ResponseFactory.php

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<?php

namespace Elgg\Http;

use Elgg\Ajax\Service as AjaxService;
use Elgg\PluginHooksService;
use ElggEntity;
use InvalidArgumentException;
use InvalidParameterException;
use Symfony\Component\HttpFoundation\RedirectResponse as SymfonyRedirectResponse;
use Symfony\Component\HttpFoundation\Response;
use Symfony\Component\HttpFoundation\ResponseHeaderBag;

class ResponseFactory {

    private $request;

    private $ajax;

    private $hooks;

    private $transport;

    private $response_sent = false;

    private $headers;

    public function __construct(Request $request, PluginHooksService $hooks, AjaxService $ajax, ResponseTransport $transport) {
        $this->request = $request;
        $this->hooks = $hooks;
        $this->ajax = $ajax;
        $this->transport = $transport;
        $this->headers = new ResponseHeaderBag();
    }

    public function setHeader($name, $value, $replace = true) {
        $this->headers->set($name, $value, $replace);
    }

    public function getHeaders($remove_existing = true) {
        // Add headers that have already been set by underlying views
        // e.g. viewtype page shells set content-type headers
        $headers_list = headers_list();
        foreach ($headers_list as $header) {
            if (stripos($header, 'HTTP/1.1') !== false) {
                continue;
            }

            list($name, $value) = explode(':', $header, 2);
            $this->setHeader($name, ltrim($value), false);
            if ($remove_existing) {
                header_remove($name);
            }
        }

        return $this->headers;
    }

    public function prepareResponse($content = '', $status = 200, array $headers = array()) {
        $header_bag = $this->getHeaders();
        $header_bag->add($headers);
        $response = new Response($content, $status, $header_bag->all());
        $response->prepare($this->request);
        return $response;
    }

    public function prepareRedirectResponse($url, $status = 302, array $headers = array()) {
        $header_bag = $this->getHeaders();
        $header_bag->add($headers);
        $response = new SymfonyRedirectResponse($url, $status, $header_bag->all());
        $response->prepare($this->request);
        return $response;
    }

    public function send(Response $response) {

        if ($this->response_sent) {
            if ($this->response_sent !== $response) {
                _elgg_services()->logger->error('Unable to send the following response: ' . PHP_EOL
                        . (string) $response . PHP_EOL
                        . 'because another response has already been sent: ' . PHP_EOL
                        . (string) $this->response_sent);
            }
        } else {
            if (!elgg_trigger_before_event('send', 'http_response', $response)) {
                return false;
            }

            if (!$this->transport->send($response)) {
                return false;
            }

            elgg_trigger_after_event('send', 'http_response', $response);
            $this->response_sent = $response;
        }

        return $this->response_sent;
    }

    public function getSentResponse() {
        return $this->response_sent;
    }

    public function respond(ResponseBuilder $response) {

        $response_type = $this->parseContext();
        $response = $this->hooks->trigger('response', $response_type, $response, $response);
        if (!$response instanceof ResponseBuilder) {
            throw new InvalidParameterException("Handlers for 'response','$response_type' plugin hook must "
            . "return an instanceof " . ResponseBuilder::class);
        }

        if ($response->isNotModified()) {
            return $this->send($this->prepareResponse('', ELGG_HTTP_NOT_MODIFIED));
        }

        $is_xhr = $this->request->isXmlHttpRequest();

        $is_action = false;
        if (0 === strpos($response_type, 'action:')) {
            $is_action = true;
        }

        if ($is_action && $response->getForwardURL() === null) {
            // actions must always set a redirect url
            $response->setForwardURL(REFERRER);
        }

        if ($response->getForwardURL() === REFERRER) {
            $response->setForwardURL($this->request->headers->get('Referer'));
        }

        if ($response->getForwardURL() !== null && !$is_xhr) {
            // non-xhr requests should issue a forward if redirect url is set
            // unless it's an error, in which case we serve an error page
            if ($this->isAction() || (!$response->isClientError() && !$response->isServerError())) {
                $response->setStatusCode(ELGG_HTTP_FOUND);
            }
        }

        if ($is_xhr && $is_action && !$this->ajax->isAjax2Request()) {
            // xhr actions using legacy ajax API should return 200 with wrapped data
            $response->setStatusCode(ELGG_HTTP_OK);
            $response->setContent($this->wrapLegacyAjaxResponse($response->getContent(), $response->getForwardURL()));
        }

        if ($is_xhr && $is_action) {
            // Actions always respond with JSON on xhr calls
            $headers = $response->getHeaders();
            $headers['Content-Type'] = 'application/json; charset=UTF-8';
            $response->setHeaders($headers);
        }

