[moodle.git] / lib / adminlib.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 * Functions and classes used during installation, upgrades and for admin settings.
 *
 *  ADMIN SETTINGS TREE INTRODUCTION
 *
 *  This file performs the following tasks:
 *   -it defines the necessary objects and interfaces to build the Moodle
 *    admin hierarchy
 *   -it defines the admin_externalpage_setup()
 *
 *  ADMIN_SETTING OBJECTS
 *
 *  Moodle settings are represented by objects that inherit from the admin_setting
 *  class. These objects encapsulate how to read a setting, how to write a new value
 *  to a setting, and how to appropriately display the HTML to modify the setting.
 *
 *  ADMIN_SETTINGPAGE OBJECTS
 *
 *  The admin_setting objects are then grouped into admin_settingpages. The latter
 *  appear in the Moodle admin tree block. All interaction with admin_settingpage
 *  objects is handled by the admin/settings.php file.
 *
 *  ADMIN_EXTERNALPAGE OBJECTS
 *
 *  There are some settings in Moodle that are too complex to (efficiently) handle
 *  with admin_settingpages. (Consider, for example, user management and displaying
 *  lists of users.) In this case, we use the admin_externalpage object. This object
 *  places a link to an external PHP file in the admin tree block.
 *
 *  If you're using an admin_externalpage object for some settings, you can take
 *  advantage of the admin_externalpage_* functions. For example, suppose you wanted
 *  to add a foo.php file into admin. First off, you add the following line to
 *  admin/settings/first.php (at the end of the file) or to some other file in
 *  admin/settings:
 * <code>
 *     $ADMIN->add('userinterface', new admin_externalpage('foo', get_string('foo'),
 *         $CFG->wwwdir . '/' . '$CFG->admin . '/foo.php', 'some_role_permission'));
 * </code>
 *
 *  Next, in foo.php, your file structure would resemble the following:
 * <code>
 *         require(__DIR__.'/../../config.php');
 *         require_once($CFG->libdir.'/adminlib.php');
 *         admin_externalpage_setup('foo');
 *         // functionality like processing form submissions goes here
 *         echo $OUTPUT->header();
 *         // your HTML goes here
 *         echo $OUTPUT->footer();
 * </code>
 *
 *  The admin_externalpage_setup() function call ensures the user is logged in,
 *  and makes sure that they have the proper role permission to access the page.
 *  It also configures all $PAGE properties needed for navigation.
 *
 *  ADMIN_CATEGORY OBJECTS
 *
 *  Above and beyond all this, we have admin_category objects. These objects
 *  appear as folders in the admin tree block. They contain admin_settingpage's,
 *  admin_externalpage's, and other admin_category's.
 *
 *  OTHER NOTES
 *
 *  admin_settingpage's, admin_externalpage's, and admin_category's all inherit
 *  from part_of_admin_tree (a pseudointerface). This interface insists that
 *  a class has a check_access method for access permissions, a locate method
 *  used to find a specific node in the admin tree and find parent path.
 *
 *  admin_category's inherit from parentable_part_of_admin_tree. This pseudo-
 *  interface ensures that the class implements a recursive add function which
 *  accepts a part_of_admin_tree object and searches for the proper place to
 *  put it. parentable_part_of_admin_tree implies part_of_admin_tree.
 *
 *  Please note that the $this->name field of any part_of_admin_tree must be
 *  UNIQUE throughout the ENTIRE admin tree.
 *
 *  The $this->name field of an admin_setting object (which is *not* part_of_
 *  admin_tree) must be unique on the respective admin_settingpage where it is
 *  used.
 *
 * Original author: Vincenzo K. Marcovecchio
 * Maintainer:      Petr Skoda
 *
 * @package    core
 * @subpackage admin
 * @copyright  1999 onwards Martin Dougiamas  http://dougiamas.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();

/// Add libraries
require_once($CFG->libdir.'/ddllib.php');
require_once($CFG->libdir.'/xmlize.php');
require_once($CFG->libdir.'/messagelib.php');

define('INSECURE_DATAROOT_WARNING', 1);
define('INSECURE_DATAROOT_ERROR', 2);

/**
 * Automatically clean-up all plugin data and remove the plugin DB tables
 *
 * NOTE: do not call directly, use new /admin/plugins.php?uninstall=component instead!
 *
 * @param string $type The plugin type, eg. 'mod', 'qtype', 'workshopgrading' etc.
 * @param string $name The plugin name, eg. 'forum', 'multichoice', 'accumulative' etc.
 * @uses global $OUTPUT to produce notices and other messages
 * @return void
 */
function uninstall_plugin($type, $name) {
    global $CFG, $DB, $OUTPUT;

    // This may take a long time.
    core_php_time_limit::raise();

    // Recursively uninstall all subplugins first.
    $subplugintypes = core_component::get_plugin_types_with_subplugins();
    if (isset($subplugintypes[$type])) {
        $base = core_component::get_plugin_directory($type, $name);

        $subpluginsfile = "{$base}/db/subplugins.json";
        if (file_exists($subpluginsfile)) {
            $subplugins = (array) json_decode(file_get_contents($subpluginsfile))->plugintypes;
        } else if (file_exists("{$base}/db/subplugins.php")) {
            debugging('Use of subplugins.php has been deprecated. ' .
                    'Please update your plugin to provide a subplugins.json file instead.',
                    DEBUG_DEVELOPER);
            $subplugins = [];
            include("{$base}/db/subplugins.php");
        }

        if (!empty($subplugins)) {
            foreach (array_keys($subplugins) as $subplugintype) {
                $instances = core_component::get_plugin_list($subplugintype);
                foreach ($instances as $subpluginname => $notusedpluginpath) {
                    uninstall_plugin($subplugintype, $subpluginname);
                }
            }
        }
    }

    $component = $type . '_' . $name;  // eg. 'qtype_multichoice' or 'workshopgrading_accumulative' or 'mod_forum'

    if ($type === 'mod') {
        $pluginname = $name;  // eg. 'forum'
        if (get_string_manager()->string_exists('modulename', $component)) {
            $strpluginname = get_string('modulename', $component);
        } else {
            $strpluginname = $component;
        }

    } else {
        $pluginname = $component;
        if (get_string_manager()->string_exists('pluginname', $component)) {
            $strpluginname = get_string('pluginname', $component);
        } else {
            $strpluginname = $component;
        }
    }

    echo $OUTPUT->heading($pluginname);

    // Delete all tag areas, collections and instances associated with this plugin.
    core_tag_area::uninstall($component);

    // Custom plugin uninstall.
    $plugindirectory = core_component::get_plugin_directory($type, $name);
    $uninstalllib = $plugindirectory . '/db/uninstall.php';
    if (file_exists($uninstalllib)) {
        require_once($uninstalllib);
        $uninstallfunction = 'xmldb_' . $pluginname . '_uninstall';    // eg. 'xmldb_workshop_uninstall()'
        if (function_exists($uninstallfunction)) {
            // Do not verify result, let plugin complain if necessary.
            $uninstallfunction();
        }
    }

    // Specific plugin type cleanup.
    $plugininfo = core_plugin_manager::instance()->get_plugin_info($component);
    if ($plugininfo) {
        $plugininfo->uninstall_cleanup();
        core_plugin_manager::reset_caches();
    }
    $plugininfo = null;

    // perform clean-up task common for all the plugin/subplugin types

    //delete the web service functions and pre-built services
    require_once($CFG->dirroot.'/lib/externallib.php');
    external_delete_descriptions($component);

    // delete calendar events
    $DB->delete_records('event', array('modulename' => $pluginname));
    $DB->delete_records('event', ['component' => $component]);

    // Delete scheduled tasks.
    $DB->delete_records('task_scheduled', array('component' => $component));

    // Delete Inbound Message datakeys.
    $DB->delete_records_select('messageinbound_datakeys',
            'handler IN (SELECT id FROM {messageinbound_handlers} WHERE component = ?)', array($component));

    // Delete Inbound Message handlers.
    $DB->delete_records('messageinbound_handlers', array('component' => $component));

    // delete all the logs
    $DB->delete_records('log', array('module' => $pluginname));

    // delete log_display information
    $DB->delete_records('log_display', array('component' => $component));

    // delete the module configuration records
    unset_all_config_for_plugin($component);
    if ($type === 'mod') {
        unset_all_config_for_plugin($pluginname);
    }

    // delete message provider
    message_provider_uninstall($component);

    // delete the plugin tables
    $xmldbfilepath = $plugindirectory . '/db/install.xml';
    drop_plugin_tables($component, $xmldbfilepath, false);
    if ($type === 'mod' or $type === 'block') {
        // non-frankenstyle table prefixes
        drop_plugin_tables($name, $xmldbfilepath, false);
    }

    // delete the capabilities that were defined by this module
    capabilities_cleanup($component);

    // Delete all remaining files in the filepool owned by the component.
    $fs = get_file_storage();
    $fs->delete_component_files($component);

    // Finally purge all caches.
    purge_all_caches();

    // Invalidate the hash used for upgrade detections.
    set_config('allversionshash', '');

    echo $OUTPUT->notification(get_string('success'), 'notifysuccess');
}

/**
 * Returns the version of installed component
 *
 * @param string $component component name
 * @param string $source either 'disk' or 'installed' - where to get the version information from
 * @return string|bool version number or false if the component is not found
 */
function get_component_version($component, $source='installed') {
    global $CFG, $DB;

    list($type, $name) = core_component::normalize_component($component);

    // moodle core or a core subsystem
    if ($type === 'core') {
        if ($source === 'installed') {
            if (empty($CFG->version)) {
                return false;
            } else {
                return $CFG->version;
            }
        } else {
            if (!is_readable($CFG->dirroot.'/version.php')) {
                return false;
            } else {
                $version = null; //initialize variable for IDEs
                include($CFG->dirroot.'/version.php');
                return $version;
            }
        }
    }

    // activity module
    if ($type === 'mod') {
        if ($source === 'installed') {
            if ($CFG->version < 2013092001.02) {
                return $DB->get_field('modules', 'version', array('name'=>$name));
            } else {
                return get_config('mod_'.$name, 'version');
            }

        } else {
            $mods = core_component::get_plugin_list('mod');
            if (empty($mods[$name]) or !is_readable($mods[$name].'/version.php')) {
                return false;
            } else {
                $plugin = new stdClass();
                $plugin->version = null;
                $module = $plugin;
                include($mods[$name].'/version.php');
                return $plugin->version;
            }
        }
    }

    // block
    if ($type === 'block') {
        if ($source === 'installed') {
            if ($CFG->version < 2013092001.02) {
                return $DB->get_field('block', 'version', array('name'=>$name));
            } else {
                return get_config('block_'.$name, 'version');
            }
        } else {
            $blocks = core_component::get_plugin_list('block');
            if (empty($blocks[$name]) or !is_readable($blocks[$name].'/version.php')) {
                return false;
            } else {
                $plugin = new stdclass();
                include($blocks[$name].'/version.php');
                return $plugin->version;
            }
        }
    }

    // all other plugin types
    if ($source === 'installed') {
        return get_config($type.'_'.$name, 'version');
    } else {
        $plugins = core_component::get_plugin_list($type);
        if (empty($plugins[$name])) {
            return false;
        } else {
            $plugin = new stdclass();
            include($plugins[$name].'/version.php');
            return $plugin->version;
        }
    }
}

