class Stack{
    private data: number[];
    private top: number;
    
    constructor(){
        this.data = [];
        this.top = -1;
    }

    public info(){
        if(this.top == -1){
            console.log("스택이 비어있습니다");
            return;
        }

        let result: string = "Stack List(" + (this.top+1).toString() + " values) : "
        for(let i=0; i<=this.top; i++){
            result += this.data[i].toString() + " ";
        }

        console.log(result);
    }

    public push(value: number){
        this.data[++(this.top)] = value;
        console.log("push 성공!");
    }

    public pop(): number | undefined {
        if(this.top === -1){
            return undefined;
        }
        return this.data[(this.top)--];
    }

    public peek(): number | undefined {
        if(this.top === -1){
            return undefined;
        }
        return this.data[this.top];
    }
}

let stack = new Stack();
let exitFlag = true;

while(exitFlag){
    console.log("++++++++++++++++명령어모음++++++++++++++++");
    console.log("push <value> | pop | peek | info | exit");
    console.log("========================================");
    console.log("명령어를 입력해주세요!");
    const input:string[] = require("fs").readFileSync(0,"utf8").toString().trim().split(" ");
    switch(input[0])
    {
        case "push":
            stack.push(Number(input[1]));
            break;
        case "pop":
            var popValue = stack.pop();
            console.log(popValue===undefined ? "스택이 비었습니다." : "pop 완료 : " + popValue.toString());
            break;
        case "peek":
            var peekValue = stack.peek();
            console.log(peekValue===undefined ? "스택이 비었습니다." : "최상단 값 : " + peekValue.toString());
            break;
        case "info":
            stack.info();
            break;
        case "exit":
            exitFlag = false;
            console.log("종료합니다.")
            break;
        default:
            console.log("제대로 입력해주세요.")
            break; 
    }
}