Created middleware for rest that reads the language from the Accept-Language header

data/docs/rest.md

@@ -15,6 +15,12 @@ Statuses:
 
 [TODO]
 
+## Language
+
+In order to set the application language, you have to pass it by using the Accept-Language header.
+
+If not provided or provided language is not supported, english (en_US) will be used.
+
 ## Endpoints
 
 #### Authenticate

module/Rest/config/middleware-pipeline.config.php

@@ -8,6 +8,7 @@ return [
             'path' => '/rest',
             'middleware' => [
                 Middleware\CheckAuthenticationMiddleware::class,
+                Middleware\LocaleMiddleware::class,
                 Middleware\CrossDomainMiddleware::class,
             ],
             'priority' => 5,

module/Rest/config/services.config.php

@@ -19,6 +19,7 @@ return [
 
             Middleware\CrossDomainMiddleware::class => InvokableFactory::class,
             Middleware\CheckAuthenticationMiddleware::class => AnnotatedFactory::class,
+            Middleware\LocaleMiddleware::class => AnnotatedFactory::class,
         ],
     ],
 

module/Rest/config/translator.config.php

@@ -0,0 +1,14 @@
+<?php
+return [
+
+    'translator' => [
+        'translation_file_patterns' => [
+            [
+                'type' => 'gettext',
+                'base_dir' => __DIR__ . '/../lang',
+                'pattern' => '%s.mo',
+            ],
+        ],
+    ],
+
+];

module/Rest/src/Middleware/LocaleMiddleware.php

@@ -0,0 +1,82 @@
+<?php
+namespace Shlinkio\Shlink\Rest\Middleware;
+
+use Acelaya\ZsmAnnotatedServices\Annotation\Inject;
+use Psr\Http\Message\ResponseInterface as Response;
+use Psr\Http\Message\ServerRequestInterface as Request;
+use Zend\I18n\Translator\Translator;
+use Zend\Stratigility\MiddlewareInterface;
+
+class LocaleMiddleware implements MiddlewareInterface
+{
+    /**
+     * @var Translator
+     */
+    private $translator;
+
+    /**
+     * LocaleMiddleware constructor.
+     * @param Translator $translator
+     *
+     * @Inject({"translator"})
+     */
+    public function __construct(Translator $translator)
+    {
+        $this->translator = $translator;
+    }
+
+    /**
+     * Process an incoming request and/or response.
+     *
+     * Accepts a server-side request and a response instance, and does
+     * something with them.
+     *
+     * If the response is not complete and/or further processing would not
+     * interfere with the work done in the middleware, or if the middleware
+     * wants to delegate to another process, it can use the `$out` callable
+     * if present.
+     *
+     * If the middleware does not return a value, execution of the current
+     * request is considered complete, and the response instance provided will
+     * be considered the response to return.
+     *
+     * Alternately, the middleware may return a response instance.
+     *
+     * Often, middleware will `return $out();`, with the assumption that a
+     * later middleware will return a response.
+     *
+     * @param Request $request
+     * @param Response $response
+     * @param null|callable $out
+     * @return null|Response
+     */
+    public function __invoke(Request $request, Response $response, callable $out = null)
+    {
+        if (! $request->hasHeader('Accept-Language')) {
+            return $out($request, $response);
+        }
+
+        $locale = $request->getHeaderLine('Accept-Language');
+        $this->translator->setLocale($this->normalizeLocale($locale));
+        return $out($request, $response);
+    }
+
+    /**
+     * @param string $locale
+     * @return string
+     */
+    protected function normalizeLocale($locale)
+    {
+        $parts = explode('_', $locale);
+        if (count($parts) > 1) {
+            return $parts[0];
+        }
+
+        $parts = explode('-', $locale);
+        if (count($parts) > 1) {
+            return $parts[0];
+        }
+
+        return $locale;
+    }
+}