# System Patterns

## Architecture Overview
The application follows a client-server architecture with containerized deployment and secure authentication:

### Authentication System
- JSON file-based user management
- Secure password hashing with bcrypt
- Session-based authentication using Flask-Login
- Protected API routes with login_required decorator
- Remember me functionality for persistent sessions

### Frontend (React)
- Single Page Application (SPA) architecture
- Authentication state management
- Protected route handling
- Component-based structure:
  - Login: User authentication interface
  - FileUpload: Handles file input and processing
  - FileList: Manages processed files
  - ModelSelector: AI model selection
  - Configurations: System settings and prompts
  - ProgressBar: Real-time processing feedback
  - Notifications: User feedback system
  - TxtToPdf: Document conversion utility
  - ImageDescription: Image analysis and description
  - ChangePassword: User password management

### Backend (Flask)
- RESTful API architecture
- Modular design with separate concerns:
  - app.py: Main application and route handlers
  - models.py: Data models and AI model management
  - utils.py: Processing utilities and helpers

## Key Technical Decisions

### Background Processing
- Asynchronous job processing using threading
- Job tracking system with unique IDs
- Real-time progress updates via polling

### File Management
- Secure file handling with unique naming
- Separate upload and output directories
- Support for multiple file formats

### AI Integration
- Modular AI model system
- Support for multiple AI providers:
  - OpenAI
  - Gemini
  - Mistral
- Configurable prompts system
- Vision AI capabilities:
  - Base64 image encoding
  - MIME type detection
  - Proper Gemini Vision API formatting

### OCR Processing
- Multiple processing modes:
  - Pure OCR (Tesseract)
  - Hybrid (OCR + AI)
  - Full AI OCR
- Page-by-page processing for large documents

### Translation System
- Language management system
- Page-by-page translation
- Progress tracking per page

### Configuration Management
- JSON-based configuration storage
- Import/export functionality
- Runtime model and prompt updates

## Error Handling
- Comprehensive error catching
- User-friendly error messages
- Job cancellation support

## Security Patterns
- Secure file uploads with sanitization
- CORS configuration with credentials support
- Environment-based configuration
- Password hashing and verification
- Session management and protection
- API route protection
- Authentication state persistence
- Secure cookie handling