/lib/coursecatlib.php

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<?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/>.

/**
 * Contains class coursecat reponsible for course category operations
 *
 * @package    core
 * @subpackage course
 * @copyright  2013 Marina Glancy
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

/**
 * Class to store, cache, render and manage course category
 *
 * @property-read int $id
 * @property-read string $name
 * @property-read string $idnumber
 * @property-read string $description
 * @property-read int $descriptionformat
 * @property-read int $parent
 * @property-read int $sortorder
 * @property-read int $coursecount
 * @property-read int $visible
 * @property-read int $visibleold
 * @property-read int $timemodified
 * @property-read int $depth
 * @property-read string $path
 * @property-read string $theme
 *
 * @package    core
 * @subpackage course
 * @copyright  2013 Marina Glancy
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class coursecat implements renderable, cacheable_object, IteratorAggregate {
    /** @var coursecat stores pseudo category with id=0. Use coursecat::get(0) to retrieve */
    protected static $coursecat0;

    /** Do not fetch course contacts more often than once per hour. */
    const CACHE_COURSE_CONTACTS_TTL = 3600;

    /** @var array list of all fields and their short name and default value for caching */
    protected static $coursecatfields = array(
        'id' => array('id', 0),
        'name' => array('na', ''),
        'idnumber' => array('in', null),
        'description' => null, // Not cached.
        'descriptionformat' => null, // Not cached.
        'parent' => array('pa', 0),
        'sortorder' => array('so', 0),
        'coursecount' => array('cc', 0),
        'visible' => array('vi', 1),
        'visibleold' => null, // Not cached.
        'timemodified' => null, // Not cached.
        'depth' => array('dh', 1),
        'path' => array('ph', null),
        'theme' => null, // Not cached.
    );

    /** @var int */
    protected $id;

    /** @var string */
    protected $name = '';

    /** @var string */
    protected $idnumber = null;

    /** @var string */
    protected $description = false;

    /** @var int */
    protected $descriptionformat = false;

    /** @var int */
    protected $parent = 0;

    /** @var int */
    protected $sortorder = 0;

    /** @var int */
    protected $coursecount = false;

    /** @var int */
    protected $visible = 1;

    /** @var int */
    protected $visibleold = false;

    /** @var int */
    protected $timemodified = false;

    /** @var int */
    protected $depth = 0;

    /** @var string */
    protected $path = '';

    /** @var string */
    protected $theme = false;

    /** @var bool */
    protected $fromcache;

    /** @var bool */
    protected $hasmanagecapability = null;

    /**
     * Magic setter method, we do not want anybody to modify properties from the outside
     *
     * @param string $name
     * @param mixed $value
     */
    public function __set($name, $value) {
        debugging('Can not change coursecat instance properties!', DEBUG_DEVELOPER);
    }

    /**
     * Magic method getter, redirects to read only values. Queries from DB the fields that were not cached
     *
     * @param string $name
     * @return mixed
     */
    public function __get($name) {
        global $DB;
        if (array_key_exists($name, self::$coursecatfields)) {
            if ($this->$name === false) {
                // Property was not retrieved from DB, retrieve all not retrieved fields.
                $notretrievedfields = array_diff_key(self::$coursecatfields, array_filter(self::$coursecatfields));
                $record = $DB->get_record('course_categories', array('id' => $this->id),
                        join(',', array_keys($notretrievedfields)), MUST_EXIST);
                foreach ($record as $key => $value) {
                    $this->$key = $value;
                }
            }
            return $this->$name;
        }
        debugging('Invalid coursecat property accessed! '.$name, DEBUG_DEVELOPER);
        return null;
    }

    /**
     * Full support for isset on our magic read only properties.
     *
     * @param string $name
     * @return bool
     */
    public function __isset($name) {
        if (array_key_exists($name, self::$coursecatfields)) {
            return isset($this->$name);
        }
        return false;
    }

    /**
     * All properties are read only, sorry.
     *
     * @param string $name
     */
    public function __unset($name) {
        debugging('Can not unset coursecat instance properties!', DEBUG_DEVELOPER);
    }

    /**
     * Create an iterator because magic vars can't be seen by 'foreach'.
     *
     * implementing method from interface IteratorAggregate
     *
     * @return ArrayIterator
     */
    public function getIterator() {
        $ret = array();
        foreach (self::$coursecatfields as $property => $unused) {
            if ($this->$property !== false) {
                $ret[$property] = $this->$property;
            }
        }
        return new ArrayIterator($ret);
    }

    /**
     * Constructor
     *
     * Constructor is protected, use coursecat::get($id) to retrieve category
     *
     * @param stdClass $record record from DB (may not contain all fields)
     * @param bool $fromcache whether it is being restored from cache
     */
    protected function __construct(stdClass $record, $fromcache = false) {
        context_helper::preload_from_record($record);
        foreach ($record as $key => $val) {
            if (array_key_exists($key, self::$coursecatfields)) {
                $this->$key = $val;
            }
        }
        $this->fromcache = $fromcache;
    }

