elgglib.php

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<?php

use Elgg\Filesystem\Directory;
use Elgg\Http\ResponseBuilder;

function elgg() {
    return Elgg\Application::$_instance;
}

function elgg_register_library($name, $location) {
    $config = _elgg_services()->config;

    $libraries = $config->get('libraries');
    if ($libraries === null) {
        $libraries = array();
    }
    $libraries[$name] = $location;
    $config->set('libraries', $libraries);
}

function elgg_load_library($name) {
    static $loaded_libraries = array();

    if (in_array($name, $loaded_libraries)) {
        return;
    }

    $libraries = _elgg_services()->config->get('libraries');

    if (!isset($libraries[$name])) {
        $error = "$name is not a registered library";
        throw new \InvalidParameterException($error);
    }

    if (!include_once($libraries[$name])) {
        $error = "Could not load the $name library from {$libraries[$name]}";
        throw new \InvalidParameterException($error);
    }

    $loaded_libraries[] = $name;
}

function forward($location = "", $reason = 'system') {
    if (headers_sent($file, $line)) {
        throw new \SecurityException("Redirect could not be issued due to headers already being sent. Halting execution for security. "
            . "Output started in file $file at line $line. Search http://learn.elgg.org/ for more information.");
    }

    _elgg_services()->responseFactory->redirect($location, $reason);
    exit;
}

function elgg_set_http_header($header, $replace = true) {
    if (headers_sent($file, $line)) {
        _elgg_services()->logger->error("Cannot modify header information - headers already sent by
            (output started at $file:$line)");
    } else {
        header($header, $replace);
    }

    if (!preg_match('~^HTTP/\\d\\.\\d~', $header)) {
        list($name, $value) = explode(':', $header, 2);
        _elgg_services()->responseFactory->setHeader($name, ltrim($value), $replace);
    }
}

function elgg_register_js($name, $url, $location = 'head', $priority = null) {
    return elgg_register_external_file('js', $name, $url, $location, $priority);
}

function elgg_define_js($name, $config) {
    $src = elgg_extract('src', $config);

    if ($src) {
        $url = elgg_normalize_url($src);
        _elgg_services()->amdConfig->addPath($name, $url);
    }

    // shimmed module
    if (isset($config['deps']) || isset($config['exports'])) {
        _elgg_services()->amdConfig->addShim($name, $config);
    }
}

function elgg_unregister_js($name) {
    return elgg_unregister_external_file('js', $name);
}

function elgg_load_js($name) {
    elgg_load_external_file('js', $name);
}


function elgg_require_js($name) {
    _elgg_services()->amdConfig->addDependency($name);
}

function elgg_unrequire_js($name) {
    _elgg_services()->amdConfig->removeDependency($name);
}

function elgg_get_loaded_js($location = 'head') {
    return elgg_get_loaded_external_files('js', $location);
}

function elgg_register_css($name, $url, $priority = null) {
    return elgg_register_external_file('css', $name, $url, 'head', $priority);
}

function elgg_unregister_css($name) {
    return elgg_unregister_external_file('css', $name);
}

function elgg_load_css($name) {
    elgg_load_external_file('css', $name);
}

function elgg_get_loaded_css() {
    return elgg_get_loaded_external_files('css', 'head');
}

function elgg_register_external_file($type, $name, $url, $location, $priority = 500) {
    return _elgg_services()->externalFiles->register($type, $name, $url, $location, $priority);
}

function elgg_unregister_external_file($type, $name) {
    return _elgg_services()->externalFiles->unregister($type, $name);
}

function elgg_load_external_file($type, $name) {
    return _elgg_services()->externalFiles->load($type, $name);
}

function elgg_get_loaded_external_files($type, $location) {
    return _elgg_services()->externalFiles->getLoadedFiles($type, $location);
}

function elgg_get_file_list($directory, $exceptions = array(), $list = array(),
$extensions = null) {

    $directory = sanitise_filepath($directory);
    if ($handle = opendir($directory)) {
        while (($file = readdir($handle)) !== false) {
            if (!is_file($directory . $file) || in_array($file, $exceptions)) {
                continue;
            }

            if (is_array($extensions)) {
                if (in_array(strrchr($file, '.'), $extensions)) {
                    $list[] = $directory . $file;
                }
            } else {
                $list[] = $directory . $file;
            }
        }
        closedir($handle);
    }

    return $list;
}

function sanitise_filepath($path, $append_slash = true) {
    // Convert to correct UNIX paths
    $path = str_replace('\\', '/', $path);
    $path = str_replace('../', '/', $path);
    // replace // with / except when preceeded by :
    $path = preg_replace("/([^:])\/\//", "$1/", $path);

