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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/>.

/**
 * Library of functions for database manipulation.
 *
 * Other main libraries:
 * - weblib.php - functions that produce web output
 * - moodlelib.php - general-purpose Moodle functions
 *
 * @package    core
 * @copyright  1999 onwards Martin Dougiamas  {@link http://moodle.com}
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

/**
 * The maximum courses in a category
 * MAX_COURSES_IN_CATEGORY * MAX_COURSE_CATEGORIES must not be more than max integer!
 */
define('MAX_COURSES_IN_CATEGORY', 10000);

/**
  * The maximum number of course categories
  * MAX_COURSES_IN_CATEGORY * MAX_COURSE_CATEGORIES must not be more than max integer!
  */
define('MAX_COURSE_CATEGORIES', 10000);

/**
 * Number of seconds to wait before updating lastaccess information in DB.
 *
 * We allow overwrites from config.php, useful to ensure coherence in performance
 * tests results.
 *
 * Note: For web service requests in the external_tokens field, we use a different constant
 * webservice::TOKEN_LASTACCESS_UPDATE_SECS.
 */
if (!defined('LASTACCESS_UPDATE_SECS')) {
    define('LASTACCESS_UPDATE_SECS', 60);
}

/**
 * Returns $user object of the main admin user
 *
 * @static stdClass $mainadmin
 * @return stdClass {@link $USER} record from DB, false if not found
 */
function get_admin() {
    global $CFG, $DB;

static $mainadmin = null;
    static $prevadmins = null;

if (empty($CFG->siteadmins)) {
        // Should not happen on an ordinary site.
        // It does however happen during unit tests.
        return false;
    }

if (isset($mainadmin) and $prevadmins === $CFG->siteadmins) {
        return clone($mainadmin);
    }

$mainadmin = null;

foreach (explode(',', $CFG->siteadmins) as $id) {
        if ($user = $DB->get_record('user', array('id'=>$id, 'deleted'=>0))) {
            $mainadmin = $user;
            break;
        }
    }

if ($mainadmin) {
        $prevadmins = $CFG->siteadmins;
        return clone($mainadmin);
    } else {
        // this should not happen
        return false;
    }
}

/**
 * Returns list of all admins, using 1 DB query
 *
 * @return array
 */
function get_admins() {
    global $DB, $CFG;

if (empty($CFG->siteadmins)) {  // Should not happen on an ordinary site
        return array();
    }

$sql = "SELECT u.*
              FROM {user} u
             WHERE u.deleted = 0 AND u.id IN ($CFG->siteadmins)";

// We want the same order as in $CFG->siteadmins.
    $records = $DB->get_records_sql($sql);
    $admins = array();
    foreach (explode(',', $CFG->siteadmins) as $id) {
        $id = (int)$id;
        if (!isset($records[$id])) {
            // User does not exist, this should not happen.
            continue;
        }
        $admins[$records[$id]->id] = $records[$id];
    }

return $admins;
}

/**
 * Search through course users
 *
 * If $coursid specifies the site course then this function searches
 * through all undeleted and confirmed users
 *
 * @global object
 * @uses SITEID
 * @uses SQL_PARAMS_NAMED
 * @uses CONTEXT_COURSE
 * @param int $courseid The course in question.
 * @param int $groupid The group in question.
 * @param string $searchtext The string to search for
 * @param string $sort A field to sort by
 * @param array $exceptions A list of IDs to ignore, eg 2,4,5,8,9,10
 * @return array
 */
function search_users($courseid, $groupid, $searchtext, $sort='', array $exceptions=null) {
    global $DB;

$fullname  = $DB->sql_fullname('u.firstname', 'u.lastname');

if (!empty($exceptions)) {
        list($exceptions, $params) = $DB->get_in_or_equal($exceptions, SQL_PARAMS_NAMED, 'ex', false);
        $except = "AND u.id $exceptions";
    } else {
        $except = "";
        $params = array();
    }

if (!empty($sort)) {
        $order = "ORDER BY $sort";
    } else {
        $order = "";
    }

$select = "u.deleted = 0 AND u.confirmed = 1 AND (".$DB->sql_like($fullname, ':search1', false)." OR ".$DB->sql_like('u.email', ':search2', false).")";
    $params['search1'] = "%$searchtext%";
    $params['search2'] = "%$searchtext%";

if (!$courseid or $courseid == SITEID) {
        $sql = "SELECT u.id, u.firstname, u.lastname, u.email
                  FROM {user} u
                 WHERE $select
                       $except
                $order";
        return $DB->get_records_sql($sql, $params);

} else {
        if ($groupid) {
            $sql = "SELECT u.id, u.firstname, u.lastname, u.email
                      FROM {user} u
                      JOIN {groups_members} gm ON gm.userid = u.id
                     WHERE $select AND gm.groupid = :groupid
                           $except
                     $order";
            $params['groupid'] = $groupid;
            return $DB->get_records_sql($sql, $params);

} else {
            $context = context_course::instance($courseid);

// We want to query both the current context and parent contexts.
            list($relatedctxsql, $relatedctxparams) = $DB->get_in_or_equal($context->get_parent_context_ids(true), SQL_PARAMS_NAMED, 'relatedctx');

$sql = "SELECT u.id, u.firstname, u.lastname, u.email
                      FROM {user} u
                      JOIN {role_assignments} ra ON ra.userid = u.id
                     WHERE $select AND ra.contextid $relatedctxsql
                           $except
                    $order";
            $params = array_merge($params, $relatedctxparams);
            return $DB->get_records_sql($sql, $params);
        }
    }
}

/**
 * Returns SQL used to search through user table to find users (in a query
 * which may also join and apply other conditions).
 *
 * You can combine this SQL with an existing query by adding 'AND $sql' to the
 * WHERE clause of your query (where $sql is the first element in the array
 * returned by this function), and merging in the $params array to the parameters
 * of your query (where $params is the second element). Your query should use
 * named parameters such as :param, rather than the question mark style.
 *
 * There are examples of basic usage in the unit test for this function.
 *
 * @param string $search the text to search for (empty string = find all)
 * @param string $u the table alias for the user table in the query being
 *     built. May be ''.
 * @param bool $searchanywhere If true (default), searches in the middle of
 *     names, otherwise only searches at start
 * @param array $extrafields Array of extra user fields to include in search
 * @param array $exclude Array of user ids to exclude (empty = don't exclude)
 * @param array $includeonly If specified, only returns users that have ids
 *     incldued in this array (empty = don't restrict)
 * @return array an array with two elements, a fragment of SQL to go in the
 *     where clause the query, and an associative array containing any required
 *     parameters (using named placeholders).
 */
function users_search_sql($search, $u = 'u', $searchanywhere = true, array $extrafields = array(),
        array $exclude = null, array $includeonly = null) {
    global $DB, $CFG;
    $params = array();
    $tests = array();

if ($u) {
        $u .= '.';
    }

// If we have a $search string, put a field LIKE '$search%' condition on each field.
    if ($search) {
        $conditions = array(
            $DB->sql_fullname($u . 'firstname', $u . 'lastname'),
            $conditions[] = $u . 'lastname'
        );
        foreach ($extrafields as $field) {
            $conditions[] = $u . $field;
        }
        if ($searchanywhere) {
            $searchparam = '%' . $search . '%';
        } else {
            $searchparam = $search . '%';
        }
        $i = 0;
        foreach ($conditions as $key => $condition) {
            $conditions[$key] = $DB->sql_like($condition, ":con{$i}00", false, false);
            $params["con{$i}00"] = $searchparam;
            $i++;
        }
        $tests[] = '(' . implode(' OR ', $conditions) . ')';
    }