        $content = $this->stringify($response->getContent());
        $status_code = $response->getStatusCode();
        $headers = $response->getHeaders();

        if ($response->isRedirection()) {
            $redirect_url = $response->getForwardURL();
            return $this->redirect($redirect_url, $status_code);
        }

        if ($this->ajax->isReady() && $response->isSuccessful()) {
            return $this->respondFromContent($content, $status_code, $headers);
        }

        if ($response->isClientError() || $response->isServerError() || $response instanceof ErrorResponse) {
            return $this->respondWithError($content, $status_code, $headers);
        }

        return $this->respondFromContent($content, $status_code, $headers);
    }

    public function respondWithError($error, $status_code = ELGG_HTTP_BAD_REQUEST, array $headers = []) {
        if ($this->ajax->isReady()) {
            return $this->send($this->ajax->respondWithError($error, $status_code));
        }

        if ($this->isXhr()) {
            // xhr calls to non-actions (e.g. ajax/view or ajax/form) need to receive proper HTTP status code
            return $this->send($this->prepareResponse($error, $status_code, $headers));
        }

        $forward_url = $this->request->headers->get('Referer');

        if (!$this->isAction()) {
            $params = [
                'current_url' => current_page_url(),
                'forward_url' => $forward_url,
            ];
            // For BC, let plugins serve their own error page
            // @see elgg_error_page_handler
            $forward_reason = (string) $status_code;

            $forward_url = $this->hooks->trigger('forward', $forward_reason, $params, $forward_url);

            if ($this->response_sent) {
                // Response was sent from a forward hook
                return $this->response_sent;
            }

            $params['type'] = $forward_reason;
            $error_page = elgg_view_resource('error', $params);
            return $this->send($this->prepareResponse($error_page, $status_code));
        }

        $forward_url = elgg_normalize_url($forward_url);
        return $this->send($this->prepareRedirectResponse($forward_url));
    }

    public function respondFromContent($content = '', $status_code = ELGG_HTTP_OK, array $headers = []) {

        if ($this->ajax->isReady()) {
            $hook_type = $this->parseContext();
            // $this->ajax->setStatusCode($status_code);
            return $this->send($this->ajax->respondFromOutput($content, $hook_type));
        }

        return $this->send($this->prepareResponse($content, $status_code, $headers));
    }

    public function wrapLegacyAjaxResponse($content = '', $forward_url = REFERRER) {

        $content = $this->stringify($content);

        if ($forward_url === REFERRER) {
            $forward_url = $this->request->headers->get('Referer');
        }

        // always pass the full structure to avoid boilerplate JS code.
        $params = [
            'output' => '',
            'status' => 0,
            'system_messages' => [
                'error' => [],
                'success' => []
            ],
            'current_url' => current_page_url(),
            'forward_url' => elgg_normalize_url($forward_url),
        ];

        $params['output'] = $this->ajax->decodeJson($content);

        // Grab any system messages so we can inject them via ajax too
        $system_messages = _elgg_services()->systemMessages->dumpRegister();

        if (isset($system_messages['success'])) {
            $params['system_messages']['success'] = $system_messages['success'];
        }

        if (isset($system_messages['error'])) {
            $params['system_messages']['error'] = $system_messages['error'];
            $params['status'] = -1;
        }

        $response_type = $this->parseContext();
        list($service, $name) = explode(':', $response_type);
        $context = [
            $service => $name,
        ];
        $params = $this->hooks->trigger('output', 'ajax', $context, $params);

        return $this->stringify($params);
    }

    public function redirect($forward_url = REFERRER, $status_code = ELGG_HTTP_FOUND) {
        $location = $forward_url;
        
        // get a secure referrer url
        $secure_referrer = function () {
            $unsafe_url = $this->request->headers->get('Referer');
            $safe_url = elgg_normalize_site_url($unsafe_url);
            if ($safe_url !== false) {
                return $safe_url;
            }
            
            return '';
        };
        