    /**
     * Returns coursecat object for requested category
     *
     * If category is not visible to user it is treated as non existing
     * unless $alwaysreturnhidden is set to true
     *
     * If id is 0, the pseudo object for root category is returned (convenient
     * for calling other functions such as get_children())
     *
     * @param int $id category id
     * @param int $strictness whether to throw an exception (MUST_EXIST) or
     *     return null (IGNORE_MISSING) in case the category is not found or
     *     not visible to current user
     * @param bool $alwaysreturnhidden set to true if you want an object to be
     *     returned even if this category is not visible to the current user
     *     (category is hidden and user does not have
     *     'moodle/category:viewhiddencategories' capability). Use with care!
     * @return null|coursecat
     * @throws moodle_exception
     */
    public static function get($id, $strictness = MUST_EXIST, $alwaysreturnhidden = false) {
        if (!$id) {
            if (!isset(self::$coursecat0)) {
                $record = new stdClass();
                $record->id = 0;
                $record->visible = 1;
                $record->depth = 0;
                $record->path = '';
                self::$coursecat0 = new coursecat($record);
            }
            return self::$coursecat0;
        }
        $coursecatrecordcache = cache::make('core', 'coursecatrecords');
        $coursecat = $coursecatrecordcache->get($id);
        if ($coursecat === false) {
            if ($records = self::get_records('cc.id = :id', array('id' => $id))) {
                $record = reset($records);
                $coursecat = new coursecat($record);
                // Store in cache.
                $coursecatrecordcache->set($id, $coursecat);
            }
        }
        if ($coursecat && ($alwaysreturnhidden || $coursecat->is_uservisible())) {
            return $coursecat;
        } else {
            if ($strictness == MUST_EXIST) {
                throw new moodle_exception('unknowcategory');
            }
        }
        return null;
    }

    /**
     * Load many coursecat objects.
     *
     * @global moodle_database $DB
     * @param array $ids An array of category ID's to load.
     * @return coursecat[]
     */
    public static function get_many(array $ids) {
        global $DB;
        $coursecatrecordcache = cache::make('core', 'coursecatrecords');
        $categories = $coursecatrecordcache->get_many($ids);
        $toload = array();
        foreach ($categories as $id => $result) {
            if ($result === false) {
                $toload[] = $id;
            }
        }
        if (!empty($toload)) {
            list($where, $params) = $DB->get_in_or_equal($toload, SQL_PARAMS_NAMED);
            $records = self::get_records('cc.id '.$where, $params);
            $toset = array();
            foreach ($records as $record) {
                $categories[$record->id] = new coursecat($record);
                $toset[$record->id] = $categories[$record->id];
            }
            $coursecatrecordcache->set_many($toset);
        }
        return $categories;
    }

    /**
     * Returns the first found category
     *
     * Note that if there are no categories visible to the current user on the first level,
     * the invisible category may be returned
     *
     * @return coursecat
     */
    public static function get_default() {
        if ($visiblechildren = self::get(0)->get_children()) {
            $defcategory = reset($visiblechildren);
        } else {
            $toplevelcategories = self::get_tree(0);
            $defcategoryid = $toplevelcategories[0];
            $defcategory = self::get($defcategoryid, MUST_EXIST, true);
        }
        return $defcategory;
    }

    /**
     * Restores the object after it has been externally modified in DB for example
     * during {@link fix_course_sortorder()}
     */
    protected function restore() {
        // Update all fields in the current object.
        $newrecord = self::get($this->id, MUST_EXIST, true);
        foreach (self::$coursecatfields as $key => $unused) {
            $this->$key = $newrecord->$key;
        }
    }

    /**
     * Creates a new category either from form data or from raw data
     *
     * Please note that this function does not verify access control.
     *
     * Exception is thrown if name is missing or idnumber is duplicating another one in the system.
     *
     * Category visibility is inherited from parent unless $data->visible = 0 is specified
     *
     * @param array|stdClass $data
     * @param array $editoroptions if specified, the data is considered to be
     *    form data and file_postupdate_standard_editor() is being called to
     *    process images in description.
     * @return coursecat
     * @throws moodle_exception
     */
    public static function create($data, $editoroptions = null) {
        global $DB, $CFG;
        $data = (object)$data;
        $newcategory = new stdClass();

        $newcategory->descriptionformat = FORMAT_MOODLE;
        $newcategory->description = '';
        // Copy all description* fields regardless of whether this is form data or direct field update.
        foreach ($data as $key => $value) {
            if (preg_match("/^description/", $key)) {
                $newcategory->$key = $value;
            }
        }

        if (empty($data->name)) {
            throw new moodle_exception('categorynamerequired');
        }
        if (core_text::strlen($data->name) > 255) {
            throw new moodle_exception('categorytoolong');
        }
        $newcategory->name = $data->name;

        // Validate and set idnumber.
        if (!empty($data->idnumber)) {
            if (core_text::strlen($data->idnumber) > 100) {
                throw new moodle_exception('idnumbertoolong');
            }
            if ($DB->record_exists('course_categories', array('idnumber' => $data->idnumber))) {
                throw new moodle_exception('categoryidnumbertaken');
            }
        }
        if (isset($data->idnumber)) {
            $newcategory->idnumber = $data->idnumber;
        }

        if (isset($data->theme) && !empty($CFG->allowcategorythemes)) {
            $newcategory->theme = $data->theme;
        }

        if (empty($data->parent)) {
            $parent = self::get(0);
        } else {
            $parent = self::get($data->parent, MUST_EXIST, true);
        }
        $newcategory->parent = $parent->id;
        $newcategory->depth = $parent->depth + 1;

