───
   app.get('/health', async () => ({

apps/backend/src/routes/nfc.ts

@@ -0,0 +1,37 @@
+import type { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
+
+export async function nfcRoutes(app: FastifyInstance) {
+  app.get('/payload', {
+    preHandler: [app.authenticate],
+  }, async (request: FastifyRequest<{ Querystring: { card?: string } }>, reply: FastifyReply) => {
+    const userId = (request.user as any).id;
+    const { card: cardId } = request.query;
+    const appUrl = process.env.PUBLIC_APP_URL || 'https://devcard.dev';
+
+    if (cardId) {
+      // Validate card ownership without fetching the user (not needed for card URL).
+      const card = await app.prisma.card.findFirst({
+        where: { id: cardId, userId },
+        select: { id: true },
+      });
+
+      if (!card) {
+        return reply.status(403).send({ error: 'Card not found or access denied' });
+      }
+
+      return { type: 'URI', payload: `${appUrl}/devcard/${cardId}` };
+    }
+
+    // Default: return the user's profile URL.
+    const user = await app.prisma.user.findUnique({
+      where: { id: userId },
+      select: { username: true },
+    });
+
+    if (!user) {
+      return reply.status(404).send({ error: 'User not found' });
+    }
+
+    return { type: 'URI', payload: `${appUrl}/u/${user.username}` };
+  });
+}