/**
 * Delete all plugin tables
 *
 * @param string $name Name of plugin, used as table prefix
 * @param string $file Path to install.xml file
 * @param bool $feedback defaults to true
 * @return bool Always returns true
 */
function drop_plugin_tables($name, $file, $feedback=true) {
    global $CFG, $DB;

    // first try normal delete
    if (file_exists($file) and $DB->get_manager()->delete_tables_from_xmldb_file($file)) {
        return true;
    }

    // then try to find all tables that start with name and are not in any xml file
    $used_tables = get_used_table_names();

    $tables = $DB->get_tables();

    /// Iterate over, fixing id fields as necessary
    foreach ($tables as $table) {
        if (in_array($table, $used_tables)) {
            continue;
        }

        if (strpos($table, $name) !== 0) {
            continue;
        }

        // found orphan table --> delete it
        if ($DB->get_manager()->table_exists($table)) {
            $xmldb_table = new xmldb_table($table);
            $DB->get_manager()->drop_table($xmldb_table);
        }
    }

    return true;
}

/**
 * Returns names of all known tables == tables that moodle knows about.
 *
 * @return array Array of lowercase table names
 */
function get_used_table_names() {
    $table_names = array();
    $dbdirs = get_db_directories();

    foreach ($dbdirs as $dbdir) {
        $file = $dbdir.'/install.xml';

        $xmldb_file = new xmldb_file($file);

        if (!$xmldb_file->fileExists()) {
            continue;
        }

        $loaded    = $xmldb_file->loadXMLStructure();
        $structure = $xmldb_file->getStructure();

        if ($loaded and $tables = $structure->getTables()) {
            foreach($tables as $table) {
                $table_names[] = strtolower($table->getName());
            }
        }
    }

    return $table_names;
}

/**
 * Returns list of all directories where we expect install.xml files
 * @return array Array of paths
 */
function get_db_directories() {
    global $CFG;

    $dbdirs = array();

    /// First, the main one (lib/db)
    $dbdirs[] = $CFG->libdir.'/db';

    /// Then, all the ones defined by core_component::get_plugin_types()
    $plugintypes = core_component::get_plugin_types();
    foreach ($plugintypes as $plugintype => $pluginbasedir) {
        if ($plugins = core_component::get_plugin_list($plugintype)) {
            foreach ($plugins as $plugin => $plugindir) {
                $dbdirs[] = $plugindir.'/db';
            }
        }
    }

    return $dbdirs;
}

/**
 * Try to obtain or release the cron lock.
 * @param string  $name  name of lock
 * @param int  $until timestamp when this lock considered stale, null means remove lock unconditionally
 * @param bool $ignorecurrent ignore current lock state, usually extend previous lock, defaults to false
 * @return bool true if lock obtained
 */
function set_cron_lock($name, $until, $ignorecurrent=false) {
    global $DB;
    if (empty($name)) {
        debugging("Tried to get a cron lock for a null fieldname");
        return false;
    }

    // remove lock by force == remove from config table
    if (is_null($until)) {
        set_config($name, null);
        return true;
    }

    if (!$ignorecurrent) {
        // read value from db - other processes might have changed it
        $value = $DB->get_field('config', 'value', array('name'=>$name));

        if ($value and $value > time()) {
            //lock active
            return false;
        }
    }

    set_config($name, $until);
    return true;
}

/**
 * Test if and critical warnings are present
 * @return bool
 */
function admin_critical_warnings_present() {
    global $SESSION;

    if (!has_capability('moodle/site:config', context_system::instance())) {
        return 0;
    }

    if (!isset($SESSION->admin_critical_warning)) {
        $SESSION->admin_critical_warning = 0;
        if (is_dataroot_insecure(true) === INSECURE_DATAROOT_ERROR) {
            $SESSION->admin_critical_warning = 1;
        }
    }

    return $SESSION->admin_critical_warning;
}

/**
 * Detects if float supports at least 10 decimal digits
 *
 * Detects if float supports at least 10 decimal digits
 * and also if float-->string conversion works as expected.
 *
 * @return bool true if problem found
 */
function is_float_problem() {
    $num1 = 2009010200.01;
    $num2 = 2009010200.02;

    return ((string)$num1 === (string)$num2 or $num1 === $num2 or $num2 <= (string)$num1);
}

/**
 * Try to verify that dataroot is not accessible from web.
 *
 * Try to verify that dataroot is not accessible from web.
 * It is not 100% correct but might help to reduce number of vulnerable sites.
 * Protection from httpd.conf and .htaccess is not detected properly.
 *
 * @uses INSECURE_DATAROOT_WARNING
 * @uses INSECURE_DATAROOT_ERROR
 * @param bool $fetchtest try to test public access by fetching file, default false
 * @return mixed empty means secure, INSECURE_DATAROOT_ERROR found a critical problem, INSECURE_DATAROOT_WARNING might be problematic
 */
function is_dataroot_insecure($fetchtest=false) {
    global $CFG;

    $siteroot = str_replace('\\', '/', strrev($CFG->dirroot.'/')); // win32 backslash workaround

    $rp = preg_replace('|https?://[^/]+|i', '', $CFG->wwwroot, 1);
    $rp = strrev(trim($rp, '/'));
    $rp = explode('/', $rp);
    foreach($rp as $r) {
        if (strpos($siteroot, '/'.$r.'/') === 0) {
            $siteroot = substr($siteroot, strlen($r)+1); // moodle web in subdirectory
        } else {
            break; // probably alias root
        }
    }

    $siteroot = strrev($siteroot);
    $dataroot = str_replace('\\', '/', $CFG->dataroot.'/');

    if (strpos($dataroot, $siteroot) !== 0) {
        return false;
    }

    if (!$fetchtest) {
        return INSECURE_DATAROOT_WARNING;
    }

    // now try all methods to fetch a test file using http protocol

    $httpdocroot = str_replace('\\', '/', strrev($CFG->dirroot.'/'));
    preg_match('|(https?://[^/]+)|i', $CFG->wwwroot, $matches);
    $httpdocroot = $matches[1];
    $datarooturl = $httpdocroot.'/'. substr($dataroot, strlen($siteroot));
    make_upload_directory('diag');
    $testfile = $CFG->dataroot.'/diag/public.txt';
    if (!file_exists($testfile)) {
        file_put_contents($testfile, 'test file, do not delete');
        @chmod($testfile, $CFG->filepermissions);
    }
    $teststr = trim(file_get_contents($testfile));
    if (empty($teststr)) {
    // hmm, strange
        return INSECURE_DATAROOT_WARNING;
    }

    $testurl = $datarooturl.'/diag/public.txt';
    if (extension_loaded('curl') and
        !(stripos(ini_get('disable_functions'), 'curl_init') !== FALSE) and
        !(stripos(ini_get('disable_functions'), 'curl_setop') !== FALSE) and
        ($ch = @curl_init($testurl)) !== false) {
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
        curl_setopt($ch, CURLOPT_HEADER, false);
        $data = curl_exec($ch);
        if (!curl_errno($ch)) {
            $data = trim($data);
            if ($data === $teststr) {
                curl_close($ch);
                return INSECURE_DATAROOT_ERROR;
            }
        }
        curl_close($ch);
    }

    if ($data = @file_get_contents($testurl)) {
        $data = trim($data);
        if ($data === $teststr) {
            return INSECURE_DATAROOT_ERROR;
        }
    }

    preg_match('|https?://([^/]+)|i', $testurl, $matches);
    $sitename = $matches[1];
    $error = 0;
    if ($fp = @fsockopen($sitename, 80, $error)) {
        preg_match('|https?://[^/]+(.*)|i', $testurl, $matches);
        $localurl = $matches[1];
        $out = "GET $localurl HTTP/1.1\r\n";
        $out .= "Host: $sitename\r\n";
        $out .= "Connection: Close\r\n\r\n";
        fwrite($fp, $out);
        $data = '';
        $incoming = false;
        while (!feof($fp)) {
            if ($incoming) {
                $data .= fgets($fp, 1024);
            } else if (@fgets($fp, 1024) === "\r\n") {
                    $incoming = true;
                }
        }
        fclose($fp);
        $data = trim($data);
        if ($data === $teststr) {
            return INSECURE_DATAROOT_ERROR;
        }
    }

    return INSECURE_DATAROOT_WARNING;
}

/**
 * Enables CLI maintenance mode by creating new dataroot/climaintenance.html file.
 */
function enable_cli_maintenance_mode() {
    global $CFG, $SITE;

    if (file_exists("$CFG->dataroot/climaintenance.html")) {
        unlink("$CFG->dataroot/climaintenance.html");
    }

    if (isset($CFG->maintenance_message) and !html_is_blank($CFG->maintenance_message)) {
        $data = $CFG->maintenance_message;
        $data = bootstrap_renderer::early_error_content($data, null, null, null);
        $data = bootstrap_renderer::plain_page(get_string('sitemaintenance', 'admin'), $data);

    } else if (file_exists("$CFG->dataroot/climaintenance.template.html")) {
        $data = file_get_contents("$CFG->dataroot/climaintenance.template.html");

    } else {
        $data = get_string('sitemaintenance', 'admin');
        $data = bootstrap_renderer::early_error_content($data, null, null, null);
        $data = bootstrap_renderer::plain_page(get_string('sitemaintenancetitle', 'admin', $SITE->fullname), $data);
    }

    file_put_contents("$CFG->dataroot/climaintenance.html", $data);
    chmod("$CFG->dataroot/climaintenance.html", $CFG->filepermissions);
}

/// CLASS DEFINITIONS /////////////////////////////////////////////////////////


/**
 * Interface for anything appearing in the admin tree
 *
 * The interface that is implemented by anything that appears in the admin tree
 * block. It forces inheriting classes to define a method for checking user permissions
 * and methods for finding something in the admin tree.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
interface part_of_admin_tree {

/**
 * Finds a named part_of_admin_tree.
 *
 * Used to find a part_of_admin_tree. If a class only inherits part_of_admin_tree
 * and not parentable_part_of_admin_tree, then this function should only check if
 * $this->name matches $name. If it does, it should return a reference to $this,
 * otherwise, it should return a reference to NULL.
 *
 * If a class inherits parentable_part_of_admin_tree, this method should be called
 * recursively on all child objects (assuming, of course, the parent object's name
 * doesn't match the search criterion).
 *
 * @param string $name The internal name of the part_of_admin_tree we're searching for.
 * @return mixed An object reference or a NULL reference.
 */
    public function locate($name);

    /**
     * Removes named part_of_admin_tree.
     *
     * @param string $name The internal name of the part_of_admin_tree we want to remove.
     * @return bool success.
     */
    public function prune($name);

    /**
     * Search using query
     * @param string $query
     * @return mixed array-object structure of found settings and pages
     */
    public function search($query);

    /**
     * Verifies current user's access to this part_of_admin_tree.
     *
     * Used to check if the current user has access to this part of the admin tree or
     * not. If a class only inherits part_of_admin_tree and not parentable_part_of_admin_tree,
     * then this method is usually just a call to has_capability() in the site context.
     *
     * If a class inherits parentable_part_of_admin_tree, this method should return the
     * logical OR of the return of check_access() on all child objects.
     *
     * @return bool True if the user has access, false if she doesn't.
     */
    public function check_access();