        // By default category is visible, unless visible = 0 is specified or parent category is hidden.
        if (isset($data->visible) && !$data->visible) {
            // Create a hidden category.
            $newcategory->visible = $newcategory->visibleold = 0;
        } else {
            // Create a category that inherits visibility from parent.
            $newcategory->visible = $parent->visible;
            // In case parent is hidden, when it changes visibility this new subcategory will automatically become visible too.
            $newcategory->visibleold = 1;
        }

        $newcategory->sortorder = 0;
        $newcategory->timemodified = time();

        $newcategory->id = $DB->insert_record('course_categories', $newcategory);

        // Update path (only possible after we know the category id.
        $path = $parent->path . '/' . $newcategory->id;
        $DB->set_field('course_categories', 'path', $path, array('id' => $newcategory->id));

        // We should mark the context as dirty.
        context_coursecat::instance($newcategory->id)->mark_dirty();

        fix_course_sortorder();

        // If this is data from form results, save embedded files and update description.
        $categorycontext = context_coursecat::instance($newcategory->id);
        if ($editoroptions) {
            $newcategory = file_postupdate_standard_editor($newcategory, 'description', $editoroptions, $categorycontext,
                                                           'coursecat', 'description', 0);

            // Update only fields description and descriptionformat.
            $updatedata = new stdClass();
            $updatedata->id = $newcategory->id;
            $updatedata->description = $newcategory->description;
            $updatedata->descriptionformat = $newcategory->descriptionformat;
            $DB->update_record('course_categories', $updatedata);
        }

        add_to_log(SITEID, "category", 'add', "editcategory.php?id=$newcategory->id", $newcategory->id);
        cache_helper::purge_by_event('changesincoursecat');

        return self::get($newcategory->id, MUST_EXIST, true);
    }

    /**
     * Updates the record with either form data or raw data
     *
     * Please note that this function does not verify access control.
     *
     * This function calls coursecat::change_parent_raw if field 'parent' is updated.
     * It also calls coursecat::hide_raw or coursecat::show_raw if 'visible' is updated.
     * Visibility is changed first and then parent is changed. This means that
     * if parent category is hidden, the current category will become hidden
     * too and it may overwrite whatever was set in field 'visible'.
     *
     * Note that fields 'path' and 'depth' can not be updated manually
     * Also coursecat::update() can not directly update the field 'sortoder'
     *
     * @param array|stdClass $data
     * @param array $editoroptions if specified, the data is considered to be
     *    form data and file_postupdate_standard_editor() is being called to
     *    process images in description.
     * @throws moodle_exception
     */
    public function update($data, $editoroptions = null) {
        global $DB, $CFG;
        if (!$this->id) {
            // There is no actual DB record associated with root category.
            return;
        }

        $data = (object)$data;
        $newcategory = new stdClass();
        $newcategory->id = $this->id;

        // Copy all description* fields regardless of whether this is form data or direct field update.
        foreach ($data as $key => $value) {
            if (preg_match("/^description/", $key)) {
                $newcategory->$key = $value;
            }
        }

        if (isset($data->name) && empty($data->name)) {
            throw new moodle_exception('categorynamerequired');
        }

        if (!empty($data->name) && $data->name !== $this->name) {
            if (core_text::strlen($data->name) > 255) {
                throw new moodle_exception('categorytoolong');
            }
            $newcategory->name = $data->name;
        }

        if (isset($data->idnumber) && $data->idnumber != $this->idnumber) {
            if (core_text::strlen($data->idnumber) > 100) {
                throw new moodle_exception('idnumbertoolong');
            }
            if ($DB->record_exists('course_categories', array('idnumber' => $data->idnumber))) {
                throw new moodle_exception('categoryidnumbertaken');
            }
            $newcategory->idnumber = $data->idnumber;
        }

        if (isset($data->theme) && !empty($CFG->allowcategorythemes)) {
            $newcategory->theme = $data->theme;
        }

        $changes = false;
        if (isset($data->visible)) {
            if ($data->visible) {
                $changes = $this->show_raw();
            } else {
                $changes = $this->hide_raw(0);
            }
        }

        if (isset($data->parent) && $data->parent != $this->parent) {
            if ($changes) {
                cache_helper::purge_by_event('changesincoursecat');
            }
            $parentcat = self::get($data->parent, MUST_EXIST, true);
            $this->change_parent_raw($parentcat);
            fix_course_sortorder();
        }

        $newcategory->timemodified = time();

        if ($editoroptions) {
            $categorycontext = $this->get_context();
            $newcategory = file_postupdate_standard_editor($newcategory, 'description', $editoroptions, $categorycontext,
                                                           'coursecat', 'description', 0);
        }
        $DB->update_record('course_categories', $newcategory);
        add_to_log(SITEID, "category", 'update', "editcategory.php?id=$this->id", $this->id);
        fix_course_sortorder();
        // Purge cache even if fix_course_sortorder() did not do it.
        cache_helper::purge_by_event('changesincoursecat');

        // Update all fields in the current object.
        $this->restore();
    }

    /**
     * Checks if this course category is visible to current user
     *
     * Please note that methods coursecat::get (without 3rd argumet),
     * coursecat::get_children(), etc. return only visible categories so it is
     * usually not needed to call this function outside of this class
     *
     * @return bool
     */
    public function is_uservisible() {
        return !$this->id || $this->visible ||
                has_capability('moodle/category:viewhiddencategories', $this->get_context());
    }

