# Services

This directory contains service modules that implement the business logic of the application. Services act as an intermediary layer between the API handlers and data models, encapsulating complex operations and enforcing business rules.

## Service Responsibilities

Services handle:

1. **Business Logic**: Implementing complex business rules and workflows
2. **Data Validation**: Ensuring data integrity before persistence
3. **Transaction Management**: Handling atomic operations across multiple entities
4. **Error Handling**: Providing consistent error responses for business logic failures
5. **Integration**: Coordinating interactions with external services and APIs

## Service Structure

Each service typically follows this pattern:

```typescript
// Service function signature
export const someServiceFunction = async (
  params: SomeParamsType,
  options?: SomeOptionsType
): Promise<SomeReturnType> => {
  try {
    // 1. Input validation
    const validatedData = someSchema.parse(params);

    // 2. Business logic implementation
    // ...

    // 3. Data persistence
    const result = await saveToDatabase(processedData);

    // 4. Return formatted response
    return result;
  } catch (error) {
    // Error handling and transformation
    if (error instanceof z.ZodError) {
      throw new ValidationError("Invalid input data", error);
    }
    // Other error handling...
    throw error;
  }
};
```

## Core Services

The application includes the following service modules:

- **auth**: User authentication and authorization
- **user**: User profile management
- **practitioner**: Practitioner profile and availability management
- **clinic**: Clinic/facility management
- **procedure**: Medical procedure and service management
- **appointment**: Appointment scheduling and management
- **review**: Practitioner review and rating
- **search**: Search functionality across entities
- **notification**: User notification delivery
- **file**: File upload and management

## Error Handling

Services use a consistent error handling approach:

- Custom error types for different failure scenarios
- Error transformation to provide meaningful context
- Detailed error information for debugging while maintaining security

## Transaction Management

For operations affecting multiple entities, services implement transaction patterns to ensure data consistency:

```typescript
// Example transaction pattern
export const complexOperation = async (data: SomeType): Promise<ResultType> => {
  // Begin transaction context
  try {
    // Multiple database operations...

    // If all succeed, return result
    return result;
  } catch (error) {
    // Handle error and ensure rollback if needed
    throw error;
  }
};
```

## Service Dependencies

Services may depend on other services to complete their operations. Dependencies are typically:

- Explicitly imported at the module level
- Passed as parameters to functions when needed for testing
- Designed to avoid circular dependencies

## Testing

Services are designed to be easily testable:

- Pure functions where possible
- External dependencies injectable for mocking
- Clear input/output contracts
- Isolated business logic
