moodle/lib/classes/task/completion_daily_task.php

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

/**
 * A scheduled task.
 *
 * @package    core
 * @copyright  2013 onwards Martin Dougiamas  http://dougiamas.com
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
namespace core\task;

/**
 * Simple task to run the daily completion cron.
 * @copyright  2013 onwards Martin Dougiamas  http://dougiamas.com.
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later.
 */
class completion_daily_task extends scheduled_task {

    /**
     * Get a descriptive name for this task (shown to admins).
     *
     * @return string
     */
    public function get_name() {
        return get_string('taskcompletiondaily', 'admin');
    }

    /**
     * Do the job.
     * Throw exceptions on errors (the job will be retried).
     */
    public function execute() {
        global $CFG, $DB;

        if ($CFG->enablecompletion) {
            require_once($CFG->libdir . "/completionlib.php");

            if (debugging()) {
                mtrace('Marking users as started');
            }
            if (!empty($CFG->gradebookroles)) {
                $roles = ' AND ra.roleid IN ('.$CFG->gradebookroles.')';
            } else {
                // This causes it to default to everyone (if there is no student role)
                $roles = '';
            }
            /**
             * A quick explaination of this horrible looking query
             *
             * It's purpose is to locate all the active participants
             * of a course with course completion enabled.
             *
             * We also only want the users with no course_completions
             * record as this functions job is to create the missing
             * ones :)
             *
             * We want to record the user's enrolment start time for the
             * course. This gets tricky because there can be multiple
             * enrolment plugins active in a course, hence the possibility
             * of multiple records for each couse/user in the results
             */
            $sql = "
        SELECT
            c.id AS course,
            u.id AS userid,
            crc.id AS completionid,
            ue.timestart AS timeenrolled,
            ue.timecreated
        FROM
            {user} u
        INNER JOIN
            {user_enrolments} ue
         ON ue.userid = u.id
        INNER JOIN
            {enrol} e
         ON e.id = ue.enrolid
        INNER JOIN
            {course} c
         ON c.id = e.courseid
        INNER JOIN
            {role_assignments} ra
         ON ra.userid = u.id
        LEFT JOIN
            {course_completions} crc
         ON crc.course = c.id
        AND crc.userid = u.id
        WHERE
            c.enablecompletion = 1
        AND crc.timeenrolled IS NULL
        AND ue.status = 0
        AND e.status = 0
        AND u.deleted = 0
        AND ue.timestart < ?
        AND (ue.timeend > ? OR ue.timeend = 0)
            $roles
        ORDER BY
            course,
            userid
    ";
            $now = time();
            $rs = $DB->get_recordset_sql($sql, array($now, $now, $now, $now));
            // Check if result is empty
            if (!$rs->valid()) {
                $rs->close(); // Not going to iterate (but exit), close rs
                return;
            }
            /**
             * An explaination of the following loop
             *
             * We are essentially doing a group by in the code here (as I can't find
             * a decent way of doing it in the sql).
             *
             * Since there can be multiple enrolment plugins for each course, we can have
             * multiple rows for each particpant in the query result. This isn't really
             * a problem until you combine it with the fact that the enrolment plugins
             * can save the enrol start time in either timestart or timeenrolled.
             *
             * The purpose of this loop is to find the earliest enrolment start time for
             * each participant in each course.
             */
            $prev = null;
            while ($rs->valid() || $prev) {
                $current = $rs->current();
                if (!isset($current->course)) {
                    $current = false;
                }
                else {
                    // Not all enrol plugins fill out timestart correctly, so use whichever
                    // is non-zero
                    $current->timeenrolled = max($current->timecreated, $current->timeenrolled);
                }
                // If we are at the last record,
                // or we aren't at the first and the record is for a diff user/course
                if ($prev &&
                    (!$rs->valid() ||
                        ($current->course != $prev->course || $current->userid != $prev->userid))) {
                    $completion = new completion_completion();
                    $completion->userid = $prev->userid;
                    $completion->course = $prev->course;
                    $completion->timeenrolled = (string) $prev->timeenrolled;
                    $completion->timestarted = 0;
                    $completion->reaggregate = time();
                    if ($prev->completionid) {
                        $completion->id = $prev->completionid;
                    }
                    $completion->mark_enrolled();
                    if (debugging()) {
                        mtrace('Marked started user '.$prev->userid.' in course '.$prev->course);
                    }
                }
                // Else, if this record is for the same user/course
                elseif ($prev && $current) {
                    // Use oldest timeenrolled
                    $current->timeenrolled = min($current->timeenrolled, $prev->timeenrolled);
                }
                // Move current record to previous
                $prev = $current;
                // Move to next record
                $rs->next();
            }
            $rs->close();
        }
    }

}