# Vendor-in-Token Architecture

## Overview

This document describes the vendor-in-token authentication architecture used for vendor API endpoints. This architecture embeds vendor context directly into JWT tokens, eliminating the need for URL-based vendor detection and enabling clean, RESTful API endpoints.

## The Problem: URL-Based Vendor Detection

### Old Pattern (Deprecated)
```python
# ❌ DEPRECATED: URL-based vendor detection
@router.get("/{product_id}")
def get_product(
    product_id: int,
    vendor: Vendor = Depends(require_vendor_context()),  # ❌ Don't use
    current_user: User = Depends(get_current_vendor_api),
    db: Session = Depends(get_db),
):
    product = product_service.get_product(db, vendor.id, product_id)
    return product
```

### Issues with URL-Based Detection

1. **Inconsistent API Routes**
   - Page routes: `/vendor/{vendor_code}/dashboard` (has vendor in URL)
   - API routes: `/api/v1/vendor/products` (no vendor in URL)
   - `require_vendor_context()` only works when vendor is in the URL path

2. **404 Errors on API Endpoints**
   - API calls to `/api/v1/vendor/products` would return 404
   - The dependency expected vendor code in URL but API routes don't have it
   - Breaking RESTful API design principles

3. **Architecture Violation**
   - Mixed concerns: URL structure determining business logic
   - Tight coupling between routing and vendor context
   - Harder to test and maintain

## The Solution: Vendor-in-Token

### Architecture Overview

```
┌─────────────────────────────────────────────────────────────────┐
│                     Vendor Login Flow                           │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│  1. Authenticate user credentials                               │
│  2. Validate vendor membership                                  │
│  3. Create JWT with vendor context:                             │
│     {                                                            │
│       "sub": "user_id",                                         │
│       "username": "john.doe",                                   │
│       "vendor_id": 123,          ← Vendor context in token     │
│       "vendor_code": "WIZAMART",  ← Vendor code in token       │
│       "vendor_role": "Owner"      ← Vendor role in token       │
│     }                                                            │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│  4. Set dual token storage:                                     │
│     - HTTP-only cookie (path=/vendor) for page navigation      │
│     - Response body for localStorage (API calls)               │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│  5. Subsequent API requests include vendor context             │
│     Authorization: Bearer <token-with-vendor-context>          │
└─────────────────────────────────────────────────────────────────┘
                              │
                              ↓
┌─────────────────────────────────────────────────────────────────┐
│  6. get_current_vendor_api() extracts vendor from token:       │
│     - current_user.token_vendor_id                              │
│     - current_user.token_vendor_code                            │
│     - current_user.token_vendor_role                            │
│  7. Validates user still has access to vendor                  │
└─────────────────────────────────────────────────────────────────┘
```

### Implementation Components

#### 1. Token Creation (middleware/auth.py)
```python
def create_access_token(
    self,
    user: User,
    vendor_id: int | None = None,
    vendor_code: str | None = None,
    vendor_role: str | None = None,
) -> dict[str, Any]:
    """Create JWT with optional vendor context."""
    payload = {
        "sub": str(user.id),
        "username": user.username,
        "email": user.email,
        "role": user.role,
        "exp": expire,
        "iat": datetime.now(UTC),
    }

    # Include vendor information in token if provided
    if vendor_id is not None:
        payload["vendor_id"] = vendor_id
    if vendor_code is not None:
        payload["vendor_code"] = vendor_code
    if vendor_role is not None:
        payload["vendor_role"] = vendor_role

    return {
        "access_token": jwt.encode(payload, self.secret_key, algorithm=self.algorithm),
        "token_type": "bearer",
        "expires_in": self.access_token_expire_minutes * 60,
    }
```

#### 2. Vendor Login (app/api/v1/vendor/auth.py)
```python
@router.post("/login", response_model=VendorLoginResponse)
def vendor_login(
    user_credentials: UserLogin,
    response: Response,
    db: Session = Depends(get_db),
):
    """
    Vendor team member login.

    Creates vendor-scoped JWT token with vendor context embedded.
    """
    # Authenticate user and determine vendor
    login_result = auth_service.login_user(db=db, user_credentials=user_credentials)
    user = login_result["user"]

    # Determine vendor and role
    vendor = determine_vendor(db, user)  # Your vendor detection logic
    vendor_role = determine_role(db, user, vendor)  # Your role detection logic

    # Create vendor-scoped access token
    token_data = auth_service.auth_manager.create_access_token(
        user=user,
        vendor_id=vendor.id,
        vendor_code=vendor.vendor_code,
        vendor_role=vendor_role,
    )

    # Set cookie and return token
    response.set_cookie(
        key="vendor_token",
        value=token_data["access_token"],
        httponly=True,
        path="/vendor",  # Restricted to vendor routes
    )

    return VendorLoginResponse(**token_data, user=user, vendor=vendor)
```

