US-C17: Building The Accounts Controller

Let's dive into the creation of the AccountsController for our system. This pivotal component will serve as the backbone for managing account-related operations through our API, ensuring that the frontend can seamlessly interact with the backend. As a developer, my primary goal is to construct a robust and well-defined controller that adheres to the outlined specifications and industry best practices.

Understanding the Requirements

At the heart of this task lies the need to create a controller that exposes various endpoints for account management. The endpoints must include functionalities for creating, listing, retrieving, updating, and deleting accounts, as well as handling account status changes and providing consolidated balance information. Given the high priority (P0) and an estimated time of 2.5 hours, efficient planning and execution are crucial.

Key Objectives

The main objectives can be summarized as follows:

• Creating the Controller: The first step involves creating the AccountsController.cs file within the API/Controllers directory.
• Adding Attributes: Decorating the controller with the [ApiController] and [Route("api/v1/contas")] attributes is essential for defining it as an API controller and specifying the routing convention.
• Implementing Endpoints: Developing the various endpoints, each corresponding to a specific action related to accounts.
• Dependency Injection: Injecting IMediator into the controller's constructor to facilitate communication with the application's business logic.
• Mapping Requests: Accurately mapping incoming requests to their corresponding commands or queries.
• Returning Appropriate Status Codes: Ensuring that the API returns the correct HTTP status codes to indicate the outcome of each request.

Detailed Breakdown of the Implementation

To ensure a comprehensive implementation, let's delve into each aspect of the controller's construction.

1. Creating the AccountsController.cs File

The initial step involves creating the AccountsController.cs file within the API/Controllers directory. This file will house the entire logic for handling account-related operations.

2. Adding Attributes

The [ApiController] attribute is crucial as it enables several features that enhance the development experience, such as automatic HTTP 400 responses for model validation errors. The [Route("api/v1/contas")] attribute defines the base route for all endpoints within this controller.

3. Implementing Endpoints

The core of the controller lies in the implementation of the various endpoints. Each endpoint corresponds to a specific action related to accounts.

• POST /api/v1/contas → CriarConta: This endpoint is responsible for creating a new account. It accepts data from the request body, maps it to a command, and then dispatches the command to the appropriate handler.
• GET /api/v1/contas → ListarContas: This endpoint retrieves a list of accounts based on the provided query parameters, such as tipo, apenasAtivas, and ordenarPor. These parameters allow for filtering and sorting the results.
• GET /api/v1/contas/{id} → ObterConta: This endpoint retrieves a specific account based on its ID. It fetches the account from the data store and returns it in the response.
• PUT /api/v1/contas/{id} → AtualizarConta: This endpoint updates an existing account with the data provided in the request body. It maps the request data to a command and dispatches it to the appropriate handler.
• PATCH /api/v1/contas/{id}/inativar → InativarConta: This endpoint deactivates a specific account. It updates the account's status to inactive.
• PATCH /api/v1/contas/{id}/reativar → ReativarConta: This endpoint reactivates a previously deactivated account. It updates the account's status to active.
• DELETE /api/v1/contas/{id} → ExcluirConta: This endpoint deletes a specific account. It accepts a query parameter confirmar to ensure that the deletion is intentional.
• GET /api/v1/contas/saldo-consolidado → SaldoConsolidado: This endpoint retrieves the consolidated balance of all accounts.

4. Injecting IMediator

Dependency injection is a crucial aspect of modern application development. By injecting IMediator into the controller's constructor, the controller can communicate with the application's business logic without directly depending on it. This promotes loose coupling and improves the testability of the code.

5. Mapping Requests

Mapping incoming requests to their corresponding commands or queries is essential for decoupling the controller from the application's business logic. This involves creating data transfer objects (DTOs) that represent the data required by the commands or queries. The controller then maps the data from the request body or query parameters to these DTOs.

6. Returning Appropriate Status Codes

Returning the correct HTTP status codes is crucial for providing feedback to the client about the outcome of each request. The following status codes should be used:

• 200 OK: Indicates that the request was successful.
• 201 Created: Indicates that a new resource was successfully created.
• 204 No Content: Indicates that the request was successful, but there is no content to return.
• 400 Bad Request: Indicates that the request was invalid due to validation errors or other issues.
• 404 Not Found: Indicates that the requested resource was not found.
• 409 Conflict: Indicates that the request could not be completed due to a conflict with the current state of the resource.

Acceptance Criteria

The successful implementation of the AccountsController must meet the following acceptance criteria:

• The API/Controllers/ContasController.cs file must be created.
• The controller must be decorated with the [ApiController] and [Route("api/v1/contas")] attributes.
• All the specified endpoints must be implemented.
• The controller must inject IMediator into its constructor.
• Incoming requests must be correctly mapped to their corresponding commands or queries.
• The API must return the appropriate HTTP status codes for each request.

Best Practices

Keep Controllers Lean

Controllers should primarily focus on routing requests, handling HTTP concerns, and orchestrating the application's components. Avoid placing business logic directly within the controller.

Implement Validation

Thoroughly validate incoming requests to ensure data integrity and prevent unexpected errors. Use data annotations or a validation framework to define validation rules.

Handle Exceptions

Implement proper exception handling to gracefully handle errors and prevent the application from crashing. Use try-catch blocks to catch exceptions and return appropriate error responses.

Write Unit Tests

Write unit tests to ensure that the controller functions as expected and to prevent regressions. Use a mocking framework to isolate the controller from its dependencies.

Conclusion

The AccountsController is a critical component of our API, serving as the gateway for managing account-related operations. By adhering to the outlined specifications, implementing best practices, and conducting thorough testing, we can ensure that the controller is robust, reliable, and maintainable. This will enable the frontend to seamlessly interact with the backend, providing a smooth and efficient user experience.

For more information on building RESTful APIs, check out Microsoft's guide to ASP.NET Core Web API.