# Architecture Analysis and Refactoring Recommendations

## Current Architecture Issues

### Current Structure
```
CalendarManagerGUI
├── Contains business logic (EZ pauschal duration)
├── Duplicated keyword handling
├── Mixed UI and business concerns
└── Direct file operations

PredictionController
├── Too thin - delegates most logic
├── Duplicated keyword categorization
└── Missing validation/error handling

DateCalculator
├── Contains high-level orchestration
├── Business rule implementations
└── Mixed mathematical and business logic

CalendarManager
├── Contains business logic (correct_dates)
├── File I/O operations
└── Mixed data and business concerns
```

## Proposed Improved Architecture

### New Structure
```
CalendarManagerGUI (UI Layer)
├── Pure UI presentation
├── User interaction handling
└── Delegates business logic to services

PredictionController (Business Logic Layer)
├── Orchestrates prediction calculation
├── Handles business rules and validation
├── Manages event categorization
└── Coordinates between services

DateCalculator (Mathematical Layer)
├── Pure mathematical operations
├── Period manipulation algorithms
└── No business logic

CalendarManager (Data Layer)
├── CRUD operations for entries
├── Data validation and integrity
└── No business logic

EventTypeHandler (Business Rules Service)
├── Event type-specific business rules
├── Duration calculations per type
└── Event categorization logic

DateService (Utility Service)
├── Centralized date formatting
├── Date parsing and validation
└── Date conversion utilities

FileService (I/O Service)
├── File operations with error handling
├── Data serialization/deserialization
└── File validation

Config (Configuration)
├── Constants and configuration
├── Keyword definitions
└── Business rule parameters
```

## Specific Refactoring Tasks

### 1. Extract Configuration
- Move hardcoded keywords to `config.py`
- Centralize business rule parameters
- Define constants for durations and limits

### 2. Refactor DateCalculator
- Remove `calculate_prediction()` orchestration
- Keep only mathematical operations
- Remove business rule implementations

### 3. Enhance PredictionController
- Move orchestration logic from DateCalculator
- Add input validation and error handling
- Implement proper business logic coordination

### 4. Create EventTypeHandler
- Extract EZ pauschal duration logic from GUI
- Implement event type-specific business rules
- Handle event categorization logic

### 5. Create DateService
- Centralize date formatting logic
- Implement date parsing and validation
- Remove duplicated date conversion code

### 6. Create FileService
- Extract file operations from CalendarManager
- Add proper error handling
- Implement data serialization logic

### 7. Simplify CalendarManager
- Remove business logic from `correct_dates()`
- Keep only CRUD operations
- Focus on data integrity

### 8. Clean CalendarManagerGUI
- Remove business logic
- Delegate to appropriate services
- Focus on UI presentation only

## Benefits of Refactoring

1. **Separation of Concerns**: Each class has a single, clear responsibility
2. **Reduced Duplication**: Centralized configuration and utilities
3. **Better Testability**: Pure functions and isolated business logic
4. **Improved Maintainability**: Clear boundaries between layers
5. **Enhanced Reusability**: Services can be reused across components
6. **Better Error Handling**: Centralized error handling in services