        // validate we forward to a (browser) supported url
        $secure_forward_url = function($forward_url) {
            $forward_url = elgg_normalize_url($forward_url);
            if (!preg_match('/^(http|https|ftp|sftp|ftps):\/\//', $forward_url)) {
                $forward_url = elgg_get_site_url();
            }
            
            return $forward_url;
        };
        
        if ($forward_url === REFERRER) {
            $forward_url = $secure_referrer();
        }

        $forward_url = $secure_forward_url($forward_url);

        // allow plugins to rewrite redirection URL
        $params = [
            'current_url' => current_page_url(),
            'forward_url' => $forward_url,
            'location' => $location,
        ];

        $forward_reason = (string) $status_code;

        $forward_url = $this->hooks->trigger('forward', $forward_reason, $params, $forward_url);

        if ($this->response_sent) {
            // Response was sent from a forward hook
            // Clearing handlers to void infinite loops
            return $this->response_sent;
        }

        if ($forward_url === REFERRER) {
            $forward_url = $secure_referrer();
        }

        if (!is_string($forward_url)) {
            throw new InvalidParameterException("'forward', '$forward_reason' hook must return a valid redirection URL");
        }

        $forward_url = $secure_forward_url($forward_url);

        switch ($status_code) {
            case 'system':
            case 'csrf':
                $status_code = ELGG_HTTP_OK;
                break;
            case 'admin':
            case 'login':
            case 'member':
            case 'walled_garden':
            default :
                $status_code = (int) $status_code;
                if (!$status_code || $status_code < 100 || $status_code > 599) {
                    $status_code = ELGG_HTTP_SEE_OTHER;
                }
                break;
        }

        if ($this->isXhr()) {
            if ($status_code < 100 || ($status_code >= 300 && $status_code <= 399) || $status_code > 599) {
                // We only want to preserve OK and error codes
                // Redirect responses should be converted to OK responses as this is an XHR request
                $status_code = ELGG_HTTP_OK;
            }
            $output = ob_get_clean();
            if (!$this->isAction() && !$this->ajax->isAjax2Request()) {
                // legacy ajax calls are always OK
                // actions are wrapped by ResponseFactory::respond()
                $status_code = ELGG_HTTP_OK;
                $output = $this->wrapLegacyAjaxResponse($output, $forward_url);
            }

            $response = new OkResponse($output, $status_code, $forward_url);
            $headers = $response->getHeaders();
            $headers['Content-Type'] = 'application/json; charset=UTF-8';
            $response->setHeaders($headers);
            return $this->respond($response);
        }

        if ($this->isAction()) {
            // actions should always redirect on non xhr-calls
            if (!is_int($status_code) || $status_code < 300 || $status_code > 399) {
                $status_code = ELGG_HTTP_SEE_OTHER;
            }
        }

        $response = new OkResponse('', $status_code, $forward_url);
        if ($response->isRedirection()) {
            return $this->send($this->prepareRedirectResponse($forward_url, $status_code));
        }
        return $this->respond($response);
    }

    public function parseContext() {

        $segments = $this->request->getUrlSegments();

        $identifier = array_shift($segments);
        switch ($identifier) {
            case 'ajax' :
                $page = array_shift($segments);
                if ($page === 'view') {
                    $view = implode('/', $segments);
                    return "view:$view";
                } else if ($page === 'form') {
                    $form = implode('/', $segments);
                    return "form:$form";
                }
                array_unshift($segments, $page);
                break;

            case 'action' :
                $action = implode('/', $segments);
                return "action:$action";
        }

        array_unshift($segments, $identifier);
        $path = implode('/', $segments);
        return "path:$path";
    }

    public function isXhr() {
        return $this->request->isXmlHttpRequest();
    }

    public function isAction() {
        if (0 === strpos($this->parseContext(), 'action:')) {
            return true;
        }
        return false;
    }

    public function normalize($content = '') {
        if ($content instanceof ElggEntity) {
            $content = (array) $content->toObject();
        }
        if (is_array($content)) {
            foreach ($content as $key => $value) {
                $content[$key] = $this->normalize($value);
            }
        }
        return $content;
    }

    public function stringify($content = '') {
        $content = $this->normalize($content);
        if (empty($content) || (is_object($content) && is_callable([$content, '__toString']))) {
            return (string) $content;
        }
        if (is_scalar($content)) {
            return $content;
        }
        return json_encode($content, ELGG_JSON_ENCODING);
    }

}