    // Sort trailing slash
    $path = trim($path);
    // rtrim defaults plus /
    $path = rtrim($path, " \n\t\0\x0B/");

    if ($append_slash) {
        $path = $path . '/';
    }

    return $path;
}

function count_messages($register = "") {
    return _elgg_services()->systemMessages->count($register);
}

function system_message($message) {
    _elgg_services()->systemMessages->addSuccessMessage($message);
    return true;
}

function register_error($error) {
    _elgg_services()->systemMessages->addErrorMessage($error);
    return true;
}

function elgg_get_system_messages() {
    return _elgg_services()->systemMessages->loadRegisters();
}

function elgg_set_system_messages(\Elgg\SystemMessages\RegisterSet $set) {
    _elgg_services()->systemMessages->saveRegisters($set);
}

function elgg_register_event_handler($event, $object_type, $callback, $priority = 500) {
    return _elgg_services()->events->registerHandler($event, $object_type, $callback, $priority);
}

function elgg_unregister_event_handler($event, $object_type, $callback) {
    return _elgg_services()->events->unregisterHandler($event, $object_type, $callback);
}

function elgg_clear_event_handlers($event, $object_type) {
    _elgg_services()->events->clearHandlers($event, $object_type);
}

function elgg_trigger_event($event, $object_type, $object = null) {
    return _elgg_services()->events->trigger($event, $object_type, $object);
}

function elgg_trigger_before_event($event, $object_type, $object = null) {
    return _elgg_services()->events->triggerBefore($event, $object_type, $object);
}

function elgg_trigger_after_event($event, $object_type, $object = null) {
    return _elgg_services()->events->triggerAfter($event, $object_type, $object);
}

function elgg_trigger_deprecated_event($event, $object_type, $object = null, $message, $version) {
    return _elgg_services()->events->triggerDeprecated($event, $object_type, $object, $message, $version);
}

function elgg_register_plugin_hook_handler($hook, $type, $callback, $priority = 500) {
    return _elgg_services()->hooks->registerHandler($hook, $type, $callback, $priority);
}

function elgg_unregister_plugin_hook_handler($hook, $entity_type, $callback) {
    _elgg_services()->hooks->unregisterHandler($hook, $entity_type, $callback);
}

function elgg_clear_plugin_hook_handlers($hook, $type) {
    _elgg_services()->hooks->clearHandlers($hook, $type);
}

function elgg_trigger_plugin_hook($hook, $type, $params = null, $returnvalue = null) {
    return _elgg_services()->hooks->trigger($hook, $type, $params, $returnvalue);
}

function elgg_get_ordered_hook_handlers($hook, $type) {
    return _elgg_services()->hooks->getOrderedHandlers($hook, $type);
}

function elgg_get_ordered_event_handlers($event, $type) {
    return _elgg_services()->events->getOrderedHandlers($event, $type);
}

function _elgg_php_exception_handler($exception) {
    $timestamp = time();
    error_log("Exception at time $timestamp: $exception");

    // Wipe any existing output buffer
    ob_end_clean();

    // make sure the error isn't cached
    header("Cache-Control: no-cache, must-revalidate", true);
    header('Expires: Fri, 05 Feb 1982 00:00:00 -0500', true);

    // we don't want the 'pagesetup', 'system' event to fire
    global $CONFIG;
    $GLOBALS['_ELGG']->pagesetupdone = true;

    try {
        // allow custom scripts to trigger on exception
        // $CONFIG->exception_include can be set locally in settings.php
        // value should be a system path to a file to include
        if (!empty($CONFIG->exception_include) && is_file($CONFIG->exception_include)) {
            ob_start();

            // don't isolate, these scripts may use the local $exception var.
            include $CONFIG->exception_include;

            $exception_output = ob_get_clean();
            
            // if content is returned from the custom handler we will output
            // that instead of our default failsafe view
            if (!empty($exception_output)) {
                echo $exception_output;
                exit;
            }
        }

        if (elgg_is_xhr()) {
            elgg_set_viewtype('json');
            $response = new \Symfony\Component\HttpFoundation\JsonResponse(null, 500);
        } else {
            elgg_set_viewtype('failsafe');
            $response = new \Symfony\Component\HttpFoundation\Response('', 500);
        }

        if (elgg_is_admin_logged_in()) {
            $body = elgg_view("messages/exceptions/admin_exception", array(
                'object' => $exception,
                'ts' => $timestamp
            ));
        } else {
            $body = elgg_view("messages/exceptions/exception", array(
                'object' => $exception,
                'ts' => $timestamp
            ));
        }

