# 🎉 NestJS Retail POS Backend - Setup Complete!

Your complete NestJS backend API for the Retail POS Flutter application has been successfully created!

---

## 📦 What's Been Created

### ✅ **Core Infrastructure**
- **NestJS Application**: Latest version with TypeScript
- **PostgreSQL Database**: Complete schema with migrations
- **Redis Caching**: Ready for performance optimization
- **JWT Authentication**: Secure token-based auth
- **Role-Based Access Control (RBAC)**: Admin, Manager, Cashier, User roles
- **Swagger Documentation**: Auto-generated API docs

### ✅ **Database Layer**
- **5 Entities**: User, Category, Product, Transaction, TransactionItem
- **Initial Migration**: Complete schema with 11 indexes
- **Seed Data**: Sample categories, products, and users
- **TypeORM Configuration**: Production-ready setup

### ✅ **API Modules**

#### 1. **Auth Module** (`/api/auth`)
- `POST /auth/register` - Register new user
- `POST /auth/login` - Login with JWT
- `GET /auth/profile` - Get current user
- `POST /auth/refresh` - Refresh token

#### 2. **Users Module** (`/api/users`)
- Complete CRUD for user management
- Admin-only access
- Password hashing with bcrypt

#### 3. **Categories Module** (`/api/categories`)
- `GET /categories` - List all categories (Public)
- `GET /categories/:id` - Get single category (Public)
- `GET /categories/:id/products` - Products by category (Public)
- `POST /categories` - Create category (Admin/Manager)
- `PUT /categories/:id` - Update category (Admin/Manager)
- `DELETE /categories/:id` - Delete category (Admin only)

#### 4. **Products Module** (`/api/products`)
- `GET /products` - List with pagination, filters, search (Public)
- `GET /products/:id` - Get single product (Public)
- `GET /products/category/:categoryId` - By category (Public)
- `GET /products/search` - Search products (Public)
- `POST /products` - Create product (Admin/Manager)
- `PUT /products/:id` - Update product (Admin/Manager)
- `DELETE /products/:id` - Delete product (Admin only)

#### 5. **Transactions Module** (`/api/transactions`)
- `GET /transactions` - List transactions (Cashier+)
- `GET /transactions/:id` - Get transaction (Cashier+)
- `POST /transactions` - Create transaction (Cashier+)
- `GET /transactions/stats` - Statistics (Manager+)
- `GET /transactions/stats/daily` - Daily sales (Manager+)

**Features**:
- ✅ Atomic transaction processing
- ✅ Stock validation and updates
- ✅ Automatic tax calculation (10%)
- ✅ Price snapshots at transaction time
- ✅ Pessimistic locking for concurrency

#### 6. **Sync Module** (`/api/sync`)
- `POST /sync` - Sync all data (Cashier+)
- `POST /sync/products` - Sync products only (Cashier+)
- `POST /sync/categories` - Sync categories only (Cashier+)
- `GET /sync/status` - Get sync status (Cashier+)

**Features**:
- ✅ Incremental sync based on timestamps
- ✅ Offline-first mobile support
- ✅ Efficient bandwidth usage

### ✅ **Common Utilities**
- **DTOs**: Pagination, API Response wrappers
- **Filters**: HTTP exception handler, catch-all filter
- **Interceptors**: Logging, response transformation, caching
- **Pipes**: Global validation pipe
- **Guards**: JWT auth guard, roles guard
- **Decorators**: @CurrentUser(), @Public(), @Roles()

### ✅ **Configuration**
- **Environment Variables**: `.env` file with dummy data
- **TypeScript Config**: Strict mode enabled
- **ESLint & Prettier**: Code formatting
- **Jest**: Testing framework setup

### ✅ **Docker Setup**
- **Dockerfile**: Multi-stage build for production
- **docker-compose.yml**: Complete stack (API, PostgreSQL, Redis, pgAdmin)
- **.dockerignore**: Optimized build context

---

## 🚀 Quick Start

### **Option 1: Local Development**

#### 1. Create Database
```bash
# Using psql
createdb retail_pos

# Or using Docker
docker-compose up -d postgres redis
```

#### 2. Configure Environment
The `.env` file is already created with dummy data. Update these values:

```bash
DB_HOST=localhost
DB_PORT=5432
DB_USERNAME=postgres
DB_PASSWORD=postgres  # Change this!
DB_DATABASE=retail_pos

JWT_SECRET=retail-pos-super-secret-key-change-in-production-2025  # Change this!
```

