import UIKit

class ViewController: UIViewController {

    var numberFromScreen : Double = 0;
    var firstNum : Double = 0;
     var operation : Int = 0;
    var mathSign : Bool = false;

    @IBOutlet weak var result: UILabel!

    @IBAction func digits(_ sender: UIButton) {
        if mathSign == true {
            result.text = String( sender.tag)
            mathSign = false
        }
        else {

        result.text = result.text! + String(sender.tag)

        }

        numberFromScreen = Double(result.text!)!
    }


    @IBAction func buttons(_ sender: UIButton) {
        if result.text != ""  &&  sender.tag != 10 && sender.tag != 15 {
            firstNum = Double(result.text!)!
            if sender.tag == 11 { // division
                 result.text = "/";

            }
            else if sender.tag == 12 { // multuply
                    result.text = "x";

            }
            else if sender.tag == 13 { // minus
                 result.text = "-";

            }
            else if sender.tag == 14 { // plus
                result.text = "+";
            }
            else if sender.tag == 17 { // plus
                result.text = String( sqrt(firstNum));
            }
            else if sender.tag == 20 { // plus
        result.text = String(firstNum * firstNum);

            } else if sender.tag == 21 { // plus
                result.text = String(firstNum * firstNum*firstNum)

            } else if sender.tag == 16 { // plus
                func factorial(_ num : Int) -> Int
                    {    var num = Int(firstNum)
                        var factorialOfNumber = 0
                        if num == 0
                        {
                            factorialOfNumber = 1
                            return factorialOfNumber
                        }
                        return (1...num).reduce(1){$0 * $1}
                        var n = ""
                        result.text = String?(n)
                        n = ((1...num).reduce(1){$0 * $1})
            }
            }

            else if sender.tag == 18 { // √
                result.text = "3.1459";

            }
            else if sender.tag == 19 { // √
                result.text = "2.73711";

            }
            operation = sender.tag
            mathSign = true
        }
        else if sender.tag == 15 { //equal to = botton
            if operation == 11 {
                result.text = String(firstNum / numberFromScreen)
            }
            else if operation == 12 {
                result.text = String( firstNum * numberFromScreen)
            }
            else if operation == 13 {
                result.text = String( firstNum - numberFromScreen)
            }
            else if operation == 14 {
                result.text = String( firstNum + numberFromScreen)
            }
            else if operation == 17 {
                result.text = String( sqrt(firstNum))
            }
            else if operation == 18 {
                result.text = String(3.1459)
            }
            else if operation == 19 {
                result.text = String(2.73911)
            }
            else if operation == 20 {
                result.text = String(firstNum * firstNum)
            }
            else if operation == 21 {
                result.text = String(firstNum * firstNum * firstNum)
            }
        else if operation == 16 {
                func factorial(_ num : Int) -> Int
                {    var num = Int(firstNum)
                    var factorialOfNumber = 0
                    if num == 0
                    {
                        factorialOfNumber = 1
                        return factorialOfNumber
                    }
                    return (1...num).reduce(1){$0 * $1}
                }
        }

        }
        else if sender.tag == 10 {
            result.text = ""
            firstNum = 0
            numberFromScreen = 0
            operation = 0
            // dispoose of any resources that can be recreated
        }

    }





    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }



}