    /**
     * Mostly useful for removing of some parts of the tree in admin tree block.
     *
     * @return True is hidden from normal list view
     */
    public function is_hidden();

    /**
     * Show we display Save button at the page bottom?
     * @return bool
     */
    public function show_save();
}


/**
 * Interface implemented by any part_of_admin_tree that has children.
 *
 * The interface implemented by any part_of_admin_tree that can be a parent
 * to other part_of_admin_tree's. (For now, this only includes admin_category.) Apart
 * from ensuring part_of_admin_tree compliancy, it also ensures inheriting methods
 * include an add method for adding other part_of_admin_tree objects as children.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
interface parentable_part_of_admin_tree extends part_of_admin_tree {

/**
 * Adds a part_of_admin_tree object to the admin tree.
 *
 * Used to add a part_of_admin_tree object to this object or a child of this
 * object. $something should only be added if $destinationname matches
 * $this->name. If it doesn't, add should be called on child objects that are
 * also parentable_part_of_admin_tree's.
 *
 * $something should be appended as the last child in the $destinationname. If the
 * $beforesibling is specified, $something should be prepended to it. If the given
 * sibling is not found, $something should be appended to the end of $destinationname
 * and a developer debugging message should be displayed.
 *
 * @param string $destinationname The internal name of the new parent for $something.
 * @param part_of_admin_tree $something The object to be added.
 * @return bool True on success, false on failure.
 */
    public function add($destinationname, $something, $beforesibling = null);

}


/**
 * The object used to represent folders (a.k.a. categories) in the admin tree block.
 *
 * Each admin_category object contains a number of part_of_admin_tree objects.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_category implements parentable_part_of_admin_tree {

    /** @var part_of_admin_tree[] An array of part_of_admin_tree objects that are this object's children */
    protected $children;
    /** @var string An internal name for this category. Must be unique amongst ALL part_of_admin_tree objects */
    public $name;
    /** @var string The displayed name for this category. Usually obtained through get_string() */
    public $visiblename;
    /** @var bool Should this category be hidden in admin tree block? */
    public $hidden;
    /** @var mixed Either a string or an array or strings */
    public $path;
    /** @var mixed Either a string or an array or strings */
    public $visiblepath;

    /** @var array fast lookup category cache, all categories of one tree point to one cache */
    protected $category_cache;

    /** @var bool If set to true children will be sorted when calling {@link admin_category::get_children()} */
    protected $sort = false;
    /** @var bool If set to true children will be sorted in ascending order. */
    protected $sortasc = true;
    /** @var bool If set to true sub categories and pages will be split and then sorted.. */
    protected $sortsplit = true;
    /** @var bool $sorted True if the children have been sorted and don't need resorting */
    protected $sorted = false;

    /**
     * Constructor for an empty admin category
     *
     * @param string $name The internal name for this category. Must be unique amongst ALL part_of_admin_tree objects
     * @param string $visiblename The displayed named for this category. Usually obtained through get_string()
     * @param bool $hidden hide category in admin tree block, defaults to false
     */
    public function __construct($name, $visiblename, $hidden=false) {
        $this->children    = array();
        $this->name        = $name;
        $this->visiblename = $visiblename;
        $this->hidden      = $hidden;
    }

    /**
     * Returns a reference to the part_of_admin_tree object with internal name $name.
     *
     * @param string $name The internal name of the object we want.
     * @param bool $findpath initialize path and visiblepath arrays
     * @return mixed A reference to the object with internal name $name if found, otherwise a reference to NULL.
     *                  defaults to false
     */
    public function locate($name, $findpath=false) {
        if (!isset($this->category_cache[$this->name])) {
            // somebody much have purged the cache
            $this->category_cache[$this->name] = $this;
        }

        if ($this->name == $name) {
            if ($findpath) {
                $this->visiblepath[] = $this->visiblename;
                $this->path[]        = $this->name;
            }
            return $this;
        }

        // quick category lookup
        if (!$findpath and isset($this->category_cache[$name])) {
            return $this->category_cache[$name];
        }

        $return = NULL;
        foreach($this->children as $childid=>$unused) {
            if ($return = $this->children[$childid]->locate($name, $findpath)) {
                break;
            }
        }

        if (!is_null($return) and $findpath) {
            $return->visiblepath[] = $this->visiblename;
            $return->path[]        = $this->name;
        }

        return $return;
    }

    /**
     * Search using query
     *
     * @param string query
     * @return mixed array-object structure of found settings and pages
     */
    public function search($query) {
        $result = array();
        foreach ($this->get_children() as $child) {
            $subsearch = $child->search($query);
            if (!is_array($subsearch)) {
                debugging('Incorrect search result from '.$child->name);
                continue;
            }
            $result = array_merge($result, $subsearch);
        }
        return $result;
    }

    /**
     * Removes part_of_admin_tree object with internal name $name.
     *
     * @param string $name The internal name of the object we want to remove.
     * @return bool success
     */
    public function prune($name) {

        if ($this->name == $name) {
            return false;  //can not remove itself
        }

        foreach($this->children as $precedence => $child) {
            if ($child->name == $name) {
                // clear cache and delete self
                while($this->category_cache) {
                    // delete the cache, but keep the original array address
                    array_pop($this->category_cache);
                }
                unset($this->children[$precedence]);
                return true;
            } else if ($this->children[$precedence]->prune($name)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Adds a part_of_admin_tree to a child or grandchild (or great-grandchild, and so forth) of this object.
     *
     * By default the new part of the tree is appended as the last child of the parent. You
     * can specify a sibling node that the new part should be prepended to. If the given
     * sibling is not found, the part is appended to the end (as it would be by default) and
     * a developer debugging message is displayed.
     *
     * @throws coding_exception if the $beforesibling is empty string or is not string at all.
     * @param string $destinationame The internal name of the immediate parent that we want for $something.
     * @param mixed $something A part_of_admin_tree or setting instance to be added.
     * @param string $beforesibling The name of the parent's child the $something should be prepended to.
     * @return bool True if successfully added, false if $something can not be added.
     */
    public function add($parentname, $something, $beforesibling = null) {
        global $CFG;

        $parent = $this->locate($parentname);
        if (is_null($parent)) {
            debugging('parent does not exist!');
            return false;
        }

        if ($something instanceof part_of_admin_tree) {
            if (!($parent instanceof parentable_part_of_admin_tree)) {
                debugging('error - parts of tree can be inserted only into parentable parts');
                return false;
            }
            if ($CFG->debugdeveloper && !is_null($this->locate($something->name))) {
                // The name of the node is already used, simply warn the developer that this should not happen.
                // It is intentional to check for the debug level before performing the check.
                debugging('Duplicate admin page name: ' . $something->name, DEBUG_DEVELOPER);
            }
            if (is_null($beforesibling)) {
                // Append $something as the parent's last child.
                $parent->children[] = $something;
            } else {
                if (!is_string($beforesibling) or trim($beforesibling) === '') {
                    throw new coding_exception('Unexpected value of the beforesibling parameter');
                }
                // Try to find the position of the sibling.
                $siblingposition = null;
                foreach ($parent->children as $childposition => $child) {
                    if ($child->name === $beforesibling) {
                        $siblingposition = $childposition;
                        break;
                    }
                }
                if (is_null($siblingposition)) {
                    debugging('Sibling '.$beforesibling.' not found', DEBUG_DEVELOPER);
                    $parent->children[] = $something;
                } else {
                    $parent->children = array_merge(
                        array_slice($parent->children, 0, $siblingposition),
                        array($something),
                        array_slice($parent->children, $siblingposition)
                    );
                }
            }
            if ($something instanceof admin_category) {
                if (isset($this->category_cache[$something->name])) {
                    debugging('Duplicate admin category name: '.$something->name);
                } else {
                    $this->category_cache[$something->name] = $something;
                    $something->category_cache =& $this->category_cache;
                    foreach ($something->children as $child) {
                        // just in case somebody already added subcategories
                        if ($child instanceof admin_category) {
                            if (isset($this->category_cache[$child->name])) {
                                debugging('Duplicate admin category name: '.$child->name);
                            } else {
                                $this->category_cache[$child->name] = $child;
                                $child->category_cache =& $this->category_cache;
                            }
                        }
                    }
                }
            }
            return true;

        } else {
            debugging('error - can not add this element');
            return false;
        }

    }

    /**
     * Checks if the user has access to anything in this category.
     *
     * @return bool True if the user has access to at least one child in this category, false otherwise.
     */
    public function check_access() {
        foreach ($this->children as $child) {
            if ($child->check_access()) {
                return true;
            }
        }
        return false;
    }

    /**
     * Is this category hidden in admin tree block?
     *
     * @return bool True if hidden
     */
    public function is_hidden() {
        return $this->hidden;
    }

    /**
     * Show we display Save button at the page bottom?
     * @return bool
     */
    public function show_save() {
        foreach ($this->children as $child) {
            if ($child->show_save()) {
                return true;
            }
        }
        return false;
    }

    /**
     * Sets sorting on this category.
     *
     * Please note this function doesn't actually do the sorting.
     * It can be called anytime.
     * Sorting occurs when the user calls get_children.
     * Code using the children array directly won't see the sorted results.
     *
     * @param bool $sort If set to true children will be sorted, if false they won't be.
     * @param bool $asc If true sorting will be ascending, otherwise descending.
     * @param bool $split If true we sort pages and sub categories separately.
     */
    public function set_sorting($sort, $asc = true, $split = true) {
        $this->sort = (bool)$sort;
        $this->sortasc = (bool)$asc;
        $this->sortsplit = (bool)$split;
    }

    /**
     * Returns the children associated with this category.
     *
     * @return part_of_admin_tree[]
     */
    public function get_children() {
        // If we should sort and it hasn't already been sorted.
        if ($this->sort && !$this->sorted) {
            if ($this->sortsplit) {
                $categories = array();
                $pages = array();
                foreach ($this->children as $child) {
                    if ($child instanceof admin_category) {
                        $categories[] = $child;
                    } else {
                        $pages[] = $child;
                    }
                }
                core_collator::asort_objects_by_property($categories, 'visiblename');
                core_collator::asort_objects_by_property($pages, 'visiblename');
                if (!$this->sortasc) {
                    $categories = array_reverse($categories);
                    $pages = array_reverse($pages);
                }
                $this->children = array_merge($pages, $categories);
            } else {
                core_collator::asort_objects_by_property($this->children, 'visiblename');
                if (!$this->sortasc) {
                    $this->children = array_reverse($this->children);
                }
            }
            $this->sorted = true;
        }
        return $this->children;
    }

    /**
     * Magically gets a property from this object.
     *
     * @param $property
     * @return part_of_admin_tree[]
     * @throws coding_exception
     */
    public function __get($property) {
        if ($property === 'children') {
            return $this->get_children();
        }
        throw new coding_exception('Invalid property requested.');
    }

    /**
     * Magically sets a property against this object.
     *
     * @param string $property
     * @param mixed $value
     * @throws coding_exception
     */
    public function __set($property, $value) {
        if ($property === 'children') {
            $this->sorted = false;
            $this->children = $value;
        } else {
            throw new coding_exception('Invalid property requested.');
        }
    }

