feat(cards): add QR code generation for shared cards

Author: Harxhit

apps/backend/src/routes/cards.ts

@@ -7,6 +7,7 @@ import type { Card } from '@devcard/shared';
 import type { FastifyInstance, FastifyRequest, FastifyReply } from 'fastify';
 import { CardVisibility } from '@prisma/client';
 import { hashIp } from '../utils/refreshToken';
+import { id } from 'zod/v4/locales';
 
 export interface CreateCardBody {
   title: string;
@@ -254,4 +255,37 @@ export async function cardRoutes(app: FastifyInstance): Promise<void> {
       handleDbError(error, request,reply)
     }
   })
+
+  app.get('/:id/qr', async(request: FastifyRequest<{Params: {id: string}}>, reply:FastifyReply) => {
+    const cardId = request.params.id
+    const userId = request.user.id
+
+    try {
+      const qrImage = await cardService.genrateQr(app, userId, cardId)
+      return reply.type('image/png').send(qrImage)
+    } catch (error:any) {
+      if (error?.code === 'CARD_NOT_FOUND') {
+        return reply.status(404).send({
+          error: error.message,
+        });
+      }
+      if (error?.code === 'CARD_PRIVATE') {
+        return reply.status(403).send({
+          error: error.message,
+        });
+      }
+      if (error?.code === 'QR_ENABLED') {
+        return reply.status(404).send({
+          error: error.message,
+        });
+      }
+      if (error?.code === 'QR_IMAGE') {
+        return reply.status(403).send({
+          error: error.message,
+        });
+      }
+      app.log.error(error)
+      handleDbError(error,request, reply)
+    }
+  })
 }

apps/backend/src/services/cardService.ts

@@ -4,6 +4,7 @@ import { generateUniqueSlug } from '../utils/slug';
 
 import type { CreateCardBody } from '../routes/cards';
 import type { FastifyInstance } from 'fastify';
+import QRCode from 'qrcode';
 
 type CardLinkResponse = { platformLink: unknown };
 type RawCard = { id: string; title: string; isDefault: boolean; cardLinks: CardLinkResponse[] };
@@ -300,4 +301,50 @@ export async function getSharedCard(app:FastifyInstance, slug:string){
   }
 
   return card
+}
+
+
+export async function genrateQr(app: FastifyInstance,userId:string, id: string){
+  const card = await app.prisma.card.findFirst({
+    where:{
+      id,
+      userId
+    }
+  })
+
+  if (!card) {
+    throw Object.assign(
+      new Error('Card not found'),
+      { code: 'CARD_NOT_FOUND' }
+    );
+  }
+
+
+  if(card?.visibility === CardVisibility.PRIVATE){
+    throw Object.assign(
+      new Error('Private cards cannot be shared'),
+      { code: 'CARD_PRIVATE' }
+    );
+  }
+
+  if(!card.qrEnabled){
+    throw Object.assign(
+      new Error('QR is not availbled for this card'),
+      { code: 'QR_ENABLED' }
+    );
+  }
+
+  const shareUrl = `${process.env.MOBILE_REDIRECT_URI}/cards/share/${card.slug}` 
+  const qrImage = await QRCode.toBuffer(shareUrl); 
+
+  if(!qrImage){
+    throw Object.assign(
+      new Error('QR generation failed'),
+      { code: 'QR_IMAGE' }
+    );
+  }
+
+  return qrImage; 
+
+
 }