Created content based error handler which allows managing errors in a different way depending on the Accepted content type from the client

module/Common/config/error-handler.config.php

@@ -0,0 +1,22 @@
+<?php
+use Shlinkio\Shlink\Common\Expressive\ContentBasedErrorHandler;
+use Zend\Expressive\Container\TemplatedErrorHandlerFactory;
+use Zend\Stratigility\FinalHandler;
+
+return [
+
+    'error_handler' => [
+        'plugins' => [
+            'invokables' => [
+                'text/plain' => FinalHandler::class,
+            ],
+            'factories' => [
+                ContentBasedErrorHandler::DEFAULT_CONTENT => TemplatedErrorHandlerFactory::class,
+            ],
+            'aliases' => [
+                'application/xhtml+xml' => ContentBasedErrorHandler::DEFAULT_CONTENT,
+            ],
+        ],
+    ],
+
+];

module/Common/src/Expressive/ContentBasedErrorHandler.php

@@ -0,0 +1,64 @@
+<?php
+namespace Shlinkio\Shlink\Common\Expressive;
+
+use Psr\Http\Message\RequestInterface as Request;
+use Psr\Http\Message\ResponseInterface as Response;
+use Shlinkio\Shlink\Common\Exception\InvalidArgumentException;
+use Zend\ServiceManager\AbstractPluginManager;
+use Zend\ServiceManager\Exception\InvalidServiceException;
+
+class ContentBasedErrorHandler extends AbstractPluginManager implements ErrorHandlerInterface
+{
+    const DEFAULT_CONTENT = 'text/html';
+
+    public function validate($instance)
+    {
+        if (is_callable($instance)) {
+            return;
+        }
+
+        throw new InvalidServiceException(sprintf(
+            'Only callables are valid plugins for "%s". "%s" provided',
+            __CLASS__,
+            is_object($instance) ? get_class($instance) : gettype($instance)
+        ));
+    }
+
+    /**
+     * Final handler for an application.
+     *
+     * @param Request $request
+     * @param Response $response
+     * @param null|mixed $err
+     * @return Response
+     */
+    public function __invoke(Request $request, Response $response, $err = null)
+    {
+        // Try to get an error handler for provided request accepted type
+        $errorHandler = $this->resolveErrorHandlerFromAcceptHeader($request);
+        return $errorHandler($request, $response, $err);
+    }
+
+    /**
+     * Tries to resolve
+     *
+     * @param Request $request
+     * @return callable
+     */
+    protected function resolveErrorHandlerFromAcceptHeader(Request $request)
+    {
+        $accepts = $request->hasHeader('Accept') ? $request->getHeaderLine('Accept') : self::DEFAULT_CONTENT;
+        $accepts = explode(',', $accepts);
+        foreach ($accepts as $accept) {
+            if (! $this->has($accept)) {
+                continue;
+            }
+
+            return $this->get($accept);
+        }
+
+        throw new InvalidArgumentException(sprintf(
+            'It wasn\'t possible to find an error handler for '
+        ));
+    }
+}

module/Common/src/Expressive/ContentBasedErrorHandlerFactory.php

@@ -0,0 +1,30 @@
+<?php
+namespace Shlinkio\Shlink\Common\Expressive;
+
+use Interop\Container\ContainerInterface;
+use Interop\Container\Exception\ContainerException;
+use Zend\ServiceManager\Exception\ServiceNotCreatedException;
+use Zend\ServiceManager\Exception\ServiceNotFoundException;
+use Zend\ServiceManager\Factory\FactoryInterface;
+
+class ContentBasedErrorHandlerFactory implements FactoryInterface
+{
+    /**
+     * Create an object
+     *
+     * @param  ContainerInterface $container
+     * @param  string $requestedName
+     * @param  null|array $options
+     * @return object
+     * @throws ServiceNotFoundException if unable to resolve the service.
+     * @throws ServiceNotCreatedException if an exception is raised when
+     *     creating a service.
+     * @throws ContainerException if any other error occurs
+     */
+    public function __invoke(ContainerInterface $container, $requestedName, array $options = null)
+    {
+        $config = $container->get('config')['error_handler'];
+        $plugins = isset($config['plugins']) ? $config['plugins'] : [];
+        return new ContentBasedErrorHandler($container, $plugins);
+    }
+}

