# Epic 3: Enhanced User Experience

## Epic Overview

**Goal**: Transform the application from a simple tool to a comprehensive platform with user accounts, advanced features, and API access. This epic enables power users and developers to integrate the summarizer into their workflows while providing advanced features for enhanced productivity.

**Priority**: Medium - Enhancement features for advanced users  
**Epic Dependencies**: Epic 2 (AI Summarization Engine)  
**Estimated Complexity**: Very High (Complex features and integrations)  

## Epic Success Criteria

Upon completion of this epic, the YouTube Summarizer will:

1. **User Account Management**
   - Secure user registration and authentication
   - Persistent summary history across devices
   - User preferences and settings management

2. **Advanced Processing Features**
   - Batch processing for multiple videos
   - Real-time progress updates via WebSocket
   - Background job management

3. **Professional Integration**
   - RESTful API for third-party integration
   - SDK support for Python and JavaScript
   - Webhook notifications for async operations

4. **Enhanced User Experience**
   - Advanced search and filtering
   - Summary sharing and collaboration
   - Personalized recommendations

## Stories in Epic 3

### Story 3.1: User Authentication System

**As a** user  
**I want** to create an account and login  
**So that** I can access my summary history across devices

#### Acceptance Criteria
1. Email/password registration with verification email
2. Secure password requirements enforced (minimum 8 characters, complexity rules)
3. JWT-based authentication with refresh tokens
4. Password reset functionality via email
5. Optional OAuth integration with Google for single sign-on
6. Session management with automatic logout after inactivity

**Status**: Ready for story creation  
**Dependencies**: Story 2.5 (Export Functionality)

### Story 3.2: Summary History Management

**As a** authenticated user  
**I want** to view and manage my summary history  
**So that** I can reference previous summaries

#### Acceptance Criteria
1. Summary history displays in reverse chronological order
2. Search functionality filters by video title, content, or date range
3. Summaries can be starred for quick access
4. Bulk delete operations with confirmation dialog
5. Summary sharing via unique URL (public or private)
6. Export entire history as JSON or CSV

**Status**: Ready for story creation  
**Dependencies**: Story 3.1 (User Authentication System)

### Story 3.3: Batch Processing

**As a** power user  
**I want** to summarize multiple videos at once  
**So that** I can process entire playlists or video series efficiently

#### Acceptance Criteria
1. Accepts multiple URLs via textarea (one per line) or file upload
2. Queue system processes videos sequentially with progress indicator
3. Partial results available as each video completes
4. Failed videos don't block subsequent processing
5. Batch results downloadable as ZIP with all formats
6. Email notification when batch processing completes

**Status**: Ready for story creation  
**Dependencies**: Story 3.2 (Summary History Management)

### Story 3.4: Real-time Updates

**As a** user  
**I want** live progress updates during processing  
**So that** I know the system is working and how long to wait

#### Acceptance Criteria
1. WebSocket connection provides real-time status updates
2. Progress stages shown: Validating → Extracting → Summarizing → Complete
3. Percentage complete based on transcript chunks processed
4. Estimated time remaining calculated from similar videos
5. Cancel button allows aborting long-running operations
6. Connection loss handled gracefully with automatic reconnection

**Status**: Ready for story creation  
**Dependencies**: Story 3.3 (Batch Processing)

### Story 3.5: API Endpoints

**As a** developer  
**I want** RESTful API access to summarization features  
**So that** I can integrate the service into my applications

#### Acceptance Criteria
1. API key generation and management in user settings
2. RESTful endpoints follow OpenAPI 3.0 specification
3. Rate limiting enforced per API key (100 requests/hour default)
4. Comprehensive API documentation with examples
5. SDKs provided for Python and JavaScript
6. Webhook support for async processing notifications

