<?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/>.


/**
 * External question API
 *
 * @package    core_question
 * @category   external
 * @copyright  2016 Pau Ferrer <pau@moodle.com>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

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

require_once("$CFG->libdir/externallib.php");
require_once($CFG->dirroot . '/question/engine/lib.php');

/**
 * Question external functions
 *
 * @package    core_question
 * @category   external
 * @copyright  2016 Pau Ferrer <pau@moodle.com>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 * @since Moodle 3.1
 */
class core_question_external extends external_api {

    /**
     * Returns description of method parameters
     *
     * @return external_function_parameters
     * @since Moodle 3.1
     */
    public static function update_flag_parameters() {
        return new external_function_parameters(
            array(
                'qubaid' => new external_value(PARAM_INT, 'the question usage id.'),
                'questionid' => new external_value(PARAM_INT, 'the question id'),
                'qaid' => new external_value(PARAM_INT, 'the question_attempt id'),
                'slot' => new external_value(PARAM_INT, 'the slot number within the usage'),
                'checksum' => new external_value(PARAM_ALPHANUM, 'computed checksum with the last three arguments and
                             the users username'),
                'newstate' => new external_value(PARAM_BOOL, 'the new state of the flag. true = flagged')
            )
        );
    }

    /**
     * Update the flag state of a question attempt.
     *
     * @param int $qubaid the question usage id.
     * @param int $questionid the question id.
     * @param int $qaid the question_attempt id.
     * @param int $slot the slot number within the usage.
     * @param string $checksum checksum, as computed by {@link get_toggle_checksum()}
     *      corresponding to the last three arguments and the users username.
     * @param bool $newstate the new state of the flag. true = flagged.
     * @return array (success infos and fail infos)
     * @since Moodle 3.1
     */
    public static function update_flag($qubaid, $questionid, $qaid, $slot, $checksum, $newstate) {
        global $CFG, $DB;

        $params = self::validate_parameters(self::update_flag_parameters(),
            array(
                'qubaid' => $qubaid,
                'questionid' => $questionid,
                'qaid' => $qaid,
                'slot' => $slot,
                'checksum' => $checksum,
                'newstate' => $newstate
            )
        );

        $warnings = array();
        self::validate_context(context_system::instance());

        // The checksum will be checked to provide security flagging other users questions.
        question_flags::update_flag($params['qubaid'], $params['questionid'], $params['qaid'], $params['slot'], $params['checksum'],
                                    $params['newstate']);

        $result = array();
        $result['status'] = true;
        $result['warnings'] = $warnings;
        return $result;
    }

    /**
     * Returns description of method result value
     *
     * @return external_description
     * @since Moodle 3.1
     */
    public static function update_flag_returns() {
        return new external_single_structure(
            array(
                'status' => new external_value(PARAM_BOOL, 'status: true if success'),
                'warnings' => new external_warnings()
            )
        );
    }
}
