#Gocha#

<?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/>.

/**
 * Drop out course target.
 *
 * @package   core
 * @copyright 2016 David Monllao {@link http://www.davidmonllao.com}
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace core\analytics\target;

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

require_once($CFG->dirroot . '/course/lib.php');
require_once($CFG->dirroot . '/lib/gradelib.php');
require_once($CFG->dirroot . '/lib/completionlib.php');
require_once($CFG->dirroot . '/completion/completion_completion.php');

/**
 * Drop out course target.
 *
 * @package   core
 * @copyright 2016 David Monllao {@link http://www.davidmonllao.com}
 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class course_dropout extends \core_analytics\local\target\binary {

/**
     * Returns the name.
     *
     * If there is a corresponding '_help' string this will be shown as well.
     *
     * @return \lang_string
     */
    public static function get_name() : \lang_string {
        return new \lang_string('target:coursedropout');
    }

/**
     * prediction_actions
     *
     * @param \core_analytics\prediction $prediction
     * @param bool $includedetailsaction
     * @return \core_analytics\prediction_action[]
     */
    public function prediction_actions(\core_analytics\prediction $prediction, $includedetailsaction = false) {
        global $USER;

$actions = array();

$sampledata = $prediction->get_sample_data();
        $studentid = $sampledata['user']->id;

$attrs = array('target' => '_blank');

// Send a message.
        $url = new \moodle_url('/message/index.php', array('user' => $USER->id, 'id' => $studentid));
        $pix = new \pix_icon('t/message', get_string('sendmessage', 'message'));
        $actions[] = new \core_analytics\prediction_action('studentmessage', $prediction, $url, $pix,
            get_string('sendmessage', 'message'), false, $attrs);

// View outline report.
        $url = new \moodle_url('/report/outline/user.php', array('id' => $studentid, 'course' => $sampledata['course']->id,
            'mode' => 'outline'));
        $pix = new \pix_icon('i/report', get_string('outlinereport'));
        $actions[] = new \core_analytics\prediction_action('viewoutlinereport', $prediction, $url, $pix,
            get_string('outlinereport'), false, $attrs);

return array_merge($actions, parent::prediction_actions($prediction, $includedetailsaction));
    }

/**
     * classes_description
     *
     * @return string[]
     */
    protected static function classes_description() {
        return array(
            get_string('targetlabelstudentdropoutno'),
            get_string('targetlabelstudentdropoutyes')
        );
    }

/**
     * Returns the predicted classes that will be ignored.
     *
     * Overwriten because we are also interested in knowing when the student is far from the risk of dropping out.
     *
     * @return array
     */
    protected function ignored_predicted_classes() {
        return array();
    }

/**
     * get_analyser_class
     *
     * @return string
     */
    public function get_analyser_class() {
        return '\core\analytics\analyser\student_enrolments';
    }

/**
     * Discards courses that are not yet ready to be used for training or prediction.
     *
     * @param \core_analytics\analysable $course
     * @param bool $fortraining
     * @return true|string
     */
    public function is_valid_analysable(\core_analytics\analysable $course, $fortraining = true) {
        global $DB;

if (!$course->was_started()) {
            return get_string('coursenotyetstarted');
        }

if (!$students = $course->get_students()) {
            return get_string('nocoursestudents');
        }

if (!course_format_uses_sections($course->get_course_data()->format)) {
            // We can not split activities in time ranges.
            return get_string('nocoursesections');
        }

if ($course->get_start() == 0) {
            // We require time start to be set.
            return get_string('nocoursestarttime');
        }

if ($course->get_end() == 0) {
            // We require time end to be set.
            return get_string('nocourseendtime');
        }

if ($course->get_end() < $course->get_start()) {
            return get_string('errorendbeforestart', 'analytics');
        }

// A course that lasts longer than 1 year probably have wrong start or end dates.
        if ($course->get_end() - $course->get_start() > (YEARSECS + (WEEKSECS * 4))) {
            return get_string('coursetoolong', 'analytics');
        }

// Finished courses can not be used to get predictions.
        if (!$fortraining && $course->is_finished()) {
            return get_string('coursealreadyfinished');
        }

// Ongoing courses data can not be used to train.
        if ($fortraining && !$course->is_finished()) {
            return get_string('coursenotyetfinished');
        }

if ($fortraining) {
            // Not a valid target for training if there are not enough course accesses between the course start and end dates.

