Implement dependency injection and middleware support in the router

config/routes.php

@@ -1,4 +1,4 @@
 <?php
 use src\Controller\HomeController;
 
-$router->get('/', [new HomeController(), 'index']);
+$router->get('/', [HomeController::class, 'index']);

public/index.php

@@ -1,13 +1,19 @@
 <?php
 require_once __DIR__ . '/../src/Autoloader.php';
 
-use src\Router;
-
 $autoloader = new Autoloader();
 $autoloader->addNamespace('src', __DIR__ . '/../src');
 $autoloader->register();
 
-$router = new Router();
+use src\Container;
+use src\Router;
+use src\Middleware\TestMiddleware;
+
+$container = new Container();
+$router = new Router($container);
+
+$router->addGlobalMiddleware(TestMiddleware::class);
+
 require_once __DIR__ . '/../config/routes.php';
 
 $router->dispatch($_SERVER['REQUEST_METHOD'], $_SERVER['REQUEST_URI']);

src/Container.php

@@ -0,0 +1,50 @@
+<?php
+namespace src;
+
+class Container
+{
+    private array $bindings = [];
+
+    public function bind(string $abstract, callable $factory): void
+    {
+        $this->bindings[$abstract] = $factory;
+    }
+
+    public function make(string $class): object
+    {
+        if (isset($this->bindings[$class])) {
+            return ($this->bindings[$class])($this);
+        }
+
+        return $this->resolve($class);
+    }
+
+    private function resolve(string $class): object
+    {
+        $reflector = new \ReflectionClass($class);
+        $constructor = $reflector->getConstructor();
+
+        if ($constructor === null) {
+            return new $class();
+        }
+
+        $dependencies = array_map(function($param) {
+            $type = $param->getType();
+
+            if ($type === null) {
+                throw new \Exception("Cannot resolve parameter \${$param->getName()} — no type hint.");
+            }
+
+            if ($type->isBuiltin()) {
+                if ($param->isDefaultValueAvailable()) {
+                    return $param->getDefaultValue();
+                }
+                throw new \Exception("Cannot resolve primitive parameter \${$param->getName()} — no default value.");
+            }
+
+            return $this->make($type->getName());
+        }, $constructor->getParameters());
+
+        return $reflector->newInstanceArgs($dependencies);
+    }
+}

src/Middleware/MiddlewareInterface.php

@@ -0,0 +1,7 @@
+<?php
+namespace src\Middleware;
+
+interface MiddlewareInterface
+{
+    public function handle(callable $next): void;
+}

src/Middleware/TestMiddleware.php

@@ -0,0 +1,11 @@
+<?php
+namespace src\Middleware;
+
+class TestMiddleware implements MiddlewareInterface
+{
+    public function handle(callable $next): void
+    {
+        error_log('TestMiddleware: Handling request...');
+        $next();
+    }
+}

src/Router.php

@@ -4,28 +4,68 @@ namespace src;
 class Router
 {
     private array $routes = [];
+    private array $globalMiddleware = [];
+    private Container $container;
 
-    public function get(string $path, callable $handler): void
+    public function __construct(Container $container)
     {
-        $this->routes['GET'][$path] = $handler;
+        $this->container = $container;
     }
 
-    public function post(string $path, callable $handler): void
+    public function get(string $path, array $handler, array $middleware = []): void
     {
-        $this->routes['POST'][$path] = $handler;
+        $this->routes['GET'][$path] = compact('handler', 'middleware');
+    }
+
+    public function post(string $path, array $handler, array $middleware = []): void
+    {
+        $this->routes['POST'][$path] = compact('handler', 'middleware');
+    }
+
+    public function addGlobalMiddleware(string $middleware): void
+    {
+        $this->globalMiddleware[] = $middleware;
     }
 
     public function dispatch(string $method, string $uri): void
     {
-        $path = parse_url($uri, PHP_URL_PATH) ?? '/';
+        $route = $this->routes[$method][$uri] ?? null;
-        $handler = $this->routes[$method][$path] ?? null;
 
-        if ($handler === null) {
+        if ($route === null) {
             http_response_code(404);
-            echo '404 Not Found';
+            require __DIR__ . '/../views/404.php';
             return;
         }
 
-        call_user_func($handler);
+        [$controllerClass, $action] = $route['handler'];
+
+        $final = function() use ($controllerClass, $action) {
+            $controller = $this->container->make($controllerClass);
+            $controller->$action();
+        };
+
+        $middleware = array_merge($this->globalMiddleware, $route['middleware']);
+        $this->run($middleware, $final);
+    }
+
+    private function run(array $middleware, callable $final): void
+    {
+        if (empty($middleware)) {
+            $final();
+            return;
+        }
+
+        $chain = array_reduce(
+            array_reverse($middleware),
+            function(callable $carry, string $middlewareClass) {
+                return function() use ($carry, $middlewareClass) {
+                    $instance = $this->container->make($middlewareClass);
+                    $instance->handle($carry);
+                };
+            },
+            $final
+        );
+
+        $chain();
     }
 }