    /**
     * Checks if an inaccessible property is set.
     *
     * @param string $property
     * @return bool
     * @throws coding_exception
     */
    public function __isset($property) {
        if ($property === 'children') {
            return isset($this->children);
        }
        throw new coding_exception('Invalid property requested.');
    }
}


/**
 * Root of admin settings tree, does not have any parent.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_root extends admin_category {
/** @var array List of errors */
    public $errors;
    /** @var string search query */
    public $search;
    /** @var bool full tree flag - true means all settings required, false only pages required */
    public $fulltree;
    /** @var bool flag indicating loaded tree */
    public $loaded;
    /** @var mixed site custom defaults overriding defaults in settings files*/
    public $custom_defaults;

    /**
     * @param bool $fulltree true means all settings required,
     *                            false only pages required
     */
    public function __construct($fulltree) {
        global $CFG;

        parent::__construct('root', get_string('administration'), false);
        $this->errors   = array();
        $this->search   = '';
        $this->fulltree = $fulltree;
        $this->loaded   = false;

        $this->category_cache = array();

        // load custom defaults if found
        $this->custom_defaults = null;
        $defaultsfile = "$CFG->dirroot/local/defaults.php";
        if (is_readable($defaultsfile)) {
            $defaults = array();
            include($defaultsfile);
            if (is_array($defaults) and count($defaults)) {
                $this->custom_defaults = $defaults;
            }
        }
    }

    /**
     * Empties children array, and sets loaded to false
     *
     * @param bool $requirefulltree
     */
    public function purge_children($requirefulltree) {
        $this->children = array();
        $this->fulltree = ($requirefulltree || $this->fulltree);
        $this->loaded   = false;
        //break circular dependencies - this helps PHP 5.2
        while($this->category_cache) {
            array_pop($this->category_cache);
        }
        $this->category_cache = array();
    }
}


/**
 * Links external PHP pages into the admin tree.
 *
 * See detailed usage example at the top of this document (adminlib.php)
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_externalpage implements part_of_admin_tree {

    /** @var string An internal name for this external page. Must be unique amongst ALL part_of_admin_tree objects */
    public $name;

    /** @var string The displayed name for this external page. Usually obtained through get_string(). */
    public $visiblename;

    /** @var string The external URL that we should link to when someone requests this external page. */
    public $url;

    /** @var array The role capability/permission a user must have to access this external page. */
    public $req_capability;

    /** @var object The context in which capability/permission should be checked, default is site context. */
    public $context;

    /** @var bool hidden in admin tree block. */
    public $hidden;

    /** @var mixed either string or array of string */
    public $path;

    /** @var array list of visible names of page parents */
    public $visiblepath;

    /**
     * Constructor for adding an external page into the admin tree.
     *
     * @param string $name The internal name for this external page. Must be unique amongst ALL part_of_admin_tree objects.
     * @param string $visiblename The displayed name for this external page. Usually obtained through get_string().
     * @param string $url The external URL that we should link to when someone requests this external page.
     * @param mixed $req_capability The role capability/permission a user must have to access this external page. Defaults to 'moodle/site:config'.
     * @param boolean $hidden Is this external page hidden in admin tree block? Default false.
     * @param stdClass $context The context the page relates to. Not sure what happens
     *      if you specify something other than system or front page. Defaults to system.
     */
    public function __construct($name, $visiblename, $url, $req_capability='moodle/site:config', $hidden=false, $context=NULL) {
        $this->name        = $name;
        $this->visiblename = $visiblename;
        $this->url         = $url;
        if (is_array($req_capability)) {
            $this->req_capability = $req_capability;
        } else {
            $this->req_capability = array($req_capability);
        }
        $this->hidden = $hidden;
        $this->context = $context;
    }

    /**
     * Returns a reference to the part_of_admin_tree object with internal name $name.
     *
     * @param string $name The internal name of the object we want.
     * @param bool $findpath defaults to false
     * @return mixed A reference to the object with internal name $name if found, otherwise a reference to NULL.
     */
    public function locate($name, $findpath=false) {
        if ($this->name == $name) {
            if ($findpath) {
                $this->visiblepath = array($this->visiblename);
                $this->path        = array($this->name);
            }
            return $this;
        } else {
            $return = NULL;
            return $return;
        }
    }

    /**
     * This function always returns false, required function by interface
     *
     * @param string $name
     * @return false
     */
    public function prune($name) {
        return false;
    }

    /**
     * Search using query
     *
     * @param string $query
     * @return mixed array-object structure of found settings and pages
     */
    public function search($query) {
        $found = false;
        if (strpos(strtolower($this->name), $query) !== false) {
            $found = true;
        } else if (strpos(core_text::strtolower($this->visiblename), $query) !== false) {
                $found = true;
            }
        if ($found) {
            $result = new stdClass();
            $result->page     = $this;
            $result->settings = array();
            return array($this->name => $result);
        } else {
            return array();
        }
    }

    /**
     * Determines if the current user has access to this external page based on $this->req_capability.
     *
     * @return bool True if user has access, false otherwise.
     */
    public function check_access() {
        global $CFG;
        $context = empty($this->context) ? context_system::instance() : $this->context;
        foreach($this->req_capability as $cap) {
            if (has_capability($cap, $context)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Is this external page hidden in admin tree block?
     *
     * @return bool True if hidden
     */
    public function is_hidden() {
        return $this->hidden;
    }

    /**
     * Show we display Save button at the page bottom?
     * @return bool
     */
    public function show_save() {
        return false;
    }
}

/**
 * Used to store details of the dependency between two settings elements.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @copyright 2017 Davo Smith, Synergy Learning
 */
class admin_settingdependency {
    /** @var string the name of the setting to be shown/hidden */
    public $settingname;
    /** @var string the setting this is dependent on */
    public $dependenton;
    /** @var string the condition to show/hide the element */
    public $condition;
    /** @var string the value to compare against */
    public $value;

    /** @var string[] list of valid conditions */
    private static $validconditions = ['checked', 'notchecked', 'noitemselected', 'eq', 'neq', 'in'];

    /**
     * admin_settingdependency constructor.
     * @param string $settingname
     * @param string $dependenton
     * @param string $condition
     * @param string $value
     * @throws \coding_exception
     */
    public function __construct($settingname, $dependenton, $condition, $value) {
        $this->settingname = $this->parse_name($settingname);
        $this->dependenton = $this->parse_name($dependenton);
        $this->condition = $condition;
        $this->value = $value;

        if (!in_array($this->condition, self::$validconditions)) {
            throw new coding_exception("Invalid condition '$condition'");
        }
    }

    /**
     * Convert the setting name into the form field name.
     * @param string $name
     * @return string
     */
    private function parse_name($name) {
        $bits = explode('/', $name);
        $name = array_pop($bits);
        $plugin = '';
        if ($bits) {
            $plugin = array_pop($bits);
            if ($plugin === 'moodle') {
                $plugin = '';
            }
        }
        return 's_'.$plugin.'_'.$name;
    }

    /**
     * Gather together all the dependencies in a format suitable for initialising javascript
     * @param admin_settingdependency[] $dependencies
     * @return array
     */
    public static function prepare_for_javascript($dependencies) {
        $result = [];
        foreach ($dependencies as $d) {
            if (!isset($result[$d->dependenton])) {
                $result[$d->dependenton] = [];
            }
            if (!isset($result[$d->dependenton][$d->condition])) {
                $result[$d->dependenton][$d->condition] = [];
            }
            if (!isset($result[$d->dependenton][$d->condition][$d->value])) {
                $result[$d->dependenton][$d->condition][$d->value] = [];
            }
            $result[$d->dependenton][$d->condition][$d->value][] = $d->settingname;
        }
        return $result;
    }
}

/**
 * Used to group a number of admin_setting objects into a page and add them to the admin tree.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_settingpage implements part_of_admin_tree {

    /** @var string An internal name for this external page. Must be unique amongst ALL part_of_admin_tree objects */
    public $name;

    /** @var string The displayed name for this external page. Usually obtained through get_string(). */
    public $visiblename;

    /** @var mixed An array of admin_setting objects that are part of this setting page. */
    public $settings;

    /** @var admin_settingdependency[] list of settings to hide when certain conditions are met */
    protected $dependencies = [];

    /** @var array The role capability/permission a user must have to access this external page. */
    public $req_capability;

    /** @var object The context in which capability/permission should be checked, default is site context. */
    public $context;

    /** @var bool hidden in admin tree block. */
    public $hidden;

    /** @var mixed string of paths or array of strings of paths */
    public $path;

    /** @var array list of visible names of page parents */
    public $visiblepath;

    /**
     * see admin_settingpage for details of this function
     *
     * @param string $name The internal name for this external page. Must be unique amongst ALL part_of_admin_tree objects.
     * @param string $visiblename The displayed name for this external page. Usually obtained through get_string().
     * @param mixed $req_capability The role capability/permission a user must have to access this external page. Defaults to 'moodle/site:config'.
     * @param boolean $hidden Is this external page hidden in admin tree block? Default false.
     * @param stdClass $context The context the page relates to. Not sure what happens
     *      if you specify something other than system or front page. Defaults to system.
     */
    public function __construct($name, $visiblename, $req_capability='moodle/site:config', $hidden=false, $context=NULL) {
        $this->settings    = new stdClass();
        $this->name        = $name;
        $this->visiblename = $visiblename;
        if (is_array($req_capability)) {
            $this->req_capability = $req_capability;
        } else {
            $this->req_capability = array($req_capability);
        }
        $this->hidden      = $hidden;
        $this->context     = $context;
    }

    /**
     * see admin_category
     *
     * @param string $name
     * @param bool $findpath
     * @return mixed Object (this) if name ==  this->name, else returns null
     */
    public function locate($name, $findpath=false) {
        if ($this->name == $name) {
            if ($findpath) {
                $this->visiblepath = array($this->visiblename);
                $this->path        = array($this->name);
            }
            return $this;
        } else {
            $return = NULL;
            return $return;
        }
    }

    /**
     * Search string in settings page.
     *
     * @param string $query
     * @return array
     */
    public function search($query) {
        $found = array();

        foreach ($this->settings as $setting) {
            if ($setting->is_related($query)) {
                $found[] = $setting;
            }
        }

        if ($found) {
            $result = new stdClass();
            $result->page     = $this;
            $result->settings = $found;
            return array($this->name => $result);
        }

        $found = false;
        if (strpos(strtolower($this->name), $query) !== false) {
            $found = true;
        } else if (strpos(core_text::strtolower($this->visiblename), $query) !== false) {
                $found = true;
            }
        if ($found) {
            $result = new stdClass();
            $result->page     = $this;
            $result->settings = array();
            return array($this->name => $result);
        } else {
            return array();
        }
    }

    /**
     * This function always returns false, required by interface
     *
     * @param string $name
     * @return bool Always false
     */
    public function prune($name) {
        return false;
    }

    /**
     * adds an admin_setting to this admin_settingpage
     *
     * not the same as add for admin_category. adds an admin_setting to this admin_settingpage. settings appear (on the settingpage) in the order in which they're added
     * n.b. each admin_setting in an admin_settingpage must have a unique internal name
     *
     * @param object $setting is the admin_setting object you want to add
     * @return bool true if successful, false if not
     */
    public function add($setting) {
        if (!($setting instanceof admin_setting)) {
            debugging('error - not a setting instance');
            return false;
        }