    /**
     * Returns all categories visible to the current user
     *
     * This is a generic function that returns an array of
     * (category id => coursecat object) sorted by sortorder
     *
     * @see coursecat::get_children()
     * @see coursecat::get_all_parents()
     *
     * @return cacheable_object_array array of coursecat objects
     */
    public static function get_all_visible() {
        global $USER;
        $coursecatcache = cache::make('core', 'coursecat');
        $ids = $coursecatcache->get('user'. $USER->id);
        if ($ids === false) {
            $all = self::get_all_ids();
            $parentvisible = $all[0];
            $rv = array();
            foreach ($all as $id => $children) {
                if ($id && in_array($id, $parentvisible) &&
                        ($coursecat = self::get($id, IGNORE_MISSING)) &&
                        (!$coursecat->parent || isset($rv[$coursecat->parent]))) {
                    $rv[$id] = $coursecat;
                    $parentvisible += $children;
                }
            }
            $coursecatcache->set('user'. $USER->id, array_keys($rv));
        } else {
            $rv = array();
            foreach ($ids as $id) {
                if ($coursecat = self::get($id, IGNORE_MISSING)) {
                    $rv[$id] = $coursecat;
                }
            }
        }
        return $rv;
    }

    /**
     * Returns the complete corresponding record from DB table course_categories
     *
     * Mostly used in deprecated functions
     *
     * @return stdClass
     */
    public function get_db_record() {
        global $DB;
        if ($record = $DB->get_record('course_categories', array('id' => $this->id))) {
            return $record;
        } else {
            return (object)convert_to_array($this);
        }
    }

    /**
     * Returns the entry from categories tree and makes sure the application-level tree cache is built
     *
     * The following keys can be requested:
     *
     * 'countall' - total number of categories in the system (always present)
     * 0 - array of ids of top-level categories (always present)
     * '0i' - array of ids of top-level categories that have visible=0 (always present but may be empty array)
     * $id (int) - array of ids of categories that are direct children of category with id $id. If
     *   category with id $id does not exist returns false. If category has no children returns empty array
     * $id.'i' - array of ids of children categories that have visible=0
     *
     * @param int|string $id
     * @return mixed
     */
    protected static function get_tree($id) {
        global $DB;
        $coursecattreecache = cache::make('core', 'coursecattree');
        $rv = $coursecattreecache->get($id);
        if ($rv !== false) {
            return $rv;
        }
        // Re-build the tree.
        $sql = "SELECT cc.id, cc.parent, cc.visible
                FROM {course_categories} cc
                ORDER BY cc.sortorder";
        $rs = $DB->get_recordset_sql($sql, array());
        $all = array(0 => array(), '0i' => array());
        $count = 0;
        foreach ($rs as $record) {
            $all[$record->id] = array();
            $all[$record->id. 'i'] = array();
            if (array_key_exists($record->parent, $all)) {
                $all[$record->parent][] = $record->id;
                if (!$record->visible) {
                    $all[$record->parent. 'i'][] = $record->id;
                }
            } else {
                // Parent not found. This is data consistency error but next fix_course_sortorder() should fix it.
                $all[0][] = $record->id;
                if (!$record->visible) {
                    $all['0i'][] = $record->id;
                }
            }
            $count++;
        }
        $rs->close();
        if (!$count) {
            // No categories found.
            // This may happen after upgrade of a very old moodle version.
            // In new versions the default category is created on install.
            $defcoursecat = self::create(array('name' => get_string('miscellaneous')));
            set_config('defaultrequestcategory', $defcoursecat->id);
            $all[0] = array($defcoursecat->id);
            $all[$defcoursecat->id] = array();
            $count++;
        }
        // We must add countall to all in case it was the requested ID.
        $all['countall'] = $count;
        foreach ($all as $key => $children) {
            $coursecattreecache->set($key, $children);
        }
        if (array_key_exists($id, $all)) {
            return $all[$id];
        }
        // Requested non-existing category.
        return array();
    }

    /**
     * Returns number of ALL categories in the system regardless if
     * they are visible to current user or not
     *
     * @return int
     */
    public static function count_all() {
        return self::get_tree('countall');
    }

    /**
     * Retrieves number of records from course_categories table
     *
     * Only cached fields are retrieved. Records are ready for preloading context
     *
     * @param string $whereclause
     * @param array $params
     * @return array array of stdClass objects
     */
    protected static function get_records($whereclause, $params) {
        global $DB;
        // Retrieve from DB only the fields that need to be stored in cache.
        $fields = array_keys(array_filter(self::$coursecatfields));
        $ctxselect = context_helper::get_preload_record_columns_sql('ctx');
        $sql = "SELECT cc.". join(',cc.', $fields). ", $ctxselect
                FROM {course_categories} cc
                JOIN {context} ctx ON cc.id = ctx.instanceid AND ctx.contextlevel = :contextcoursecat
                WHERE ". $whereclause." ORDER BY cc.sortorder";
        return $DB->get_records_sql($sql,
                array('contextcoursecat' => CONTEXT_COURSECAT) + $params);
    }

