<?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/>.

/**
 * Cron job for reviewing and aggregating course completion criteria
 *
 * @package core_completion
 * @category completion
 * @copyright 2009 Catalyst IT Ltd
 * @author Aaron Barnes <aaronb@catalyst.net.nz>
 * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

defined('MOODLE_INTERNAL') || die();
require_once($CFG->libdir.'/completionlib.php');

/**
 * Update user's course completion statuses
 *
 * First update all criteria completions, then aggregate all criteria completions
 * and update overall course completions
 */
function completion_cron() {

    completion_cron_mark_started();

    completion_cron_criteria();

    completion_cron_completions();
}

/**
 * Mark users as started if the config option is set
 *
 * @return void
 */
function completion_cron_mark_started() {
    global $CFG, $DB;

    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();
}

/**
 * Run installed criteria's data aggregation methods
 *
 * Loop through each installed criteria and run the
 * cron() method if it exists
 *
 * @return void
 */
function completion_cron_criteria() {

    // Process each criteria type
    global $CFG, $COMPLETION_CRITERIA_TYPES;

    foreach ($COMPLETION_CRITERIA_TYPES as $type) {

        $object = 'completion_criteria_'.$type;
        require_once $CFG->dirroot.'/completion/criteria/'.$object.'.php';

        $class = new $object();

        // Run the criteria type's cron method, if it has one
        if (method_exists($class, 'cron')) {

            if (debugging()) {
                mtrace('Running '.$object.'->cron()');
            }
            $class->cron();
        }
    }
}

/**
 * Aggregate each user's criteria completions
 */
function completion_cron_completions() {
    global $DB;

    if (debugging()) {
        mtrace('Aggregating completions');
    }

    // Save time started
    $timestarted = time();

    // Grab all criteria and their associated criteria completions
    $sql = '
        SELECT DISTINCT
            c.id AS course,
            cr.id AS criteriaid,
            crc.userid AS userid,
            cr.criteriatype AS criteriatype,
            cc.timecompleted AS timecompleted
        FROM
            {course_completion_criteria} cr
        INNER JOIN
            {course} c
         ON cr.course = c.id
        INNER JOIN
            {course_completions} crc
         ON crc.course = c.id
        LEFT JOIN
            {course_completion_crit_compl} cc
         ON cc.criteriaid = cr.id
        AND crc.userid = cc.userid
        WHERE
            c.enablecompletion = 1
        AND crc.timecompleted IS NULL
        AND crc.reaggregate > 0
        AND crc.reaggregate < :timestarted
        ORDER BY
            course,
            userid
    ';

    $rs = $DB->get_recordset_sql($sql, array('timestarted' => $timestarted));

    // Check if result is empty
    if (!$rs->valid()) {
        $rs->close(); // Not going to iterate (but exit), close rs
        return;
    }

    $current_user = null;
    $current_course = null;
    $completions = array();

    while (1) {

        // Grab records for current user/course
        foreach ($rs as $record) {
            // If we are still grabbing the same users completions
            if ($record->userid === $current_user && $record->course === $current_course) {
                $completions[$record->criteriaid] = $record;
            } else {
                break;
            }
        }

        // Aggregate
        if (!empty($completions)) {

            if (debugging()) {
                mtrace('Aggregating completions for user '.$current_user.' in course '.$current_course);
            }

            // Get course info object
            $info = new completion_info((object)array('id' => $current_course));

            // Setup aggregation
            $overall = $info->get_aggregation_method();
            $activity = $info->get_aggregation_method(COMPLETION_CRITERIA_TYPE_ACTIVITY);
            $prerequisite = $info->get_aggregation_method(COMPLETION_CRITERIA_TYPE_COURSE);
            $role = $info->get_aggregation_method(COMPLETION_CRITERIA_TYPE_ROLE);

            $overall_status = null;
            $activity_status = null;
            $prerequisite_status = null;
            $role_status = null;

            // Get latest timecompleted
            $timecompleted = null;

            // Check each of the criteria
            foreach ($completions as $params) {
                $timecompleted = max($timecompleted, $params->timecompleted);

                $completion = new completion_criteria_completion((array)$params, false);

                // Handle aggregation special cases
                if ($params->criteriatype == COMPLETION_CRITERIA_TYPE_ACTIVITY) {
                    completion_cron_aggregate($activity, $completion->is_complete(), $activity_status);
                } else if ($params->criteriatype == COMPLETION_CRITERIA_TYPE_COURSE) {
                    completion_cron_aggregate($prerequisite, $completion->is_complete(), $prerequisite_status);
                } else if ($params->criteriatype == COMPLETION_CRITERIA_TYPE_ROLE) {
                    completion_cron_aggregate($role, $completion->is_complete(), $role_status);
                } else {
                    completion_cron_aggregate($overall, $completion->is_complete(), $overall_status);
                }
            }

            // Include role criteria aggregation in overall aggregation
            if ($role_status !== null) {
                completion_cron_aggregate($overall, $role_status, $overall_status);
            }

            // Include activity criteria aggregation in overall aggregation
            if ($activity_status !== null) {
                completion_cron_aggregate($overall, $activity_status, $overall_status);
            }

            // Include prerequisite criteria aggregation in overall aggregation
            if ($prerequisite_status !== null) {
                completion_cron_aggregate($overall, $prerequisite_status, $overall_status);
            }

            // If aggregation status is true, mark course complete for user
            if ($overall_status) {
                if (debugging()) {
                    mtrace('Marking complete');
                }

                $ccompletion = new completion_completion(array('course' => $params->course, 'userid' => $params->userid));
                $ccompletion->mark_complete($timecompleted);
            }
        }

        // If this is the end of the recordset, break the loop
        if (!$rs->valid()) {
            $rs->close();
            break;
        }

        // New/next user, update user details, reset completions
        $current_user = $record->userid;
        $current_course = $record->course;
        $completions = array();
        $completions[$record->criteriaid] = $record;
    }

    // Mark all users as aggregated
    $sql = "
        UPDATE
            {course_completions}
        SET
            reaggregate = 0
        WHERE
            reaggregate < :timestarted
        AND reaggregate > 0
    ";

    $DB->execute($sql, array('timestarted' => $timestarted));
}

/**
 * Aggregate criteria status's as per configured aggregation method
 *
 * @param int $method COMPLETION_AGGREGATION_* constant
 * @param bool $data Criteria completion status
 * @param bool|null $state Aggregation state
 */
function completion_cron_aggregate($method, $data, &$state) {
    if ($method == COMPLETION_AGGREGATION_ALL) {
        if ($data && $state !== false) {
            $state = true;
        } else {
            $state = false;
        }
    } elseif ($method == COMPLETION_AGGREGATION_ANY) {
        if ($data) {
            $state = true;
        } else if (!$data && $state === null) {
            $state = false;
        }
    }
}