        $name = $setting->name;
        if ($setting->plugin) {
            $name = $setting->plugin . $name;
        }
        $this->settings->{$name} = $setting;
        return true;
    }

    /**
     * Hide the named setting if the specified condition is matched.
     *
     * @param string $settingname
     * @param string $dependenton
     * @param string $condition
     * @param string $value
     */
    public function hide_if($settingname, $dependenton, $condition = 'notchecked', $value = '1') {
        $this->dependencies[] = new admin_settingdependency($settingname, $dependenton, $condition, $value);

        // Reformat the dependency name to the plugin | name format used in the display.
        $dependenton = str_replace('/', ' | ', $dependenton);

        // Let the setting know, so it can be displayed underneath.
        $findname = str_replace('/', '', $settingname);
        foreach ($this->settings as $name => $setting) {
            if ($name === $findname) {
                $setting->add_dependent_on($dependenton);
            }
        }
    }

    /**
     * see admin_externalpage
     *
     * @return bool Returns true for yes false for no
     */
    public function check_access() {
        global $CFG;
        $context = empty($this->context) ? context_system::instance() : $this->context;
        foreach($this->req_capability as $cap) {
            if (has_capability($cap, $context)) {
                return true;
            }
        }
        return false;
    }

    /**
     * outputs this page as html in a table (suitable for inclusion in an admin pagetype)
     * @return string Returns an XHTML string
     */
    public function output_html() {
        $adminroot = admin_get_root();
        $return = '<fieldset>'."\n".'<div class="clearer"><!-- --></div>'."\n";
        foreach($this->settings as $setting) {
            $fullname = $setting->get_full_name();
            if (array_key_exists($fullname, $adminroot->errors)) {
                $data = $adminroot->errors[$fullname]->data;
            } else {
                $data = $setting->get_setting();
                // do not use defaults if settings not available - upgrade settings handles the defaults!
            }
            $return .= $setting->output_html($data);
        }
        $return .= '</fieldset>';
        return $return;
    }

    /**
     * Is this settings page hidden in admin tree block?
     *
     * @return bool True if hidden
     */
    public function is_hidden() {
        return $this->hidden;
    }

    /**
     * Show we display Save button at the page bottom?
     * @return bool
     */
    public function show_save() {
        foreach($this->settings as $setting) {
            if (empty($setting->nosave)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Should any of the settings on this page be shown / hidden based on conditions?
     * @return bool
     */
    public function has_dependencies() {
        return (bool)$this->dependencies;
    }

    /**
     * Format the setting show/hide conditions ready to initialise the page javascript
     * @return array
     */
    public function get_dependencies_for_javascript() {
        if (!$this->has_dependencies()) {
            return [];
        }
        return admin_settingdependency::prepare_for_javascript($this->dependencies);
    }
}


/**
 * Admin settings class. Only exists on setting pages.
 * Read & write happens at this level; no authentication.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
abstract class admin_setting {
    /** @var string unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins. */
    public $name;
    /** @var string localised name */
    public $visiblename;
    /** @var string localised long description in Markdown format */
    public $description;
    /** @var mixed Can be string or array of string */
    public $defaultsetting;
    /** @var string */
    public $updatedcallback;
    /** @var mixed can be String or Null.  Null means main config table */
    public $plugin; // null means main config table
    /** @var bool true indicates this setting does not actually save anything, just information */
    public $nosave = false;
    /** @var bool if set, indicates that a change to this setting requires rebuild course cache */
    public $affectsmodinfo = false;
    /** @var array of admin_setting_flag - These are extra checkboxes attached to a setting. */
    private $flags = array();
    /** @var bool Whether this field must be forced LTR. */
    private $forceltr = null;
    /** @var array list of other settings that may cause this setting to be hidden */
    private $dependenton = [];
    /** @var bool Whether this setting uses a custom form control */
    protected $customcontrol = false;

    /**
     * Constructor
     * @param string $name unique ascii name, either 'mysetting' for settings that in config,
     *                     or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised name
     * @param string $description localised long description
     * @param mixed $defaultsetting string or array depending on implementation
     */
    public function __construct($name, $visiblename, $description, $defaultsetting) {
        $this->parse_setting_name($name);
        $this->visiblename    = $visiblename;
        $this->description    = $description;
        $this->defaultsetting = $defaultsetting;
    }

    /**
     * Generic function to add a flag to this admin setting.
     *
     * @param bool $enabled - One of self::OPTION_ENABLED or self::OPTION_DISABLED
     * @param bool $default - The default for the flag
     * @param string $shortname - The shortname for this flag. Used as a suffix for the setting name.
     * @param string $displayname - The display name for this flag. Used as a label next to the checkbox.
     */
    protected function set_flag_options($enabled, $default, $shortname, $displayname) {
        if (empty($this->flags[$shortname])) {
            $this->flags[$shortname] = new admin_setting_flag($enabled, $default, $shortname, $displayname);
        } else {
            $this->flags[$shortname]->set_options($enabled, $default);
        }
    }

    /**
     * Set the enabled options flag on this admin setting.
     *
     * @param bool $enabled - One of self::OPTION_ENABLED or self::OPTION_DISABLED
     * @param bool $default - The default for the flag
     */
    public function set_enabled_flag_options($enabled, $default) {
        $this->set_flag_options($enabled, $default, 'enabled', new lang_string('enabled', 'core_admin'));
    }

    /**
     * Set the advanced options flag on this admin setting.
     *
     * @param bool $enabled - One of self::OPTION_ENABLED or self::OPTION_DISABLED
     * @param bool $default - The default for the flag
     */
    public function set_advanced_flag_options($enabled, $default) {
        $this->set_flag_options($enabled, $default, 'adv', new lang_string('advanced'));
    }


    /**
     * Set the locked options flag on this admin setting.
     *
     * @param bool $enabled - One of self::OPTION_ENABLED or self::OPTION_DISABLED
     * @param bool $default - The default for the flag
     */
    public function set_locked_flag_options($enabled, $default) {
        $this->set_flag_options($enabled, $default, 'locked', new lang_string('locked', 'core_admin'));
    }

    /**
     * Set the required options flag on this admin setting.
     *
     * @param bool $enabled - One of self::OPTION_ENABLED or self::OPTION_DISABLED.
     * @param bool $default - The default for the flag.
     */
    public function set_required_flag_options($enabled, $default) {
        $this->set_flag_options($enabled, $default, 'required', new lang_string('required', 'core_admin'));
    }

    /**
     * Get the currently saved value for a setting flag
     *
     * @param admin_setting_flag $flag - One of the admin_setting_flag for this admin_setting.
     * @return bool
     */
    public function get_setting_flag_value(admin_setting_flag $flag) {
        $value = $this->config_read($this->name . '_' . $flag->get_shortname());
        if (!isset($value)) {
            $value = $flag->get_default();
        }

        return !empty($value);
    }

    /**
     * Get the list of defaults for the flags on this setting.
     *
     * @param array of strings describing the defaults for this setting. This is appended to by this function.
     */
    public function get_setting_flag_defaults(& $defaults) {
        foreach ($this->flags as $flag) {
            if ($flag->is_enabled() && $flag->get_default()) {
                $defaults[] = $flag->get_displayname();
            }
        }
    }

    /**
     * Output the input fields for the advanced and locked flags on this setting.
     *
     * @param bool $adv - The current value of the advanced flag.
     * @param bool $locked - The current value of the locked flag.
     * @return string $output - The html for the flags.
     */
    public function output_setting_flags() {
        $output = '';

        foreach ($this->flags as $flag) {
            if ($flag->is_enabled()) {
                $output .= $flag->output_setting_flag($this);
            }
        }

        if (!empty($output)) {
            return html_writer::tag('span', $output, array('class' => 'adminsettingsflags'));
        }
        return $output;
    }

    /**
     * Write the values of the flags for this admin setting.
     *
     * @param array $data - The data submitted from the form or null to set the default value for new installs.
     * @return bool - true if successful.
     */
    public function write_setting_flags($data) {
        $result = true;
        foreach ($this->flags as $flag) {
            $result = $result && $flag->write_setting_flag($this, $data);
        }
        return $result;
    }

    /**
     * Set up $this->name and potentially $this->plugin
     *
     * Set up $this->name and possibly $this->plugin based on whether $name looks
     * like 'settingname' or 'plugin/settingname'. Also, do some sanity checking
     * on the names, that is, output a developer debug warning if the name
     * contains anything other than [a-zA-Z0-9_]+.
     *
     * @param string $name the setting name passed in to the constructor.
     */
    private function parse_setting_name($name) {
        $bits = explode('/', $name);
        if (count($bits) > 2) {
            throw new moodle_exception('invalidadminsettingname', '', '', $name);
        }
        $this->name = array_pop($bits);
        if (!preg_match('/^[a-zA-Z0-9_]+$/', $this->name)) {
            throw new moodle_exception('invalidadminsettingname', '', '', $name);
        }
        if (!empty($bits)) {
            $this->plugin = array_pop($bits);
            if ($this->plugin === 'moodle') {
                $this->plugin = null;
            } else if (!preg_match('/^[a-zA-Z0-9_]+$/', $this->plugin)) {
                    throw new moodle_exception('invalidadminsettingname', '', '', $name);
                }
        }
    }

    /**
     * Returns the fullname prefixed by the plugin
     * @return string
     */
    public function get_full_name() {
        return 's_'.$this->plugin.'_'.$this->name;
    }

    /**
     * Returns the ID string based on plugin and name
     * @return string
     */
    public function get_id() {
        return 'id_s_'.$this->plugin.'_'.$this->name;
    }

    /**
     * @param bool $affectsmodinfo If true, changes to this setting will
     *   cause the course cache to be rebuilt
     */
    public function set_affects_modinfo($affectsmodinfo) {
        $this->affectsmodinfo = $affectsmodinfo;
    }

    /**
     * Returns the config if possible
     *
     * @return mixed returns config if successful else null
     */
    public function config_read($name) {
        global $CFG;
        if (!empty($this->plugin)) {
            $value = get_config($this->plugin, $name);
            return $value === false ? NULL : $value;

        } else {
            if (isset($CFG->$name)) {
                return $CFG->$name;
            } else {
                return NULL;
            }
        }
    }

    /**
     * Used to set a config pair and log change
     *
     * @param string $name
     * @param mixed $value Gets converted to string if not null
     * @return bool Write setting to config table
     */
    public function config_write($name, $value) {
        global $DB, $USER, $CFG;

        if ($this->nosave) {
            return true;
        }

        // make sure it is a real change
        $oldvalue = get_config($this->plugin, $name);
        $oldvalue = ($oldvalue === false) ? null : $oldvalue; // normalise
        $value = is_null($value) ? null : (string)$value;

        if ($oldvalue === $value) {
            return true;
        }

        // store change
        set_config($name, $value, $this->plugin);

        // Some admin settings affect course modinfo
        if ($this->affectsmodinfo) {
            // Clear course cache for all courses
            rebuild_course_cache(0, true);
        }

        $this->add_to_config_log($name, $oldvalue, $value);

        return true; // BC only
    }

    /**
     * Log config changes if necessary.
     * @param string $name
     * @param string $oldvalue
     * @param string $value
     */
    protected function add_to_config_log($name, $oldvalue, $value) {
        add_to_config_log($name, $oldvalue, $value, $this->plugin);
    }

