# RedAI Zalo SDK Architecture

## Overview

RedAI Zalo SDK là một TypeScript SDK hoàn chỉnh cho các API của Zalo, được thiết kế với kiến trúc modular và type-safe.

## Cấu trúc thư mục

```
redai-zalo-sdk/
├── src/
│   ├── types/           # Type definitions
│   │   ├── common.ts    # Common types và interfaces
│   │   ├── auth.ts      # Authentication types
│   │   ├── oa.ts        # Official Account types
│   │   ├── message.ts   # Message types
│   │   └── webhook.ts   # Webhook types
│   ├── clients/         # HTTP clients
│   │   ├── base-client.ts    # Base HTTP client
│   │   └── zalo-client.ts    # Zalo-specific client
│   ├── services/        # Business logic services
│   │   ├── auth.service.ts     # Authentication service
│   │   ├── oa.service.ts       # Official Account service
│   │   └── message.service.ts  # Message service
│   ├── utils/           # Utility functions
│   ├── index.ts         # Main export file
│   └── zalo-sdk.ts      # Main SDK class
├── examples/            # Usage examples
├── dist/               # Build output
├── package.json
├── tsconfig.json
└── README.md
```

## Kiến trúc chính

### 1. Layered Architecture

SDK được thiết kế theo kiến trúc phân lớp:

```
┌─────────────────┐
│   Main SDK      │  ← ZaloSDK class (public API)
├─────────────────┤
│   Services      │  ← Business logic (AuthService, OAService, MessageService)
├─────────────────┤
│   Clients       │  ← HTTP communication (BaseClient, ZaloClient)
├─────────────────┤
│   Types         │  ← Type definitions và interfaces
└─────────────────┘
```

### 2. Core Components

#### ZaloSDK (Main Class)
- Entry point cho tất cả các chức năng
- Khởi tạo và quản lý các services
- Cung cấp quick methods cho các tác vụ phổ biến
- Quản lý configuration và lifecycle

#### BaseClient
- HTTP client cơ bản với axios
- Retry mechanism
- Error handling
- Request/response logging
- File upload support

#### ZaloClient
- Extends BaseClient
- Zalo-specific endpoints
- API versioning support
- OAuth và ZNS endpoint handling

#### Services
- **AuthService**: OAuth flows, token management
- **OAService**: Official Account operations
- **MessageService**: Message sending và file upload

### 3. Type System

#### Comprehensive Types
- Tất cả API responses được type-safe
- Union types cho message types
- Enum cho constants
- Generic types cho reusability

#### Error Handling
- Custom `ZaloSDKError` class
- Structured error information
- Error code mapping

### 4. Configuration

```typescript
interface ZaloSDKConfig {
  appId: string;
  appSecret: string;
  timeout?: number;
  debug?: boolean;
  apiBaseUrl?: string;
  retry?: {
    attempts?: number;
    delay?: number;
  };
}
```

## Design Patterns

### 1. Builder Pattern
SDK configuration với default values và validation.

### 2. Service Pattern
Mỗi service chịu trách nhiệm cho một domain cụ thể.

### 3. Factory Pattern
Client creation và service initialization.

### 4. Strategy Pattern
Different authentication flows (OA vs Social).

### 5. Observer Pattern
Webhook event handling (planned).

## Key Features

### 1. Type Safety
- Full TypeScript support
- Comprehensive type definitions
- Generic types cho flexibility
- Union types cho message variants

### 2. Error Handling
- Structured error responses
- Retry mechanism
- Detailed error information
- Error code mapping

### 3. Authentication
- OAuth 2.0 flows
- PKCE support
- Token refresh
- Multiple auth scopes

### 4. Extensibility
- Modular architecture
- Easy to add new services
- Plugin-ready design
- Custom request support

### 5. Developer Experience
- IntelliSense support
- Comprehensive documentation
- Usage examples
- Debug logging

## API Design Principles

### 1. Consistency
- Consistent naming conventions
- Uniform error handling
- Standard response formats

### 2. Simplicity
- Easy-to-use public API
- Quick methods cho common tasks
- Sensible defaults

### 3. Flexibility
- Low-level access khi cần
- Custom request support
- Configurable behavior

### 4. Reliability
- Retry mechanisms
- Error recovery
- Connection testing

## Future Enhancements

### 1. Additional Services
- ZNS Service (Zalo Notification Service)
- User Management Service
- Group Management Service
- Webhook Service

### 2. Advanced Features
- Rate limiting
- Caching
- Batch operations
- Real-time subscriptions

### 3. Developer Tools
- CLI tools
- Testing utilities
- Mock server
- Documentation generator

## Testing Strategy

### 1. Unit Tests
- Service logic testing
- Type validation
- Error handling

### 2. Integration Tests
- API endpoint testing
- Authentication flows
- File upload/download

### 3. E2E Tests
- Complete workflows
- Real API interactions
- Error scenarios

## Performance Considerations

### 1. HTTP Optimization
- Connection pooling
- Request compression
- Timeout management

### 2. Memory Management
- Efficient data structures
- Stream processing cho large files
- Garbage collection friendly

### 3. Network Efficiency
- Batch requests
- Caching strategies
- Retry with backoff

## Security

### 1. Token Management
- Secure token storage
- Automatic refresh
- Token validation

### 2. Request Security
- HTTPS only
- Request signing
- Parameter validation

### 3. Error Information
- Sanitized error messages
- No sensitive data in logs
- Secure debugging

## Deployment

### 1. Package Distribution
- NPM package
- TypeScript declarations
- Source maps

### 2. Versioning
- Semantic versioning
- Backward compatibility
- Migration guides

### 3. Documentation
- API documentation
- Usage examples
- Migration guides