        $response->setContent(elgg_view_page(elgg_echo('exception:title'), $body));
        $response->send();
    } catch (Exception $e) {
        $timestamp = time();
        $message = $e->getMessage();
        http_response_code(500);
        echo "Fatal error in exception handler. Check log for Exception at time $timestamp";
        error_log("Exception at time $timestamp : fatal error in exception handler : $message");
    }
}

function _elgg_php_error_handler($errno, $errmsg, $filename, $linenum, $vars) {

    // Elgg 2.0 no longer uses ext/mysql, so these warnings are just a nuisance for 1.x site
    // owners and plugin devs.
    if (0 === strpos($errmsg, "mysql_connect(): The mysql extension is deprecated")) {
        // only suppress core's usage
        if (preg_match('~/classes/Elgg/Database\.php$~', strtr($filename, '\\', '/'))) {
            return true;
        }
    }

    $error = date("Y-m-d H:i:s (T)") . ": \"$errmsg\" in file $filename (line $linenum)";

    switch ($errno) {
        case E_USER_ERROR:
            if (!elgg_log("PHP: $error", 'ERROR')) {
                error_log("PHP ERROR: $error");
            }
            register_error("ERROR: $error");

            // Since this is a fatal error, we want to stop any further execution but do so gracefully.
            throw new \Exception($error);
            break;

        case E_WARNING :
        case E_USER_WARNING :
        case E_RECOVERABLE_ERROR: // (e.g. type hint violation)
            
            // check if the error wasn't suppressed by the error control operator (@)
            if (error_reporting() && !elgg_log("PHP: $error", 'WARNING')) {
                error_log("PHP WARNING: $error");
            }
            break;

        default:
            global $CONFIG;
            if (isset($CONFIG->debug) && $CONFIG->debug === 'NOTICE') {
                if (!elgg_log("PHP (errno $errno): $error", 'NOTICE')) {
                    error_log("PHP NOTICE: $error");
                }
            }
    }

    return true;
}


function elgg_log($message, $level = 'NOTICE') {
    static $levels = array(
        'INFO' => 200,
        'NOTICE' => 250,
        'WARNING' => 300,
        'DEBUG' => 300,
        'ERROR' => 400,
    );

    if ($level == 'DEBUG') {
        elgg_deprecated_notice("The 'DEBUG' level for logging has been deprecated.", 1.9);
    }

    $level = $levels[$level];
    return _elgg_services()->logger->log($message, $level);
}

function elgg_dump($value, $to_screen = true) {
    _elgg_services()->logger->dump($value, $to_screen);
}

function elgg_get_version($human_readable = false) {
    static $version, $release;
    
    if (!isset($version) || !isset($release)) {
        $path = \Elgg\Application::elggDir()->getPath('version.php');
        if (!is_file($path)) {
            return false;
        }
        include $path;
    }
    
    return $human_readable ? $release : $version;
}

function elgg_deprecated_notice($msg, $dep_version, $backtrace_level = 1) {
    $backtrace_level += 1;
    return _elgg_services()->deprecation->sendNotice($msg, $dep_version, $backtrace_level);
}

function elgg_http_build_url(array $parts, $html_encode = true) {
    // build only what's given to us.
    $scheme = isset($parts['scheme']) ? "{$parts['scheme']}://" : '';
    $host = isset($parts['host']) ? "{$parts['host']}" : '';
    $port = isset($parts['port']) ? ":{$parts['port']}" : '';
    $path = isset($parts['path']) ? "{$parts['path']}" : '';
    $query = isset($parts['query']) ? "?{$parts['query']}" : '';
    $fragment = isset($parts['fragment']) ? "#{$parts['fragment']}" : '';

    $string = $scheme . $host . $port . $path . $query . $fragment;

    if ($html_encode) {
        return elgg_format_url($string);
    } else {
        return $string;
    }
}

function elgg_add_action_tokens_to_url($url, $html_encode = false) {
    $url = elgg_normalize_url($url);
    $components = parse_url($url);

    if (isset($components['query'])) {
        $query = elgg_parse_str($components['query']);
    } else {
        $query = array();
    }

    if (isset($query['__elgg_ts']) && isset($query['__elgg_token'])) {
        return $url;
    }

    // append action tokens to the existing query
    $query['__elgg_ts'] = time();
    $query['__elgg_token'] = generate_action_token($query['__elgg_ts']);
    $components['query'] = http_build_query($query);