#### 3. Run Migrations
```bash
npm run migration:run
```

#### 4. Seed Database (Optional)
```bash
npm run seed:run
```

This creates:
- **Categories**: 6 retail categories (Electronics, Clothing, Food, etc.)
- **Products**: 14 sample products
- **Users**:
  - Admin: `admin@retailpos.com` / `Admin123!`
  - Manager: `manager@retailpos.com` / `Manager123!`
  - Cashier: `cashier@retailpos.com` / `Cashier123!`

#### 5. Start Server
```bash
# Development mode with hot-reload
npm run start:dev

# Production mode
npm run build
npm run start:prod
```

#### 6. Access Application
- **API**: http://localhost:3000/api
- **Swagger Docs**: http://localhost:3000/api/docs
- **Health Check**: http://localhost:3000/health

---

### **Option 2: Docker Deployment**

#### Start All Services
```bash
# Start API, PostgreSQL, Redis
docker-compose up -d

# View logs
docker-compose logs -f api

# Include pgAdmin for database management
docker-compose --profile tools up -d
```

#### Run Migrations in Docker
```bash
docker-compose exec api npm run migration:run
docker-compose exec api npm run seed:run
```

#### Access Services
- **API**: http://localhost:3000/api
- **Swagger**: http://localhost:3000/api/docs
- **pgAdmin**: http://localhost:5050 (admin@retailpos.com / admin123)
- **PostgreSQL**: localhost:5432
- **Redis**: localhost:6379

---

## 🔐 Test the API

### 1. Login to Get Token
```bash
curl -X POST http://localhost:3000/api/auth/login \
  -H "Content-Type: application/json" \
  -d '{"email": "admin@retailpos.com", "password": "Admin123!"}'
```

**Response**:
```json
{
  "access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "user": {
    "id": "uuid",
    "email": "admin@retailpos.com",
    "name": "Admin User",
    "roles": ["admin"]
  }
}
```

### 2. List Products (Public)
```bash
curl http://localhost:3000/api/products
```

### 3. Create Product (Auth Required)
```bash
curl -X POST http://localhost:3000/api/products \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Gaming Mouse",
    "price": 49.99,
    "categoryId": "CATEGORY_UUID",
    "stockQuantity": 100
  }'
```

### 4. Create Transaction
```bash
curl -X POST http://localhost:3000/api/transactions \
  -H "Authorization: Bearer YOUR_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "items": [
      {"productId": "PRODUCT_UUID", "quantity": 2}
    ],
    "paymentMethod": "cash",
    "discount": 5.00
  }'
```

---

## 📚 Project Structure

```
retail-nest/
├── src/
│   ├── common/                 # Global utilities
│   │   ├── decorators/         # @CurrentUser, @Public, @Roles
│   │   ├── dto/                # PaginationDto, ApiResponseDto
│   │   ├── filters/            # Exception handlers
│   │   ├── guards/             # JWT, Roles guards
│   │   ├── interceptors/       # Logging, Transform, Cache
│   │   └── pipes/              # Validation pipe
│   ├── config/                 # Configuration modules
│   │   ├── app.config.ts
│   │   ├── database.config.ts
│   │   ├── jwt.config.ts
│   │   └── redis.config.ts
│   ├── database/
│   │   ├── migrations/         # TypeORM migrations
│   │   └── seeds/              # Database seeds
│   ├── modules/
│   │   ├── auth/               # Authentication
│   │   ├── users/              # User management
│   │   ├── categories/         # Category API
│   │   ├── products/           # Product API
│   │   ├── transactions/       # Transaction API
│   │   └── sync/               # Mobile sync API
│   ├── app.module.ts
│   └── main.ts
├── test/                       # Unit & E2E tests
├── .env                        # Environment variables
├── .env.example                # Environment template
├── Dockerfile                  # Production Docker image
├── docker-compose.yml          # Full stack setup
└── package.json
```

---

## 🎯 Key Features

### Security
✅ JWT authentication with refresh tokens
✅ Password hashing with bcrypt (10 rounds)
✅ Role-based access control (RBAC)
✅ Rate limiting (100 req/min)
✅ CORS protection
✅ Helmet security headers

### Performance
✅ Redis caching layer
✅ Database query optimization with indexes
✅ Pessimistic locking for transactions
✅ Pagination for large datasets
✅ Response compression (gzip)

### Data Integrity
✅ Database transactions for critical operations
✅ Foreign key constraints
✅ Unique constraints
✅ Stock validation before transactions
✅ Price snapshots in transactions

### Developer Experience
✅ Swagger/OpenAPI documentation
✅ TypeScript with strict mode
✅ Hot-reload in development
✅ Docker support for easy deployment
✅ Comprehensive error handling