// Add some additional sensible conditions.
    $tests[] = $u . "id <> :guestid";
    $params['guestid'] = $CFG->siteguest;
    $tests[] = $u . 'deleted = 0';
    $tests[] = $u . 'confirmed = 1';

// If we are being asked to exclude any users, do that.
    if (!empty($exclude)) {
        list($usertest, $userparams) = $DB->get_in_or_equal($exclude, SQL_PARAMS_NAMED, 'ex', false);
        $tests[] = $u . 'id ' . $usertest;
        $params = array_merge($params, $userparams);
    }

// If we are validating a set list of userids, add an id IN (...) test.
    if (!empty($includeonly)) {
        list($usertest, $userparams) = $DB->get_in_or_equal($includeonly, SQL_PARAMS_NAMED, 'val');
        $tests[] = $u . 'id ' . $usertest;
        $params = array_merge($params, $userparams);
    }

// In case there are no tests, add one result (this makes it easier to combine
    // this with an existing query as you can always add AND $sql).
    if (empty($tests)) {
        $tests[] = '1 = 1';
    }

// Combing the conditions and return.
    return array(implode(' AND ', $tests), $params);
}

/**
 * This function generates the standard ORDER BY clause for use when generating
 * lists of users. If you don't have a reason to use a different order, then
 * you should use this method to generate the order when displaying lists of users.
 *
 * If the optional $search parameter is passed, then exact matches to the search
 * will be sorted first. For example, suppose you have two users 'Al Zebra' and
 * 'Alan Aardvark'. The default sort is Alan, then Al. If, however, you search for
 * 'Al', then Al will be listed first. (With two users, this is not a big deal,
 * but with thousands of users, it is essential.)
 *
 * The list of fields scanned for exact matches are:
 *  - firstname
 *  - lastname
 *  - $DB->sql_fullname
 *  - those returned by get_extra_user_fields
 *
 * If named parameters are used (which is the default, and highly recommended),
 * then the parameter names are like :usersortexactN, where N is an int.
 *
 * The simplest possible example use is:
 * list($sort, $params) = users_order_by_sql();
 * $sql = 'SELECT * FROM {users} ORDER BY ' . $sort;
 *
 * A more complex example, showing that this sort can be combined with other sorts:
 * list($sort, $sortparams) = users_order_by_sql('u');
 * $sql = "SELECT g.id AS groupid, gg.groupingid, u.id AS userid, u.firstname, u.lastname, u.idnumber, u.username
 *           FROM {groups} g
 *      LEFT JOIN {groupings_groups} gg ON g.id = gg.groupid
 *      LEFT JOIN {groups_members} gm ON g.id = gm.groupid
 *      LEFT JOIN {user} u ON gm.userid = u.id
 *          WHERE g.courseid = :courseid $groupwhere $groupingwhere
 *       ORDER BY g.name, $sort";
 * $params += $sortparams;
 *
 * An example showing the use of $search:
 * list($sort, $sortparams) = users_order_by_sql('u', $search, $this->get_context());
 * $order = ' ORDER BY ' . $sort;
 * $params += $sortparams;
 * $availableusers = $DB->get_records_sql($fields . $sql . $order, $params, $page*$perpage, $perpage);
 *
 * @param string $usertablealias (optional) any table prefix for the {users} table. E.g. 'u'.
 * @param string $search (optional) a current search string. If given,
 *      any exact matches to this string will be sorted first.
 * @param context $context the context we are in. Use by get_extra_user_fields.
 *      Defaults to $PAGE->context.
 * @return array with two elements:
 *      string SQL fragment to use in the ORDER BY clause. For example, "firstname, lastname".
 *      array of parameters used in the SQL fragment.
 */
function users_order_by_sql($usertablealias = '', $search = null, context $context = null) {
    global $DB, $PAGE;

if ($usertablealias) {
        $tableprefix = $usertablealias . '.';
    } else {
        $tableprefix = '';
    }

$sort = "{$tableprefix}lastname, {$tableprefix}firstname, {$tableprefix}id";
    $params = array();

if (!$search) {
        return array($sort, $params);
    }

if (!$context) {
        $context = $PAGE->context;
    }

$exactconditions = array();
    $paramkey = 'usersortexact1';

$exactconditions[] = $DB->sql_fullname($tableprefix . 'firstname', $tableprefix  . 'lastname') .
            ' = :' . $paramkey;
    $params[$paramkey] = $search;
    $paramkey++;

$fieldstocheck = array_merge(array('firstname', 'lastname'), get_extra_user_fields($context));
    foreach ($fieldstocheck as $key => $field) {
        $exactconditions[] = 'LOWER(' . $tableprefix . $field . ') = LOWER(:' . $paramkey . ')';
        $params[$paramkey] = $search;
        $paramkey++;
    }

$sort = 'CASE WHEN ' . implode(' OR ', $exactconditions) .
            ' THEN 0 ELSE 1 END, ' . $sort;

return array($sort, $params);
}

/**
 * Returns a subset of users
 *
 * @global object
 * @uses DEBUG_DEVELOPER
 * @uses SQL_PARAMS_NAMED
 * @param bool $get If false then only a count of the records is returned
 * @param string $search A simple string to search for
 * @param bool $confirmed A switch to allow/disallow unconfirmed users
 * @param array $exceptions A list of IDs to ignore, eg 2,4,5,8,9,10
 * @param string $sort A SQL snippet for the sorting criteria to use
 * @param string $firstinitial Users whose first name starts with $firstinitial
 * @param string $lastinitial Users whose last name starts with $lastinitial
 * @param string $page The page or records to return
 * @param string $recordsperpage The number of records to return per page
 * @param string $fields A comma separated list of fields to be returned from the chosen table.
 * @return array|int|bool  {@link $USER} records unless get is false in which case the integer count of the records found is returned.
 *                        False is returned if an error is encountered.
 */
function get_users($get=true, $search='', $confirmed=false, array $exceptions=null, $sort='firstname ASC',
                   $firstinitial='', $lastinitial='', $page='', $recordsperpage='', $fields='*', $extraselect='', array $extraparams=null) {
    global $DB, $CFG;

if ($get && !$recordsperpage) {
        debugging('Call to get_users with $get = true no $recordsperpage limit. ' .
                'On large installations, this will probably cause an out of memory error. ' .
                'Please think again and change your code so that it does not try to ' .
                'load so much data into memory.', DEBUG_DEVELOPER);
    }

$fullname  = $DB->sql_fullname();

$select = " id <> :guestid AND deleted = 0";
    $params = array('guestid'=>$CFG->siteguest);

if (!empty($search)){
        $search = trim($search);
        $select .= " AND (".$DB->sql_like($fullname, ':search1', false)." OR ".$DB->sql_like('email', ':search2', false)." OR username = :search3)";
        $params['search1'] = "%$search%";
        $params['search2'] = "%$search%";
        $params['search3'] = "$search";
    }

if ($confirmed) {
        $select .= " AND confirmed = 1";
    }

if ($exceptions) {
        list($exceptions, $eparams) = $DB->get_in_or_equal($exceptions, SQL_PARAMS_NAMED, 'ex', false);
        $params = $params + $eparams;
        $select .= " AND id $exceptions";
    }

if ($firstinitial) {
        $select .= " AND ".$DB->sql_like('firstname', ':fni', false, false);
        $params['fni'] = "$firstinitial%";
    }
    if ($lastinitial) {
        $select .= " AND ".$DB->sql_like('lastname', ':lni', false, false);
        $params['lni'] = "$lastinitial%";
    }

if ($extraselect) {
        $select .= " AND $extraselect";
        $params = $params + (array)$extraparams;
    }

if ($get) {
        return $DB->get_records_select('user', $select, $params, $sort, $fields, $page, $recordsperpage);
    } else {
        return $DB->count_records_select('user', $select, $params);
    }
}

