Responder Generator

Responder Generator

Generate ADR-compliant Responder classes for HTTP response building.

Responder Characteristics

• Response Building: Creates complete HTTP Response (status, headers, body)
• No Business Logic: Only format and transform data
• No Domain Access: No repository or service calls
• Error Mapping: Maps domain errors to HTTP status codes
• Content Type: Sets appropriate Content-Type header
• PSR Compliance: Uses PSR-7 and PSR-17 interfaces

Template

<?php

declare(strict_types=1);

namespace Presentation\Api\{Context}\{Action};

use Application\{Context}\UseCase\{Action}\{Action}Result;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class {Action}Responder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond({Action}Result $result): ResponseInterface
    {
        if ($result->isFailure()) {
            return $this->handleFailure($result);
        }

        return $this->success($result);
    }

    private function success({Action}Result $result): ResponseInterface
    {
        {successResponse}
    }

    private function handleFailure({Action}Result $result): ResponseInterface
    {
        return match ($result->failureReason()) {
            {errorMapping}
            default => $this->badRequest($result->errorMessage()),
        };
    }

    private function json(array $data, int $status = 200): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR | JSON_UNESCAPED_UNICODE)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json; charset=utf-8')
            ->withBody($body);
    }

    {helperMethods}
}

Test Template

<?php

declare(strict_types=1);

namespace Tests\Unit\Presentation\Api\{Context}\{Action};

use Application\{Context}\UseCase\{Action}\{Action}Result;
use PHPUnit\Framework\Attributes\CoversClass;
use PHPUnit\Framework\Attributes\Group;
use PHPUnit\Framework\TestCase;
use Presentation\Api\{Context}\{Action}\{Action}Responder;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;
use Psr\Http\Message\StreamInterface;

#[Group('unit')]
#[CoversClass({Action}Responder::class)]
final class {Action}ResponderTest extends TestCase
{
    private ResponseFactoryInterface $responseFactory;
    private StreamFactoryInterface $streamFactory;
    private {Action}Responder $responder;

    protected function setUp(): void
    {
        $this->responseFactory = $this->createMock(ResponseFactoryInterface::class);
        $this->streamFactory = $this->createMock(StreamFactoryInterface::class);
        $this->responder = new {Action}Responder(
            $this->responseFactory,
            $this->streamFactory,
        );

        $this->setupMocks();
    }

    public function testSuccessReturns{ExpectedStatus}(): void
    {
        $result = {Action}Result::success({successData});

        $response = $this->responder->respond($result);

        self::assertSame({expectedStatusCode}, $response->getStatusCode());
    }

    {failureTests}

    private function setupMocks(): void
    {
        $stream = $this->createMock(StreamInterface::class);
        $this->streamFactory->method('createStream')->willReturn($stream);

        $response = $this->createMock(ResponseInterface::class);
        $response->method('withHeader')->willReturnSelf();
        $response->method('withBody')->willReturnSelf();
        $response->method('getStatusCode')->willReturnCallback(
            fn () => $this->responseFactory->lastStatus ?? 200
        );

        $this->responseFactory->method('createResponse')->willReturnCallback(
            function (int $status) use ($response) {
                $this->responseFactory->lastStatus = $status;
                $mock = clone $response;
                $mock->method('getStatusCode')->willReturn($status);
                return $mock;
            }
        );
    }
}

Responder Patterns

Create Responder (201)

<?php

declare(strict_types=1);

namespace Presentation\Api\User\Create;

use Application\User\UseCase\CreateUser\CreateUserResult;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class CreateUserResponder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond(CreateUserResult $result): ResponseInterface
    {
        if ($result->isFailure()) {
            return match ($result->failureReason()) {
                'email_exists' => $this->conflict('User with this email already exists'),
                'invalid_email' => $this->badRequest('Invalid email format'),
                default => $this->badRequest($result->errorMessage()),
            };
        }

        return $this->created([
            'id' => $result->userId(),
            'email' => $result->email(),
        ]);
    }

    private function created(array $data): ResponseInterface
    {
        return $this->json($data, 201);
    }

    private function conflict(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 409);
    }

    private function badRequest(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 400);
    }

    private function json(array $data, int $status): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json')
            ->withBody($body);
    }
}

Get Responder (200/​404)

<?php

declare(strict_types=1);

namespace Presentation\Api\User\GetById;

use Application\User\UseCase\GetUserById\GetUserByIdResult;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class GetUserByIdResponder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond(GetUserByIdResult $result): ResponseInterface
    {
        if ($result->isNotFound()) {
            return $this->notFound('User not found');
        }

        $user = $result->user();

        return $this->json([
            'id' => $user->id()->toString(),
            'email' => $user->email()->value(),
            'name' => $user->name(),
            'created_at' => $user->createdAt()->format('c'),
        ]);
    }

    private function notFound(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 404);
    }

    private function json(array $data, int $status = 200): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json')
            ->withBody($body);
    }
}

List Responder with Pagination

<?php

declare(strict_types=1);

namespace Presentation\Api\User\ListAll;

use Application\User\UseCase\ListUsers\ListUsersResult;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class ListUsersResponder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond(ListUsersResult $result): ResponseInterface
    {
        $users = array_map(
            fn ($user) => [
                'id' => $user->id()->toString(),
                'email' => $user->email()->value(),
                'name' => $user->name(),
            ],
            $result->users()
        );

        return $this->json([
            'data' => $users,
            'meta' => [
                'total' => $result->total(),
                'page' => $result->page(),
                'per_page' => $result->perPage(),
                'total_pages' => $result->totalPages(),
            ],
        ]);
    }

    private function json(array $data, int $status = 200): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json')
            ->withBody($body);
    }
}

Delete Responder (204)

<?php

declare(strict_types=1);

namespace Presentation\Api\User\Delete;

use Application\User\UseCase\DeleteUser\DeleteUserResult;
use Psr\Http\Message\ResponseFactoryInterface;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\StreamFactoryInterface;

final readonly class DeleteUserResponder
{
    public function __construct(
        private ResponseFactoryInterface $responseFactory,
        private StreamFactoryInterface $streamFactory,
    ) {
    }

    public function respond(DeleteUserResult $result): ResponseInterface
    {
        if ($result->isNotFound()) {
            return $this->notFound('User not found');
        }

        if ($result->isFailure()) {
            return $this->badRequest($result->errorMessage());
        }

        return $this->noContent();
    }

    private function noContent(): ResponseInterface
    {
        return $this->responseFactory->createResponse(204);
    }

    private function notFound(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 404);
    }

    private function badRequest(string $message): ResponseInterface
    {
        return $this->json(['error' => $message], 400);
    }

    private function json(array $data, int $status): ResponseInterface
    {
        $body = $this->streamFactory->createStream(
            json_encode($data, JSON_THROW_ON_ERROR)
        );

        return $this->responseFactory->createResponse($status)
            ->withHeader('Content-Type', 'application/​json')
            ->withBody($body);
    }
}

HTTP Status Mapping

File Placement

Generation Instructions

When asked to create a Responder:

1. Identify operation type (create, read, update, delete)
2. Determine success status (201, 200, 204)
3. List possible failures and their HTTP codes
4. Define response structure (what data to return)
5. Generate Responder class with proper namespace
6. Generate test for each status code path

Naming Conventions

References

For detailed patterns and examples:

• references/​templates.md — Additional Responder templates
• references/​examples.md — Real-world Responder examples