package stack;

import java.util.Scanner;
import java.util.regex.Pattern;

public class CalculatorByStack {

    private final static int ADD = 1;

    private final static int SUB = 2;

    private final static int MUL = 3;

    private final static int DIV = 4;

    private ArrayStack<Integer> numStack = new ArrayStack(10);

    private ArrayStack<Integer> operStack = new ArrayStack(10);

    public void calculate(String expression) {
        int length = expression.length();
        String numStr = "";
        for (int i = 0; i<length;i++){
            String str = expression.substring(i,i+1);
            String operRegex = "[+\\-*/]";
            Pattern operPattern = Pattern.compile(operRegex);
            if (operPattern.matcher(str).matches()) {
                if("+".equals(str)){
                    if(operStack.isEmpty()){
                        operStack.push(ADD);
                        continue;
                    }
                    cal();
                    operStack.push(ADD);
                }
                if("-".equals(str)){
                    if(operStack.isEmpty()){
                        operStack.push(SUB);
                        continue;
                    }
                    cal();
                    operStack.push(SUB);
                }
                if("*".equals(str)){
                    if(operStack.isEmpty() || operStack.top() < 3){
                        operStack.push(MUL);
                        continue;
                    }
                    cal();
                    operStack.push(MUL);
                }
                if("/".equals(str)){
                    if(operStack.isEmpty() || operStack.top() < 3){
                        operStack.push(DIV);
                        continue;
                    }
                    cal();
                    operStack.push(DIV);
                }
            }else {
                numStr += str;
                if (i == expression.length()-1){
                    numStack.push(Integer.parseInt(numStr));
                    continue;
                }
                if (operPattern.matcher(expression.substring(i+1,i+2)).matches()){
                    numStack.push(Integer.parseInt(numStr));
                    numStr = "";
                }
            }
        }

        // 开始进行计算
        while (true) {
            if(numStack.isEmpty()){
                System.out.println("当前无计算公式");
            }
            if(numStack.getTop() == 0){
                System.out.println("计算结果为:" + numStack.pop());
                break;
            }
            cal();
        }

    }

    public void cal(){
        int oper = operStack.pop();
        if(oper == ADD){
            int num1 = numStack.pop();
            int num2 = numStack.pop();
            int result = num1 + num2;
            numStack.push(result);
        }
        if(oper == SUB){
            int num1 = numStack.pop();
            int num2 = numStack.pop();
            int result = num2 - num1;
            numStack.push(result);
        }
        if(oper == MUL){
            int num1 = numStack.pop();
            int num2 = numStack.pop();
            int result = num2 * num1;
            numStack.push(result);
        }
        if(oper == DIV){
            int num1 = numStack.pop();
            int num2 = numStack.pop();
            int result = num2/num1;
            numStack.push(result);
        }
    }

    private void show(){
        System.out.println("数栈数据:");
        numStack.show();
        System.out.println("符号栈数据:");
        operStack.show();
    }

    public static void main(String[] args) {
        CalculatorByStack calcStack = new CalculatorByStack();
        Scanner scan = new Scanner(System.in);
        while (true) {
            System.out.println("c计算, s查看, exit退出:");
            String handle = scan.next();
            if ("exit".equals(handle)){
                break;
            }
            if ("c".equals(handle)){
                System.out.println("请输入计算表达式:");
                String expression = scan.next();
                calcStack.calculate(expression);
            }
            if ("s".equals(handle)){
                calcStack.show();
            }
        }
        scan.close();
    }
}