Created middleware which injects default short code length from config when a value was not explicitly provided

module/Rest/config/dependencies.config.php

@@ -38,6 +38,7 @@ return [
             Middleware\CrossDomainMiddleware::class => InvokableFactory::class,
             Middleware\ShortUrl\CreateShortUrlContentNegotiationMiddleware::class => InvokableFactory::class,
             Middleware\ShortUrl\DropDefaultDomainFromRequestMiddleware::class => ConfigAbstractFactory::class,
+            Middleware\ShortUrl\DefaultShortCodesLengthMiddleware::class => ConfigAbstractFactory::class,
         ],
     ],
 
@@ -75,6 +76,9 @@ return [
         Action\Tag\UpdateTagAction::class => [Service\Tag\TagService::class, LoggerInterface::class],
 
         Middleware\ShortUrl\DropDefaultDomainFromRequestMiddleware::class => ['config.url_shortener.domain.hostname'],
+        Middleware\ShortUrl\DefaultShortCodesLengthMiddleware::class => [
+            'config.url_shortener.default_short_codes_length',
+        ],
     ],
 
 ];

module/Rest/config/routes.config.php

@@ -13,7 +13,11 @@ return [
         Action\HealthAction::getRouteDef(),
 
         // Short codes
-        Action\ShortUrl\CreateShortUrlAction::getRouteDef([$contentNegotiationMiddleware, $dropDomainMiddleware]),
+        Action\ShortUrl\CreateShortUrlAction::getRouteDef([
+            $contentNegotiationMiddleware,
+            $dropDomainMiddleware,
+            Middleware\ShortUrl\DefaultShortCodesLengthMiddleware::class,
+        ]),
         Action\ShortUrl\SingleStepCreateShortUrlAction::getRouteDef([$contentNegotiationMiddleware]),
         Action\ShortUrl\EditShortUrlAction::getRouteDef([$dropDomainMiddleware]),
         Action\ShortUrl\DeleteShortUrlAction::getRouteDef([$dropDomainMiddleware]),

module/Rest/src/Middleware/ShortUrl/DefaultShortCodesLengthMiddleware.php

@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shlinkio\Shlink\Rest\Middleware\ShortUrl;
+
+use Psr\Http\Message\ResponseInterface;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\MiddlewareInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Core\Validation\ShortUrlMetaInputFilter;
+
+class DefaultShortCodesLengthMiddleware implements MiddlewareInterface
+{
+    private int $defaultShortCodesLength;
+
+    public function __construct(int $defaultShortCodesLength)
+    {
+        $this->defaultShortCodesLength = $defaultShortCodesLength;
+    }
+
+    public function process(ServerRequestInterface $request, RequestHandlerInterface $handler): ResponseInterface
+    {
+        $body = $request->getParsedBody();
+        if (! isset($body[ShortUrlMetaInputFilter::SHORT_CODE_LENGTH])) {
+            $body[ShortUrlMetaInputFilter::SHORT_CODE_LENGTH] = $this->defaultShortCodesLength;
+        }
+
+        return $handler->handle($request->withParsedBody($body));
+    }
+}

module/Rest/test/Middleware/ShortUrl/DefaultShortCodesLengthMiddlewareTest.php

@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ShlinkioApiTest\Shlink\Rest\Middleware\ShortUrl;
+
+use Laminas\Diactoros\Response;
+use Laminas\Diactoros\ServerRequestFactory;
+use PHPUnit\Framework\Assert;
+use PHPUnit\Framework\TestCase;
+use Prophecy\Argument;
+use Prophecy\Prophecy\ObjectProphecy;
+use Psr\Http\Message\ServerRequestInterface;
+use Psr\Http\Server\RequestHandlerInterface;
+use Shlinkio\Shlink\Core\Validation\ShortUrlMetaInputFilter;
+use Shlinkio\Shlink\Rest\Middleware\ShortUrl\DefaultShortCodesLengthMiddleware;
+
+class DefaultShortCodesLengthMiddlewareTest extends TestCase
+{
+    private DefaultShortCodesLengthMiddleware $middleware;
+    private ObjectProphecy $handler;
+
+    public function setUp(): void
+    {
+        $this->handler = $this->prophesize(RequestHandlerInterface::class);
+        $this->middleware = new DefaultShortCodesLengthMiddleware(8);
+    }
+
+    /**
+     * @test
+     * @dataProvider provideBodies
+     */
+    public function defaultValueIsInjectedInBodyWhenNotProvided(array $body, int $expectedLength): void
+    {
+        $request = ServerRequestFactory::fromGlobals()->withParsedBody($body);
+        $handle = $this->handler->handle(Argument::that(function (ServerRequestInterface $req) use ($expectedLength) {
+            $parsedBody = $req->getParsedBody();
+            Assert::assertArrayHasKey(ShortUrlMetaInputFilter::SHORT_CODE_LENGTH, $parsedBody);
+            Assert::assertEquals($expectedLength, $parsedBody[ShortUrlMetaInputFilter::SHORT_CODE_LENGTH]);
+
+            return $req;
+        }))->willReturn(new Response());
+
+        $this->middleware->process($request, $this->handler->reveal());
+
+        $handle->shouldHaveBeenCalledOnce();
+    }
+
+    public function provideBodies(): iterable
+    {
+        yield 'value provided' => [[ShortUrlMetaInputFilter::SHORT_CODE_LENGTH => 6], 6];
+        yield 'value not provided' => [[], 8];
+    }
+}