feat: implement persistent personalized certificates

- Modified encodeCertificateId to include userId parameter
- Updated decodeCertificateId to extract and return userId
- Added backward compatibility for old 2-part certificate IDs
- Certificate page now fetches and displays certificate owner's name
- Submission page passes current user's ID when generating certificate
- Fixed certificate template to use certificate owner's name instead of team leader
- Certificates now show the encoded user's name regardless of who views them

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

apps/hackathon/src/app/certificate/[certId]/page.tsx

@@ -5,6 +5,8 @@ import { decodeCertificateId } from '../../../utils/certificate';
 import {
   useTeamById,
   useTeamSubmission,
+  useAuthStore,
+  useUserById,
 } from '@imphnen-frontend-service/service';
 import QRCode from 'qrcode';
 import html2canvas from 'html2canvas';
@@ -12,11 +14,13 @@ import html2canvas from 'html2canvas';
 interface DecodedCert {
   teamId: string;
   submissionId: string;
+  userId: string;
 }
 
 const CertificatePage: FC = (): ReactElement => {
   const { certId } = useParams<{ certId: string }>();
   const navigate = useNavigate();
+  const { session } = useAuthStore();
   const [decodedInfo, setDecodedInfo] = useState<DecodedCert | null>(null);
   const [error, setError] = useState<string | null>(null);
   const teamNameRef = useRef<HTMLHeadingElement>(null);
@@ -65,11 +69,21 @@ const CertificatePage: FC = (): ReactElement => {
   const { data: submissionData, isLoading: isLoadingSubmission } =
     useTeamSubmission(decodedInfo?.teamId || '', !!decodedInfo?.teamId);
 
+  // Fetch the certificate owner's user data
+  const { data: certificateUserData, isLoading: isLoadingCertUser } = useUserById(
+    decodedInfo?.userId || '',
+    !!decodedInfo?.userId
+  );
+
   const team = teamData?.data;
   const submission = submissionData?.data;
+  const certificateUser = certificateUserData?.data;
 
   const isLoading =
-    (!decodedInfo && !error) || isLoadingTeam || isLoadingSubmission;
+    (!decodedInfo && !error) || isLoadingTeam || isLoadingSubmission || isLoadingCertUser;
+
+  // Certificate name: Use the user from the certificate ID, fallback to team leader
+  const certificateName = certificateUser?.fullname || team?.leader?.fullname;
 
   // Dynamic font sizing: shrink by 2px if height exceeds 80px
   useEffect(() => {
@@ -98,7 +112,7 @@ const CertificatePage: FC = (): ReactElement => {
     }, 0);
 
     return () => clearTimeout(timer);
-  }, [team?.name, team?.leader?.fullname]);
+  }, [team?.name, certificateName]);
 
   // Generate certificate canvas screenshot
   useEffect(() => {
@@ -335,7 +349,7 @@ const CertificatePage: FC = (): ReactElement => {
                   margin: 0,
                 }}
               >
-                {team?.leader?.fullname || 'N/A'}
+                {certificateName || 'N/A'}
               </h3>
             </div>
 

apps/hackathon/src/app/teams/[teamId]/submission/page.tsx

@@ -1,12 +1,13 @@
 import { FC, ReactElement } from 'react';
 import { Button } from '@imphnen-frontend-service/ui/atoms';
 import { useNavigate, useParams } from 'react-router';
-import { useTeamById, useTeamSubmission } from '@imphnen-frontend-service/service';
+import { useTeamById, useTeamSubmission, useAuthStore } from '@imphnen-frontend-service/service';
 import { encodeCertificateId } from '../../../../utils/certificate';
 
 const SubmissionViewPage: FC = (): ReactElement => {
   const { teamId } = useParams<{ teamId: string }>();
   const navigate = useNavigate();
+  const { session } = useAuthStore();
 
   const { data: teamData } = useTeamById(teamId || '');
   const { data: submissionData, isLoading } = useTeamSubmission(teamId || '', !!teamId);
@@ -113,13 +114,17 @@ const SubmissionViewPage: FC = (): ReactElement => {
                     View Your Certificate
                   </h3>
                   <p className="text-amber-700 dark:text-amber-300 text-sm">
-                    Congratulations! Your certificate is ready to download and share.
+                    Congratulations! Your personalized certificate is ready to download and share.
                   </p>
                 </div>
               </div>
               <button
                 onClick={async () => {
-                  const certId = await encodeCertificateId(teamId || '', submission.id);
+                  const certId = await encodeCertificateId(
+                    teamId || '',
+                    submission.id,
+                    session?.user?.id || ''
+                  );
                   navigate(`/certificate/${encodeURIComponent(certId)}`);
                 }}
                 className="shrink-0 px-6 py-2 bg-amber-600 hover:bg-amber-700 dark:bg-amber-600 dark:hover:bg-amber-700 text-white font-medium rounded-lg transition-colors"

apps/hackathon/src/utils/certificate.ts

@@ -3,27 +3,38 @@ import { decryptText, encryptText } from "./aesclient";
 const SECRET_KEY = 'imphnen-hackathon-2025';
 
 /**
- * Encode teamId and submissionId into a certificate ID
+ * Encode teamId, submissionId, and userId into a certificate ID
- * Uses base64 encoding for simple obfuscation
+ * Uses AES encryption for secure encoding
  * @param teamId - The team ID
  * @param submissionId - The submission ID
+ * @param userId - The user ID (team member)
  * @returns Encoded certificate ID
  */
-export const encodeCertificateId = async (teamId: string, submissionId: string): Promise<string> => {
+export const encodeCertificateId = async (teamId: string, submissionId: string, userId: string): Promise<string> => {
-  const combined = `${teamId}::${submissionId}`;
+  const combined = `${teamId}::${submissionId}::${userId}`;
   return encryptText(combined, SECRET_KEY);
 };
 
 /**
- * Decode certificate ID back to teamId and submissionId
+ * Decode certificate ID back to teamId, submissionId, and userId
  * @param certId - The encoded certificate ID
- * @returns Object containing teamId and submissionId
+ * @returns Object containing teamId, submissionId, and userId
  */
-export const decodeCertificateId = async (certId: string): Promise<{ teamId: string; submissionId: string }> => {
+export const decodeCertificateId = async (certId: string): Promise<{ teamId: string; submissionId: string; userId: string }> => {
   try {
     const decoded = await decryptText(certId, SECRET_KEY);
-    const [teamId, submissionId] = decoded.split('::');
+    const parts = decoded.split('::');
-    return { teamId, submissionId };
+
+    // Handle both old format (teamId::submissionId) and new format (teamId::submissionId::userId)
+    if (parts.length === 2) {
+      const [teamId, submissionId] = parts;
+      return { teamId, submissionId, userId: '' };
+    } else if (parts.length === 3) {
+      const [teamId, submissionId, userId] = parts;
+      return { teamId, submissionId, userId };
+    }
+
+    throw new Error('Invalid certificate format');
   } catch {
     throw new Error('Invalid certificate ID');
   }