<?php
// This file is part of the Studyplan plugin for Moodle
//
// 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 <https://www.gnu.org/licenses/>.
/**
 *
 * @package    local_treestudyplan
 * @copyright  2023 P.M. Kuipers
 * @license    https://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace local_treestudyplan;
require_once($CFG->libdir.'/externallib.php');

class studyitemconnection {

    const TABLE = "local_treestudyplan_connect";

    private $r;
    private $id;


    protected function __construct($r) {
        $this->r = $r;
        $this->id = $r->id;
    }

    public static function structure($value=VALUE_REQUIRED) {
        return new \external_single_structure([
            'id' => new \external_value(PARAM_INT, 'id of connection'),
            'from_id' => new \external_value(PARAM_INT, 'id of start item'),
            'to_id' => new \external_value(PARAM_INT, 'id of end item'),
        ], '', $value);
    }

    public function model() {
        return ['id' => $this->r->id, 'from_id' => $this->r->from_id, 'to_id' => $this->r->to_id];
    }

    public function from_item() {
        return studyitem::findById($this->r->from_id);
    }

    public function to_item() {
        return studyitem::findById($this->r->to_id);
    }

    public function from_id() {
        return $this->r->from_id;
    }

    public function to_id() {
        return $this->r->to_id;
    }


    public static function find_outgoing($item_id) {
        global $DB;
        $list = [];
        $conn_out = $DB->get_records(self::TABLE, ['from_id' => $item_id]);
        foreach ($conn_out as $c) {
            $list[] = new self($c);
        }
        return $list;
    }

    public static function find_incoming($item_id) {
        global $DB;
        $list = [];
        $conn_in = $DB->get_records(self::TABLE, ['to_id' => $item_id]);
        foreach ($conn_in as $c) {
            $list[] = new self($c);
        }
        return $list;
    }

    public static function connect($from_id, $to_id) {
        global $DB;

        //check if link already exists.

        if (!$DB->record_exists(self::TABLE, ['from_id' => $from_id, 'to_id' => $to_id])) {
            $id = $DB->insert_record(self::TABLE, [
                'from_id' => $from_id,
                'to_id' => $to_id,
            ]);

            return new self($DB->get_record(self::TABLE, ['id' => $id]));

        } else {
            return new self($DB->get_record(self::TABLE, ['from_id' => $from_id, 'to_id' => $to_id]));
        }
    }

    public static function disconnect($from_id, $to_id) {
        global $DB;

        if ($DB->record_exists(self::TABLE, ['from_id' => $from_id, 'to_id' => $to_id])) {
            $DB->delete_records(self::TABLE, [
                'from_id' => $from_id,
                'to_id' => $to_id,
            ]);

            return success::success('Items Disconnected');
        } else {
            return success::success('Connection does not exist');
        }
    }

    public static function clear($id) {
        global $DB;
        $DB->delete_records(self::TABLE, ['from_id' => $id]);
        $DB->delete_records(self::TABLE, ['to_id' => $id]);
    }

}