simple_pipe.php

<?php

interface Middelware {
	public function run(Request $request, Response $response, Pipe $next);
}

interface Pipe {
	public function __invoke(Request $request, Response $response);
}

interface MiddelwarePipe {
	public function add(Middelware $middelware);
}

interface RoutePipe {
	public function add($path, Middelware $middelware);
}

interface Session {
	public function setSessionId($sessionId);
	public function set($key, $value);
	public function get($key);
}

interface Auth {
	public function isAddmin($userId);
}

interface HttpClient {
	public function send(Response $response);
}

class SimplePipe implements Pipe {

	private $middelwares = [];

	public function add(Middelware $middelware) {
		$this->middelwares[] = $middelware;
	}

	public function __invoke(Request $request, Response $response) {
		
		if(empty($this->middelwares)) {
			return $response;
		}

		$nextMiddelware = array_shift($this->middelwares);
		return $nextMiddelware->run($request, $response, $this);
	}
}

class RoutePipeMiddelware implements Pipe, RoutePipe, Middelware {
	
	private $middelwares = [];
	private $path;

	public function add($path, Middelware $middelware) {
		$this->middelwares[$path][] = $middelware;
	}

	public function run(Request $request, Response $response, Pipe $next) {
		$this->path = $request->getPath();
		$response = $this->__invoke($request, $response);
		return $next($request, $response);
	}

	public function __invoke(Request $request, Response $response) {
		
		if(empty($this->middelwares[$this->path])) {
			return $response;
		}

		$nextMiddelware = array_shift($this->middelwares[$this->path]);
		return $nextMiddelware->run($request, $response, $this);
	}
}

class SessionMiddelware implements Middelware {
	
	private $session;

	public function __construct(Session $session) {
		$this->session = $session;
	}

	public function run(Request $request, Response $response, Pipe $next) {
		$this->session->setSessionId($request->get('session_id'));
		return $next($request, $response);
	}
}

class AuthMiddelware implements Middelware {

	private $session;
	private $auth;

	public function __construct(Session $session, Auth $auth) {
		$this->session = $session;
		$this->auth = $auth;
	}

	public function run(Request $request, Response $response, Pipe $next) {
		$userId = $this->session->get('user_id');
		
		if(!$auth->isAdmin($userId)) {
			return $response->status('303');
		}

		return $next($request, $response);
	}
}

class AdminMiddelware implements Middelware {
	public function run(Request $request, Response $response) {
		return $response->setBody('Admin panel');
	}
}

class SimpleSession {

	public function setSessionId($sessionId) {}
	public function set($key, $value) {}
	public function get($key) {}
}

class SimpleAuth {
	public function isAdmin($userId) {}
}

class SimpleHttpClient implements HttpClient {
	public function send(Request $response) {}
}

$session = new SimpleSession;
$auth = new SimpleAuth;

$pipe = new SimplePipe;
$pipe->add(new SessionMiddelware($session));

$routePipe = new RoutePipeMiddelware();
$routePipe->add('\admin', new AuthMiddelware($session, $auth));
$routePipe->add('\admin', new AdminMiddelware);

$pipe->add($routePipe);

$request = new Request;
$response = new Response;

$response = $pipe($request, $response);

$httpClient = new HttpClient;

$httpClient->send($response);