/**
 * Return filtered (if provided) list of users in site, except guest and deleted users.
 *
 * @param string $sort An SQL field to sort by
 * @param string $dir The sort direction ASC|DESC
 * @param int $page The page or records to return
 * @param int $recordsperpage The number of records to return per page
 * @param string $search A simple string to search for
 * @param string $firstinitial Users whose first name starts with $firstinitial
 * @param string $lastinitial Users whose last name starts with $lastinitial
 * @param string $extraselect An additional SQL select statement to append to the query
 * @param array $extraparams Additional parameters to use for the above $extraselect
 * @param stdClass $extracontext If specified, will include user 'extra fields'
 *   as appropriate for current user and given context
 * @return array Array of {@link $USER} records
 */
function get_users_listing($sort='lastaccess', $dir='ASC', $page=0, $recordsperpage=0,
                           $search='', $firstinitial='', $lastinitial='', $extraselect='',
                           array $extraparams=null, $extracontext = null) {
    global $DB, $CFG;

$fullname  = $DB->sql_fullname();

$select = "deleted <> 1 AND id <> :guestid";
    $params = array('guestid' => $CFG->siteguest);

if (!empty($search)) {
        $search = trim($search);
        $select .= " AND (". $DB->sql_like($fullname, ':search1', false, false).
                   " OR ". $DB->sql_like('email', ':search2', false, false).
                   " OR username = :search3)";
        $params['search1'] = "%$search%";
        $params['search2'] = "%$search%";
        $params['search3'] = "$search";
    }

if ($firstinitial) {
        $select .= " AND ". $DB->sql_like('firstname', ':fni', false, false);
        $params['fni'] = "$firstinitial%";
    }
    if ($lastinitial) {
        $select .= " AND ". $DB->sql_like('lastname', ':lni', false, false);
        $params['lni'] = "$lastinitial%";
    }

if ($extraselect) {
        $select .= " AND $extraselect";
        $params = $params + (array)$extraparams;
    }

if ($sort) {
        $sort = " ORDER BY $sort $dir";
    }

// If a context is specified, get extra user fields that the current user
    // is supposed to see.
    $extrafields = '';
    if ($extracontext) {
        $extrafields = get_extra_user_fields_sql($extracontext, '', '',
                array('id', 'username', 'email', 'firstname', 'lastname', 'city', 'country',
                'lastaccess', 'confirmed', 'mnethostid'));
    }
    $namefields = get_all_user_name_fields(true);
    $extrafields = "$extrafields, $namefields";

// warning: will return UNCONFIRMED USERS
    return $DB->get_records_sql("SELECT id, username, email, city, country, lastaccess, confirmed, mnethostid, suspended $extrafields
                                   FROM {user}
                                  WHERE $select
                                  $sort", $params, $page, $recordsperpage);

}

/**
 * Full list of users that have confirmed their accounts.
 *
 * @global object
 * @return array of unconfirmed users
 */
function get_users_confirmed() {
    global $DB, $CFG;
    return $DB->get_records_sql("SELECT *
                                   FROM {user}
                                  WHERE confirmed = 1 AND deleted = 0 AND id <> ?", array($CFG->siteguest));
}

/// OTHER SITE AND COURSE FUNCTIONS /////////////////////////////////////////////

/**
 * Returns $course object of the top-level site.
 *
 * @return object A {@link $COURSE} object for the site, exception if not found
 */
function get_site() {
    global $SITE, $DB;

if (!empty($SITE->id)) {   // We already have a global to use, so return that
        return $SITE;
    }

if ($course = $DB->get_record('course', array('category'=>0))) {
        return $course;
    } else {
        // course table exists, but the site is not there,
        // unfortunately there is no automatic way to recover
        throw new moodle_exception('nosite', 'error');
    }
}

/**
 * Gets a course object from database. If the course id corresponds to an
 * already-loaded $COURSE or $SITE object, then the loaded object will be used,
 * saving a database query.
 *
 * If it reuses an existing object, by default the object will be cloned. This
 * means you can modify the object safely without affecting other code.
 *
 * @param int $courseid Course id
 * @param bool $clone If true (default), makes a clone of the record
 * @return stdClass A course object
 * @throws dml_exception If not found in database
 */
function get_course($courseid, $clone = true) {
    global $DB, $COURSE, $SITE;
    if (!empty($COURSE->id) && $COURSE->id == $courseid) {
        return $clone ? clone($COURSE) : $COURSE;
    } else if (!empty($SITE->id) && $SITE->id == $courseid) {
        return $clone ? clone($SITE) : $SITE;
    } else {
        return $DB->get_record('course', array('id' => $courseid), '*', MUST_EXIST);
    }
}

/**
 * Returns list of courses, for whole site, or category
 *
 * Returns list of courses, for whole site, or category
 * Important: Using c.* for fields is extremely expensive because
 *            we are using distinct. You almost _NEVER_ need all the fields
 *            in such a large SELECT
 *
 * Consider using core_course_category::get_courses()
 * or core_course_category::search_courses() instead since they use caching.
 *
 * @global object
 * @global object
 * @global object
 * @uses CONTEXT_COURSE
 * @param string|int $categoryid Either a category id or 'all' for everything
 * @param string $sort A field and direction to sort by
 * @param string $fields The additional fields to return
 * @return array Array of courses
 */
function get_courses($categoryid="all", $sort="c.sortorder ASC", $fields="c.*") {

global $USER, $CFG, $DB;

$params = array();

if ($categoryid !== "all" && is_numeric($categoryid)) {
        $categoryselect = "WHERE c.category = :catid";
        $params['catid'] = $categoryid;
    } else {
        $categoryselect = "";
    }

if (empty($sort)) {
        $sortstatement = "";
    } else {
        $sortstatement = "ORDER BY $sort";
    }

$visiblecourses = array();

$ccselect = ', ' . context_helper::get_preload_record_columns_sql('ctx');
    $ccjoin = "LEFT JOIN {context} ctx ON (ctx.instanceid = c.id AND ctx.contextlevel = :contextlevel)";
    $params['contextlevel'] = CONTEXT_COURSE;

$sql = "SELECT $fields $ccselect
              FROM {course} c
           $ccjoin
              $categoryselect
              $sortstatement";

// pull out all course matching the cat
    if ($courses = $DB->get_records_sql($sql, $params)) {

// loop throught them
        foreach ($courses as $course) {
            context_helper::preload_from_record($course);
            if (core_course_category::can_view_course_info($course)) {
                $visiblecourses [$course->id] = $course;
            }
        }
    }
    return $visiblecourses;
}

/**
 * A list of courses that match a search
 *
 * @global object
 * @global object
 * @param array $searchterms An array of search criteria
 * @param string $sort A field and direction to sort by
 * @param int $page The page number to get
 * @param int $recordsperpage The number of records per page
 * @param int $totalcount Passed in by reference.
 * @param array $requiredcapabilities Extra list of capabilities used to filter courses
 * @param array $searchcond additional search conditions, for example ['c.enablecompletion = :p1']
 * @param array $params named parameters for additional search conditions, for example ['p1' => 1]
 * @return stdClass[] {@link $COURSE} records
 */
function get_courses_search($searchterms, $sort, $page, $recordsperpage, &$totalcount,
                            $requiredcapabilities = array(), $searchcond = [], $params = []) {
    global $CFG, $DB;

if ($DB->sql_regex_supported()) {
        $REGEXP    = $DB->sql_regex(true);
        $NOTREGEXP = $DB->sql_regex(false);
    }

$i = 0;

