'use strict'
/**
 * Copyright (c) 2017~2019, OBCon Inc.
 * All rights reserved.
 */

/**
 * @file
 * @copyright 2017~2019, OBCon Inc.
 * @author gye hyun james kim [pnuskgh@gmail.com]
 */

class Stack {                                               //--- LIFO (Last In First Out)
    constructor(data) {
        this.data = data || [];
    }

    getBuffer() {                                           //--- Stack 복사
        return this.data.slice();
    }

    isEmpty() {
        return this.data.length == 0;
    }

    peek() {                                                //--- 최상위 항목을 조회
        return (this.isEmpty()) ? null : this.data[this.data.length - 1];
    }

    push(item) {                                            //--- 항목 추가
        this.data.push(item);
    }

    pop() {                                                 //--- 항목 제거
        return this.data.pop();
    }
}

module.exports = Stack;