"use strict";

function BinOperation(a, b) {
    this.a = a;
    this.b = b;

    this.evaluate = (...args) => this.evaluateImpl(a.evaluate(...args), b.evaluate(...args));
    this.toString = () => a.toString() + " " + b.toString() + " " + this.Operation;
}

function Add(a, b) {
    BinOperation.call(this, a, b);

    this.Operation = "+";
    this.evaluateImpl = (a, b) => a + b;
    this.diff = (name) => new Add(this.a.diff(name), this.b.diff(name));
}

function Subtract(a, b) {
    BinOperation.call(this, a, b);

    this.Operation = "-";
    this.evaluateImpl = (a, b) => a - b;
    this.diff = (name) => new Subtract(this.a.diff(name), this.b.diff(name));
}

function Multiply(a, b) {
    BinOperation.call(this, a, b);

    this.Operation = "*";
    this.evaluateImpl = (a, b) => a * b;
    this.diff = (name) => new Add(
        new Multiply(this.a.diff(name), this.b),
        new Multiply(this.a, this.b.diff(name))
    );
}

function Divide(a, b) {
    BinOperation.call(this, a, b);

    this.Operation = "/";
    this.evaluateImpl = (a, b) => a / b;

    this.diff = (name) => new Divide(
        new Subtract(
            new Multiply(this.a.diff(name), this.b),
            new Multiply(this.a, this.b.diff(name))
        ),
        new Multiply(this.b, this.b)
    );
}


function Variable(name) {
    this.name = name;

    this.evaluate = function(...args) {
        if (this.name === 'x') return args[0];
        if (this.name === 'y') return args[1];
        if (this.name === 'z') return args[2];
    }

    this.toString = () => this.name;

    this.diff = (name) => this.name === name ? new Const(1) : new Const(0);
}

function Const(val) {
    this.val = val;

    this.evaluate = () => this.val;
    this.toString = () => this.val.toString();

    this.diff = (name) => new Const(0);
}

function Negate(a) {
    this.a = a;

    this.evaluate = (...args) => (-1) * this.a.evaluate(...args);
    this.toString = () => a.toString() + " negate";

    this.diff = (name) => new Negate(this.a.diff(name));
}

const operationToArity = {
    'negate': 1,
    '+' : 2,
    '-' : 2,
    '*' : 2,
    '/' : 2,
};

const parse = function(expression) {
    let stack = [];
    let tokens = expression.split(' ').filter((word) => word !== '');
    for (let token of tokens) {
        let arity = token in operationToArity ? operationToArity[token] : 0;
        let args = [];
        for (let i = 0; i < arity; i++) {
            args.push(stack.pop());
        }
        args = args.reverse();
        //stack.push(operationToFuncrion[token](...args));
        stack.push(makeOperation(token, ...args));
    }
    return stack.pop();
}

const makeOperation = function (token, ...args) {
    switch (token) {
        case 'negate': return new Negate(...args);
        case "+": return new Add(...args);
        case "-": return new Subtract(...args);
        case "*": return new Multiply(...args);
        case "/": return new Divide(...args);
        case "x": return new Variable("x");
        case "y": return new Variable("y");
        case "z": return new Variable("z");
    }
    return new Const(Number.parseInt(token));
}