Manipulate (e.g. sanitize) incoming request parameter before deserialize-operation

[Moongazer]

Is there a way to manipulate incoming request parameter in a custom operation-handler, before the deserialize-operation is called? For example to sanitize certain input values, similar to what we can do in Extbase's initializeMyAction().

The $request parameter of the handle() method seems to be read-only, so it is not possible to overwrite some of the payload-content (e.g. for a PATCH request which contains a JSON string with the object values to update).

Use-case:
A user should enter its size in centimeter, but very often they write e.g. 1.79 into the input-field (instead of 179). Because the "size" attribute in the model is of type int, currently everything behind the comma/dot is removed, resulting in a value of 1 which is saved into the database.

In an Extbase controller we could solve this like this:

        $arguments['size'] = str_replace('.', '', $arguments['size'] ?? '0');
        $this->request = $this->request->withArguments($arguments);

Is there something similar we can do in T3API?

[maikschneider]

t3api uses PSR-15 middleware to generate the output. You could create your own middleware to modify the query parameter for your endpoint. Try something like this:

<?php

namespace Vendor\YourExtension\Middleware;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\Server\MiddlewareInterface;
use Psr\Http\Server\RequestHandlerInterface;
use SourceBroker\T3api\Service\RouteService;

class ApiManipulation implements MiddlewareInterface
{
    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
    {
        // check for t3api requests
        if (!RouteService::routeHasT3ApiResourceEnhancerQueryParam($request)) {
            return $handler->handle($request);
        }

        // or check if the request is for a specific path with $request->getUri()->getPath()

        $queryParams = $request->getQueryParams();
        if (isset($queryParams['size'])) {
            $queryParams['size'] = str_replace('.', '', $queryParams['size']);
            $request = $request->withQueryParams($queryParams);
        }

        return $handler->handle($request);
    }
}

Make sure to register the middleware between the two middlewares of t3api:

RequestMiddlewares.php:

<?php

return [
    'frontend' => [
        'vendor/your-extension' => [
            'target' => \Vendor\YourExtension\Middleware\ApiManipulation::class,
            'before' => [
                'sourcebroker/t3api/process-api-request',
            ],
            'after' => [
                'sourcebroker/t3api/prepare-api-request',
            ],
        ],
    ],
];

[kszymukowicz]

Maybe we will extend build in events in future but at this moment this the very valid answer.
Tnx @maikschneider!