<?php

/**
 * pjdietz\WellRESTed\Handler
 *
 * @author PJ Dietz <pj@pjdietz.com>
 * @copyright Copyright 2014 by PJ Dietz
 * @license MIT
 */

namespace pjdietz\WellRESTed;

use pjdietz\WellRESTed\Exceptions\HttpExceptions\HttpException;
use pjdietz\WellRESTed\Interfaces\HandlerInterface;
use pjdietz\WellRESTed\Interfaces\RequestInterface;
use pjdietz\WellRESTed\Interfaces\ResponseInterface;

/**
 * Responds to a request based on the HTTP method.
 *
 * To use Handler, create a subclass and implement the methods for any HTTP
 * verbs you would like to support. (get() for GET, post() for POST, etc).
 * <br /><br />
 * - Access the request via the protected member $this->request<br />
 * - Access a map of arguments via $this->args (e.g., URI path variables)<br />
 * - Modify $this->response to provide the response the instance will return<br />
 */
abstract class Handler implements HandlerInterface
{
    /** @var array  Map of variables to supplement the request, usually path variables. */
    protected $args;
    /** @var RequestInterface  The HTTP request to respond to. */
    protected $request;
    /** @var ResponseInterface  The HTTP response to send based on the request. */
    protected $response;

    /**
     * Return the handled response.
     *
     * @param RequestInterface $request
     * @param array|null $args
     * @return ResponseInterface
     */
    public function getResponse(RequestInterface $request, array $args = null)
    {
        $this->request = $request;
        $this->args = $args;
        $this->response = new Response();
        try {
            $this->buildResponse();
        } catch (HttpException $e) {
            $this->response->setStatusCode($e->getCode());
            $this->response->setBody($e->getMessage());
        }
        return $this->response;
    }

    /**
     * Prepare the Response. Override this method if your subclass needs to
     * repond to any non-standard HTTP methods. Otherwise, override the
     * get, post, put, etc. methods.
     *
     * An uncaught HttpException (or subclass) will be converted to a response
     * using the exception's code as the status code and the exceptios message
     * as the body.
     */
    protected function buildResponse()
    {
        switch ($this->request->getMethod()) {
            case 'GET':
                $this->get();
                break;
            case 'HEAD':
                $this->head();
                break;
            case 'POST':
                $this->post();
                break;
            case 'PUT':
                $this->put();
                break;
            case 'DELETE':
                $this->delete();
                break;
            case 'PATCH':
                $this->patch();
                break;
            case 'OPTIONS':
                $this->options();
                break;
            default:
                $this->respondWithMethodNotAllowed();
        }
    }

    /**
     * Method for handling HTTP GET requests.
     *
     * This method should modify the instance's response member.
     */
    protected function get()
    {
        $this->respondWithMethodNotAllowed();
    }

    /**
     * Method for handling HTTP HEAD requests.
     *
     * This method should modify the instance's response member.
     */
    protected function head()
    {
        // The default function calls the instance's get() method, then sets
        // the resonse's body member to an empty string.
        $this->get();
        $this->response->setBody('', false);
    }

    /**
     * Method for handling HTTP POST requests.
     *
     * This method should modify the instance's response member.
     */
    protected function post()
    {
        $this->respondWithMethodNotAllowed();
    }

    /**
     * Method for handling HTTP PUT requests.
     *
     * This method should modify the instance's response member.
     */
    protected function put()
    {
        $this->respondWithMethodNotAllowed();
    }

    /**
     * Method for handling HTTP DELETE requests.
     *
     * This method should modify the instance's response member.
     */
    protected function delete()
    {
        $this->respondWithMethodNotAllowed();
    }

    /**
     * Method for handling HTTP PATCH requests.
     *
     * This method should modify the instance's response member.
     */
    protected function patch()
    {
        $this->respondWithMethodNotAllowed();
    }

    /**
     * Method for handling HTTP OPTION requests.
     *
     * This method should modify the instance's response member.
     */
    protected function options()
    {
        if ($this->addAllowHeader()) {
            $this->response->setStatusCode(200);
        } else {
            $this->response->setStatusCode(405);
        }
    }

    /**
     * Provide a default response for unsupported methods.
     */
    protected function respondWithMethodNotAllowed()
    {
        $this->response->setStatusCode(405);
        $this->addAllowHeader();
    }

    /**
     * Return an array of HTTP verbs this handler supports.
     *
     * For example, to support GET and POST, return array("GET","POST");
     *
     * @return array
     */
    protected function getAllowedMethods()
    {
    }

    /**
     * Add an Allow: header using the methods returned by getAllowedMethods()
     *
     * @return bool  The header was added.
     */
    protected function addAllowHeader()
    {
        $methods = $this->getAllowedMethods();
        if ($methods) {
            $this->response->setHeader('Allow', join($methods, ', '));
            return true;
        }
        return false;
    }

}