    // rebuild the full url
    return elgg_http_build_url($components, $html_encode);
}

function elgg_http_remove_url_query_element($url, $element) {
    return elgg_http_add_url_query_elements($url, array($element => null));
}

function elgg_http_add_url_query_elements($url, array $elements) {
    $url_array = parse_url($url);

    if (isset($url_array['query'])) {
        $query = elgg_parse_str($url_array['query']);
    } else {
        $query = array();
    }

    foreach ($elements as $k => $v) {
        if ($v === null) {
            unset($query[$k]);
        } else {
            $query[$k] = $v;
        }
    }

    // why check path? A: if no path, this may be a relative URL like "?foo=1". In this case,
    // the output "" would be interpreted the current URL, so in this case we *must* set
    // a query to make sure elements are removed.
    if ($query || empty($url_array['path'])) {
        $url_array['query'] = http_build_query($query);
    } else {
        unset($url_array['query']);
    }
    $string = elgg_http_build_url($url_array, false);

    return $string;
}

function elgg_http_url_is_identical($url1, $url2, $ignore_params = array('offset', 'limit')) {
    $url1 = elgg_normalize_url($url1);
    $url2 = elgg_normalize_url($url2);

    // @todo - should probably do something with relative URLs

    if ($url1 == $url2) {
        return true;
    }

    $url1_info = parse_url($url1);
    $url2_info = parse_url($url2);

    if (isset($url1_info['path'])) {
        $url1_info['path'] = trim($url1_info['path'], '/');
    }
    if (isset($url2_info['path'])) {
        $url2_info['path'] = trim($url2_info['path'], '/');
    }

    // compare basic bits
    $parts = array('scheme', 'host', 'path');

    foreach ($parts as $part) {
        if ((isset($url1_info[$part]) && isset($url2_info[$part]))
        && $url1_info[$part] != $url2_info[$part]) {
            return false;
        } elseif (isset($url1_info[$part]) && !isset($url2_info[$part])) {
            return false;
        } elseif (!isset($url1_info[$part]) && isset($url2_info[$part])) {
            return false;
        }
    }

    // quick compare of get params
    if (isset($url1_info['query']) && isset($url2_info['query'])
    && $url1_info['query'] == $url2_info['query']) {
        return true;
    }

    // compare get params that might be out of order
    $url1_params = array();
    $url2_params = array();

    if (isset($url1_info['query'])) {
        if ($url1_info['query'] = html_entity_decode($url1_info['query'])) {
            $url1_params = elgg_parse_str($url1_info['query']);
        }
    }

    if (isset($url2_info['query'])) {
        if ($url2_info['query'] = html_entity_decode($url2_info['query'])) {
            $url2_params = elgg_parse_str($url2_info['query']);
        }
    }

    // drop ignored params
    foreach ($ignore_params as $param) {
        if (isset($url1_params[$param])) {
            unset($url1_params[$param]);
        }
        if (isset($url2_params[$param])) {
            unset($url2_params[$param]);
        }
    }

    // array_diff_assoc only returns the items in arr1 that aren't in arrN
    // but not the items that ARE in arrN but NOT in arr1
    // if arr1 is an empty array, this function will return 0 no matter what.
    // since we only care if they're different and not how different,
    // add the results together to get a non-zero (ie, different) result
    $diff_count = count(array_diff_assoc($url1_params, $url2_params));
    $diff_count += count(array_diff_assoc($url2_params, $url1_params));
    if ($diff_count > 0) {
        return false;
    }

    return true;
}

function elgg_http_get_signed_url($url, $expires = false) {
    return _elgg_services()->urlSigner->sign($url, $expires);
}

function elgg_http_validate_signed_url($url) {
    return _elgg_services()->urlSigner->isValid($url);
}

function elgg_signed_request_gatekeeper() {
    if (!elgg_http_validate_signed_url(current_page_url())) {
        register_error(elgg_echo('invalid_request_signature'));
        forward('', '403');
    }
}

function elgg_extract($key, $array, $default = null, $strict = true) {
    if (!is_array($array)) {
        return $default;
    }

    if ($strict) {
        return (isset($array[$key])) ? $array[$key] : $default;
    } else {
        return (isset($array[$key]) && !empty($array[$key])) ? $array[$key] : $default;
    }
}

function elgg_extract_class(array $array, $existing = []) {
    $existing = empty($existing) ? [] : (array) $existing;

    $merge = (array) elgg_extract('class', $array, []);

    array_splice($existing, count($existing), 0, $merge);

    return array_values(array_unique($existing));
}

function elgg_sort_3d_array_by_value(&$array, $element, $sort_order = SORT_ASC,
$sort_type = SORT_LOCALE_STRING) {