**Status**: Ready for story creation  
**Dependencies**: Story 3.4 (Real-time Updates)

## Technical Architecture Context

### Advanced Architecture Components

```
┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
│   Web App       │    │   API Gateway   │    │   Background    │
│                 │    │                 │    │   Workers       │
│ • Auth UI       │◄──►│ • Rate Limiting │◄──►│ • Batch Jobs    │
│ • History Mgmt  │    │ • API Keys      │    │ • Webhooks      │
│ • Real-time UI  │    │ • WebSocket     │    │ • Email Notify  │
│                 │    │   Proxy         │    │                 │
└─────────────────┘    └─────────────────┘    └─────────────────┘
        │                       │                       │
        │                       ▼                       ▼
        │               ┌─────────────────┐    ┌─────────────────┐
        │               │   User DB       │    │   Job Queue     │
        └──────────────►│                 │    │                 │
                        │ • Users         │    │ • Batch Jobs    │
                        │ • API Keys      │    │ • Status        │
                        │ • Sessions      │    │ • Results       │
                        └─────────────────┘    └─────────────────┘
```

### Authentication Architecture

#### JWT Token Strategy
```python
class AuthService:
    def generate_tokens(self, user_id: str) -> Tuple[str, str]:
        """Generate access and refresh token pair"""
        
    def verify_token(self, token: str) -> Dict[str, Any]:
        """Verify and decode JWT token"""
        
    def refresh_access_token(self, refresh_token: str) -> str:
        """Generate new access token from refresh token"""
```

#### User Model
```python
class User(Base):
    __tablename__ = "users"
    
    id = Column(UUID(as_uuid=True), primary_key=True)
    email = Column(String(255), unique=True, nullable=False)
    password_hash = Column(String(255), nullable=False)
    is_verified = Column(Boolean, default=False)
    created_at = Column(DateTime, default=datetime.utcnow)
    last_login = Column(DateTime)
    
    # Preferences
    default_model = Column(String(50), default="openai")
    summary_length = Column(String(20), default="standard")
    
    # API access
    api_keys = relationship("APIKey", back_populates="user")
    summaries = relationship("Summary", back_populates="user")
```

### WebSocket Architecture

#### Real-time Progress Updates
```typescript
interface ProgressUpdate {
  job_id: string;
  status: "validating" | "extracting" | "summarizing" | "completed" | "failed";
  progress_percentage: number;
  current_step: string;
  estimated_time_remaining?: number;
  error_message?: string;
}

class WebSocketClient {
  connect(job_id: string): Promise<void>;
  onProgress(callback: (update: ProgressUpdate) => void): void;
  disconnect(): void;
}
```

### Batch Processing Architecture

#### Job Queue System
```python
class BatchJob(Base):
    __tablename__ = "batch_jobs"
    
    id = Column(UUID(as_uuid=True), primary_key=True)
    user_id = Column(UUID(as_uuid=True), nullable=False)
    name = Column(String(255))
    
    # Job configuration
    urls = Column(JSON)  # List of YouTube URLs
    model = Column(String(50))
    options = Column(JSON)
    
    # Progress tracking
    total_videos = Column(Integer)
    completed_videos = Column(Integer, default=0)
    failed_videos = Column(Integer, default=0)
    status = Column(Enum(BatchJobStatus))
    
    # Results
    results = Column(JSON)  # Array of summary IDs
    download_url = Column(String(500))  # ZIP download link
    
    created_at = Column(DateTime, default=datetime.utcnow)
    completed_at = Column(DateTime)
```

## Non-Functional Requirements for Epic 3

### Security
- **Authentication**: Secure JWT implementation with refresh tokens
- **API Security**: Rate limiting and API key management
- **Data Privacy**: User data encryption and secure storage
- **Session Management**: Automatic logout and session timeouts

### Performance
- **Concurrent Users**: Support 100+ concurrent authenticated users
- **Batch Processing**: Handle 50+ videos in single batch job
- **Real-time Updates**: Sub-second WebSocket message delivery
- **API Response**: < 500ms for authenticated API calls

### Scalability
- **User Growth**: Architecture supports 10,000+ registered users
- **Batch Scaling**: Queue system handles multiple concurrent batch jobs
- **API Usage**: Rate limiting prevents abuse while enabling legitimate usage

### Reliability
- **WebSocket Resilience**: Automatic reconnection and message queuing
- **Batch Recovery**: Failed batch jobs can be resumed
- **Data Integrity**: User summaries never lost due to system failures

