BE_18 - Session QR Generation

[notjackl3]

Summary

Implement QR code generation for session registration URLs to enable quick mobile registration.
[Estimated hours: 2-3]

Objectives

• Create GET /api/sessions/[sessionId]/qr endpoint
• Generate QR codes encoding session registration URL
• Support multiple output formats (SVG, PNG, data URL)
• Add customization options (size, colors)
• Implement caching for generated QR codes

Description

Professors need to display QR codes in class (first day, syllabus, slides) for students to quickly register for the semester-long session on their mobile devices. Scanning the QR code opens the session registration page with the code pre-filled.

Technical Details

File Structure

src/app/api/sessions/[sessionId]/qr/
└── route.ts                      # GET QR code handler

src/lib/
├── qrCode.ts                     # QR code generation logic
│   Functions:
│   - generateQRCode(url, options)
│   - generateSessionJoinQR(sessionId, joinCode, options)
│   - getCachedQR(sessionId, options)
│   - cacheQR(sessionId, options, data)
└── qrCodeValidation.ts           # Validation for QR operations
    Functions:
    - validateQROptions(options)
    - validateSessionForQR(sessionId, userId)

Acceptance Criteria

• QR code encodes full registration URL (e.g., https://app.example.com/join/ABC123)
• SVG format returns valid SVG with correct Content-Type header
• PNG format returns valid PNG with correct Content-Type header
• Data URL format returns JSON with base64-encoded image
• Size parameter works (64-1024 pixels, default 256)
• Invalid size returns 400 (< 64 or > 1024)
• Margin parameter works (0-10 modules, default 2)
• Dark/light color parameters work (valid hex colors)
• Invalid color format returns 400
• Only session creator (professor) can generate QR codes (403 for others)
• Non-existent session returns 404
• Generated QR codes are cached in Redis (1 hour TTL)
• Cache key includes options hash for different configurations
• Same request returns cached result within TTL
• Code regeneration invalidates cached QR codes
• Rate limited to 20 requests per minute per user
• QR code scannable by standard phone camera apps
• Error correction level 'M' allows ~15% damage tolerance
• Join URL uses NEXT_PUBLIC_APP_URL environment variable
• Follow existing validation pattern (ValidationResult interface)
• Error messages follow existing API error format