Hotbar.php

<?php
 
/*
 *
 *  ____            _        _   __  __ _                  __  __ ____
 * |  _ \ ___   ___| | _____| |_|  \/  (_)_ __   ___      |  \/  |  _ \
 * | |_) / _ \ / __| |/ / _ \ __| |\/| | | '_ \ / _ \_____| |\/| | |_) |
 * |  __/ (_) | (__|   <  __/ |_| |  | | | | | |  __/_____| |  | |  __/
 * |_|   \___/ \___|_|\_\___|\__|_|  |_|_|_| |_|\___|     |_|  |_|_|
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * @author PocketMine Team
 * @link http://www.pocketmine.net/
 *
 *
 */
 
declare(strict_types=1);
 
namespace pocketmine\inventory;
 
use pocketmine\utils\ObjectSet;
 
final class Hotbar{
    protected int $selectedIndex = 0;
 
    protected ObjectSet $selectedIndexChangeListeners;
 
    public function __construct(
        private int $size = 9
    ){
        $this->selectedIndexChangeListeners = new ObjectSet();
    }
 
    public function isHotbarSlot(int $slot) : bool{
        return $slot >= 0 && $slot < $this->getSize();
    }
 
    private function throwIfNotHotbarSlot(int $slot) : void{
        if(!$this->isHotbarSlot($slot)){
            throw new \InvalidArgumentException("$slot is not a valid hotbar slot index (expected 0 - " . ($this->getSize() - 1) . ")");
        }
    }
 
    public function getSelectedIndex() : int{
        return $this->selectedIndex;
    }
 
    public function setSelectedIndex(int $hotbarSlot) : void{
        $this->throwIfNotHotbarSlot($hotbarSlot);
 
        $oldIndex = $this->selectedIndex;
        $this->selectedIndex = $hotbarSlot;
 
        foreach($this->selectedIndexChangeListeners as $callback){
            $callback($oldIndex);
        }
    }
 
    public function getSelectedIndexChangeListeners() : ObjectSet{ return $this->selectedIndexChangeListeners; }
 
    public function getSize() : int{
        return $this->size;
    }
}