## API Specification for Epic 3

### Authentication Endpoints

#### POST /api/auth/register
```typescript
interface RegisterRequest {
  email: string;
  password: string;
  confirm_password: string;
}

interface AuthResponse {
  user: UserProfile;
  access_token: string;
  refresh_token: string;
  expires_in: number;
}
```

#### POST /api/auth/login
```typescript
interface LoginRequest {
  email: string;
  password: string;
}
```

### User Management Endpoints

#### GET /api/user/profile
```typescript
interface UserProfile {
  id: string;
  email: string;
  created_at: string;
  preferences: UserPreferences;
  api_usage: APIUsageStats;
}
```

#### GET /api/user/summaries
```typescript
interface UserSummariesResponse {
  summaries: Summary[];
  total_count: number;
  pagination: PaginationInfo;
}
```

### Batch Processing Endpoints

#### POST /api/batch/create
```typescript
interface BatchRequest {
  name?: string;
  urls: string[];
  model?: string;
  options?: SummaryOptions;
  notify_email?: boolean;
}

interface BatchResponse {
  job_id: string;
  status: "queued";
  total_videos: number;
  estimated_completion: string;
}
```

#### GET /api/batch/{job_id}
```typescript
interface BatchStatus {
  job_id: string;
  status: BatchJobStatus;
  progress: {
    total: number;
    completed: number;
    failed: number;
    percentage: number;
  };
  results: Summary[];
  download_url?: string;
}
```

### API Key Management

#### POST /api/user/api-keys
```typescript
interface CreateAPIKeyRequest {
  name: string;
  permissions: APIPermission[];
  rate_limit?: number;
}

interface APIKey {
  id: string;
  key: string;  // Only returned once
  name: string;
  permissions: APIPermission[];
  created_at: string;
  last_used?: string;
}
```

## Definition of Done for Epic 3

- [ ] All 5 stories completed and validated
- [ ] User registration and authentication working
- [ ] Summary history persistent across sessions
- [ ] Batch processing handles multiple videos
- [ ] Real-time progress updates via WebSocket
- [ ] Public API available with documentation
- [ ] API keys generation and management
- [ ] SDK packages published (Python + JavaScript)
- [ ] Webhook system operational
- [ ] Performance targets met for all features

## Security Considerations

### Authentication Security
- Password hashing with bcrypt (minimum cost factor 12)
- JWT tokens with short expiration (15 minutes access, 7 days refresh)
- Secure session management with httpOnly cookies
- Rate limiting on authentication endpoints

### API Security
- API key authentication with scoped permissions
- Request rate limiting per API key
- Input validation and sanitization for all endpoints
- CORS configuration for allowed origins

### Data Privacy
- User data encryption at rest
- Secure password reset flows
- GDPR compliance for data export/deletion
- Audit logging for sensitive operations

## Risks and Mitigation

### Technical Risks
1. **WebSocket Scale**: Load testing and connection pooling
2. **Batch Job Memory**: Streaming processing and cleanup
3. **Database Growth**: Partitioning and archival strategies

### Security Risks
1. **Authentication Attacks**: Rate limiting and monitoring
2. **API Abuse**: Usage quotas and anomaly detection
3. **Data Leaks**: Access controls and audit logs

### User Experience Risks
1. **Complexity**: Progressive disclosure and onboarding
2. **Performance**: Background processing and caching
3. **Reliability**: Comprehensive error handling and recovery

## Success Metrics

### User Engagement
- **Registration Rate**: > 10% of anonymous users register
- **Return Usage**: > 60% of registered users return within 7 days
- **Feature Adoption**: > 40% of users try batch processing

### Technical Performance
- **Authentication Speed**: < 200ms login time
- **Batch Throughput**: > 10 videos processed per minute
- **WebSocket Reliability**: < 1% connection failures

### API Usage
- **Developer Adoption**: > 50 API keys generated within 30 days
- **API Success Rate**: > 99% successful API calls
- **SDK Downloads**: > 100 combined Python + JavaScript downloads

---

**Epic Status**: Ready for Planning  
**Dependencies**: Epic 2 must be completed first  
**Next Action**: Wait for Epic 2 completion, then create Story 3.1  
**Epic Owner**: Bob (Scrum Master)  
**Last Updated**: 2025-01-25