    /**
     * Returns current value of this setting
     * @return mixed array or string depending on instance, NULL means not set yet
     */
    public abstract function get_setting();

    /**
     * Returns default setting if exists
     * @return mixed array or string depending on instance; NULL means no default, user must supply
     */
    public function get_defaultsetting() {
        $adminroot =  admin_get_root(false, false);
        if (!empty($adminroot->custom_defaults)) {
            $plugin = is_null($this->plugin) ? 'moodle' : $this->plugin;
            if (isset($adminroot->custom_defaults[$plugin])) {
                if (array_key_exists($this->name, $adminroot->custom_defaults[$plugin])) { // null is valid value here ;-)
                    return $adminroot->custom_defaults[$plugin][$this->name];
                }
            }
        }
        return $this->defaultsetting;
    }

    /**
     * Store new setting
     *
     * @param mixed $data string or array, must not be NULL
     * @return string empty string if ok, string error message otherwise
     */
    public abstract function write_setting($data);

    /**
     * Return part of form with setting
     * This function should always be overwritten
     *
     * @param mixed $data array or string depending on setting
     * @param string $query
     * @return string
     */
    public function output_html($data, $query='') {
    // should be overridden
        return;
    }

    /**
     * Function called if setting updated - cleanup, cache reset, etc.
     * @param string $functionname Sets the function name
     * @return void
     */
    public function set_updatedcallback($functionname) {
        $this->updatedcallback = $functionname;
    }

    /**
     * Execute postupdatecallback if necessary.
     * @param mixed $original original value before write_setting()
     * @return bool true if changed, false if not.
     */
    public function post_write_settings($original) {
        // Comparison must work for arrays too.
        if (serialize($original) === serialize($this->get_setting())) {
            return false;
        }

        $callbackfunction = $this->updatedcallback;
        if (!empty($callbackfunction) and is_callable($callbackfunction)) {
            $callbackfunction($this->get_full_name());
        }
        return true;
    }

    /**
     * Is setting related to query text - used when searching
     * @param string $query
     * @return bool
     */
    public function is_related($query) {
        if (strpos(strtolower($this->name), $query) !== false) {
            return true;
        }
        if (strpos(core_text::strtolower($this->visiblename), $query) !== false) {
            return true;
        }
        if (strpos(core_text::strtolower($this->description), $query) !== false) {
            return true;
        }
        $current = $this->get_setting();
        if (!is_null($current)) {
            if (is_string($current)) {
                if (strpos(core_text::strtolower($current), $query) !== false) {
                    return true;
                }
            }
        }
        $default = $this->get_defaultsetting();
        if (!is_null($default)) {
            if (is_string($default)) {
                if (strpos(core_text::strtolower($default), $query) !== false) {
                    return true;
                }
            }
        }
        return false;
    }

    /**
     * Get whether this should be displayed in LTR mode.
     *
     * @return bool|null
     */
    public function get_force_ltr() {
        return $this->forceltr;
    }

    /**
     * Set whether to force LTR or not.
     *
     * @param bool $value True when forced, false when not force, null when unknown.
     */
    public function set_force_ltr($value) {
        $this->forceltr = $value;
    }

    /**
     * Add a setting to the list of those that could cause this one to be hidden
     * @param string $dependenton
     */
    public function add_dependent_on($dependenton) {
        $this->dependenton[] = $dependenton;
    }

    /**
     * Get a list of the settings that could cause this one to be hidden.
     * @return array
     */
    public function get_dependent_on() {
        return $this->dependenton;
    }

    /**
     * Whether this setting uses a custom form control.
     * This function is especially useful to decide if we should render a label element for this setting or not.
     *
     * @return bool
     */
    public function has_custom_form_control(): bool {
        return $this->customcontrol;
    }
}

/**
 * An additional option that can be applied to an admin setting.
 * The currently supported options are 'ADVANCED', 'LOCKED' and 'REQUIRED'.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_flag {
    /** @var bool Flag to indicate if this option can be toggled for this setting */
    private $enabled = false;
    /** @var bool Flag to indicate if this option defaults to true or false */
    private $default = false;
    /** @var string Short string used to create setting name - e.g. 'adv' */
    private $shortname = '';
    /** @var string String used as the label for this flag */
    private $displayname = '';
    /** @const Checkbox for this flag is displayed in admin page */
    const ENABLED = true;
    /** @const Checkbox for this flag is not displayed in admin page */
    const DISABLED = false;

    /**
     * Constructor
     *
     * @param bool $enabled Can this option can be toggled.
     *                      Should be one of admin_setting_flag::ENABLED or admin_setting_flag::DISABLED.
     * @param bool $default The default checked state for this setting option.
     * @param string $shortname The shortname of this flag. Currently supported flags are 'locked' and 'adv'
     * @param string $displayname The displayname of this flag. Used as a label for the flag.
     */
    public function __construct($enabled, $default, $shortname, $displayname) {
        $this->shortname = $shortname;
        $this->displayname = $displayname;
        $this->set_options($enabled, $default);
    }

    /**
     * Update the values of this setting options class
     *
     * @param bool $enabled Can this option can be toggled.
     *                      Should be one of admin_setting_flag::ENABLED or admin_setting_flag::DISABLED.
     * @param bool $default The default checked state for this setting option.
     */
    public function set_options($enabled, $default) {
        $this->enabled = $enabled;
        $this->default = $default;
    }

    /**
     * Should this option appear in the interface and be toggleable?
     *
     * @return bool Is it enabled?
     */
    public function is_enabled() {
        return $this->enabled;
    }

    /**
     * Should this option be checked by default?
     *
     * @return bool Is it on by default?
     */
    public function get_default() {
        return $this->default;
    }

    /**
     * Return the short name for this flag. e.g. 'adv' or 'locked'
     *
     * @return string
     */
    public function get_shortname() {
        return $this->shortname;
    }

    /**
     * Return the display name for this flag. e.g. 'Advanced' or 'Locked'
     *
     * @return string
     */
    public function get_displayname() {
        return $this->displayname;
    }

    /**
     * Save the submitted data for this flag - or set it to the default if $data is null.
     *
     * @param admin_setting $setting - The admin setting for this flag
     * @param array $data - The data submitted from the form or null to set the default value for new installs.
     * @return bool
     */
    public function write_setting_flag(admin_setting $setting, $data) {
        $result = true;
        if ($this->is_enabled()) {
            if (!isset($data)) {
                $value = $this->get_default();
            } else {
                $value = !empty($data[$setting->get_full_name() . '_' . $this->get_shortname()]);
            }
            $result = $setting->config_write($setting->name . '_' . $this->get_shortname(), $value);
        }

        return $result;

    }

    /**
     * Output the checkbox for this setting flag. Should only be called if the flag is enabled.
     *
     * @param admin_setting $setting - The admin setting for this flag
     * @return string - The html for the checkbox.
     */
    public function output_setting_flag(admin_setting $setting) {
        global $OUTPUT;

        $value = $setting->get_setting_flag_value($this);

        $context = new stdClass();
        $context->id = $setting->get_id() . '_' . $this->get_shortname();
        $context->name = $setting->get_full_name() .  '_' . $this->get_shortname();
        $context->value = 1;
        $context->checked = $value ? true : false;
        $context->label = $this->get_displayname();

        return $OUTPUT->render_from_template('core_admin/setting_flag', $context);
    }
}


/**
 * No setting - just heading and text.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_heading extends admin_setting {

    /**
     * not a setting, just text
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $heading heading
     * @param string $information text in box
     */
    public function __construct($name, $heading, $information) {
        $this->nosave = true;
        parent::__construct($name, $heading, $information, '');
    }

    /**
     * Always returns true
     * @return bool Always returns true
     */
    public function get_setting() {
        return true;
    }

    /**
     * Always returns true
     * @return bool Always returns true
     */
    public function get_defaultsetting() {
        return true;
    }

    /**
     * Never write settings
     * @return string Always returns an empty string
     */
    public function write_setting($data) {
    // do not write any setting
        return '';
    }

    /**
     * Returns an HTML string
     * @return string Returns an HTML string
     */
    public function output_html($data, $query='') {
        global $OUTPUT;
        $context = new stdClass();
        $context->title = $this->visiblename;
        $context->description = $this->description;
        $context->descriptionformatted = highlight($query, markdown_to_html($this->description));
        return $OUTPUT->render_from_template('core_admin/setting_heading', $context);
    }
}

/**
 * No setting - just name and description in same row.
 *
 * @copyright 2018 onwards Amaia Anabitarte
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_description extends admin_setting {

    /**
     * Not a setting, just text
     *
     * @param string $name
     * @param string $visiblename
     * @param string $description
     */
    public function __construct($name, $visiblename, $description) {
        $this->nosave = true;
        parent::__construct($name, $visiblename, $description, '');
    }

    /**
     * Always returns true
     *
     * @return bool Always returns true
     */
    public function get_setting() {
        return true;
    }

    /**
     * Always returns true
     *
     * @return bool Always returns true
     */
    public function get_defaultsetting() {
        return true;
    }

    /**
     * Never write settings
     *
     * @param mixed $data Gets converted to str for comparison against yes value
     * @return string Always returns an empty string
     */
    public function write_setting($data) {
        // Do not write any setting.
        return '';
    }

    /**
     * Returns an HTML string
     *
     * @param string $data
     * @param string $query
     * @return string Returns an HTML string
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        $context = new stdClass();
        $context->title = $this->visiblename;
        $context->description = $this->description;

        return $OUTPUT->render_from_template('core_admin/setting_description', $context);
    }
}


/**
 * The most flexible setting, the user enters text.
 *
 * This type of field should be used for config settings which are using
 * English words and are not localised (passwords, database name, list of values, ...).
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configtext extends admin_setting {

    /** @var mixed int means PARAM_XXX type, string is a allowed format in regex */
    public $paramtype;
    /** @var int default field size */
    public $size;

    /**
     * Config text constructor
     *
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string $defaultsetting
     * @param mixed $paramtype int means PARAM_XXX type, string is a allowed format in regex
     * @param int $size default field size
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $paramtype=PARAM_RAW, $size=null) {
        $this->paramtype = $paramtype;
        if (!is_null($size)) {
            $this->size  = $size;
        } else {
            $this->size  = ($paramtype === PARAM_INT) ? 5 : 30;
        }
        parent::__construct($name, $visiblename, $description, $defaultsetting);
    }

    /**
     * Get whether this should be displayed in LTR mode.
     *
     * Try to guess from the PARAM type unless specifically set.
     */
    public function get_force_ltr() {
        $forceltr = parent::get_force_ltr();
        if ($forceltr === null) {
            return !is_rtl_compatible($this->paramtype);
        }
        return $forceltr;
    }

    /**
     * Return the setting
     *
     * @return mixed returns config if successful else null
     */
    public function get_setting() {
        return $this->config_read($this->name);
    }

    public function write_setting($data) {
        if ($this->paramtype === PARAM_INT and $data === '') {
        // do not complain if '' used instead of 0
            $data = 0;
        }
        // $data is a string
        $validated = $this->validate($data);
        if ($validated !== true) {
            return $validated;
        }
        return ($this->config_write($this->name, $data) ? '' : get_string('errorsetting', 'admin'));
    }