    $sort = array();

    foreach ($array as $v) {
        if (isset($v[$element])) {
            $sort[] = strtolower($v[$element]);
        } else {
            $sort[] = null;
        }
    };

    return array_multisort($sort, $sort_order, $sort_type, $array);
}

function ini_get_bool($ini_get_arg) {
    $temp = strtolower(ini_get($ini_get_arg));

    if ($temp == '1' || $temp == 'on' || $temp == 'true') {
        return true;
    }
    return false;
}

function elgg_get_ini_setting_in_bytes($setting) {
    // retrieve INI setting
    $val = ini_get($setting);

    // convert INI setting when shorthand notation is used
    $last = strtolower($val[strlen($val) - 1]);
    if (in_array($last, ['g', 'm', 'k'])) {
        $val = substr($val, 0, -1);
    }
    $val = (int) $val;
    switch($last) {
        case 'g':
            $val *= 1024;
            // fallthrough intentional
        case 'm':
            $val *= 1024;
            // fallthrough intentional
        case 'k':
            $val *= 1024;
    }

    // return byte value
    return $val;
}

function is_not_null($string) {
    if (($string === '') || ($string === false) || ($string === null)) {
        return false;
    }

    return true;
}

function _elgg_normalize_plural_options_array($options, $singulars) {
    foreach ($singulars as $singular) {
        $plural = $singular . 's';

        if (array_key_exists($singular, $options)) {
            if ($options[$singular] === ELGG_ENTITIES_ANY_VALUE) {
                $options[$plural] = $options[$singular];
            } else {
                // Test for array refs #2641
                if (!is_array($options[$singular])) {
                    $options[$plural] = array($options[$singular]);
                } else {
                    $options[$plural] = $options[$singular];
                }
            }
        }

        unset($options[$singular]);
    }

    return $options;
}

function _elgg_shutdown_hook() {
    try {
        _elgg_services()->logger->setDisplay(false);
        elgg_trigger_event('shutdown', 'system');

        $time = (float)(microtime(true) - $GLOBALS['START_MICROTIME']);
        $uri = _elgg_services()->request->server->get('REQUEST_URI', 'CLI');
        // demoted to NOTICE from DEBUG so javascript is not corrupted
        elgg_log("Page {$uri} generated in $time seconds", 'INFO');
    } catch (Exception $e) {
        $message = 'Error: ' . get_class($e) . ' thrown within the shutdown handler. ';
        $message .= "Message: '{$e->getMessage()}' in file {$e->getFile()} (line {$e->getLine()})";
        error_log($message);
        error_log("Exception trace stack: {$e->getTraceAsString()}");
    }

    // Prevent an APC session bug: https://bugs.php.net/bug.php?id=60657
    session_write_close();
}

function _elgg_js_page_handler($page) {
    return _elgg_cacheable_view_page_handler($page, 'js');
}

function _elgg_ajax_page_handler($segments) {
    elgg_ajax_gatekeeper();

    if (count($segments) < 2) {
        return false;
    }

    if ($segments[0] === 'view' || $segments[0] === 'form') {
        if ($segments[0] === 'view') {
            // ignore 'view/'
            $view = implode('/', array_slice($segments, 1));
        } else {
            // form views start with "forms", not "form"
            $view = 'forms/' . implode('/', array_slice($segments, 1));
        }

        $ajax_api = _elgg_services()->ajax;
        $allowed_views = $ajax_api->getViews();
        
        // cacheable views are always allowed
        if (!in_array($view, $allowed_views) && !_elgg_services()->views->isCacheableView($view)) {
            return elgg_error_response("Ajax view '$view' was not registered", REFERRER, ELGG_HTTP_FORBIDDEN);
        }

        // pull out GET parameters through filter
        $vars = array();
        foreach (_elgg_services()->request->query->keys() as $name) {
            $vars[$name] = get_input($name);
        }

        if (isset($vars['guid'])) {
            $vars['entity'] = get_entity($vars['guid']);
        }

        $content_type = '';
        if ($segments[0] === 'view') {
            $output = elgg_view($view, $vars);