// Thanks Oracle for your non-ansi concat and type limits in coalesce. MDL-29912
    if ($DB->get_dbfamily() == 'oracle') {
        $concat = "(c.summary|| ' ' || c.fullname || ' ' || c.idnumber || ' ' || c.shortname)";
    } else {
        $concat = $DB->sql_concat("COALESCE(c.summary, '')", "' '", 'c.fullname', "' '", 'c.idnumber', "' '", 'c.shortname');
    }

foreach ($searchterms as $searchterm) {
        $i++;

$NOT = false; /// Initially we aren't going to perform NOT LIKE searches, only MSSQL and Oracle
                   /// will use it to simulate the "-" operator with LIKE clause

/// Under Oracle and MSSQL, trim the + and - operators and perform
    /// simpler LIKE (or NOT LIKE) queries
        if (!$DB->sql_regex_supported()) {
            if (substr($searchterm, 0, 1) == '-') {
                $NOT = true;
            }
            $searchterm = trim($searchterm, '+-');
        }

// TODO: +- may not work for non latin languages

if (substr($searchterm,0,1) == '+') {
            $searchterm = trim($searchterm, '+-');
            $searchterm = preg_quote($searchterm, '|');
            $searchcond[] = "$concat $REGEXP :ss$i";
            $params['ss'.$i] = "(^|[^a-zA-Z0-9])$searchterm([^a-zA-Z0-9]|$)";

} else if ((substr($searchterm,0,1) == "-") && (core_text::strlen($searchterm) > 1)) {
            $searchterm = trim($searchterm, '+-');
            $searchterm = preg_quote($searchterm, '|');
            $searchcond[] = "$concat $NOTREGEXP :ss$i";
            $params['ss'.$i] = "(^|[^a-zA-Z0-9])$searchterm([^a-zA-Z0-9]|$)";

} else {
            $searchcond[] = $DB->sql_like($concat,":ss$i", false, true, $NOT);
            $params['ss'.$i] = "%$searchterm%";
        }
    }

if (empty($searchcond)) {
        $searchcond = array('1 = 1');
    }

$searchcond = implode(" AND ", $searchcond);

$courses = array();
    $c = 0; // counts how many visible courses we've seen

// Tiki pagination
    $limitfrom = $page * $recordsperpage;
    $limitto   = $limitfrom + $recordsperpage;

$sql = "SELECT c.* $ccselect
              FROM {course} c
           $ccjoin
             WHERE $searchcond AND c.id <> ".SITEID."
          ORDER BY $sort";

$mycourses = enrol_get_my_courses();
    $rs = $DB->get_recordset_sql($sql, $params);
    foreach($rs as $course) {
        // Preload contexts only for hidden courses or courses we need to return.
        context_helper::preload_from_record($course);
        $coursecontext = context_course::instance($course->id);
        if (!array_key_exists($course->id, $mycourses) && !core_course_category::can_view_course_info($course)) {
            continue;
        }
        if (!empty($requiredcapabilities)) {
            if (!has_all_capabilities($requiredcapabilities, $coursecontext)) {
                continue;
            }
        }
        // Don't exit this loop till the end
        // we need to count all the visible courses
        // to update $totalcount
        if ($c >= $limitfrom && $c < $limitto) {
            $courses[$course->id] = $course;
        }
        $c++;
    }
    $rs->close();

// our caller expects 2 bits of data - our return
    // array, and an updated $totalcount
    $totalcount = $c;
    return $courses;
}

/**
 * Fixes course category and course sortorder, also verifies category and course parents and paths.
 * (circular references are not fixed)
 *
 * @global object
 * @global object
 * @uses MAX_COURSES_IN_CATEGORY
 * @uses MAX_COURSE_CATEGORIES
 * @uses SITEID
 * @uses CONTEXT_COURSE
 * @return void
 */
function fix_course_sortorder() {
    global $DB, $SITE;

//WARNING: this is PHP5 only code!

// if there are any changes made to courses or categories we will trigger
    // the cache events to purge all cached courses/categories data
    $cacheevents = array();

if ($unsorted = $DB->get_records('course_categories', array('sortorder'=>0))) {
        //move all categories that are not sorted yet to the end
        $DB->set_field('course_categories', 'sortorder', MAX_COURSES_IN_CATEGORY*MAX_COURSE_CATEGORIES, array('sortorder'=>0));
        $cacheevents['changesincoursecat'] = true;
    }

$allcats = $DB->get_records('course_categories', null, 'sortorder, id', 'id, sortorder, parent, depth, path');
    $topcats    = array();
    $brokencats = array();
    foreach ($allcats as $cat) {
        $sortorder = (int)$cat->sortorder;
        if (!$cat->parent) {
            while(isset($topcats[$sortorder])) {
                $sortorder++;
            }
            $topcats[$sortorder] = $cat;
            continue;
        }
        if (!isset($allcats[$cat->parent])) {
            $brokencats[] = $cat;
            continue;
        }
        if (!isset($allcats[$cat->parent]->children)) {
            $allcats[$cat->parent]->children = array();
        }
        while(isset($allcats[$cat->parent]->children[$sortorder])) {
            $sortorder++;
        }
        $allcats[$cat->parent]->children[$sortorder] = $cat;
    }
    unset($allcats);

// add broken cats to category tree
    if ($brokencats) {
        $defaultcat = reset($topcats);
        foreach ($brokencats as $cat) {
            $topcats[] = $cat;
        }
    }

// now walk recursively the tree and fix any problems found
    $sortorder = 0;
    $fixcontexts = array();
    if (_fix_course_cats($topcats, $sortorder, 0, 0, '', $fixcontexts)) {
        $cacheevents['changesincoursecat'] = true;
    }

// detect if there are "multiple" frontpage courses and fix them if needed
    $frontcourses = $DB->get_records('course', array('category'=>0), 'id');
    if (count($frontcourses) > 1) {
        if (isset($frontcourses[SITEID])) {
            $frontcourse = $frontcourses[SITEID];
            unset($frontcourses[SITEID]);
        } else {
            $frontcourse = array_shift($frontcourses);
        }
        $defaultcat = reset($topcats);
        foreach ($frontcourses as $course) {
            $DB->set_field('course', 'category', $defaultcat->id, array('id'=>$course->id));
            $context = context_course::instance($course->id);
            $fixcontexts[$context->id] = $context;
            $cacheevents['changesincourse'] = true;
        }
        unset($frontcourses);
    } else {
        $frontcourse = reset($frontcourses);
    }

// now fix the paths and depths in context table if needed
    if ($fixcontexts) {
        foreach ($fixcontexts as $fixcontext) {
            $fixcontext->reset_paths(false);
        }
        context_helper::build_all_paths(false);
        unset($fixcontexts);
        $cacheevents['changesincourse'] = true;
        $cacheevents['changesincoursecat'] = true;
    }

// release memory
    unset($topcats);
    unset($brokencats);
    unset($fixcontexts);

// fix frontpage course sortorder
    if ($frontcourse->sortorder != 1) {
        $DB->set_field('course', 'sortorder', 1, array('id'=>$frontcourse->id));
        $cacheevents['changesincourse'] = true;
    }

