function isOperator(value) {
    var operatorString = '+-*/()×÷';
    return operatorString.indexOf(value) > -1;
}

function getPrioraty(value) {
    if(value == '-' || value == '+') {
        return 1;
    } else if(value == '*' || value == '/' || value == '×' || value == '÷' ) {
        return 2;
    } else{
        return 0;
    }
}

function prioraty(v1, v2) {
    return getPrioraty(v1) <= getPrioraty(v2);
}

function outputRpn(exp) {
    var inputStack = [];
    var outputStack = [];
    var outputQueue = [];
    var firstIsOperator = false;
    exp.replace(/\s/g,'');
    if(isOperator(exp[0])){
        exp = exp.substring(1);
        firstIsOperator = true;
    }
    for(var i = 0, max = exp.length; i < max; i++) {
        if(!isOperator(exp[i]) && !isOperator(exp[i-1]) && (i != 0)) {
            inputStack[inputStack.length-1] = inputStack[inputStack.length-1] + exp[i] + '';
        } else {
            inputStack.push(exp[i]);
        }
    }
    if(firstIsOperator) {
        inputStack[0] = -inputStack[0] 
    }
    while(inputStack.length > 0) {
        var cur = inputStack.shift();
        if(isOperator(cur)) {
            if (cur == '(') {
                outputStack.push(cur);
            } else if (cur == ')') {
                var po = outputStack.pop();
                while(po != '(' && outputStack.length > 0) {
                    outputQueue.push(po);
                    po = outputStack.pop();
                }
            } else {
                while(prioraty(cur,outputStack[outputStack.length - 1]) && outputStack.length > 0) {
                    outputQueue.push(outputStack.pop());
                }
                outputStack.push(cur)
            }
        } else {
            outputQueue.push(Number(cur));
        }
    }
    if(outputStack.length > 0){
        while (outputStack.length > 0) {
            outputQueue.push(outputStack.pop());
        }
    }
    return outputQueue;
}

function calRpnExp(rpnArr) {
    var stack = [];
    for(var i = 0, max = rpnArr.length; i < max; i++) {
        if(!isOperator(rpnArr[i])) {
            stack.push(rpnArr[i]);
        } else {
            var num1 = stack.pop();
            var num2 = stack.pop();
            if(rpnArr[i] == '-') {
                var num = num2 - num1;
            } else if(rpnArr[i] == '+') {
                var num = num2 + num1;
            } else if(rpnArr[i] == '*' || rpnArr[i] == '×') {
                var num = num2 * num1;
            } else if(rpnArr[i] == '/' || rpnArr[i] == '÷') {
                var num = num2/num1;
            }
            stack.push(num);
        }
    }
    return stack[0];
}

export function calCommonExp(exp) {
    var rpnArr = outputRpn(exp);
    return calRpnExp(rpnArr)
}