    /**
     * Given list of DB records from table course populates each record with list of users with course contact roles
     *
     * This function fills the courses with raw information as {@link get_role_users()} would do.
     * See also {@link course_in_list::get_course_contacts()} for more readable return
     *
     * $courses[$i]->managers = array(
     *   $roleassignmentid => $roleuser,
     *   ...
     * );
     *
     * where $roleuser is an stdClass with the following properties:
     *
     * $roleuser->raid - role assignment id
     * $roleuser->id - user id
     * $roleuser->username
     * $roleuser->firstname
     * $roleuser->lastname
     * $roleuser->rolecoursealias
     * $roleuser->rolename
     * $roleuser->sortorder - role sortorder
     * $roleuser->roleid
     * $roleuser->roleshortname
     *
     * @todo MDL-38596 minimize number of queries to preload contacts for the list of courses
     *
     * @param array $courses
     */
    public static function preload_course_contacts(&$courses) {
        global $CFG, $DB;
        if (empty($courses) || empty($CFG->coursecontact)) {
            return;
        }
        $managerroles = explode(',', $CFG->coursecontact);
        $cache = cache::make('core', 'coursecontacts');
        $cacheddata = $cache->get_many(array_merge(array('basic'), array_keys($courses)));
        // Check if cache was set for the current course contacts and it is not yet expired.
        if (empty($cacheddata['basic']) || $cacheddata['basic']['roles'] !== $CFG->coursecontact ||
                $cacheddata['basic']['lastreset'] < time() - self::CACHE_COURSE_CONTACTS_TTL) {
            // Reset cache.
            $cache->purge();
            $cache->set('basic', array('roles' => $CFG->coursecontact, 'lastreset' => time()));
            $cacheddata = $cache->get_many(array_merge(array('basic'), array_keys($courses)));
        }
        $courseids = array();
        foreach (array_keys($courses) as $id) {
            if ($cacheddata[$id] !== false) {
                $courses[$id]->managers = $cacheddata[$id];
            } else {
                $courseids[] = $id;
            }
        }

        // Array $courseids now stores list of ids of courses for which we still need to retrieve contacts.
        if (empty($courseids)) {
            return;
        }

        // First build the array of all context ids of the courses and their categories.
        $allcontexts = array();
        foreach ($courseids as $id) {
            $context = context_course::instance($id);
            $courses[$id]->managers = array();
            foreach (preg_split('|/|', $context->path, 0, PREG_SPLIT_NO_EMPTY) as $ctxid) {
                if (!isset($allcontexts[$ctxid])) {
                    $allcontexts[$ctxid] = array();
                }
                $allcontexts[$ctxid][] = $id;
            }
        }

        // Fetch list of all users with course contact roles in any of the courses contexts or parent contexts.
        list($sql1, $params1) = $DB->get_in_or_equal(array_keys($allcontexts), SQL_PARAMS_NAMED, 'ctxid');
        list($sql2, $params2) = $DB->get_in_or_equal($managerroles, SQL_PARAMS_NAMED, 'rid');
        list($sort, $sortparams) = users_order_by_sql('u');
        $notdeleted = array('notdeleted'=>0);
        $allnames = get_all_user_name_fields(true, 'u');
        $sql = "SELECT ra.contextid, ra.id AS raid,
                       r.id AS roleid, r.name AS rolename, r.shortname AS roleshortname,
                       rn.name AS rolecoursealias, u.id, u.username, $allnames
                  FROM {role_assignments} ra
                  JOIN {user} u ON ra.userid = u.id
                  JOIN {role} r ON ra.roleid = r.id
             LEFT JOIN {role_names} rn ON (rn.contextid = ra.contextid AND rn.roleid = r.id)
                WHERE  ra.contextid ". $sql1." AND ra.roleid ". $sql2." AND u.deleted = :notdeleted
             ORDER BY r.sortorder, $sort";
        $rs = $DB->get_recordset_sql($sql, $params1 + $params2 + $notdeleted + $sortparams);
        $checkenrolments = array();
        foreach ($rs as $ra) {
            foreach ($allcontexts[$ra->contextid] as $id) {
                $courses[$id]->managers[$ra->raid] = $ra;
                if (!isset($checkenrolments[$id])) {
                    $checkenrolments[$id] = array();
                }
                $checkenrolments[$id][] = $ra->id;
            }
        }
        $rs->close();

        // Remove from course contacts users who are not enrolled in the course.
        $enrolleduserids = self::ensure_users_enrolled($checkenrolments);
        foreach ($checkenrolments as $id => $userids) {
            if (empty($enrolleduserids[$id])) {
                $courses[$id]->managers = array();
            } else if ($notenrolled = array_diff($userids, $enrolleduserids[$id])) {
                foreach ($courses[$id]->managers as $raid => $ra) {
                    if (in_array($ra->id, $notenrolled)) {
                        unset($courses[$id]->managers[$raid]);
                    }
                }
            }
        }

        // Set the cache.
        $values = array();
        foreach ($courseids as $id) {
            $values[$id] = $courses[$id]->managers;
        }
        $cache->set_many($values);
    }