            // Try to guess the mime-type
            switch ($segments[1]) {
                case "js":
                    $content_type = 'text/javascript;charset=utf-8';
                    break;
                case "css":
                    $content_type = 'text/css;charset=utf-8';
                    break;
                default :
                    if (_elgg_services()->views->isCacheableView($view)) {
                        $file = _elgg_services()->views->findViewFile($view, elgg_get_viewtype());
                        $content_type = (new \Elgg\Filesystem\MimeTypeDetector())->getType($file, 'text/html');
                    }
                    break;
            }
        } else {
            $action = implode('/', array_slice($segments, 1));
            $output = elgg_view_form($action, array(), $vars);
        }

        if ($content_type) {
            elgg_set_http_header("Content-Type: $content_type");
        }
        
        return elgg_ok_response($output);
    }

    return false;
}

function _elgg_css_page_handler($page) {
    if (!isset($page[0])) {
        // default css
        $page[0] = 'elgg';
    }
    
    return _elgg_cacheable_view_page_handler($page, 'css');
}

function _elgg_favicon_page_handler($segments) {
    header("HTTP/1.1 404 Not Found", true, 404);

    header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', strtotime("+1 week")), true);
    header("Pragma: public", true);
    header("Cache-Control: public", true);

    // TODO in next 1.x send our default icon
    //header('Content-Type: image/x-icon');
    //echo elgg_view('favicon.ico');

    return true;
}

function _elgg_cacheable_view_page_handler($page, $type) {

    switch ($type) {
        case 'js':
            $content_type = 'text/javascript';
            break;

        case 'css':
            $content_type = 'text/css';
            break;

        default:
            return false;
            break;
    }

    if ($page) {
        // the view file names can have multiple dots
        // eg: views/default/js/calendars/jquery.fullcalendar.min.php
        // translates to the url /js/<ts>/calendars/jquery.fullcalendar.min.js
        // and the view js/calendars/jquery.fullcalendar.min
        // we ignore the last two dots for the ts and the ext.
        // Additionally, the timestamp is optional.
        $page = implode('/', $page);
        $regex = '|(.+?)\.\w+$|';
        if (!preg_match($regex, $page, $matches)) {
            return false;
        }
        $view = "$type/{$matches[1]}";
        if (!elgg_view_exists($view)) {
            return false;
        }

        $msg = 'URLs starting with /js/ and /css/ are deprecated. Use elgg_get_simplecache_url().';
        elgg_deprecated_notice($msg, '2.1');

        $return = elgg_view($view);

        header("Content-type: $content_type;charset=utf-8");

        // @todo should js be cached when simple cache turned off
        //header('Expires: ' . gmdate('D, d M Y H:i:s \G\M\T', strtotime("+10 days")), true);
        //header("Pragma: public");
        //header("Cache-Control: public");
        //header("Content-Length: " . strlen($return));

        echo $return;
        return true;
    }
    return false;
}

function _elgg_sql_reverse_order_by_clause($order_by) {
    $order_by = strtolower($order_by);

    if (strpos($order_by, ' asc') !== false) {
        $return = str_replace(' asc', ' desc', $order_by);
    } elseif (strpos($order_by, ' desc') !== false) {
        $return = str_replace(' desc', ' asc', $order_by);
    } else {
        // no order specified, so default to desc since mysql defaults to asc
        $return = $order_by . ' desc';
    }

    return $return;
}

function elgg_batch_enable_callback($object) {
    // our db functions return the number of rows affected...
    return $object->enable() ? true : false;
}

function elgg_batch_disable_callback($object) {
    // our db functions return the number of rows affected...
    return $object->disable() ? true : false;
}

function elgg_batch_delete_callback($object) {
    // our db functions return the number of rows affected...
    return $object->delete() ? true : false;
}

function _elgg_is_valid_options_for_batch_operation($options, $type) {
    if (!$options || !is_array($options)) {
        return false;
    }

    // at least one of these is required.
    $required = array(
        // generic restraints
        'guid', 'guids'
    );

    switch ($type) {
        case 'metadata':
            $metadata_required = array(
                'metadata_owner_guid', 'metadata_owner_guids',
                'metadata_name', 'metadata_names',
                'metadata_value', 'metadata_values'
            );

            $required = array_merge($required, $metadata_required);
            break;

        case 'annotations':
        case 'annotation':
            $annotations_required = array(
                'annotation_owner_guid', 'annotation_owner_guids',
                'annotation_name', 'annotation_names',
                'annotation_value', 'annotation_values'
            );

            $required = array_merge($required, $annotations_required);
            break;

        default:
            return false;
    }

    foreach ($required as $key) {
        // check that it exists and is something.
        if (isset($options[$key]) && $options[$key]) {
            return true;
        }
    }

    return false;
}

function _elgg_walled_garden_index() {
    return elgg_ok_response(elgg_view_resource('walled_garden'));
}


function _elgg_walled_garden_ajax_handler($page) {
    $view = $page[0];
    if (!elgg_view_exists("core/walled_garden/$view")) {
        return false;
    }
    $params = array(
        'content' => elgg_view("core/walled_garden/$view"),
        'class' => 'elgg-walledgarden-single hidden',
        'id' => str_replace('_', '-', "elgg-walledgarden-$view"),
    );
    echo elgg_view_layout('walled_garden', $params);
    return true;
}

function _elgg_walled_garden_init() {
    global $CONFIG;

    elgg_register_css('elgg.walled_garden', elgg_get_simplecache_url('walled_garden.css'));

