# PayFast Package Architecture

## Architecture Decision: Event-Based vs Service-Based

### Recommendation: **Hybrid Approach (Service-Based with Event-Driven Components)**

After reviewing the PayFast payment gateway package, I recommend a **hybrid architecture** that primarily uses **Service-Based Architecture** with **Event-Driven components** for cross-cutting concerns.

### Why Service-Based Architecture is Better for This Project

#### 1. **Payment Gateway Characteristics**

- Payment gateways require **synchronous, sequential operations**
- Each payment step depends on the previous step's result
- Need immediate feedback and error handling
- Transaction state must be managed explicitly

#### 2. **Service-Based Benefits**

- **Clear Control Flow**: Easy to follow payment processing steps
- **Explicit Error Handling**: Errors can be caught and handled immediately
- **Transaction Management**: Better suited for database transactions
- **Testing**: Easier to unit test individual services
- **Debugging**: Simpler to trace execution flow

#### 3. **Event-Driven Components (Where They Help)**

Events are used for:

- **Logging**: Automatic logging of payment activities
- **Audit Trails**: Storing payment records without blocking main flow
- **Notifications**: Sending emails/SMS after payment completion
- **Analytics**: Tracking payment metrics
- **Side Effects**: Actions that don't affect payment processing

### Architecture Overview

```
┌─────────────────────────────────────────────────────────────┐
│                      PayFast Facade                          │
└───────────────────────┬─────────────────────────────────────┘
                        │
                        ▼
┌─────────────────────────────────────────────────────────────┐
│                    PayFast (Main Class)                     │
│  - Orchestrates payment flow                                │
│  - Handles authentication                                    │
│  - Manages transaction state                                 │
└───────────────┬─────────────────────────────────────────────┘
                │
        ┌───────┴────────┬──────────────┬──────────────┐
        │                 │              │              │
        ▼                 ▼              ▼              ▼
┌──────────────┐  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐
│Authentication│  │   Payment    │  │ Transaction  │  │    Config    │
│   Service    │  │   Service    │  │   Service    │  │   Service    │
└──────┬───────┘  └──────┬───────┘  └──────┬───────┘  └──────────────┘
       │                 │                 │
       └─────────────────┴─────────────────┘
                        │
                        ▼
              ┌──────────────────┐
              │  HttpClient      │
              │  Service         │
              └──────────────────┘

        ┌─────────────────────────────────────┐
        │      Event System (Side Effects)    │
        ├─────────────────────────────────────┤
        │  - PaymentInitiated                 │
        │  - PaymentValidated                 │
        │  - PaymentCompleted                 │
        │  - PaymentFailed                    │
        │  - TokenRefreshed                   │
        └──────────────┬──────────────────────┘
                       │
        ┌──────────────┴──────────────┐
        │                             │
        ▼                             ▼
┌──────────────┐            ┌──────────────┐
│ Log Activity │            │ Store Record │
│  Listener    │            │  Listener    │
└──────────────┘            └──────────────┘

        ┌─────────────────────────────────────┐
        │      Repository Pattern             │
        ├─────────────────────────────────────┤
        │  ProcessPaymentRepository          │
        │  - create()                        │
        │  - findByTransactionId()           │
        │  - findByBasketId()                │
        │  - update()                        │
        └─────────────────────────────────────┘
```

## Key Design Patterns Implemented

### 1. **Repository Pattern**

- Abstracts data access layer
- Makes testing easier (can mock repositories)
- Follows Single Responsibility Principle

### 2. **Service Layer Pattern**

- Each service has a single responsibility:
  - `AuthenticationService`: Token management
  - `PaymentService`: Payment processing
  - `TransactionService`: Transaction queries
  - `HttpClientService`: HTTP communication

### 3. **DTO Pattern (Data Transfer Objects)**

- `PaymentRequestDTO`: Encapsulates payment request data
- Type-safe data transfer
- Validation at DTO level

### 4. **Dependency Injection**

- All dependencies injected via constructor
- Interfaces for all services (Dependency Inversion Principle)
- Easy to mock for testing

### 5. **Event-Driven Components**

- Used for side effects only
- Doesn't block main payment flow
- Allows extensibility without modifying core code

## Design Principles Applied

### Single Responsibility Principle (SRP)

- Each class has one reason to change
- `AuthenticationService` only handles authentication
- `PaymentService` only handles payments
- `TransactionService` only handles transaction queries

### Open/Closed Principle (OCP)

- Open for extension via events
- Closed for modification (core services don't change)
- New features can be added via event listeners

### Liskov Substitution Principle (LSP)

- All implementations can be substituted with their interfaces
- Repository implementations are interchangeable

### Interface Segregation Principle (ISP)

- Small, focused interfaces
- `HttpClientInterface` only has GET/POST methods
- Services don't depend on methods they don't use

### Dependency Inversion Principle (DIP)

- High-level modules depend on abstractions (interfaces)
- Low-level modules implement interfaces
- All dependencies injected via constructor

## PSR-12 Compliance

All code follows PSR-12 coding standards:

- Proper spacing and indentation
- Type declarations on all methods
- Strict types enabled (`declare(strict_types=1)`)
- Consistent naming conventions
- Proper visibility modifiers
- DocBlocks for all classes and methods

## Benefits of This Architecture

1. **Maintainability**: Clear separation of concerns
2. **Testability**: Easy to unit test each component
3. **Extensibility**: Add new features via events or new services
4. **Scalability**: Services can be optimized independently
5. **Reliability**: Explicit error handling and transaction management
6. **Type Safety**: Strong typing throughout

## Migration Notes

The old `Payment` and `PayfastService` classes are deprecated. Use the new service-based architecture:

**Old Way:**

```php
$payfast = new PayFast();
$payfast->GetToken();
```

**New Way:**

```php
$payfast = app('payfast');
$payfast->getToken();
```

All methods now follow camelCase naming (PSR-12 compliant).