    /**
     * Validate data before storage
     * @param string data
     * @return mixed true if ok string if error found
     */
    public function validate($data) {
        // allow paramtype to be a custom regex if it is the form of /pattern/
        if (preg_match('#^/.*/$#', $this->paramtype)) {
            if (preg_match($this->paramtype, $data)) {
                return true;
            } else {
                return get_string('validateerror', 'admin');
            }

        } else if ($this->paramtype === PARAM_RAW) {
            return true;

        } else {
            $cleaned = clean_param($data, $this->paramtype);
            if ("$data" === "$cleaned") { // implicit conversion to string is needed to do exact comparison
                return true;
            } else {
                return get_string('validateerror', 'admin');
            }
        }
    }

    /**
     * Return an XHTML string for the setting
     * @return string Returns an XHTML string
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        $default = $this->get_defaultsetting();
        $context = (object) [
            'size' => $this->size,
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'value' => $data,
            'forceltr' => $this->get_force_ltr(),
        ];
        $element = $OUTPUT->render_from_template('core_admin/setting_configtext', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $default, $query);
    }
}

/**
 * Text input with a maximum length constraint.
 *
 * @copyright 2015 onwards Ankit Agarwal
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configtext_with_maxlength extends admin_setting_configtext {

    /** @var int maximum number of chars allowed. */
    protected $maxlength;

    /**
     * Config text constructor
     *
     * @param string $name unique ascii name, either 'mysetting' for settings that in config,
     *                     or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string $defaultsetting
     * @param mixed $paramtype int means PARAM_XXX type, string is a allowed format in regex
     * @param int $size default field size
     * @param mixed $maxlength int maxlength allowed, 0 for infinite.
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $paramtype=PARAM_RAW,
                                $size=null, $maxlength = 0) {
        $this->maxlength = $maxlength;
        parent::__construct($name, $visiblename, $description, $defaultsetting, $paramtype, $size);
    }

    /**
     * Validate data before storage
     *
     * @param string $data data
     * @return mixed true if ok string if error found
     */
    public function validate($data) {
        $parentvalidation = parent::validate($data);
        if ($parentvalidation === true) {
            if ($this->maxlength > 0) {
                // Max length check.
                $length = core_text::strlen($data);
                if ($length > $this->maxlength) {
                    return get_string('maximumchars', 'moodle',  $this->maxlength);
                }
                return true;
            } else {
                return true; // No max length check needed.
            }
        } else {
            return $parentvalidation;
        }
    }
}

/**
 * General text area without html editor.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configtextarea extends admin_setting_configtext {
    private $rows;
    private $cols;

    /**
     * @param string $name
     * @param string $visiblename
     * @param string $description
     * @param mixed $defaultsetting string or array
     * @param mixed $paramtype
     * @param string $cols The number of columns to make the editor
     * @param string $rows The number of rows to make the editor
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $paramtype=PARAM_RAW, $cols='60', $rows='8') {
        $this->rows = $rows;
        $this->cols = $cols;
        parent::__construct($name, $visiblename, $description, $defaultsetting, $paramtype);
    }

    /**
     * Returns an XHTML string for the editor
     *
     * @param string $data
     * @param string $query
     * @return string XHTML string for the editor
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        $default = $this->get_defaultsetting();
        $defaultinfo = $default;
        if (!is_null($default) and $default !== '') {
            $defaultinfo = "\n".$default;
        }

        $context = (object) [
            'cols' => $this->cols,
            'rows' => $this->rows,
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'value' => $data,
            'forceltr' => $this->get_force_ltr(),
        ];
        $element = $OUTPUT->render_from_template('core_admin/setting_configtextarea', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $defaultinfo, $query);
    }
}

/**
 * General text area with html editor.
 */
class admin_setting_confightmleditor extends admin_setting_configtextarea {

    /**
     * @param string $name
     * @param string $visiblename
     * @param string $description
     * @param mixed $defaultsetting string or array
     * @param mixed $paramtype
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $paramtype=PARAM_RAW, $cols='60', $rows='8') {
        parent::__construct($name, $visiblename, $description, $defaultsetting, $paramtype, $cols, $rows);
        $this->set_force_ltr(false);
        editors_head_setup();
    }

    /**
     * Returns an XHTML string for the editor
     *
     * @param string $data
     * @param string $query
     * @return string XHTML string for the editor
     */
    public function output_html($data, $query='') {
        $editor = editors_get_preferred_editor(FORMAT_HTML);
        $editor->set_text($data);
        $editor->use_editor($this->get_id(), array('noclean'=>true));
        return parent::output_html($data, $query);
    }

    /**
     * Checks if data has empty html.
     *
     * @param string $data
     * @return string Empty when no errors.
     */
    public function write_setting($data) {
        if (trim(html_to_text($data)) === '') {
            $data = '';
        }
        return parent::write_setting($data);
    }
}


/**
 * Password field, allows unmasking of password
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configpasswordunmask extends admin_setting_configtext {

    /**
     * Constructor
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string $defaultsetting default password
     */
    public function __construct($name, $visiblename, $description, $defaultsetting) {
        parent::__construct($name, $visiblename, $description, $defaultsetting, PARAM_RAW, 30);
    }

    /**
     * Log config changes if necessary.
     * @param string $name
     * @param string $oldvalue
     * @param string $value
     */
    protected function add_to_config_log($name, $oldvalue, $value) {
        if ($value !== '') {
            $value = '********';
        }
        if ($oldvalue !== '' and $oldvalue !== null) {
            $oldvalue = '********';
        }
        parent::add_to_config_log($name, $oldvalue, $value);
    }

    /**
     * Returns HTML for the field.
     *
     * @param   string  $data       Value for the field
     * @param   string  $query      Passed as final argument for format_admin_setting
     * @return  string              Rendered HTML
     */
    public function output_html($data, $query='') {
        global $OUTPUT, $CFG;
        $forced = false;
        if (empty($this->plugin)) {
            if (array_key_exists($this->name, $CFG->config_php_settings)) {
                $forced = true;
            }
        } else {
            if (array_key_exists($this->plugin, $CFG->forced_plugin_settings)
                and array_key_exists($this->name, $CFG->forced_plugin_settings[$this->plugin])) {
                $forced = true;
            }
        }
        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'size' => $this->size,
            'value' => $forced ? null : $data,
            'forceltr' => $this->get_force_ltr(),
            'forced' => $forced
        ];
        $element = $OUTPUT->render_from_template('core_admin/setting_configpasswordunmask', $context);
        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', null, $query);
    }
}

/**
 * Password field, allows unmasking of password, with an advanced checkbox that controls an additional $name.'_adv' setting.
 *
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @copyright 2018 Paul Holden (pholden@greenhead.ac.uk)
 */
class admin_setting_configpasswordunmask_with_advanced extends admin_setting_configpasswordunmask {

    /**
     * Constructor
     *
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param array $defaultsetting ('value'=>string, 'adv'=>bool)
     */
    public function __construct($name, $visiblename, $description, $defaultsetting) {
        parent::__construct($name, $visiblename, $description, $defaultsetting['value']);
        $this->set_advanced_flag_options(admin_setting_flag::ENABLED, !empty($defaultsetting['adv']));
    }
}

/**
 * Empty setting used to allow flags (advanced) on settings that can have no sensible default.
 * Note: Only advanced makes sense right now - locked does not.
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configempty extends admin_setting_configtext {

    /**
     * @param string $name
     * @param string $visiblename
     * @param string $description
     */
    public function __construct($name, $visiblename, $description) {
        parent::__construct($name, $visiblename, $description, '', PARAM_RAW);
    }

    /**
     * Returns an XHTML string for the hidden field
     *
     * @param string $data
     * @param string $query
     * @return string XHTML string for the editor
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name()
        ];
        $element = $OUTPUT->render_from_template('core_admin/setting_configempty', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', get_string('none'), $query);
    }
}


/**
 * Path to directory
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configfile extends admin_setting_configtext {
    /**
     * Constructor
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string $defaultdirectory default directory location
     */
    public function __construct($name, $visiblename, $description, $defaultdirectory) {
        parent::__construct($name, $visiblename, $description, $defaultdirectory, PARAM_RAW, 50);
    }

    /**
     * Returns XHTML for the field
     *
     * Returns XHTML for the field and also checks whether the file
     * specified in $data exists using file_exists()
     *
     * @param string $data File name and path to use in value attr
     * @param string $query
     * @return string XHTML field
     */
    public function output_html($data, $query='') {
        global $CFG, $OUTPUT;

        $default = $this->get_defaultsetting();
        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'size' => $this->size,
            'value' => $data,
            'showvalidity' => !empty($data),
            'valid' => $data && file_exists($data),
            'readonly' => !empty($CFG->preventexecpath),
            'forceltr' => $this->get_force_ltr(),
        ];

        if ($context->readonly) {
            $this->visiblename .= '<div class="alert alert-info">'.get_string('execpathnotallowed', 'admin').'</div>';
        }

        $element = $OUTPUT->render_from_template('core_admin/setting_configfile', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $default, $query);
    }

    /**
     * Checks if execpatch has been disabled in config.php
     */
    public function write_setting($data) {
        global $CFG;
        if (!empty($CFG->preventexecpath)) {
            if ($this->get_setting() === null) {
                // Use default during installation.
                $data = $this->get_defaultsetting();
                if ($data === null) {
                    $data = '';
                }
            } else {
                return '';
            }
        }
        return parent::write_setting($data);
    }

}


/**
 * Path to executable file
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configexecutable extends admin_setting_configfile {

    /**
     * Returns an XHTML field
     *
     * @param string $data This is the value for the field
     * @param string $query
     * @return string XHTML field
     */
    public function output_html($data, $query='') {
        global $CFG, $OUTPUT;
        $default = $this->get_defaultsetting();
        require_once("$CFG->libdir/filelib.php");

        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'size' => $this->size,
            'value' => $data,
            'showvalidity' => !empty($data),
            'valid' => $data && file_exists($data) && !is_dir($data) && file_is_executable($data),
            'readonly' => !empty($CFG->preventexecpath),
            'forceltr' => $this->get_force_ltr()
        ];

        if (!empty($CFG->preventexecpath)) {
            $this->visiblename .= '<div class="alert alert-info">'.get_string('execpathnotallowed', 'admin').'</div>';
        }

        $element = $OUTPUT->render_from_template('core_admin/setting_configexecutable', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $default, $query);
    }
}


/**
 * Path to directory
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configdirectory extends admin_setting_configfile {

    /**
     * Returns an XHTML field
     *
     * @param string $data This is the value for the field
     * @param string $query
     * @return string XHTML
     */
    public function output_html($data, $query='') {
        global $CFG, $OUTPUT;
        $default = $this->get_defaultsetting();

        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'size' => $this->size,
            'value' => $data,
            'showvalidity' => !empty($data),
            'valid' => $data && file_exists($data) && is_dir($data),
            'readonly' => !empty($CFG->preventexecpath),
            'forceltr' => $this->get_force_ltr()
        ];

        if (!empty($CFG->preventexecpath)) {
            $this->visiblename .= '<div class="alert alert-info">'.get_string('execpathnotallowed', 'admin').'</div>';
        }