    // Deprecated, but registered for BC
    // @todo: remove in 3.x
    elgg_register_js('elgg.walled_garden', elgg_get_simplecache_url('walled_garden.js'));

    elgg_register_page_handler('walled_garden', '_elgg_walled_garden_ajax_handler');

    // check for external page view
    if (isset($CONFIG->site) && $CONFIG->site instanceof \ElggSite) {
        $CONFIG->site->checkWalledGarden();
    }

    // For BC, we are extending the views to make sure that sites that customized walled garden get the updates
    // @todo: in 3.0, move this into the layout view
    elgg_extend_view('page/layouts/walled_garden', 'page/layouts/walled_garden/cancel_button');
}

function _elgg_walled_garden_remove_public_access($hook, $type, $accesses) {
    
    if (!elgg_get_config('walled_garden')) {
        return;
    }
    
    if (isset($accesses[ACCESS_PUBLIC])) {
        unset($accesses[ACCESS_PUBLIC]);
    }
    
    return $accesses;
}

function _elgg_init() {
    elgg_register_action('entity/delete');
    elgg_register_action('comment/save');
    elgg_register_action('comment/delete');

    elgg_register_page_handler('js', '_elgg_js_page_handler');
    elgg_register_page_handler('css', '_elgg_css_page_handler');
    elgg_register_page_handler('ajax', '_elgg_ajax_page_handler');
    elgg_register_page_handler('favicon.ico', '_elgg_favicon_page_handler');

    elgg_register_page_handler('manifest.json', function() {
        $site = elgg_get_site_entity();
        $resource = new \Elgg\Http\WebAppManifestResource($site);
        header('Content-Type: application/json;charset=utf-8');
        echo json_encode($resource->get());
        return true;
    });

    elgg_register_plugin_hook_handler('head', 'page', function($hook, $type, array $result) {
        $result['links']['manifest'] = [
            'rel' => 'manifest',
            'href' => elgg_normalize_url('/manifest.json'),
        ];

        return $result;
    });
    
    elgg_register_plugin_hook_handler('access:collections:write', 'all', '_elgg_walled_garden_remove_public_access', 9999);

    if (_elgg_services()->config->getVolatile('enable_profiling')) {
        elgg_register_plugin_hook_handler('output', 'page', [\Elgg\Profiler::class, 'handlePageOutput'], 999);
    }
}

function _elgg_api_test($hook, $type, $value, $params) {
    global $CONFIG;
    $value[] = $CONFIG->path . 'engine/tests/ElggTravisInstallTest.php';
    $value[] = $CONFIG->path . 'engine/tests/ElggCoreHelpersTest.php';
    $value[] = $CONFIG->path . 'engine/tests/ElggCoreRegressionBugsTest.php';
    $value[] = $CONFIG->path . 'engine/tests/ElggBatchTest.php';
    return $value;
}

define('ACCESS_DEFAULT', -1);
define('ACCESS_PRIVATE', 0);
define('ACCESS_LOGGED_IN', 1);
define('ACCESS_PUBLIC', 2);
define('ACCESS_FRIENDS', -2);
define('ELGG_ENTITIES_ANY_VALUE', null);

define('ELGG_ENTITIES_NO_VALUE', 0);

define('REFERRER', -1);

define('REFERER', -1);

