# API Compatibility Verification

This document describes the API compatibility verification process implemented as part of the task service refactoring. It ensures that no breaking changes were introduced during the architectural changes.

## Overview

The task service refactoring involved significant changes to the internal architecture:
- Removed the application layer TaskService
- Consolidated functionality into the domain layer TaskService
- Updated dependency injection patterns
- Maintained all existing API endpoints and contracts

## Verification Strategy

### 1. Automated Testing

#### Unit Tests
- **Location**: `core/tests/integration/test_api_compatibility.py`
- **Purpose**: Test all API endpoints using FastAPI TestClient
- **Coverage**: 
  - Agent endpoints (`/api/v1/agents/*`)
  - Task endpoints (`/api/v1/tasks/*`, `/api/v1/agents/{id}/tasks/*`)
  - A2A protocol endpoints (`/api/v1/agents/{id}/a2a/*`)
  - Error handling and edge cases

#### Integration Tests
- **Location**: `core/test_api_compatibility.py`
- **Purpose**: Test against running API server
- **Coverage**:
  - End-to-end API workflows
  - Service dependency injection
  - Error response formats

### 2. API Contract Verification

#### Request/Response Formats
All existing API contracts are maintained:

```python
# Task Creation Request (unchanged)
{
    "description": "string",
    "parameters": {"key": "value"},
    "user_id": "string",
    "enable_agent_communication": true
}

# Task Response Format (unchanged)
{
    "id": "uuid",
    "agent_id": "uuid", 
    "description": "string",
    "parameters": {"key": "value"},
    "status": "string",
    "result": {"key": "value"} | null,
    "created_at": "datetime",
    "execution_id": "string" | null
}
```

#### HTTP Status Codes
- `200 OK`: Successful operations
- `404 Not Found`: Resource not found
- `400 Bad Request`: Invalid request data
- `500 Internal Server Error`: Server errors

### 3. Dependency Injection Verification

#### Service Dependencies
The refactored system maintains proper dependency injection:

```python
# TaskService Dependencies (updated)
async def get_task_service(
    db_session: DatabaseSessionDep,
    event_broker: EventBrokerDep,
) -> TaskService:
    task_repository = await get_task_repository(db_session)
    agent_repository = await get_agent_repository(db_session)
    task_manager = TemporalTaskManager(task_repository)
    
    return TaskService(
        task_repository=task_repository,
        event_broker=event_broker,
        task_manager=task_manager,
        agent_repository=agent_repository,
    )
```

#### Backward Compatibility
The new TaskService provides compatibility methods:
- `update_task_status()`: For status updates
- `list_agent_tasks()`: For agent task listing
- `get_task_status()`: For status queries
- `get_task_result()`: For result retrieval

## Test Execution

### Running Unit Tests

```bash
cd core
pytest tests/integration/test_api_compatibility.py -v
```

### Running Integration Tests

```bash
# Start the API server first
cd core
python -m uvicorn agentarea_api.main:app --host 0.0.0.0 --port 8000

# In another terminal, run the integration tests
python test_api_compatibility.py
```

### Expected Results

#### Successful Test Run
```
============================================================
API COMPATIBILITY TEST REPORT
============================================================
Total Tests: 6
Passed: 6
Failed: 0
Overall Status: PASS
Breaking Changes: NO
============================================================

All tests passed! No breaking changes detected.
```

#### Test Coverage
- ✅ Health endpoint functionality
- ✅ Agent CRUD operations
- ✅ Task CRUD operations
- ✅ A2A protocol endpoints
- ✅ Dependency injection
- ✅ Error handling

## Compatibility Guarantees

### API Endpoints
All existing endpoints remain functional:
- `GET /api/v1/agents` - List agents
- `GET /api/v1/agents/{id}` - Get agent
- `GET /api/v1/tasks` - List all tasks
- `GET /api/v1/agents/{id}/tasks` - List agent tasks
- `POST /api/v1/agents/{id}/tasks` - Create task
- `GET /api/v1/agents/{id}/tasks/{task_id}` - Get task
- `GET /api/v1/agents/{id}/tasks/{task_id}/status` - Get task status
- `DELETE /api/v1/agents/{id}/tasks/{task_id}` - Cancel task
- `POST /api/v1/agents/{id}/tasks/{task_id}/pause` - Pause task
- `POST /api/v1/agents/{id}/tasks/{task_id}/resume` - Resume task
- `GET /api/v1/agents/{id}/a2a/well-known` - A2A discovery
- `POST /api/v1/agents/{id}/a2a/rpc` - A2A JSON-RPC

### Service Interfaces
All service methods remain available:
- Task creation and management
- Agent validation
- Event publishing
- Status tracking
- Result retrieval

### Data Models
All response models maintain the same structure:
- `TaskResponse`
- `TaskWithAgent`
- `TaskCreate`
- `TaskEvent`
- `AgentCard`

## Migration Notes

### For API Consumers
No changes required. All existing API calls will continue to work as before.

### For Internal Services
Services using the old application layer TaskService should update their imports:

```python
# Old import (deprecated)
from agentarea_tasks.application.task_service import TaskService

# New import (recommended)
from agentarea_tasks.task_service import TaskService
```

The new TaskService provides all the same methods with improved architecture.

## Monitoring and Validation

### Continuous Testing
- API compatibility tests run as part of CI/CD pipeline
- Integration tests validate end-to-end functionality
- Performance tests ensure no regression

### Error Tracking
- All API errors are logged with context
- Breaking changes trigger alerts
- Response time monitoring

### Version Compatibility
- API versioning maintained (`/api/v1/`)
- Backward compatibility guaranteed within major versions
- Deprecation notices for future changes

## Troubleshooting

### Common Issues

#### Test Failures
1. **Server not running**: Ensure API server is started for integration tests
2. **Database connection**: Verify database is accessible
3. **Service dependencies**: Check all required services are available

#### API Errors
1. **404 errors**: Verify resource exists and IDs are correct
2. **500 errors**: Check service configuration and dependencies
3. **Timeout errors**: Verify Temporal workflow service is running

### Debug Commands

```bash
# Check API health
curl http://localhost:8000/health

# List agents
curl http://localhost:8000/api/v1/agents

# Check service logs
docker-compose logs api

# Run specific test
pytest tests/integration/test_api_compatibility.py::TestAPICompatibility::test_list_agents_endpoint -v
```

## Conclusion

The API compatibility verification process ensures that the task service refactoring maintains full backward compatibility. All existing API consumers can continue using the system without any changes, while benefiting from the improved internal architecture.

The comprehensive test suite provides confidence that:
1. No breaking changes were introduced
2. All API contracts are maintained
3. Service dependencies work correctly
4. Error handling remains consistent
5. Performance characteristics are preserved

This verification process will be maintained for future changes to ensure continued API stability.