# Vehicles Feature Capsule

## Quick Summary (50 tokens)
Primary entity for vehicle management with VIN decoding via NHTSA vPIC API. Handles CRUD operations, automatic vehicle data population, user ownership validation, caching strategy (VIN lookups: 30 days, user lists: 5 minutes). Foundation for fuel-logs and maintenance features.

## API Endpoints
- `POST /api/vehicles` - Create new vehicle with VIN decoding
- `GET /api/vehicles` - List all user's vehicles (cached 5 min)
- `GET /api/vehicles/:id` - Get specific vehicle
- `PUT /api/vehicles/:id` - Update vehicle details
- `DELETE /api/vehicles/:id` - Soft delete vehicle

## Authentication Required
All endpoints require valid JWT token with user context.

## Request/Response Examples

### Create Vehicle
```json
POST /api/vehicles
{
  "vin": "1HGBH41JXMN109186",
  "nickname": "My Honda",
  "color": "Blue",
  "licensePlate": "ABC123",
  "odometerReading": 50000
}

Response (201):
{
  "id": "uuid-here",
  "userId": "user-id",
  "vin": "1HGBH41JXMN109186",
  "make": "Honda", // Auto-decoded
  "model": "Civic", // Auto-decoded
  "year": 2021, // Auto-decoded
  "nickname": "My Honda",
  "color": "Blue",
  "licensePlate": "ABC123",
  "odometerReading": 50000,
  "isActive": true,
  "createdAt": "2024-01-01T00:00:00Z",
  "updatedAt": "2024-01-01T00:00:00Z"
}
```

## Feature Architecture

### Complete Self-Contained Structure
```
vehicles/
├── README.md              # This file
├── index.ts               # Public API exports
├── api/                   # HTTP layer
│   ├── vehicles.controller.ts
│   ├── vehicles.routes.ts
│   └── vehicles.validation.ts
├── domain/                # Business logic
│   ├── vehicles.service.ts
│   └── vehicles.types.ts
├── data/                  # Database layer
│   └── vehicles.repository.ts
├── migrations/            # Feature schema
│   └── 001_create_vehicles_tables.sql
├── external/              # External APIs
│   └── vpic/
│       ├── vpic.client.ts
│       └── vpic.types.ts
├── tests/                 # All tests
│   ├── unit/
│   │   ├── vehicles.service.test.ts
│   │   └── vpic.client.test.ts
│   └── integration/
│       └── vehicles.integration.test.ts
└── docs/                  # Additional docs
```

## Key Features

### 🔍 Automatic VIN Decoding
- **External API**: NHTSA vPIC (Vehicle Product Information Catalog)
- **Caching**: 30-day Redis cache for VIN lookups
- **Fallback**: Graceful handling of decode failures
- **Validation**: 17-character VIN format validation

### 🏗️ Database Schema
- **Primary Table**: `vehicles` with soft delete
- **Cache Table**: `vin_cache` for external API results
- **Indexes**: Optimized for user queries and VIN lookups
- **Constraints**: Unique VIN per user, proper foreign keys

### 🚀 Performance Optimizations
- **Redis Caching**: User vehicle lists cached for 5 minutes
- **VIN Cache**: 30-day persistent cache in PostgreSQL
- **Indexes**: Strategic database indexes for fast queries
- **Soft Deletes**: Maintains referential integrity

## Business Rules

### VIN Validation
- Must be exactly 17 characters
- Cannot contain letters I, O, or Q
- Must pass basic checksum validation
- Auto-populates make, model, year from vPIC API

### User Ownership
- Each user can have multiple vehicles
- Same VIN cannot be registered twice by same user
- All operations validate user ownership
- Soft delete preserves data for audit trail

## Dependencies

### Internal Core Services
- `core/auth` - JWT authentication middleware
- `core/config` - Database pool, Redis cache
- `core/logging` - Structured logging with Winston
- `shared-minimal/utils` - Pure validation utilities

### External Services
- **NHTSA vPIC API** - VIN decoding service
- **PostgreSQL** - Primary data storage
- **Redis** - Caching layer

### Database Tables
- `vehicles` - Primary vehicle data
- `vin_cache` - External API response cache

## Caching Strategy

### VIN Decode Cache (30 days)
- **Key**: `vpic:vin:{vin}`
- **TTL**: 2,592,000 seconds (30 days)
- **Rationale**: Vehicle specifications never change

### User Vehicle List (5 minutes)
- **Key**: `vehicles:user:{userId}`
- **TTL**: 300 seconds (5 minutes)
- **Invalidation**: On create, update, delete

## Testing

### Unit Tests
- `vehicles.service.test.ts` - Business logic with mocked dependencies
- `vpic.client.test.ts` - External API client with mocked HTTP

### Integration Tests
- `vehicles.integration.test.ts` - Complete API workflow with test database

### Run Tests
```bash
# All vehicle tests
npm test -- features/vehicles

# Unit tests only
npm test -- features/vehicles/tests/unit

# Integration tests only  
npm test -- features/vehicles/tests/integration

# With coverage
npm test -- features/vehicles --coverage
```

## Error Handling

### Client Errors (4xx)
- `400` - Invalid VIN format, validation errors
- `401` - Missing or invalid JWT token
- `403` - User not authorized for vehicle
- `404` - Vehicle not found
- `409` - Duplicate VIN for user

### Server Errors (5xx)
- `500` - Database connection, VIN API failures
- Graceful degradation when vPIC API unavailable

## Future Considerations

### Dependent Features
- **fuel-logs** - Will reference `vehicle_id`
- **maintenance** - Will reference `vehicle_id`
- Both features depend on vehicles as primary entity

### Potential Enhancements
- Vehicle image uploads (MinIO integration)
- VIN decode webhook for real-time updates
- Vehicle value estimation integration
- Maintenance scheduling based on vehicle age/mileage

## Development Commands

```bash
# Run migrations
make migrate

# Start development environment
make dev

# View feature logs
make logs-backend | grep vehicles

# Open container shell
make shell-backend

# Inside container - run feature tests
npm test -- features/vehicles
```