action extraction

gistfile1.php

<?php
use Psr\Http\Message\ResponseInterface as Response;
use Psr\Http\Message\ServerRequestInterface as Request;

class Action
{
    // specifications to be resolved
    protected $input;
    protected $domain;
    protected $responder;

    public function __construct($input, $domain, $responder)
    {
        $this->input = $input;
        $this->domain = $domain;
        $this->responder = $responder;
    }

    public function getInput()
    {
        return $this->input;
    }

    public function getDomain()
    {
        return $this->domain;
    }

    public function getResponder()
    {
        return $this->responder;
    }
}

class ActionFactory
{
    public function newInstance($input, $domain, $responder)
    {
        return new Action($input, $domain, $responder);
    }
}

class ActionHandler
{
    protected $resolver;

    public function __construct(callable $resolver = null)
    {
        $this->resolver = $resolver;
    }

    public function handle(Request $request, Response $response, Action $action)
    {
        $responder = $this->resolve($action->getResponder());

        $domainSpec = $action->getDomain();
        if (! $domainSpec) {
            return $responder($request, $response);
        }

        $domain = $this->resolve($domainSpec);
        $params = $this->params($request, $action);
        $payload = call_user_func_array($domain, $params);
        return $responder($request, $response, $payload);
    }

    protected function params(Request $request, Action $action)
    {
        $inputSpec = $action->getInput();
        if (! $inputSpec) {
            return [];
        }

        $input = $this->resolve($inputSpec);
        return (array) $input($request);
    }

    protected function resolve($spec)
    {
        if (! $this->resolver) {
            return $spec;
        }
        
        return call_user_func($this->resolver, $spec);
    }
}

// alternatively, the middleware could compose ActionHandler
class Middleware extends ActionHandler
{
    public function __invoke(Request $request, Response $response, callable $next)
    {
        $action = $request->getAttribute('vendor/package:action');
        $request = $request->withoutAttribute('vendor/package:action');
        $response = $this->handle($request, $response, $action);
        return $next($request, $response);
    }
}