<?php

namespace WellRESTed\Dispatching;

use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;
use Psr\Http\ServerMiddleware\MiddlewareInterface;

class Dispatcher implements DispatcherInterface
{
    /**
     * @param mixed $dispatchable
     * @param ServerRequestInterface $request
     * @param ResponseInterface $response
     * @param callable $next
     * @return ResponseInterface
     * @throws DispatchException Unable to dispatch $middleware
     */
    public function dispatch(
        $dispatchable,
        ServerRequestInterface $request,
        ResponseInterface $response,
        $next
    ) {
        if (is_callable($dispatchable)) {
            $dispatchable = $dispatchable($request, $response, $next);
        } elseif (is_string($dispatchable)) {
            $dispatchable = new $dispatchable();
        } elseif (is_array($dispatchable)) {
            $dispatchable = $this->getDispatchStack($dispatchable);
        }

        if (is_callable($dispatchable)) {
            return $dispatchable($request, $response, $next);
        } elseif ($dispatchable instanceof MiddlewareInterface) {
            $delegate = new DispatcherDelegate($response, $next);
            return $dispatchable->process($request, $delegate);
        } elseif ($dispatchable instanceof ResponseInterface) {
            return $dispatchable;
        } else {
            throw new DispatchException("Unable to dispatch middleware.");
        }
    }

    protected function getDispatchStack($dispatchables)
    {
        $stack = new DispatchStack($this);
        foreach ($dispatchables as $dispatchable) {
            $stack->add($dispatchable);
        }
        return $stack;
    }
}