---

## 🧪 Available Scripts

```bash
# Development
npm run start:dev          # Start with hot-reload
npm run start:debug        # Start with debugger

# Production
npm run build              # Build for production
npm run start:prod         # Run production build

# Database
npm run migration:generate # Generate migration
npm run migration:create   # Create empty migration
npm run migration:run      # Run migrations
npm run migration:revert   # Revert last migration
npm run seed:run           # Seed database

# Testing
npm run test               # Run unit tests
npm run test:watch         # Watch mode
npm run test:cov           # With coverage
npm run test:e2e           # E2E tests

# Code Quality
npm run lint               # Lint code
npm run format             # Format with Prettier
```

---

## 🔧 Environment Variables

All required environment variables are in `.env` (already created):

```bash
# Application
NODE_ENV=development
PORT=3000
API_PREFIX=api

# Database
DB_HOST=localhost
DB_PORT=5432
DB_USERNAME=postgres
DB_PASSWORD=postgres
DB_DATABASE=retail_pos

# JWT
JWT_SECRET=your-secret-key-here
JWT_EXPIRES_IN=1d

# Redis
REDIS_HOST=localhost
REDIS_PORT=6379
CACHE_TTL=300

# CORS
CORS_ORIGIN=http://localhost:3000,capacitor://localhost

# Rate Limiting
THROTTLE_TTL=60
THROTTLE_LIMIT=100

# Security
BCRYPT_ROUNDS=10
```

---

## 📖 API Documentation

### Access Swagger UI
Once the server is running, visit:
- **Swagger UI**: http://localhost:3000/api/docs
- **OpenAPI JSON**: http://localhost:3000/api/docs-json

### Default Users
| Role | Email | Password |
|------|-------|----------|
| Admin | admin@retailpos.com | Admin123! |
| Manager | manager@retailpos.com | Manager123! |
| Cashier | cashier@retailpos.com | Cashier123! |

---

## 🎨 Response Format

All API responses follow a consistent format:

### Success Response
```json
{
  "success": true,
  "data": { /* your data */ },
  "message": "Operation successful"
}
```

### Paginated Response
```json
{
  "success": true,
  "data": [ /* items */ ],
  "meta": {
    "page": 1,
    "limit": 20,
    "total": 100,
    "totalPages": 5
  }
}
```

### Error Response
```json
{
  "success": false,
  "error": {
    "statusCode": 400,
    "message": "Validation failed",
    "details": ["error details"]
  },
  "timestamp": "2025-10-10T12:00:00.000Z",
  "path": "/api/products"
}
```

---

## 🚀 Next Steps

### 1. **Update Environment Variables**
Edit `.env` file with your actual database credentials and JWT secret.

### 2. **Run Migrations**
```bash
npm run migration:run
```

### 3. **Seed Database**
```bash
npm run seed:run
```

### 4. **Start Development Server**
```bash
npm run start:dev
```

### 5. **Test API**
Visit http://localhost:3000/api/docs to test endpoints.

### 6. **Integrate with Flutter App**
- Update Flutter app API base URL to `http://localhost:3000/api`
- Use JWT token from login response for authenticated requests
- Implement offline sync using `/api/sync` endpoints

---

## 📝 Additional Documentation

Created documentation files:
- `DATABASE_SETUP.md` - Complete database guide
- `DATABASE_SUMMARY.md` - Quick database reference
- `AUTH_SYSTEM.md` - Authentication system details
- `IMPLEMENTATION_SUMMARY.md` - Implementation guide

---

## ✨ What Makes This Production-Ready

✅ **Security First**: JWT auth, bcrypt hashing, RBAC, rate limiting
✅ **Scalable Architecture**: Modular design, dependency injection
✅ **Performance Optimized**: Redis caching, database indexes, query optimization
✅ **Data Integrity**: Transactions, constraints, stock validation
✅ **Developer Friendly**: Swagger docs, TypeScript, hot-reload
✅ **Docker Ready**: Multi-stage builds, docker-compose stack
✅ **Testing Ready**: Jest setup, unit & E2E test structure
✅ **Mobile Ready**: Sync API for offline-first Flutter app

---

## 🎉 You're All Set!

Your NestJS Retail POS Backend is **production-ready** and waiting for you to:

1. Update `.env` with your credentials
2. Run migrations: `npm run migration:run`
3. Seed data: `npm run seed:run`
4. Start server: `npm run start:dev`
5. Open Swagger: http://localhost:3000/api/docs

**Happy coding!** 🚀