#### 3. Token Verification (app/api/deps.py)
```python
def get_current_vendor_api(
    authorization: str | None = Header(None, alias="Authorization"),
    db: Session = Depends(get_db),
) -> User:
    """
    Get current vendor API user from Authorization header.

    Extracts vendor context from JWT token and validates access.
    """
    if not authorization or not authorization.startswith("Bearer "):
        raise AuthenticationException("Authorization header required for API calls")

    token = authorization.replace("Bearer ", "")
    user = auth_service.auth_manager.get_current_user(token, db)

    # Validate vendor access if token is vendor-scoped
    if hasattr(user, "token_vendor_id"):
        vendor_id = user.token_vendor_id

        # Verify user still has access to this vendor
        if not user.is_member_of(vendor_id):
            raise InsufficientPermissionsException(
                "Access to vendor has been revoked. Please login again."
            )

    return user
```

#### 4. Endpoint Usage (app/api/v1/vendor/products.py)
```python
@router.get("", response_model=ProductListResponse)
def get_vendor_products(
    skip: int = Query(0, ge=0),
    limit: int = Query(100, ge=1, le=1000),
    current_user: User = Depends(get_current_vendor_api),  # ✅ Only need this
    db: Session = Depends(get_db),
):
    """
    Get all products in vendor catalog.

    Vendor is determined from JWT token (vendor_id claim).
    """
    # Extract vendor ID from token
    if not hasattr(current_user, "token_vendor_id"):
        raise HTTPException(
            status_code=400,
            detail="Token missing vendor information. Please login again.",
        )

    vendor_id = current_user.token_vendor_id

    # Use vendor_id from token for business logic
    products, total = product_service.get_vendor_products(
        db=db,
        vendor_id=vendor_id,
        skip=skip,
        limit=limit,
    )

    return ProductListResponse(products=products, total=total)
```

## Migration Guide

### Step 1: Identify Endpoints Using require_vendor_context()

Search for all occurrences:
```bash
grep -r "require_vendor_context" app/api/v1/vendor/
```

### Step 2: Update Endpoint Signature

**Before:**
```python
@router.get("/{product_id}")
def get_product(
    product_id: int,
    vendor: Vendor = Depends(require_vendor_context()),  # ❌ Remove this
    current_user: User = Depends(get_current_vendor_api),
    db: Session = Depends(get_db),
):
```

**After:**
```python
@router.get("/{product_id}")
def get_product(
    product_id: int,
    current_user: User = Depends(get_current_vendor_api),  # ✅ Only need this
    db: Session = Depends(get_db),
):
```

### Step 3: Extract Vendor from Token

**Before:**
```python
product = product_service.get_product(db, vendor.id, product_id)
```

**After:**
```python
from fastapi import HTTPException

# Extract vendor ID from token
if not hasattr(current_user, "token_vendor_id"):
    raise HTTPException(
        status_code=400,
        detail="Token missing vendor information. Please login again.",
    )

vendor_id = current_user.token_vendor_id

# Use vendor_id from token
product = product_service.get_product(db, vendor_id, product_id)
```

### Step 4: Update Logging References

**Before:**
```python
logger.info(f"Product updated for vendor {vendor.vendor_code}")
```

**After:**
```python
logger.info(f"Product updated for vendor {current_user.token_vendor_code}")
```

### Complete Migration Example

**Before (URL-based vendor detection):**
```python
@router.put("/{product_id}", response_model=ProductResponse)
def update_product(
    product_id: int,
    product_data: ProductUpdate,
    vendor: Vendor = Depends(require_vendor_context()),  # ❌
    current_user: User = Depends(get_current_vendor_api),
    db: Session = Depends(get_db),
):
    """Update product in vendor catalog."""
    product = product_service.update_product(
        db=db,
        vendor_id=vendor.id,  # ❌ From URL
        product_id=product_id,
        product_update=product_data
    )

    logger.info(
        f"Product {product_id} updated by {current_user.username} "
        f"for vendor {vendor.vendor_code}"  # ❌ From URL
    )

    return ProductResponse.model_validate(product)
```

**After (Token-based vendor context):**
```python
@router.put("/{product_id}", response_model=ProductResponse)
def update_product(
    product_id: int,
    product_data: ProductUpdate,
    current_user: User = Depends(get_current_vendor_api),  # ✅ Only dependency
    db: Session = Depends(get_db),
):
    """Update product in vendor catalog."""
    from fastapi import HTTPException

    # Extract vendor ID from token
    if not hasattr(current_user, "token_vendor_id"):
        raise HTTPException(
            status_code=400,
            detail="Token missing vendor information. Please login again.",
        )

    vendor_id = current_user.token_vendor_id  # ✅ From token

    product = product_service.update_product(
        db=db,
        vendor_id=vendor_id,  # ✅ From token
        product_id=product_id,
        product_update=product_data
    )

    logger.info(
        f"Product {product_id} updated by {current_user.username} "
        f"for vendor {current_user.token_vendor_code}"  # ✅ From token
    )

    return ProductResponse.model_validate(product)
```