// now fix the course counts in category records if needed
    $sql = "SELECT cc.id, cc.coursecount, COUNT(c.id) AS newcount
              FROM {course_categories} cc
              LEFT JOIN {course} c ON c.category = cc.id
          GROUP BY cc.id, cc.coursecount
            HAVING cc.coursecount <> COUNT(c.id)";

if ($updatecounts = $DB->get_records_sql($sql)) {
        // categories with more courses than MAX_COURSES_IN_CATEGORY
        $categories = array();
        foreach ($updatecounts as $cat) {
            $cat->coursecount = $cat->newcount;
            if ($cat->coursecount >= MAX_COURSES_IN_CATEGORY) {
                $categories[] = $cat->id;
            }
            unset($cat->newcount);
            $DB->update_record_raw('course_categories', $cat, true);
        }
        if (!empty($categories)) {
            $str = implode(', ', $categories);
            debugging("The number of courses (category id: $str) has reached MAX_COURSES_IN_CATEGORY (" . MAX_COURSES_IN_CATEGORY . "), it will cause a sorting performance issue, please increase the value of MAX_COURSES_IN_CATEGORY in lib/datalib.php file. See tracker issue: MDL-25669", DEBUG_DEVELOPER);
        }
        $cacheevents['changesincoursecat'] = true;
    }

// now make sure that sortorders in course table are withing the category sortorder ranges
    $sql = "SELECT DISTINCT cc.id, cc.sortorder
              FROM {course_categories} cc
              JOIN {course} c ON c.category = cc.id
             WHERE c.sortorder < cc.sortorder OR c.sortorder > cc.sortorder + ".MAX_COURSES_IN_CATEGORY;

if ($fixcategories = $DB->get_records_sql($sql)) {
        //fix the course sortorder ranges
        foreach ($fixcategories as $cat) {
            $sql = "UPDATE {course}
                       SET sortorder = ".$DB->sql_modulo('sortorder', MAX_COURSES_IN_CATEGORY)." + ?
                     WHERE category = ?";
            $DB->execute($sql, array($cat->sortorder, $cat->id));
        }
        $cacheevents['changesincoursecat'] = true;
    }
    unset($fixcategories);

// categories having courses with sortorder duplicates or having gaps in sortorder
    $sql = "SELECT DISTINCT c1.category AS id , cc.sortorder
              FROM {course} c1
              JOIN {course} c2 ON c1.sortorder = c2.sortorder
              JOIN {course_categories} cc ON (c1.category = cc.id)
             WHERE c1.id <> c2.id";
    $fixcategories = $DB->get_records_sql($sql);

$sql = "SELECT cc.id, cc.sortorder, cc.coursecount, MAX(c.sortorder) AS maxsort, MIN(c.sortorder) AS minsort
              FROM {course_categories} cc
              JOIN {course} c ON c.category = cc.id
          GROUP BY cc.id, cc.sortorder, cc.coursecount
            HAVING (MAX(c.sortorder) <>  cc.sortorder + cc.coursecount) OR (MIN(c.sortorder) <>  cc.sortorder + 1)";
    $gapcategories = $DB->get_records_sql($sql);

foreach ($gapcategories as $cat) {
        if (isset($fixcategories[$cat->id])) {
            // duplicates detected already

} else if ($cat->minsort == $cat->sortorder and $cat->maxsort == $cat->sortorder + $cat->coursecount - 1) {
            // easy - new course inserted with sortorder 0, the rest is ok
            $sql = "UPDATE {course}
                       SET sortorder = sortorder + 1
                     WHERE category = ?";
            $DB->execute($sql, array($cat->id));

} else {
            // it needs full resorting
            $fixcategories[$cat->id] = $cat;
        }
        $cacheevents['changesincourse'] = true;
    }
    unset($gapcategories);

// fix course sortorders in problematic categories only
    foreach ($fixcategories as $cat) {
        $i = 1;
        $courses = $DB->get_records('course', array('category'=>$cat->id), 'sortorder ASC, id DESC', 'id, sortorder');
        foreach ($courses as $course) {
            if ($course->sortorder != $cat->sortorder + $i) {
                $course->sortorder = $cat->sortorder + $i;
                $DB->update_record_raw('course', $course, true);
                $cacheevents['changesincourse'] = true;
            }
            $i++;
        }
    }

// advise all caches that need to be rebuilt
    foreach (array_keys($cacheevents) as $event) {
        cache_helper::purge_by_event($event);
    }
}

/**
 * Internal recursive category verification function, do not use directly!
 *
 * @todo Document the arguments of this function better
 *
 * @global object
 * @uses MAX_COURSES_IN_CATEGORY
 * @uses CONTEXT_COURSECAT
 * @param array $children
 * @param int $sortorder
 * @param string $parent
 * @param int $depth
 * @param string $path
 * @param array $fixcontexts
 * @return bool if changes were made
 */
function _fix_course_cats($children, &$sortorder, $parent, $depth, $path, &$fixcontexts) {
    global $DB;

$depth++;
    $changesmade = false;

foreach ($children as $cat) {
        $sortorder = $sortorder + MAX_COURSES_IN_CATEGORY;
        $update = false;
        if ($parent != $cat->parent or $depth != $cat->depth or $path.'/'.$cat->id != $cat->path) {
            $cat->parent = $parent;
            $cat->depth  = $depth;
            $cat->path   = $path.'/'.$cat->id;
            $update = true;

// make sure context caches are rebuild and dirty contexts marked
            $context = context_coursecat::instance($cat->id);
            $fixcontexts[$context->id] = $context;
        }
        if ($cat->sortorder != $sortorder) {
            $cat->sortorder = $sortorder;
            $update = true;
        }
        if ($update) {
            $DB->update_record('course_categories', $cat, true);
            $changesmade = true;
        }
        if (isset($cat->children)) {
            if (_fix_course_cats($cat->children, $sortorder, $cat->id, $cat->depth, $cat->path, $fixcontexts)) {
                $changesmade = true;
            }
        }
    }
    return $changesmade;
}

/**
 * List of remote courses that a user has access to via MNET.
 * Works only on the IDP
 *
 * @global object
 * @global object
 * @param int @userid The user id to get remote courses for
 * @return array Array of {@link $COURSE} of course objects
 */
function get_my_remotecourses($userid=0) {
    global $DB, $USER;

if (empty($userid)) {
        $userid = $USER->id;
    }

// we can not use SELECT DISTINCT + text field (summary) because of MS SQL and Oracle, subselect used therefore
    $sql = "SELECT c.id, c.remoteid, c.shortname, c.fullname,
                   c.hostid, c.summary, c.summaryformat, c.categoryname AS cat_name,
                   h.name AS hostname
              FROM {mnetservice_enrol_courses} c
              JOIN (SELECT DISTINCT hostid, remotecourseid
                      FROM {mnetservice_enrol_enrolments}
                     WHERE userid = ?
                   ) e ON (e.hostid = c.hostid AND e.remotecourseid = c.remoteid)
              JOIN {mnet_host} h ON h.id = c.hostid";

return $DB->get_records_sql($sql, array($userid));
}

/**
 * List of remote hosts that a user has access to via MNET.
 * Works on the SP
 *
 * @global object
 * @global object
 * @return array|bool Array of host objects or false
 */
function get_my_remotehosts() {
    global $CFG, $USER;

if ($USER->mnethostid == $CFG->mnet_localhost_id) {
        return false; // Return nothing on the IDP
    }
    if (!empty($USER->mnet_foreign_host_array) && is_array($USER->mnet_foreign_host_array)) {
        return $USER->mnet_foreign_host_array;
    }
    return false;
}

/**
 * Returns a menu of all available scales from the site as well as the given course
 *
 * @global object
 * @param int $courseid The id of the course as found in the 'course' table.
 * @return array
 */
function get_scales_menu($courseid=0) {
    global $DB;

$sql = "SELECT id, name, courseid
              FROM {scale}
             WHERE courseid = 0 or courseid = ?
          ORDER BY courseid ASC, name ASC";
    $params = array($courseid);
    $scales = array();
    $results = $DB->get_records_sql($sql, $params);
    foreach ($results as $index => $record) {
        $context = empty($record->courseid) ? context_system::instance() : context_course::instance($record->courseid);
        $scales[$index] = format_string($record->name, false, ["context" => $context]);
    }
    // Format: [id => 'scale name'].
    return $scales;
}

