package week5

import swing._
import javax.swing._
import java.awt.BorderLayout
import scala.swing.event._

object Calculator extends SimpleSwingApplication {
  final val INFO_FIELD_TEXT_DEFAULT = "------------------------------"
  def numberField = new TextField {
    text = "0"
    columns = 5
  }

  val a = numberField
  val b = numberField
  val plusButton = new Button("+")
  val minusButton = new Button("-")
  val timesButton = new Button("*")
  val divisionButton = new Button("/")
  val info = new TextField(INFO_FIELD_TEXT_DEFAULT)

  def top = new MainFrame {
    title = "Kuljulator"
    contents = new FlowPanel(
        new FlowPanel(a, b),
        new FlowPanel(plusButton, minusButton, timesButton, divisionButton),
        new FlowPanel(info))
  }

  listenTo(plusButton, minusButton, timesButton, divisionButton)
  reactions += {
    case ButtonClicked(x) => x.text match {
      case "+" => calculate((x, y) => x+y)
      case "-" => calculate((x, y) => x-y)
      case "*" => calculate((x, y) => x*y)
      case "/" => calculate(divide)
    }
  }

  def calculate(operation : (Double, Double) => Double) {
    try {
      val x = a.text.replace(',', '.').toDouble
      val y = b.text.replace(',', '.').toDouble

      a.text = (operation(x, y)).toString
      b.text = "0"
      info.text = INFO_FIELD_TEXT_DEFAULT
    } catch {
      case e : Exception => info.text = e.getMessage()
    }
  }

  def divide (x : Double, y : Double) : Double = {
    if (y == 0) // Otherwise there's going to be NaN instead (why?!)
      throw new ArithmeticException("Division by zero")
    else
      x/y
  }
}