module/Common/src/Expressive/ErrorHandlerInterface.php

@@ -0,0 +1,18 @@
+<?php
+namespace Shlinkio\Shlink\Common\Expressive;
+
+use Psr\Http\Message\RequestInterface as Request;
+use Psr\Http\Message\ResponseInterface as Response;
+
+interface ErrorHandlerInterface
+{
+    /**
+     * Final handler for an application.
+     *
+     * @param Request $request
+     * @param Response $response
+     * @param null|mixed $err
+     * @return Response
+     */
+    public function __invoke(Request $request, Response $response, $err = null);
+}

module/Rest/config/error-handler.config.php

@@ -0,0 +1,18 @@
+<?php
+use Shlinkio\Shlink\Rest\Expressive\JsonErrorHandler;
+
+return [
+
+    'error_handler' => [
+        'plugins' => [
+            'invokables' => [
+                'application/json' => JsonErrorHandler::class,
+            ],
+            'aliases' => [
+                'application/x-json' => 'application/json',
+                'text/json' => 'application/json',
+            ],
+        ],
+    ],
+
+];

module/Rest/lang/es.po

@@ -1,9 +1,9 @@
 msgid ""
 msgstr ""
 "Project-Id-Version: Shlink 1.0\n"
-"POT-Creation-Date: 2016-07-21 16:39+0200\n"
-"PO-Revision-Date: 2016-07-21 16:40+0200\n"
-"Last-Translator: \n"
+"POT-Creation-Date: 2016-07-27 08:53+0200\n"
+"PO-Revision-Date: 2016-07-27 08:53+0200\n"
+"Last-Translator: Alejandro Celaya <alejandro@alejandrocelaya.com>\n"
 "Language-Team: \n"
 "Language: es_ES\n"
 "MIME-Version: 1.0\n"
@@ -52,9 +52,12 @@ msgid ""
 "Missing or invalid auth token provided. Perform a new authentication request "
 "and send provided token on every new request on the \"%s\" header"
 msgstr ""
-"No se ha proporcionado token de autenticación o este es inválido. Realia una "
-"nueva petición de autenticación y envía el token proporcionado en cada nueva "
-"petición en la cabecera \"%s\""
+"No se ha proporcionado token de autenticación o este es inválido. Realiza "
+"una nueva petición de autenticación y envía el token proporcionado en cada "
+"nueva petición en la cabecera \"%s\""
+
+msgid "Requested route does not exist."
+msgstr "La ruta solicitada no existe."
 
 #~ msgid "RestToken not found for token \"%s\""
 #~ msgstr "No se ha encontrado un RestToken para el token \"%s\""

module/Rest/src/Expressive/JsonErrorHandler.php

@@ -0,0 +1,39 @@
+<?php
+namespace Shlinkio\Shlink\Rest\Expressive;
+
+use Psr\Http\Message\RequestInterface as Request;
+use Psr\Http\Message\ResponseInterface as Response;
+use Shlinkio\Shlink\Common\Expressive\ErrorHandlerInterface;
+use Zend\Diactoros\Response\JsonResponse;
+
+class JsonErrorHandler implements ErrorHandlerInterface
+{
+    /**
+     * Final handler for an application.
+     *
+     * @param Request $request
+     * @param Response $response
+     * @param null|mixed $err
+     * @return Response
+     */
+    public function __invoke(Request $request, Response $response, $err = null)
+    {
+        $status = $response->getStatusCode();
+        $responsePhrase = $status < 400 ? 'Internal Server Error' : $response->getReasonPhrase();
+        $status = $status < 400 ? 500 : $status;
+
+        return new JsonResponse([
+            'error' => $this->responsePhraseToCode($responsePhrase),
+            'message' => $responsePhrase,
+        ], $status);
+    }
+
+    /**
+     * @param string $responsePhrase
+     * @return string
+     */
+    protected function responsePhraseToCode($responsePhrase)
+    {
+        return strtoupper(str_replace(' ', '_', $responsePhrase));
+    }
+}