define('ELGG_HTTP_CONTINUE', 100);
define('ELGG_HTTP_SWITCHING_PROTOCOLS', 101);
define('ELGG_HTTP_PROCESSING', 102);// RFC2518
define('ELGG_HTTP_OK', 200);
define('ELGG_HTTP_CREATED', 201);
define('ELGG_HTTP_ACCEPTED', 202);
define('ELGG_HTTP_NON_AUTHORITATIVE_INFORMATION', 203);
define('ELGG_HTTP_NO_CONTENT', 204);
define('ELGG_HTTP_RESET_CONTENT', 205);
define('ELGG_HTTP_PARTIAL_CONTENT', 206);
define('ELGG_HTTP_MULTI_STATUS', 207); // RFC4918
define('ELGG_HTTP_ALREADY_REPORTED', 208); // RFC5842
define('ELGG_HTTP_IM_USED', 226); // RFC3229
define('ELGG_HTTP_MULTIPLE_CHOICES', 300);
define('ELGG_HTTP_MOVED_PERMANENTLY', 301);
define('ELGG_HTTP_FOUND', 302);
define('ELGG_HTTP_SEE_OTHER', 303);
define('ELGG_HTTP_NOT_MODIFIED', 304);
define('ELGG_HTTP_USE_PROXY', 305);
define('ELGG_HTTP_RESERVED', 306);
define('ELGG_HTTP_TEMPORARY_REDIRECT', 307);
define('ELGG_HTTP_PERMANENTLY_REDIRECT', 308); // RFC7238
define('ELGG_HTTP_BAD_REQUEST', 400);
define('ELGG_HTTP_UNAUTHORIZED', 401);
define('ELGG_HTTP_PAYMENT_REQUIRED', 402);
define('ELGG_HTTP_FORBIDDEN', 403);
define('ELGG_HTTP_NOT_FOUND', 404);
define('ELGG_HTTP_METHOD_NOT_ALLOWED', 405);
define('ELGG_HTTP_NOT_ACCEPTABLE', 406);
define('ELGG_HTTP_PROXY_AUTHENTICATION_REQUIRED', 407);
define('ELGG_HTTP_REQUEST_TIMEOUT', 408);
define('ELGG_HTTP_CONFLICT', 409);
define('ELGG_HTTP_GONE', 410);
define('ELGG_HTTP_LENGTH_REQUIRED', 411);
define('ELGG_HTTP_PRECONDITION_FAILED', 412);
define('ELGG_HTTP_REQUEST_ENTITY_TOO_LARGE', 413);
define('ELGG_HTTP_REQUEST_URI_TOO_LONG', 414);
define('ELGG_HTTP_UNSUPPORTED_MEDIA_TYPE', 415);
define('ELGG_HTTP_REQUESTED_RANGE_NOT_SATISFIABLE', 416);
define('ELGG_HTTP_EXPECTATION_FAILED', 417);
define('ELGG_HTTP_I_AM_A_TEAPOT', 418); // RFC2324
define('ELGG_HTTP_UNPROCESSABLE_ENTITY', 422);// RFC4918
define('ELGG_HTTP_LOCKED', 423); // RFC4918
define('ELGG_HTTP_FAILED_DEPENDENCY', 424); // RFC4918
define('ELGG_HTTP_RESERVED_FOR_WEBDAV_ADVANCED_COLLECTIONS_EXPIRED_PROPOSAL', 425); // RFC2817
define('ELGG_HTTP_UPGRADE_REQUIRED', 426);// RFC2817
define('ELGG_HTTP_PRECONDITION_REQUIRED', 428); // RFC6585
define('ELGG_HTTP_TOO_MANY_REQUESTS', 429); // RFC6585
define('ELGG_HTTP_REQUEST_HEADER_FIELDS_TOO_LARGE', 431); // RFC6585
define('ELGG_HTTP_INTERNAL_SERVER_ERROR', 500);
define('ELGG_HTTP_NOT_IMPLEMENTED', 501);
define('ELGG_HTTP_BAD_GATEWAY', 502);
define('ELGG_HTTP_SERVICE_UNAVAILABLE', 503);
define('ELGG_HTTP_GATEWAY_TIMEOUT', 504);
define('ELGG_HTTP_VERSION_NOT_SUPPORTED', 505);
define('ELGG_HTTP_VARIANT_ALSO_NEGOTIATES_EXPERIMENTAL', 506);// RFC2295
define('ELGG_HTTP_INSUFFICIENT_STORAGE', 507);// RFC4918
define('ELGG_HTTP_LOOP_DETECTED', 508); // RFC5842
define('ELGG_HTTP_NOT_EXTENDED', 510);// RFC2774
define('ELGG_HTTP_NETWORK_AUTHENTICATION_REQUIRED', 511); // RFC6585

define('ELGG_JSON_ENCODING', JSON_HEX_TAG | JSON_HEX_APOS | JSON_HEX_AMP | JSON_HEX_QUOT);

return function(\Elgg\EventsService $events, \Elgg\HooksRegistrationService $hooks) {
    $events->registerHandler('boot', 'system', function () {
        _elgg_services()->boot->boot();
    }, 1);
    $events->registerHandler('cache:flush', 'system', function () {
        _elgg_services()->boot->invalidateCache();
    });

    $events->registerHandler('init', 'system', '_elgg_init');
    $events->registerHandler('init', 'system', '_elgg_walled_garden_init', 1000);

    $hooks->registerHandler('unit_test', 'system', '_elgg_api_test');
};