## Files to Migrate

Current files still using `require_vendor_context()`:
- `app/api/v1/vendor/customers.py`
- `app/api/v1/vendor/notifications.py`
- `app/api/v1/vendor/media.py`
- `app/api/v1/vendor/marketplace.py`
- `app/api/v1/vendor/inventory.py`
- `app/api/v1/vendor/settings.py`
- `app/api/v1/vendor/analytics.py`
- `app/api/v1/vendor/payments.py`
- `app/api/v1/vendor/profile.py`

## Benefits of Vendor-in-Token

### 1. Clean RESTful APIs
```
✅ /api/v1/vendor/products
✅ /api/v1/vendor/orders
✅ /api/v1/vendor/customers

❌ /api/v1/vendor/{vendor_code}/products  (unnecessary vendor in URL)
```

### 2. Security
- Vendor context cryptographically signed in JWT
- Cannot be tampered with by client
- Automatic validation on every request
- Token revocation possible via database checks

### 3. Consistency
- Same authentication mechanism for all vendor API endpoints
- No confusion between page routes and API routes
- Single source of truth (the token)

### 4. Performance
- No database lookup for vendor context on every request
- Vendor information already in token payload
- Optional validation for revoked access

### 5. Maintainability
- Simpler endpoint signatures
- Less boilerplate code
- Easier to test
- Follows architecture rule API-002 (no DB queries in endpoints)

## Security Considerations

### Token Validation
The token vendor context is validated on every request:
1. JWT signature verification (ensures token not tampered with)
2. Token expiration check (typically 30 minutes)
3. Optional: Verify user still member of vendor (database check)

### Access Revocation
If a user's vendor access is revoked:
1. Existing tokens remain valid until expiration
2. `get_current_vendor_api()` performs optional database check
3. User forced to re-login after token expires
4. New login will fail if access revoked

### Token Refresh
Tokens should be refreshed periodically:
- Default: 30 minutes expiration
- Refresh before expiration for seamless UX
- New login creates new token with current vendor membership

## Testing

### Unit Tests
```python
def test_vendor_in_token():
    """Test vendor context in JWT token."""
    # Create token with vendor context
    token_data = auth_manager.create_access_token(
        user=user,
        vendor_id=123,
        vendor_code="WIZAMART",
        vendor_role="Owner",
    )

    # Verify token contains vendor data
    payload = jwt.decode(token_data["access_token"], secret_key)
    assert payload["vendor_id"] == 123
    assert payload["vendor_code"] == "WIZAMART"
    assert payload["vendor_role"] == "Owner"

def test_api_endpoint_uses_token_vendor():
    """Test API endpoint extracts vendor from token."""
    response = client.get(
        "/api/v1/vendor/products",
        headers={"Authorization": f"Bearer {token}"}
    )
    assert response.status_code == 200
    # Verify products are filtered by token vendor_id
```

### Integration Tests
```python
def test_vendor_login_and_api_access():
    """Test full vendor login and API access flow."""
    # Login as vendor user
    response = client.post("/api/v1/vendor/auth/login", json={
        "username": "john.doe",
        "password": "password123"
    })
    assert response.status_code == 200
    token = response.json()["access_token"]

    # Access vendor API with token
    response = client.get(
        "/api/v1/vendor/products",
        headers={"Authorization": f"Bearer {token}"}
    )
    assert response.status_code == 200

    # Verify vendor context from token
    products = response.json()["products"]
    # All products should belong to token vendor
```

## Architecture Rules

See `docs/architecture/rules/API-VND-001.md` for the formal architecture rule enforcing this pattern.

## Related Documentation

- [Vendor RBAC System](./vendor-rbac.md) - Role-based access control for vendors
- [Vendor Authentication](./vendor-authentication.md) - Complete authentication guide
- [Architecture Rules](../architecture/rules/) - All architecture rules
- [API Design Guidelines](../architecture/api-design.md) - RESTful API patterns

## Summary

The vendor-in-token architecture:
- ✅ Embeds vendor context in JWT tokens
- ✅ Eliminates URL-based vendor detection
- ✅ Enables clean RESTful API endpoints
- ✅ Improves security and performance
- ✅ Simplifies endpoint implementation
- ✅ Follows architecture best practices

**Migration Status:** In progress - 9 endpoint files remaining to migrate