    /**
     * Verify user enrollments for multiple course-user combinations
     *
     * @param array $courseusers array where keys are course ids and values are array
     *     of users in this course whose enrolment we wish to verify
     * @return array same structure as input array but values list only users from input
     *     who are enrolled in the course
     */
    protected static function ensure_users_enrolled($courseusers) {
        global $DB;
        // If the input array is too big, split it into chunks.
        $maxcoursesinquery = 20;
        if (count($courseusers) > $maxcoursesinquery) {
            $rv = array();
            for ($offset = 0; $offset < count($courseusers); $offset += $maxcoursesinquery) {
                $chunk = array_slice($courseusers, $offset, $maxcoursesinquery, true);
                $rv = $rv + self::ensure_users_enrolled($chunk);
            }
            return $rv;
        }

        // Create a query verifying valid user enrolments for the number of courses.
        $sql = "SELECT DISTINCT e.courseid, ue.userid
          FROM {user_enrolments} ue
          JOIN {enrol} e ON e.id = ue.enrolid
          WHERE ue.status = :active
            AND e.status = :enabled
            AND ue.timestart < :now1 AND (ue.timeend = 0 OR ue.timeend > :now2)";
        $now = round(time(), -2); // Rounding helps caching in DB.
        $params = array('enabled' => ENROL_INSTANCE_ENABLED,
            'active' => ENROL_USER_ACTIVE,
            'now1' => $now, 'now2' => $now);
        $cnt = 0;
        $subsqls = array();
        $enrolled = array();
        foreach ($courseusers as $id => $userids) {
            $enrolled[$id] = array();
            if (count($userids)) {
                list($sql2, $params2) = $DB->get_in_or_equal($userids, SQL_PARAMS_NAMED, 'userid'.$cnt.'_');
                $subsqls[] = "(e.courseid = :courseid$cnt AND ue.userid ".$sql2.")";
                $params = $params + array('courseid'.$cnt => $id) + $params2;
                $cnt++;
            }
        }
        if (count($subsqls)) {
            $sql .= "AND (". join(' OR ', $subsqls).")";
            $rs = $DB->get_recordset_sql($sql, $params);
            foreach ($rs as $record) {
                $enrolled[$record->courseid][] = $record->userid;
            }
            $rs->close();
        }
        return $enrolled;
    }

    /**
     * Retrieves number of records from course table
     *
     * Not all fields are retrieved. Records are ready for preloading context
     *
     * @param string $whereclause
     * @param array $params
     * @param array $options may indicate that summary and/or coursecontacts need to be retrieved
     * @param bool $checkvisibility if true, capability 'moodle/course:viewhiddencourses' will be checked
     *     on not visible courses
     * @return array array of stdClass objects
     */
    protected static function get_course_records($whereclause, $params, $options, $checkvisibility = false) {
        global $DB;
        $ctxselect = context_helper::get_preload_record_columns_sql('ctx');
        $fields = array('c.id', 'c.category', 'c.sortorder',
                        'c.shortname', 'c.fullname', 'c.idnumber',
                        'c.startdate', 'c.visible', 'c.cacherev');
        if (!empty($options['summary'])) {
            $fields[] = 'c.summary';
            $fields[] = 'c.summaryformat';
        } else {
            $fields[] = $DB->sql_substr('c.summary', 1, 1). ' as hassummary';
        }
        $sql = "SELECT ". join(',', $fields). ", $ctxselect
                FROM {course} c
                JOIN {context} ctx ON c.id = ctx.instanceid AND ctx.contextlevel = :contextcourse
                WHERE ". $whereclause." ORDER BY c.sortorder";
        $list = $DB->get_records_sql($sql,
                array('contextcourse' => CONTEXT_COURSE) + $params);

        if ($checkvisibility) {
            // Loop through all records and make sure we only return the courses accessible by user.
            foreach ($list as $course) {
                if (isset($list[$course->id]->hassummary)) {
                    $list[$course->id]->hassummary = strlen($list[$course->id]->hassummary) > 0;
                }
                if (empty($course->visible)) {
                    // Load context only if we need to check capability.
                    context_helper::preload_from_record($course);
                    if (!has_capability('moodle/course:viewhiddencourses', context_course::instance($course->id))) {
                        unset($list[$course->id]);
                    }
                }
            }
        }

        // Preload course contacts if necessary.
        if (!empty($options['coursecontacts'])) {
            self::preload_course_contacts($list);
        }
        return $list;
    }

    /**
     * Returns array of ids of children categories that current user can not see
     *
     * This data is cached in user session cache
     *
     * @return array
     */
    protected function get_not_visible_children_ids() {
        global $DB;
        $coursecatcache = cache::make('core', 'coursecat');
        if (($invisibleids = $coursecatcache->get('ic'. $this->id)) === false) {
            // We never checked visible children before.
            $hidden = self::get_tree($this->id.'i');
            $invisibleids = array();
            if ($hidden) {
                // Preload categories contexts.
                list($sql, $params) = $DB->get_in_or_equal($hidden, SQL_PARAMS_NAMED, 'id');
                $ctxselect = context_helper::get_preload_record_columns_sql('ctx');
                $contexts = $DB->get_records_sql("SELECT $ctxselect FROM {context} ctx
                    WHERE ctx.contextlevel = :contextcoursecat AND ctx.instanceid ".$sql,
                        array('contextcoursecat' => CONTEXT_COURSECAT) + $params);
                foreach ($contexts as $record) {
                    context_helper::preload_from_record($record);
                }
                // Check that user has 'viewhiddencategories' capability for each hidden category.
                foreach ($hidden as $id) {
                    if (!has_capability('moodle/category:viewhiddencategories', context_coursecat::instance($id))) {
                        $invisibleids[] = $id;
                    }
                }
            }
            $coursecatcache->set('ic'. $this->id, $invisibleids);
        }
        return $invisibleids;
    }