        $element = $OUTPUT->render_from_template('core_admin/setting_configdirectory', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $default, $query);
    }
}


/**
 * Checkbox
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configcheckbox extends admin_setting {
    /** @var string Value used when checked */
    public $yes;
    /** @var string Value used when not checked */
    public $no;

    /**
     * Constructor
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string $defaultsetting
     * @param string $yes value used when checked
     * @param string $no value used when not checked
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $yes='1', $no='0') {
        parent::__construct($name, $visiblename, $description, $defaultsetting);
        $this->yes = (string)$yes;
        $this->no  = (string)$no;
    }

    /**
     * Retrieves the current setting using the objects name
     *
     * @return string
     */
    public function get_setting() {
        return $this->config_read($this->name);
    }

    /**
     * Sets the value for the setting
     *
     * Sets the value for the setting to either the yes or no values
     * of the object by comparing $data to yes
     *
     * @param mixed $data Gets converted to str for comparison against yes value
     * @return string empty string or error
     */
    public function write_setting($data) {
        if ((string)$data === $this->yes) { // convert to strings before comparison
            $data = $this->yes;
        } else {
            $data = $this->no;
        }
        return ($this->config_write($this->name, $data) ? '' : get_string('errorsetting', 'admin'));
    }

    /**
     * Returns an XHTML checkbox field
     *
     * @param string $data If $data matches yes then checkbox is checked
     * @param string $query
     * @return string XHTML field
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
            'no' => $this->no,
            'value' => $this->yes,
            'checked' => (string) $data === $this->yes,
        ];

        $default = $this->get_defaultsetting();
        if (!is_null($default)) {
            if ((string)$default === $this->yes) {
                $defaultinfo = get_string('checkboxyes', 'admin');
            } else {
                $defaultinfo = get_string('checkboxno', 'admin');
            }
        } else {
            $defaultinfo = NULL;
        }

        $element = $OUTPUT->render_from_template('core_admin/setting_configcheckbox', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, true, '', $defaultinfo, $query);
    }
}


/**
 * Multiple checkboxes, each represents different value, stored in csv format
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configmulticheckbox extends admin_setting {
    /** @var array Array of choices value=>label */
    public $choices;

    /**
     * Constructor: uses parent::__construct
     *
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param array $defaultsetting array of selected
     * @param array $choices array of $value=>$label for each checkbox
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $choices) {
        $this->choices = $choices;
        parent::__construct($name, $visiblename, $description, $defaultsetting);
    }

    /**
     * This public function may be used in ancestors for lazy loading of choices
     *
     * @todo Check if this function is still required content commented out only returns true
     * @return bool true if loaded, false if error
     */
    public function load_choices() {
        /*
        if (is_array($this->choices)) {
            return true;
        }
        .... load choices here
        */
        return true;
    }

    /**
     * Is setting related to query text - used when searching
     *
     * @param string $query
     * @return bool true on related, false on not or failure
     */
    public function is_related($query) {
        if (!$this->load_choices() or empty($this->choices)) {
            return false;
        }
        if (parent::is_related($query)) {
            return true;
        }

        foreach ($this->choices as $desc) {
            if (strpos(core_text::strtolower($desc), $query) !== false) {
                return true;
            }
        }
        return false;
    }

    /**
     * Returns the current setting if it is set
     *
     * @return mixed null if null, else an array
     */
    public function get_setting() {
        $result = $this->config_read($this->name);

        if (is_null($result)) {
            return NULL;
        }
        if ($result === '') {
            return array();
        }
        $enabled = explode(',', $result);
        $setting = array();
        foreach ($enabled as $option) {
            $setting[$option] = 1;
        }
        return $setting;
    }

    /**
     * Saves the setting(s) provided in $data
     *
     * @param array $data An array of data, if not array returns empty str
     * @return mixed empty string on useless data or bool true=success, false=failed
     */
    public function write_setting($data) {
        if (!is_array($data)) {
            return ''; // ignore it
        }
        if (!$this->load_choices() or empty($this->choices)) {
            return '';
        }
        unset($data['xxxxx']);
        $result = array();
        foreach ($data as $key => $value) {
            if ($value and array_key_exists($key, $this->choices)) {
                $result[] = $key;
            }
        }
        return $this->config_write($this->name, implode(',', $result)) ? '' : get_string('errorsetting', 'admin');
    }

    /**
     * Returns XHTML field(s) as required by choices
     *
     * Relies on data being an array should data ever be another valid vartype with
     * acceptable value this may cause a warning/error
     * if (!is_array($data)) would fix the problem
     *
     * @todo Add vartype handling to ensure $data is an array
     *
     * @param array $data An array of checked values
     * @param string $query
     * @return string XHTML field
     */
    public function output_html($data, $query='') {
        global $OUTPUT;

        if (!$this->load_choices() or empty($this->choices)) {
            return '';
        }

        $default = $this->get_defaultsetting();
        if (is_null($default)) {
            $default = array();
        }
        if (is_null($data)) {
            $data = array();
        }

        $context = (object) [
            'id' => $this->get_id(),
            'name' => $this->get_full_name(),
        ];

        $options = array();
        $defaults = array();
        foreach ($this->choices as $key => $description) {
            if (!empty($default[$key])) {
                $defaults[] = $description;
            }

            $options[] = [
                'key' => $key,
                'checked' => !empty($data[$key]),
                'label' => highlightfast($query, $description)
            ];
        }

        if (is_null($default)) {
            $defaultinfo = null;
        } else if (!empty($defaults)) {
            $defaultinfo = implode(', ', $defaults);
        } else {
            $defaultinfo = get_string('none');
        }

        $context->options = $options;
        $context->hasoptions = !empty($options);

        $element = $OUTPUT->render_from_template('core_admin/setting_configmulticheckbox', $context);

        return format_admin_setting($this, $this->visiblename, $element, $this->description, false, '', $defaultinfo, $query);

    }
}


/**
 * Multiple checkboxes 2, value stored as string 00101011
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configmulticheckbox2 extends admin_setting_configmulticheckbox {

    /**
     * Returns the setting if set
     *
     * @return mixed null if not set, else an array of set settings
     */
    public function get_setting() {
        $result = $this->config_read($this->name);
        if (is_null($result)) {
            return NULL;
        }
        if (!$this->load_choices()) {
            return NULL;
        }
        $result = str_pad($result, count($this->choices), '0');
        $result = preg_split('//', $result, -1, PREG_SPLIT_NO_EMPTY);
        $setting = array();
        foreach ($this->choices as $key=>$unused) {
            $value = array_shift($result);
            if ($value) {
                $setting[$key] = 1;
            }
        }
        return $setting;
    }

    /**
     * Save setting(s) provided in $data param
     *
     * @param array $data An array of settings to save
     * @return mixed empty string for bad data or bool true=>success, false=>error
     */
    public function write_setting($data) {
        if (!is_array($data)) {
            return ''; // ignore it
        }
        if (!$this->load_choices() or empty($this->choices)) {
            return '';
        }
        $result = '';
        foreach ($this->choices as $key=>$unused) {
            if (!empty($data[$key])) {
                $result .= '1';
            } else {
                $result .= '0';
            }
        }
        return $this->config_write($this->name, $result) ? '' : get_string('errorsetting', 'admin');
    }
}


/**
 * Select one value from list
 *
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class admin_setting_configselect extends admin_setting {
    /** @var array Array of choices value=>label */
    public $choices;
    /** @var array Array of choices grouped using optgroups */
    public $optgroups;
    /** @var callable|null Loader function for choices */
    protected $choiceloader = null;
    /** @var callable|null Validation function */
    protected $validatefunction = null;

    /**
     * Constructor.
     *
     * If you want to lazy-load the choices, pass a callback function that returns a choice
     * array for the $choices parameter.
     *
     * @param string $name unique ascii name, either 'mysetting' for settings that in config, or 'myplugin/mysetting' for ones in config_plugins.
     * @param string $visiblename localised
     * @param string $description long localised info
     * @param string|int $defaultsetting
     * @param array|callable|null $choices array of $value=>$label for each selection, or callback
     */
    public function __construct($name, $visiblename, $description, $defaultsetting, $choices) {
        // Look for optgroup and single options.
        if (is_array($choices)) {
            $this->choices = [];
            foreach ($choices as $key => $val) {
                if (is_array($val)) {
                    $this->optgroups[$key] = $val;
                    $this->choices = array_merge($this->choices, $val);
                } else {
                    $this->choices[$key] = $val;
                }
            }
        }
        if (is_callable($choices)) {
            $this->choiceloader = $choices;
        }

        parent::__construct($name, $visiblename, $description, $defaultsetting);
    }

    /**
     * Sets a validate function.
     *
     * The callback will be passed one parameter, the new setting value, and should return either
     * an empty string '' if the value is OK, or an error message if not.
     *
     * @param callable|null $validatefunction Validate function or null to clear
     * @since Moodle 3.10
     */
    public function set_validate_function(?callable $validatefunction = null) {
        $this->validatefunction = $validatefunction;
    }

    /**
     * This function may be used in ancestors for lazy loading of choices
     *
     * Override this method if loading of choices is expensive, such
     * as when it requires multiple db requests.
     *
     * @return bool true if loaded, false if error
     */
    public function load_choices() {
        if ($this->choiceloader) {
            if (!is_array($this->choices)) {
                $this->choices = call_user_func($this->choiceloader);
            }
            return true;
        }
        return true;
    }

    /**
     * Check if this is $query is related to a choice
     *
     * @param string $query
     * @return bool true if related, false if not
     */
    public function is_related($query) {
        if (parent::is_related($query)) {
            return true;
        }
        if (!$this->load_choices()) {
            return false;
        }
        foreach ($this->choices as $key=>$value) {
            if (strpos(core_text::strtolower($key), $query) !== false) {
                return true;
            }
            if (strpos(core_text::strtolower($value), $query) !== false) {
                return true;
            }
        }
        return false;
    }

    /**
     * Return the setting
     *
     * @return mixed returns config if successful else null
     */
    public function get_setting() {
        return $this->config_read($this->name);
    }

    /**
     * Save a setting
     *
     * @param string $data
     * @return string empty of error string
     */
    public function write_setting($data) {
        if (!$this->load_choices() or empty($this->choices)) {
            return '';
        }
        if (!array_key_exists($data, $this->choices)) {
            return ''; // ignore it
        }

        // Validate the new setting.
        $error = $this->validate_setting($data);
        if ($error) {
            return $error;
        }

        return ($this->config_write($this->name, $data) ? '' : get_string('errorsetting', 'admin'));
    }

    /**
     * Validate the setting. This uses the callback function if provided; subclasses could override
     * to carry out validation directly in the class.
     *
     * @param string $data New value being set
     * @return string Empty string if valid, or error message text
     * @since Moodle 3.10
     */
    protected function validate_setting(string $data): string {
        // If validation function is specified, call it now.
        if ($this->validatefunction) {
            return call_user_func($this->validatefunction, $data);
        } else {
            return '';
        }
    }

    /**
     * Returns XHTML select field
     *
     * Ensure the options are loaded, and generate the XHTML for the select
     * element and any warning message. Separating this out from output_html
     * makes it easier to subclass this class.
     *
     * @param string $data the option to show as selected.
     * @param string $current the currently selected option in the database, null if none.
     * @param string $default the default selected option.