Proyectos de Subversion Moodle

<?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/>.

/**

 * Time splitting method that generates predictions regularly.

 *

 * @package   core_analytics

 * @copyright 2019 David Monllao {@link http://www.davidmonllao.com}

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

namespace core_analytics\local\time_splitting;

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

/**

 * Time splitting method that generates predictions periodically.

 *

 * @package   core_analytics

 * @copyright 2019 David Monllao {@link http://www.davidmonllao.com}

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

abstract class periodic extends base {

    /**

     * The periodicity of the predictions / training data generation.

     *

     * @return \DateInterval

     */

    abstract protected function periodicity();

    /**

     * Gets the next range with start on the provided time.

     *

     * @param  \DateTimeImmutable $time

     * @return array

     */

    abstract protected function get_next_range(\DateTimeImmutable $time);

    /**

     * Get the start of the first time range.

     *

     * @return int A timestamp.

     */

    abstract protected function get_first_start();

    /**

     * Returns whether the analysable can be processed by this time splitting method or not.

     *

     * @param \core_analytics\analysable $analysable

     * @return bool

     */

    public function is_valid_analysable(\core_analytics\analysable $analysable) {

        if (!$analysable->get_start()) {

            return false;

        }

        return true;

    }

    /**

     * define_ranges

     *

     * @return array

     */

    protected function define_ranges() {

        $periodicity = $this->periodicity();

        if ($this->analysable->get_end()) {

            $end = (new \DateTimeImmutable())->setTimestamp($this->analysable->get_end());

        }

        $nexttime = (new \DateTimeImmutable())->setTimestamp($this->get_first_start());

        $now = new \DateTimeImmutable('now', \core_date::get_server_timezone_object());

        $range = $this->get_next_range($nexttime);

        if (!$range) {

            $nexttime = $nexttime->add($periodicity);

            $range = $this->get_next_range($nexttime);

            if (!$range) {

                throw new \coding_exception('The get_next_range implementation is broken. The difference between two consecutive

                    ranges can not be more than the periodicity.');

            }

        }

        $ranges = [];

        $endreached = false;

        while (($this->ready_to_predict($range) || $this->ready_to_train($range)) && !$endreached) {

            $ranges[] = $range;

            $nexttime = $nexttime->add($periodicity);

            $range = $this->get_next_range($nexttime);

            $endreached = (!empty($end) && $nexttime > $end);

        }

        if ($ranges && !$endreached) {

            // If this analysable is not finished we adjust the start and end of the last element in $ranges

            // so that it ends in time().The reason is that the start of these ranges is based on the analysable

            // start and the end is calculated based on the start. This is to prevent the same issue we had in MDL-65348.

            //

            // An example of the situation we want to avoid is:

            // A course started on a Monday, in 2015. It has no end date. Now the system is upgraded to Moodle 3.8, which

            // includes this code. This happens on Wednesday. Periodic ranges (e.g. weekly) will be calculated from a Monday

            // so the data provided by the time-splitting method would be from Monday to Monday, when we really want to

            // provide data from Wednesday to the past Wednesday.

            $ranges = $this->update_last_range($ranges);

        }

        return $ranges;

    }

    /**

     * Overwritten as all generated rows are comparable.

     *

     * @return bool

     */

    public function include_range_info_in_training_data() {

        return false;

    }

    /**

     * Overwritting as the last range may be for prediction.

     *

     * @return array

     */

    public function get_training_ranges() {

        // Cloning the array.

        $trainingranges = $this->ranges;

        foreach ($trainingranges as $rangeindex => $range) {

            if (!$this->ready_to_train($range)) {

                unset($trainingranges[$rangeindex]);

            }

        }

        return $trainingranges;

    }

    /**

     * Allows child classes to update the last range provided.

     *

     * @param  array  $ranges

     * @return array

     */

    protected function update_last_range(array $ranges) {

        return $ranges;

    }

}