# Authentication Usage Examples

This document provides practical examples of how to use the authentication system in the Ecommerce Backend API.

## Overview

The API uses JWT (JSON Web Token) authentication with the following workflow:
1. Register a new user account
2. Login to receive a JWT token
3. Include the token in the `Authorization` header for protected endpoints
4. Token expires after 30 minutes (configurable)

## Python Examples

### Basic Authentication Functions

```python
import requests

# API Base URL
BASE_URL = "http://localhost:8000"

def register_user(email, username, password):
    """Register a new user"""
    response = requests.post(
        f"{BASE_URL}/register",
        json={"email": email, "username": username, "password": password},
    )
    return response.json()

def login_user(username, password):
    """Login and get JWT token"""
    response = requests.post(
        f"{BASE_URL}/login", json={"username": username, "password": password}
    )
    if response.status_code == 200:
        data = response.json()
        return data["access_token"]
    else:
        print(f"Login failed: {response.json()}")
        return None

def get_user_info(token):
    """Get current user info"""
    headers = {"Authorization": f"Bearer {token}"}
    response = requests.get(f"{BASE_URL}/me", headers=headers)
    return response.json()
```

### Using Protected Endpoints

```python
def get_products(token, skip=0, limit=10):
    """Get products (requires authentication)"""
    headers = {"Authorization": f"Bearer {token}"}
    response = requests.get(
        f"{BASE_URL}/products?skip={skip}&limit={limit}", headers=headers
    )
    return response.json()

def create_product(token, product_data):
    """Create a new product (requires authentication)"""
    headers = {"Authorization": f"Bearer {token}"}
    response = requests.post(f"{BASE_URL}/products", json=product_data, headers=headers)
    return response.json()
```

### Complete Workflow Example

```python
# Example usage workflow
if __name__ == "__main__":
    # 1. Register a new user
    print("1. Registering new user...")
    try:
        user_result = register_user("test@example.com", "testuser", "password123")
        print(f"User registered: {user_result}")
    except Exception as e:
        print(f"Registration failed: {e}")

    # 2. Login with default admin user
    print("\n2. Logging in as admin...")
    admin_token = login_user("admin", "admin123")
    if admin_token:
        print(f"Admin login successful! Token: {admin_token[:50]}...")

        # 3. Get user info
        print("\n3. Getting admin user info...")
        user_info = get_user_info(admin_token)
        print(f"User info: {user_info}")

        # 4. Create a sample product
        print("\n4. Creating a sample product...")
        sample_product = {
            "marketplace_product_id": "TEST001",
            "title": "Test MarketplaceProduct",
            "description": "A test product for demonstration",
            "price": "19.99",
            "brand": "Test Brand",
            "availability": "in inventory",
        }

        product_result = create_product(admin_token, sample_product)
        print(f"MarketplaceProduct created: {product_result}")

        # 5. Get products list
        print("\n5. Getting products list...")
        products = get_products(admin_token)
        print(f"Products: {products}")

    # 6. Login with regular user
    print("\n6. Logging in as regular user...")
    user_token = login_user("testuser", "password123")
    if user_token:
        print(f"User login successful! Token: {user_token[:50]}...")

        # Regular users can also access protected endpoints
        user_info = get_user_info(user_token)
        print(f"Regular user info: {user_info}")

        products = get_products(user_token, limit=5)
        print(
            f"Products accessible to regular user: {len(products.get('products', []))} products"
        )

    print("\nAuthentication example completed!")
```

## cURL Examples

### Register a New User

```bash
curl -X POST "http://localhost:8000/register" \
     -H "Content-Type: application/json" \
     -d '{
       "email": "user@example.com", 
       "username": "newuser", 
       "password": "password123"
     }'
```

**Response:**
```json
{
  "id": 2,
  "email": "user@example.com",
  "username": "newuser",
  "role": "user",
  "is_active": true,
  "created_at": "2024-01-15T10:30:00Z"
}
```

### Login (Get JWT Token)

```bash
curl -X POST "http://localhost:8000/login" \
     -H "Content-Type: application/json" \
     -d '{
       "username": "admin", 
       "password": "admin123"
     }'
```

**Response:**
```json
{
  "access_token": "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...",
  "token_type": "bearer",
  "expires_in": 1800,
  "user": {
    "id": 1,
    "username": "admin",
    "email": "admin@example.com",
    "role": "admin",
    "is_active": true
  }
}
```