/**
 * Increment standard revision field.
 *
 * The revision are based on current time and are incrementing.
 * There is a protection for runaway revisions, it may not go further than
 * one hour into future.
 *
 * The field has to be XMLDB_TYPE_INTEGER with size 10.
 *
 * @param string $table
 * @param string $field name of the field containing revision
 * @param string $select use empty string when updating all records
 * @param array $params optional select parameters
 */
function increment_revision_number($table, $field, $select, array $params = null) {
    global $DB;

$now = time();
    $sql = "UPDATE {{$table}}
                   SET $field = (CASE
                       WHEN $field IS NULL THEN $now
                       WHEN $field < $now THEN $now
                       WHEN $field > $now + 3600 THEN $now
                       ELSE $field + 1 END)";
    if ($select) {
        $sql = $sql . " WHERE $select";
    }
    $DB->execute($sql, $params);
}

/// MODULE FUNCTIONS /////////////////////////////////////////////////

/**
 * Just gets a raw list of all modules in a course
 *
 * @global object
 * @param int $courseid The id of the course as found in the 'course' table.
 * @return array
 */
function get_course_mods($courseid) {
    global $DB;

if (empty($courseid)) {
        return false; // avoid warnings
    }

return $DB->get_records_sql("SELECT cm.*, m.name as modname
                                   FROM {modules} m, {course_modules} cm
                                  WHERE cm.course = ? AND cm.module = m.id AND m.visible = 1",
                                array($courseid)); // no disabled mods
}

/**
 * Given an id of a course module, finds the coursemodule description
 *
 * Please note that this function performs 1-2 DB queries. When possible use cached
 * course modinfo. For example get_fast_modinfo($courseorid)->get_cm($cmid)
 * See also {@link cm_info::get_course_module_record()}
 *
 * @global object
 * @param string $modulename name of module type, eg. resource, assignment,... (optional, slower and less safe if not specified)
 * @param int $cmid course module id (id in course_modules table)
 * @param int $courseid optional course id for extra validation
 * @param bool $sectionnum include relative section number (0,1,2 ...)
 * @param int $strictness IGNORE_MISSING means compatible mode, false returned if record not found, debug message if more found;
 *                        IGNORE_MULTIPLE means return first, ignore multiple records found(not recommended);
 *                        MUST_EXIST means throw exception if no record or multiple records found
 * @return stdClass
 */
function get_coursemodule_from_id($modulename, $cmid, $courseid=0, $sectionnum=false, $strictness=IGNORE_MISSING) {
    global $DB;

$params = array('cmid'=>$cmid);

if (!$modulename) {
        if (!$modulename = $DB->get_field_sql("SELECT md.name
                                                 FROM {modules} md
                                                 JOIN {course_modules} cm ON cm.module = md.id
                                                WHERE cm.id = :cmid", $params, $strictness)) {
            return false;
        }
    } else {
        if (!core_component::is_valid_plugin_name('mod', $modulename)) {
            throw new coding_exception('Invalid modulename parameter');
        }
    }

$params['modulename'] = $modulename;

$courseselect = "";
    $sectionfield = "";
    $sectionjoin  = "";

if ($courseid) {
        $courseselect = "AND cm.course = :courseid";
        $params['courseid'] = $courseid;
    }

if ($sectionnum) {
        $sectionfield = ", cw.section AS sectionnum";
        $sectionjoin  = "LEFT JOIN {course_sections} cw ON cw.id = cm.section";
    }

$sql = "SELECT cm.*, m.name, md.name AS modname $sectionfield
              FROM {course_modules} cm
                   JOIN {modules} md ON md.id = cm.module
                   JOIN {".$modulename."} m ON m.id = cm.instance
                   $sectionjoin
             WHERE cm.id = :cmid AND md.name = :modulename
                   $courseselect";

return $DB->get_record_sql($sql, $params, $strictness);
}

/**
 * Given an instance number of a module, finds the coursemodule description
 *
 * Please note that this function performs DB query. When possible use cached course
 * modinfo. For example get_fast_modinfo($courseorid)->instances[$modulename][$instance]
 * See also {@link cm_info::get_course_module_record()}
 *
 * @global object
 * @param string $modulename name of module type, eg. resource, assignment,...
 * @param int $instance module instance number (id in resource, assignment etc. table)
 * @param int $courseid optional course id for extra validation
 * @param bool $sectionnum include relative section number (0,1,2 ...)
 * @param int $strictness IGNORE_MISSING means compatible mode, false returned if record not found, debug message if more found;
 *                        IGNORE_MULTIPLE means return first, ignore multiple records found(not recommended);
 *                        MUST_EXIST means throw exception if no record or multiple records found
 * @return stdClass
 */
function get_coursemodule_from_instance($modulename, $instance, $courseid=0, $sectionnum=false, $strictness=IGNORE_MISSING) {
    global $DB;

if (!core_component::is_valid_plugin_name('mod', $modulename)) {
        throw new coding_exception('Invalid modulename parameter');
    }

$params = array('instance'=>$instance, 'modulename'=>$modulename);

$courseselect = "";
    $sectionfield = "";
    $sectionjoin  = "";

if ($courseid) {
        $courseselect = "AND cm.course = :courseid";
        $params['courseid'] = $courseid;
    }

if ($sectionnum) {
        $sectionfield = ", cw.section AS sectionnum";
        $sectionjoin  = "LEFT JOIN {course_sections} cw ON cw.id = cm.section";
    }

$sql = "SELECT cm.*, m.name, md.name AS modname $sectionfield
              FROM {course_modules} cm
                   JOIN {modules} md ON md.id = cm.module
                   JOIN {".$modulename."} m ON m.id = cm.instance
                   $sectionjoin
             WHERE m.id = :instance AND md.name = :modulename
                   $courseselect";

return $DB->get_record_sql($sql, $params, $strictness);
}

/**
 * Returns all course modules of given activity in course
 *
 * @param string $modulename The module name (forum, quiz, etc.)
 * @param int $courseid The course id to get modules for
 * @param string $extrafields extra fields starting with m.
 * @return array Array of results
 */
function get_coursemodules_in_course($modulename, $courseid, $extrafields='') {
    global $DB;

if (!core_component::is_valid_plugin_name('mod', $modulename)) {
        throw new coding_exception('Invalid modulename parameter');
    }

if (!empty($extrafields)) {
        $extrafields = ", $extrafields";
    }
    $params = array();
    $params['courseid'] = $courseid;
    $params['modulename'] = $modulename;

return $DB->get_records_sql("SELECT cm.*, m.name, md.name as modname $extrafields
                                   FROM {course_modules} cm, {modules} md, {".$modulename."} m
                                  WHERE cm.course = :courseid AND
                                        cm.instance = m.id AND
                                        md.name = :modulename AND
                                        md.id = cm.module", $params);
}

/**
 * Returns an array of all the active instances of a particular module in given courses, sorted in the order they are defined
 *
 * Returns an array of all the active instances of a particular
 * module in given courses, sorted in the order they are defined
 * in the course. Returns an empty array on any errors.
 *
 * The returned objects includle the columns cw.section, cm.visible,
 * cm.groupmode, and cm.groupingid, and are indexed by cm.id.
 *
 * @global object
 * @global object
 * @param string $modulename The name of the module to get instances for
 * @param array $courses an array of course objects.
 * @param int $userid
 * @param int $includeinvisible
 * @return array of module instance objects, including some extra fields from the course_modules
 *          and course_sections tables, or an empty array if an error occurred.
 */
function get_all_instances_in_courses($modulename, $courses, $userid=NULL, $includeinvisible=false) {
    global $CFG, $DB;

if (!core_component::is_valid_plugin_name('mod', $modulename)) {
        throw new coding_exception('Invalid modulename parameter');
    }

