# SOLID Principles Implementation

This project has been refactored to follow the SOLID principles of Object-Oriented Programming.

## Overview

The codebase is organized into:
- **Interfaces** (`src/interfaces/`) - Define contracts following Interface Segregation Principle
- **Classes** (`src/classes/`) - Implementations following Single Responsibility Principle
- **Main** (`src/main.ts`) - Entry point that uses Dependency Inversion Principle

## SOLID Principles Applied

### 1. Single Responsibility Principle (SRP)
Each class has one reason to change:

- **`VideoSource`**: Only responsible for managing video source elements
- **`VideoSeekController`**: Only responsible for seeking operations
- **`AudioController`**: Only responsible for audio control (mute/unmute)
- **`VideoPlayer`**: Only responsible for orchestrating the components

### 2. Open/Closed Principle (OCP)
The system is open for extension but closed for modification:

- New video source types can be added by implementing `IVideoSource`
- New seeking strategies can be added by implementing `IVideoSeekController`
- New audio control mechanisms can be added by implementing `IAudioController`
- The `VideoPlayer` class doesn't need modification when adding new implementations

### 3. Liskov Substitution Principle (LSP)
Any implementation of an interface can be substituted without breaking functionality:

- Any class implementing `IVideoSource` can replace `VideoSource`
- Any class implementing `IVideoSeekController` can replace `VideoSeekController`
- Any class implementing `IAudioController` can replace `AudioController`

### 4. Interface Segregation Principle (ISP)
Interfaces are small and focused on specific behaviors:

- **`IVideoSource`**: Only methods related to video source management
- **`IVideoSeekController`**: Only methods related to seeking
- **`IAudioController`**: Only methods related to audio control
- **`IVideoPlayer`**: High-level interface for the complete player

### 5. Dependency Inversion Principle (DIP)
High-level modules depend on abstractions, not concrete implementations:

- `VideoPlayer` depends on interfaces (`IVideoSource`, `IVideoSeekController`, `IAudioController`)
- Concrete implementations are injected via constructor
- This allows easy testing and swapping of implementations

## Architecture Benefits

1. **Testability**: Each component can be tested in isolation
2. **Maintainability**: Changes to one component don't affect others
3. **Extensibility**: New features can be added without modifying existing code
4. **Flexibility**: Implementations can be swapped easily (e.g., for testing or different behaviors)

## Example: Adding a New Feature

To add a new video source type (e.g., DASH streaming):

1. Create a new class `DashVideoSource` implementing `IVideoSource`
2. Use it in `VideoPlayer` constructor: `this.videoSource = new DashVideoSource()`
3. No other code needs to change!

## File Structure

```
src/
├── interfaces/
│   ├── IVideoSource.ts          # Video source contract
│   ├── IVideoSeekController.ts  # Seeking contract
│   ├── IAudioController.ts      # Audio control contract
│   └── IVideoPlayer.ts          # Main player contract
├── classes/
│   ├── VideoSource.ts           # Video source implementation
│   ├── VideoSeekController.ts   # Seeking implementation
│   ├── AudioController.ts       # Audio control implementation
│   └── VideoPlayer.ts           # Main player orchestrator
└── main.ts                      # Application entry point
```