### Use Token for Protected Endpoints

#### Get Current User Info

```bash
curl -X GET "http://localhost:8000/me" \
     -H "Authorization: Bearer YOUR_JWT_TOKEN_HERE"
```

#### Get Products List

```bash
curl -X GET "http://localhost:8000/products" \
     -H "Authorization: Bearer YOUR_JWT_TOKEN_HERE"
```

#### Create a MarketplaceProduct

```bash
curl -X POST "http://localhost:8000/products" \
     -H "Authorization: Bearer YOUR_JWT_TOKEN_HERE" \
     -H "Content-Type: application/json" \
     -d '{
       "marketplace_product_id": "TEST001", 
       "title": "Test MarketplaceProduct", 
       "description": "A test product for demonstration",
       "price": "19.99",
       "brand": "Test Brand",
       "availability": "in inventory"
     }'
```

## Default Accounts

### Admin Account
- **Username**: `admin`
- **Password**: `admin123`
- **Email**: `admin@example.com`
- **Role**: `admin`

**Security Note**: Change the admin password immediately in production environments!

## Authentication Headers

All protected endpoints require the JWT token in the Authorization header:

```
Authorization: Bearer <your_jwt_token>
```

## Error Handling

### Common Authentication Errors

#### Invalid Credentials (Login)
```json
{
  "detail": "Invalid credentials"
}
```

#### Missing or Invalid Token
```json
{
  "detail": "Not authenticated"
}
```

#### Expired Token
```json
{
  "detail": "Token has expired"
}
```

#### Insufficient Permissions
```json
{
  "detail": "Not enough permissions"
}
```

### Error Handling in Python

```python
def safe_api_call(token, endpoint, method="GET", data=None):
    """Make API call with proper error handling"""
    headers = {"Authorization": f"Bearer {token}"}
    
    try:
        if method == "GET":
            response = requests.get(f"{BASE_URL}{endpoint}", headers=headers)
        elif method == "POST":
            response = requests.post(f"{BASE_URL}{endpoint}", json=data, headers=headers)
        
        if response.status_code == 401:
            print("Authentication failed - token may be expired")
            return None
        elif response.status_code == 403:
            print("Access denied - insufficient permissions")
            return None
        elif response.status_code == 200:
            return response.json()
        else:
            print(f"API call failed: {response.status_code} - {response.text}")
            return None
            
    except requests.exceptions.RequestException as e:
        print(f"Request failed: {e}")
        return None
```

## Best Practices

### Token Management

1. **Store tokens securely** - Don't expose tokens in logs or client-side code
2. **Handle token expiration** - Implement automatic token refresh or re-login
3. **Use HTTPS in production** - Never send tokens over unencrypted connections

### Password Security

1. **Use strong passwords** - Minimum 6 characters (configurable)
2. **Don't hardcode passwords** - Use environment variables or secure configuration
3. **Regular password updates** - Especially for admin accounts

### API Integration

1. **Include error handling** - Always check response status codes
2. **Implement retry logic** - Handle temporary network issues
3. **Rate limiting awareness** - Respect API rate limits

## Testing Authentication

You can test the authentication system using the provided Python script or with make commands:

```bash
# Run authentication tests
make test-auth

# Run all tests including authentication
make test
```

## Integration with Frontend

### JavaScript/TypeScript Example

```javascript
class APIClient {
    constructor(baseURL = 'http://localhost:8000') {
        this.baseURL = baseURL;
        this.token = localStorage.getItem('jwt_token');
    }

    async login(username, password) {
        const response = await fetch(`${this.baseURL}/login`, {
            method: 'POST',
            headers: {'Content-Type': 'application/json'},
            body: JSON.stringify({username, password})
        });
        
        if (response.ok) {
            const data = await response.json();
            this.token = data.access_token;
            localStorage.setItem('jwt_token', this.token);
            return data;
        } else {
            throw new Error('Login failed');
        }
    }

    async apiCall(endpoint, method = 'GET', data = null) {
        const headers = {
            'Authorization': `Bearer ${this.token}`,
            'Content-Type': 'application/json'
        };

        const config = {method, headers};
        if (data) config.body = JSON.stringify(data);

        const response = await fetch(`${this.baseURL}${endpoint}`, config);
        
        if (response.status === 401) {
            // Token expired, redirect to login
            localStorage.removeItem('jwt_token');
            window.location.href = '/login';
            return;
        }
        
        return response.json();
    }
}
```

This authentication system provides secure access control for all API endpoints while maintaining ease of use for developers integrating with the system.