    /**
     * Sorts list of records by several fields
     *
     * @param array $records array of stdClass objects
     * @param array $sortfields assoc array where key is the field to sort and value is 1 for asc or -1 for desc
     * @return int
     */
    protected static function sort_records(&$records, $sortfields) {
        if (empty($records)) {
            return;
        }
        // If sorting by course display name, calculate it (it may be fullname or shortname+fullname).
        if (array_key_exists('displayname', $sortfields)) {
            foreach ($records as $key => $record) {
                if (!isset($record->displayname)) {
                    $records[$key]->displayname = get_course_display_name_for_list($record);
                }
            }
        }
        // Sorting by one field - use core_collator.
        if (count($sortfields) == 1) {
            $property = key($sortfields);
            if (in_array($property, array('sortorder', 'id', 'visible', 'parent', 'depth'))) {
                $sortflag = core_collator::SORT_NUMERIC;
            } else if (in_array($property, array('idnumber', 'displayname', 'name', 'shortname', 'fullname'))) {
                $sortflag = core_collator::SORT_STRING;
            } else {
                $sortflag = core_collator::SORT_REGULAR;
            }
            core_collator::asort_objects_by_property($records, $property, $sortflag);
            if ($sortfields[$property] < 0) {
                $records = array_reverse($records, true);
            }
            return;
        }
        $records = coursecat_sortable_records::sort($records, $sortfields);
    }

    /**
     * Returns array of children categories visible to the current user
     *
     * @param array $options options for retrieving children
     *    - sort - list of fields to sort. Example
     *             array('idnumber' => 1, 'name' => 1, 'id' => -1)
     *             will sort by idnumber asc, name asc and id desc.
     *             Default: array('sortorder' => 1)
     *             Only cached fields may be used for sorting!
     *    - offset
     *    - limit - maximum number of children to return, 0 or null for no limit
     * @return coursecat[] Array of coursecat objects indexed by category id
     */
    public function get_children($options = array()) {
        global $DB;
        $coursecatcache = cache::make('core', 'coursecat');

        // Get default values for options.
        if (!empty($options['sort']) && is_array($options['sort'])) {
            $sortfields = $options['sort'];
        } else {
            $sortfields = array('sortorder' => 1);
        }
        $limit = null;
        if (!empty($options['limit']) && (int)$options['limit']) {
            $limit = (int)$options['limit'];
        }
        $offset = 0;
        if (!empty($options['offset']) && (int)$options['offset']) {
            $offset = (int)$options['offset'];
        }

        // First retrieve list of user-visible and sorted children ids from cache.
        $sortedids = $coursecatcache->get('c'. $this->id. ':'.  serialize($sortfields));
        if ($sortedids === false) {
            $sortfieldskeys = array_keys($sortfields);
            if ($sortfieldskeys[0] === 'sortorder') {
                // No DB requests required to build the list of ids sorted by sortorder.
                // We can easily ignore other sort fields because sortorder is always different.
                $sortedids = self::get_tree($this->id);
                if ($sortedids && ($invisibleids = $this->get_not_visible_children_ids())) {
                    $sortedids = array_diff($sortedids, $invisibleids);
                    if ($sortfields['sortorder'] == -1) {
                        $sortedids = array_reverse($sortedids, true);
                    }
                }
            } else {
                // We need to retrieve and sort all children. Good thing that it is done only on first request.
                if ($invisibleids = $this->get_not_visible_children_ids()) {
                    list($sql, $params) = $DB->get_in_or_equal($invisibleids, SQL_PARAMS_NAMED, 'id', false);
                    $records = self::get_records('cc.parent = :parent AND cc.id '. $sql,
                            array('parent' => $this->id) + $params);
                } else {
                    $records = self::get_records('cc.parent = :parent', array('parent' => $this->id));
                }
                self::sort_records($records, $sortfields);
                $sortedids = array_keys($records);
            }
            $coursecatcache->set('c'. $this->id. ':'.serialize($sortfields), $sortedids);
        }

        if (empty($sortedids)) {
            return array();
        }

        // Now retrieive and return categories.
        if ($offset || $limit) {
            $sortedids = array_slice($sortedids, $offset, $limit);
        }
        if (isset($records)) {
            // Easy, we have already retrieved records.
            if ($offset || $limit) {
                $records = array_slice($records, $offset, $limit, true);
            }
        } else {
            list($sql, $params) = $DB->get_in_or_equal($sortedids, SQL_PARAMS_NAMED, 'id');
            $records = self::get_records('cc.id '. $sql, array('parent' => $this->id) + $params);
        }

        $rv = array();
        foreach ($sortedids as $id) {
            if (isset($records[$id])) {
                $rv[$id] = new coursecat($records[$id]);
            }
        }
        return $rv;
    }

    /**
     * Returns true if the user has the manage capability on any category.
     *
     * This method uses the coursecat cache and an entry `has_manage_capability` to speed up
     * calls to this method.
     *
     * @return bool
     */
    public static function has_manage_capability_on_any() {
        return self::has_capability_on_any('moodle/category:manage');
    }