$outputarray = array();

if (empty($courses) || !is_array($courses) || count($courses) == 0) {
        return $outputarray;
    }

list($coursessql, $params) = $DB->get_in_or_equal(array_keys($courses), SQL_PARAMS_NAMED, 'c0');
    $params['modulename'] = $modulename;

if (!$rawmods = $DB->get_records_sql("SELECT cm.id AS coursemodule, m.*, cw.section, cm.visible AS visible,
                                                 cm.groupmode, cm.groupingid
                                            FROM {course_modules} cm, {course_sections} cw, {modules} md,
                                                 {".$modulename."} m
                                           WHERE cm.course $coursessql AND
                                                 cm.instance = m.id AND
                                                 cm.section = cw.id AND
                                                 md.name = :modulename AND
                                                 md.id = cm.module", $params)) {
        return $outputarray;
    }

foreach ($courses as $course) {
        $modinfo = get_fast_modinfo($course, $userid);

if (empty($modinfo->instances[$modulename])) {
            continue;
        }

foreach ($modinfo->instances[$modulename] as $cm) {
            if (!$includeinvisible and !$cm->uservisible) {
                continue;
            }
            if (!isset($rawmods[$cm->id])) {
                continue;
            }
            $instance = $rawmods[$cm->id];
            if (!empty($cm->extra)) {
                $instance->extra = $cm->extra;
            }
            $outputarray[] = $instance;
        }
    }

return $outputarray;
}

/**
 * Returns an array of all the active instances of a particular module in a given course,
 * sorted in the order they are defined.
 *
 * Returns an array of all the active instances of a particular
 * module in a given course, sorted in the order they are defined
 * in the course. Returns an empty array on any errors.
 *
 * The returned objects includle the columns cw.section, cm.visible,
 * cm.groupmode, and cm.groupingid, and are indexed by cm.id.
 *
 * Simply calls {@link all_instances_in_courses()} with a single provided course
 *
 * @param string $modulename The name of the module to get instances for
 * @param object $course The course obect.
 * @return array of module instance objects, including some extra fields from the course_modules
 *          and course_sections tables, or an empty array if an error occurred.
 * @param int $userid
 * @param int $includeinvisible
 */
function get_all_instances_in_course($modulename, $course, $userid=NULL, $includeinvisible=false) {
    return get_all_instances_in_courses($modulename, array($course->id => $course), $userid, $includeinvisible);
}

/**
 * Determine whether a module instance is visible within a course
 *
 * Given a valid module object with info about the id and course,
 * and the module's type (eg "forum") returns whether the object
 * is visible or not according to the 'eye' icon only.
 *
 * NOTE: This does NOT take into account visibility to a particular user.
 * To get visibility access for a specific user, use get_fast_modinfo, get a
 * cm_info object from this, and check the ->uservisible property; or use
 * the \core_availability\info_module::is_user_visible() static function.
 *
 * @global object

* @param $moduletype Name of the module eg 'forum'
 * @param $module Object which is the instance of the module
 * @return bool Success
 */
function instance_is_visible($moduletype, $module) {
    global $DB;

if (!empty($module->id)) {
        $params = array('courseid'=>$module->course, 'moduletype'=>$moduletype, 'moduleid'=>$module->id);
        if ($records = $DB->get_records_sql("SELECT cm.instance, cm.visible, cm.groupingid, cm.id, cm.course
                                               FROM {course_modules} cm, {modules} m
                                              WHERE cm.course = :courseid AND
                                                    cm.module = m.id AND
                                                    m.name = :moduletype AND
                                                    cm.instance = :moduleid", $params)) {

foreach ($records as $record) { // there should only be one - use the first one
                return $record->visible;
            }
        }
    }
    return true;  // visible by default!
}

/// LOG FUNCTIONS /////////////////////////////////////////////////////

/**
 * Get instance of log manager.
 *
 * @param bool $forcereload
 * @return \core\log\manager
 */
function get_log_manager($forcereload = false) {
    /** @var \core\log\manager $singleton */
    static $singleton = null;

if ($forcereload and isset($singleton)) {
        $singleton->dispose();
        $singleton = null;
    }

if (isset($singleton)) {
        return $singleton;
    }

$classname = '\tool_log\log\manager';
    if (defined('LOG_MANAGER_CLASS')) {
        $classname = LOG_MANAGER_CLASS;
    }

if (!class_exists($classname)) {
        if (!empty($classname)) {
            debugging("Cannot find log manager class '$classname'.", DEBUG_DEVELOPER);
        }
        $classname = '\core\log\dummy_manager';
    }

$singleton = new $classname();
    return $singleton;
}

/**
 * Add an entry to the config log table.
 *
 * These are "action" focussed rather than web server hits,
 * and provide a way to easily reconstruct changes to Moodle configuration.
 *
 * @package core
 * @category log
 * @global moodle_database $DB
 * @global stdClass $USER
 * @param    string  $name     The name of the configuration change action
                               For example 'filter_active' when activating or deactivating a filter
 * @param    string  $oldvalue The config setting's previous value
 * @param    string  $value    The config setting's new value
 * @param    string  $plugin   Plugin name, for example a filter name when changing filter configuration
 * @return void
 */
function add_to_config_log($name, $oldvalue, $value, $plugin) {
    global $USER, $DB;

$log = new stdClass();
    // Use 0 as user id during install.
    $log->userid       = during_initial_install() ? 0 : $USER->id;
    $log->timemodified = time();
    $log->name         = $name;
    $log->oldvalue  = $oldvalue;
    $log->value     = $value;
    $log->plugin    = $plugin;

$id = $DB->insert_record('config_log', $log);

$event = core\event\config_log_created::create(array(
            'objectid' => $id,
            'userid' => $log->userid,
            'context' => \context_system::instance(),
            'other' => array(
                'name' => $log->name,
                'oldvalue' => $log->oldvalue,
                'value' => $log->value,
                'plugin' => $log->plugin
            )
        ));
    $event->trigger();
}

/**
 * Store user last access times - called when use enters a course or site
 *
 * @package core
 * @category log
 * @global stdClass $USER
 * @global stdClass $CFG
 * @global moodle_database $DB
 * @uses LASTACCESS_UPDATE_SECS
 * @uses SITEID
 * @param int $courseid  empty courseid means site
 * @return void
 */
function user_accesstime_log($courseid=0) {
    global $USER, $CFG, $DB;

if (!isloggedin() or \core\session\manager::is_loggedinas()) {
        // no access tracking
        return;
    }

if (isguestuser()) {
        // Do not update guest access times/ips for performance.
        return;
    }

if (empty($courseid)) {
        $courseid = SITEID;
    }

$timenow = time();

/// Store site lastaccess time for the current user
    if ($timenow - $USER->lastaccess > LASTACCESS_UPDATE_SECS) {
    /// Update $USER->lastaccess for next checks
        $USER->lastaccess = $timenow;

$last = new stdClass();
        $last->id         = $USER->id;
        $last->lastip     = getremoteaddr();
        $last->lastaccess = $timenow;

$DB->update_record_raw('user', $last);
    }

if ($courseid == SITEID) {
    ///  no user_lastaccess for frontpage
        return;
    }

/// Store course lastaccess times for the current user
    if (empty($USER->currentcourseaccess[$courseid]) or ($timenow - $USER->currentcourseaccess[$courseid] > LASTACCESS_UPDATE_SECS)) {

