Improve ease of extention

In our usage we need to extend the ControllerInvoker to have responses
normalised from a generic Payload into a standard Response.

To make this easier it would be helpful if some private methods were
instead protected and the Invoker fetching the default resolver chain
were separated out from the creation of the ControllerInvoker.

Fixes #105

src/Bridge.php

@@ -39,7 +39,13 @@ public static function create(?ContainerInterface $container = null): App
         return $app;
     }
 
-    private static function createControllerInvoker(ContainerInterface $container): ControllerInvoker
+    /**
+     * Create an invoker with the default resolvers.
+     *
+     * @param ContainerInterface $container
+     * @return Invoker
+     */
+    protected static function createInvoker(ContainerInterface $container): Invoker
     {
         $resolvers = [
             // Inject parameters by name first
@@ -50,8 +56,17 @@ private static function createControllerInvoker(ContainerInterface $container):
             new DefaultValueResolver,
         ];
 
-        $invoker = new Invoker(new ResolverChain($resolvers), $container);
+        return new Invoker(new ResolverChain($resolvers), $container);
+    }
 
-        return new ControllerInvoker($invoker);
+    /**
+     * Create a controller invoker with the default resolvers.
+     *
+     * @param ContainerInterface $container
+     * @return ControllerInvoker
+     */
+    protected static function createControllerInvoker(ContainerInterface $container): ControllerInvoker
+    {
+        return new ControllerInvoker(self::createInvoker($container));
     }
 }

src/ControllerInvoker.php

@@ -42,10 +42,28 @@ public function __invoke(
         // Inject the attributes defined on the request
         $parameters += $request->getAttributes();
 
-        return $this->invoker->call($callable, $parameters);
+        return $this->processResponse($this->invoker->call($callable, $parameters));
     }
 
-    private static function injectRouteArguments(ServerRequestInterface $request, array $routeArguments): ServerRequestInterface
+    /**
+     * Allow for child classes to process the response.
+     *
+     * @param ResponseInterface|string The response from the callable.
+     * @return ResponseInterface|string The processed response
+     */
+    protected function processResponse($response)
+    {
+        return $response;
+    }
+
+    /**
+     * Inject route arguments into the request.
+     *
+     * @param ServerRequestInterface $request
+     * @param array                  $routeArguments
+     * @return ServerRequestInterface
+     */
+    protected static function injectRouteArguments(ServerRequestInterface $request, array $routeArguments): ServerRequestInterface
     {
         $requestWithArgs = $request;
         foreach ($routeArguments as $key => $value) {