    /**
     * Checks if the user has at least one of the given capabilities on any category.
     *
     * @param array|string $capabilities One or more capabilities to check. Check made is an OR.
     * @return bool
     */
    public static function has_capability_on_any($capabilities) {
        global $DB;
        if (!isloggedin() || isguestuser()) {
            return false;
        }

        if (!is_array($capabilities)) {
            $capabilities = array($capabilities);
        }
        $keys = array();
        foreach ($capabilities as $capability) {
            $keys[$capability] = sha1($capability);
        }

        /* @var cache_session $cache */
        $cache = cache::make('core', 'coursecat');
        $hascapability = $cache->get_many($keys);
        $needtoload = false;
        foreach ($hascapability as $capability) {
            if ($capability === '1') {
                return true;
            } else if ($capability === false) {
                $needtoload = true;
            }
        }
        if ($needtoload === false) {
            // All capabilities were retrieved and the user didn't have any.
            return false;
        }

        $haskey = null;
        $fields = context_helper::get_preload_record_columns_sql('ctx');
        $sql = "SELECT ctx.instanceid AS categoryid, $fields
                      FROM {context} ctx
                     WHERE contextlevel = :contextlevel
                  ORDER BY depth ASC";
        $params = array('contextlevel' => CONTEXT_COURSECAT);
        $recordset = $DB->get_recordset_sql($sql, $params);
        foreach ($recordset as $context) {
            context_helper::preload_from_record($context);
            $context = context_coursecat::instance($context->categoryid);
            foreach ($capabilities as $capability) {
                if (has_capability($capability, $context)) {
                    $haskey = $capability;
                    break 2;
                }
            }
        }
        $recordset->close();
        if ($haskey === null) {
            $data = array();
            foreach ($keys as $key) {
                $data[$key] = '0';
            }
            $cache->set_many($data);
            return false;
        } else {
            $cache->set($haskey, '1');
            return true;
        }
    }

    /**
     * Returns true if the user can resort any category.
     * @return bool
     */
    public static function can_resort_any() {
        return self::has_manage_capability_on_any();
    }

    /**
     * Returns true if the user can change the parent of any category.
     * @return bool
     */
    public static function can_change_parent_any() {
        return self::has_manage_capability_on_any();
    }

    /**
     * Returns number of subcategories visible to the current user
     *
     * @return int
     */
    public function get_children_count() {
        $sortedids = self::get_tree($this->id);
        $invisibleids = $this->get_not_visible_children_ids();
        return count($sortedids) - count($invisibleids);
    }

    /**
     * Returns true if the category has ANY children, including those not visible to the user
     *
     * @return boolean
     */
    public function has_children() {
        $allchildren = self::get_tree($this->id);
        return !empty($allchildren);
    }

    /**
     * Returns true if the category has courses in it (count does not include courses
     * in child categories)
     *
     * @return bool
     */
    public function has_courses() {
        global $DB;
        return $DB->record_exists_sql("select 1 from {course} where category = ?",
                array($this->id));
    }

    /**
     * Searches courses
     *
     * List of found course ids is cached for 10 minutes. Cache may be purged prior
     * to this when somebody edits courses or categories, however it is very
     * difficult to keep track of all possible changes that may affect list of courses.
     *
     * @param array $search contains search criterias, such as:
     *     - search - search string
     *     - blocklist - id of block (if we are searching for courses containing specific block0
     *     - modulelist - name of module (if we are searching for courses containing specific module
     *     - tagid - id of tag
     * @param array $options display options, same as in get_courses() except 'recursive' is ignored -
     *                       search is always category-independent
     * @return course_in_list[]
     */
    public static function search_courses($search, $options = array()) {
        global $DB;
        $offset = !empty($options['offset']) ? $options['offset'] : 0;
        $limit = !empty($options['limit']) ? $options['limit'] : null;
        $sortfields = !empty($options['sort']) ? $options['sort'] : array('sortorder' => 1);

        $coursecatcache = cache::make('core', 'coursecat');
        $cachekey = 's-'. serialize($search + array('sort' => $sortfields));
        $cntcachekey = 'scnt-'. serialize($search);

        $ids = $coursecatcache->get($cachekey);
        if ($ids !== false) {
            // We already cached last search result.
            $ids = array_slice($ids, $offset, $limit);
            $courses = array();
            if (!empty($ids)) {
                list($sql, $params) = $DB->get_in_or_equal($ids, SQL_PARAMS_NAMED, 'id');
                $records = self::get_course_records("c.id ". $sql, $params, $options);
                // Preload course contacts if necessary - saves DB queries later to do it for each course separately.
                if (!empty($options['coursecontacts'])) {
                    self::preload_course_contacts($records);
                }
                // If option 'idonly' is specified no further action is needed, just return list of ids.
                if (!empty($options['idonly'])) {
                    return array_keys($records);
                }
                // Prepare the list of course_in_list objects.
                foreach ($ids as $id) {
                    $courses[$id] = new course_in_list($records[$id]);
                }
            }
            return $courses;
        }

        $preloadcoursecontacts = !empty($options['coursecontacts']);
        unset($options['coursecontacts']);

        if (!empty($search['search'])) {
            // Search courses that have specified words in their names/summaries.
            $searchterms = preg_split('|\s+|', trim($search['search']), 0, PREG_SPLIT_NO_EMPTY);
            $searchterms = array_filter($searchterms, create_function('$v', 'return strlen($v) > 1;'…