$params = array('courseid' => $course->get_id(), 'anonymous' => 0, 'start' => $course->get_start(),
                'end' => $course->get_end());
            list($studentssql, $studentparams) = $DB->get_in_or_equal($students, SQL_PARAMS_NAMED);
            // Using anonymous to use the db index, not filtering by timecreated to speed it up.
            $select = 'courseid = :courseid AND anonymous = :anonymous AND timecreated > :start AND timecreated < :end ' .
                'AND userid ' . $studentssql;

if (!$logstore = \core_analytics\manager::get_analytics_logstore()) {
                throw new \coding_exception('No available log stores');
            }
            $nlogs = $logstore->get_events_select_count($select, array_merge($params, $studentparams));

// At least a minimum of students activity.
            $nstudents = count($students);
            if ($nlogs / $nstudents < 10) {
                return get_string('nocourseactivity');
            }
        }

return true;
    }

/**
     * Discard student enrolments that are invalid.
     *
     * @param int $sampleid
     * @param \core_analytics\analysable $course
     * @param bool $fortraining
     * @return bool
     */
    public function is_valid_sample($sampleid, \core_analytics\analysable $course, $fortraining = true) {

$userenrol = $this->retrieve('user_enrolments', $sampleid);
        if ($userenrol->timeend && $course->get_start() > $userenrol->timeend) {
            // Discard enrolments which time end is prior to the course start. This should get rid of
            // old user enrolments that remain on the course.
            return false;
        }

$limit = $course->get_start() - (YEARSECS + (WEEKSECS * 4));
        if (($userenrol->timestart && $userenrol->timestart < $limit) ||
                (!$userenrol->timestart && $userenrol->timecreated < $limit)) {
            // Following what we do in is_valid_sample, we will discard enrolments that last more than 1 academic year
            // because they have incorrect start and end dates or because they are reused along multiple years
            // without removing previous academic years students. This may not be very accurate because some courses
            // can last just some months, but it is better than nothing and they will be flagged as drop out anyway
            // in most of the cases.
            return false;
        }

if (($userenrol->timestart && $userenrol->timestart > $course->get_end()) ||
                (!$userenrol->timestart && $userenrol->timecreated > $course->get_end())) {
            // Discard user enrolments that starts after the analysable official end.
            return false;
        }

return true;
    }

/**
     * calculate_sample
     *
     * The meaning of a drop out changes depending on the settings enabled in the course. Following these priorities order:
     * 1.- Course completion
     * 2.- No logs during the last quarter of the course
     *
     * @param int $sampleid
     * @param \core_analytics\analysable $course
     * @param int $starttime
     * @param int $endtime
     * @return float 0 -> not at risk, 1 -> at risk
     */
    protected function calculate_sample($sampleid, \core_analytics\analysable $course, $starttime = false, $endtime = false) {

$userenrol = $this->retrieve('user_enrolments', $sampleid);

// We use completion as a success metric only when it is enabled.
        $completion = new \completion_info($course->get_course_data());
        if ($completion->is_enabled() && $completion->has_criteria()) {
            $ccompletion = new \completion_completion(array('userid' => $userenrol->userid, 'course' => $course->get_id()));
            if ($ccompletion->is_complete()) {
                return 0;
            } else {
                return 1;
            }
        }

if (!$logstore = \core_analytics\manager::get_analytics_logstore()) {
            throw new \coding_exception('No available log stores');
        }

// No logs during the last quarter of the course.
        $courseduration = $course->get_end() - $course->get_start();
        $limit = intval($course->get_end() - ($courseduration / 4));
        $select = "courseid = :courseid AND userid = :userid AND timecreated > :limit";
        $params = array('userid' => $userenrol->userid, 'courseid' => $course->get_id(), 'limit' => $limit);
        $nlogs = $logstore->get_events_select_count($select, $params);
        if ($nlogs == 0) {
            return 1;
        }
        return 0;
    }
}