$lastaccess = $DB->get_field('user_lastaccess', 'timeaccess', array('userid'=>$USER->id, 'courseid'=>$courseid));

if ($lastaccess === false) {
            // Update course lastaccess for next checks
            $USER->currentcourseaccess[$courseid] = $timenow;

$last = new stdClass();
            $last->userid     = $USER->id;
            $last->courseid   = $courseid;
            $last->timeaccess = $timenow;
            try {
                $DB->insert_record_raw('user_lastaccess', $last, false);
            } catch (dml_write_exception $e) {
                // During a race condition we can fail to find the data, then it appears.
                // If we still can't find it, rethrow the exception.
                $lastaccess = $DB->get_field('user_lastaccess', 'timeaccess', array('userid' => $USER->id,
                                                                                    'courseid' => $courseid));
                if ($lastaccess === false) {
                    throw $e;
                }
                // If we did find it, the race condition was true and another thread has inserted the time for us.
                // We can just continue without having to do anything.
            }

} else if ($timenow - $lastaccess <  LASTACCESS_UPDATE_SECS) {
            // no need to update now, it was updated recently in concurrent login ;-)

} else {
            // Update course lastaccess for next checks
            $USER->currentcourseaccess[$courseid] = $timenow;

$DB->set_field('user_lastaccess', 'timeaccess', $timenow, array('userid'=>$USER->id, 'courseid'=>$courseid));
        }
    }
}

/// GENERAL HELPFUL THINGS  ///////////////////////////////////

/**
 * Dumps a given object's information for debugging purposes
 *
 * When used in a CLI script, the object's information is written to the standard
 * error output stream. When used in a web script, the object is dumped to a
 * pre-formatted block with the "notifytiny" CSS class.
 *
 * @param mixed $object The data to be printed
 * @return void output is echo'd
 */
function print_object($object) {

// we may need a lot of memory here
    raise_memory_limit(MEMORY_EXTRA);

if (CLI_SCRIPT) {
        fwrite(STDERR, print_r($object, true));
        fwrite(STDERR, PHP_EOL);
    } else {
        echo html_writer::tag('pre', s(print_r($object, true)), array('class' => 'notifytiny'));
    }
}

/**
 * This function is the official hook inside XMLDB stuff to delegate its debug to one
 * external function.
 *
 * Any script can avoid calls to this function by defining XMLDB_SKIP_DEBUG_HOOK before
 * using XMLDB classes. Obviously, also, if this function doesn't exist, it isn't invoked ;-)
 *
 * @uses DEBUG_DEVELOPER
 * @param string $message string contains the error message
 * @param object $object object XMLDB object that fired the debug
 */
function xmldb_debug($message, $object) {

debugging($message, DEBUG_DEVELOPER);
}

/**
 * @global object
 * @uses CONTEXT_COURSECAT
 * @return boolean Whether the user can create courses in any category in the system.
 */
function user_can_create_courses() {
    global $DB;
    $catsrs = $DB->get_recordset('course_categories');
    foreach ($catsrs as $cat) {
        if (has_capability('moodle/course:create', context_coursecat::instance($cat->id))) {
            $catsrs->close();
            return true;
        }
    }
    $catsrs->close();
    return false;
}

/**
 * This method can update the values in mulitple database rows for a colum with
 * a unique index, without violating that constraint.
 *
 * Suppose we have a table with a unique index on (otherid, sortorder), and
 * for a particular value of otherid, we want to change all the sort orders.
 * You have to do this carefully or you will violate the unique index at some time.
 * This method takes care of the details for you.
 *
 * Note that, it is the responsibility of the caller to make sure that the
 * requested rename is legal. For example, if you ask for [1 => 2, 2 => 2]
 * then you will get a unique key violation error from the database.
 *
 * @param string $table The database table to modify.
 * @param string $field the field that contains the values we are going to change.
 * @param array $newvalues oldvalue => newvalue how to change the values.
 *      E.g. [1 => 4, 2 => 1, 3 => 3, 4 => 2].
 * @param array $otherconditions array fieldname => requestedvalue extra WHERE clause
 *      conditions to restrict which rows are affected. E.g. array('otherid' => 123).
 * @param int $unusedvalue (defaults to -1) a value that is never used in $ordercol.
 */
function update_field_with_unique_index($table, $field, array $newvalues,
        array $otherconditions, $unusedvalue = -1) {
    global $DB;
    $safechanges = decompose_update_into_safe_changes($newvalues, $unusedvalue);

$transaction = $DB->start_delegated_transaction();
    foreach ($safechanges as $change) {
        list($from, $to) = $change;
        $otherconditions[$field] = $from;
        $DB->set_field($table, $field, $to, $otherconditions);
    }
    $transaction->allow_commit();
}

/**
 * Helper used by {@link update_field_with_unique_index()}. Given a desired
 * set of changes, break them down into single udpates that can be done one at
 * a time without breaking any unique index constraints.
 *
 * Suppose the input is array(1 => 2, 2 => 1) and -1. Then the output will be
 * array (array(1, -1), array(2, 1), array(-1, 2)). This function solves this
 * problem in the general case, not just for simple swaps. The unit tests give
 * more examples.
 *
 * Note that, it is the responsibility of the caller to make sure that the
 * requested rename is legal. For example, if you ask for something impossible
 * like array(1 => 2, 2 => 2) then the results are undefined. (You will probably
 * get a unique key violation error from the database later.)
 *
 * @param array $newvalues The desired re-ordering.
 *      E.g. array(1 => 4, 2 => 1, 3 => 3, 4 => 2).
 * @param int $unusedvalue A value that is not currently used.
 * @return array A safe way to perform the re-order. An array of two-element
 *      arrays array($from, $to).
 *      E.g. array(array(1, -1), array(2, 1), array(4, 2), array(-1, 4)).
 */
function decompose_update_into_safe_changes(array $newvalues, $unusedvalue) {
    $nontrivialmap = array();
    foreach ($newvalues as $from => $to) {
        if ($from == $unusedvalue || $to == $unusedvalue) {
            throw new \coding_exception('Supposedly unused value ' . $unusedvalue . ' is actually used!');
        }
        if ($from != $to) {
            $nontrivialmap[$from] = $to;
        }
    }

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

// First we deal with all renames that are not part of cycles.
    // This bit is O(n^2) and it ought to be possible to do better,
    // but it does not seem worth the effort.
    $safechanges = array();
    $nontrivialmapchanged = true;
    while ($nontrivialmapchanged) {
        $nontrivialmapchanged = false;

foreach ($nontrivialmap as $from => $to) {
            if (array_key_exists($to, $nontrivialmap)) {
                continue; // Cannot currenly do this rename.
            }
            // Is safe to do this rename now.
            $safechanges[] = array($from, $to);
            unset($nontrivialmap[$from]);
            $nontrivialmapchanged = true;
        }
    }

// Are we done?
    if (empty($nontrivialmap)) {
        return $safechanges;
    }

// Now what is left in $nontrivialmap must be a permutation,
    // which must be a combination of disjoint cycles. We need to break them.
    while (!empty($nontrivialmap)) {
        // Extract the first cycle.
        reset($nontrivialmap);
        $current = $cyclestart = key($nontrivialmap);
        $cycle = array();
        do {
            $cycle[] = $current;
            $next = $nontrivialmap[$current];
            unset($nontrivialmap[$current]);
            $current = $next;
        } while ($current != $cyclestart);

// Now convert it to a sequence of safe renames by using a temp.
        $safechanges[] = array($cyclestart, $unusedvalue);
        $cycle[0] = $unusedvalue;
        $to = $cyclestart;
        while ($from = array_pop($cycle)) {
            $safechanges[] = array($from, $to);
            $to = $from;
        }
    }

return $safechanges;
}