Style-sheet like properties

Properties.scala

object UnitType extends Enumeration {
  val Em = Value("em")
  val Px = Value("px")
  val Pc = Value("%")
}

import UnitType._

case class Dimension(
  val length : Double = 0.0, 
  val unit : UnitType.Value = Px) {

  override def toString = "%.2f".format(length) + unit  
}

case class Color(
  val red : Double = 1.0, 
  val green : Double = 1.0, 
  val blue : Double = 1.0, 
  val alpha : Double = 1.0) {

  override def toString = "#" + hex(red) + hex(green) + hex(blue) + hex(alpha)
  def hex(x : Double) : String = "%02x".format((x * 255).toInt)
}

sealed abstract class Property[T](val name : String, val value : T) {
  override def equals(other : Any) : Boolean =
    other match {
      case x : Property[_] => name == x.name
      case _ => false
    }

  def +(other : Property[_]) : Set[Property[_]] = Set(this, other)
}

case class Width(v : Dimension = Dimension()) extends Property("width", v)
case class Height(v : Dimension = Dimension()) extends Property("height", v)
case class BackgroundColor(v : Color = Color()) extends Property("bgcolor", v)

val props : Set[Property[_]] = 
  Set(
    Width(Dimension(15, Px)), 
    BackgroundColor(Color(0.5, 0, 0)), 
    Width(Dimension(20, Px))
  )

val props2 : Set[Property[_]] = 
  Width(Dimension(15)) +
  Height(Dimension(100, Pc)) +
  Height(Dimension(100, Px))

println(props)
println(props2)

props foreach { 
  _ match {
    case Width(x) => println("we have a width of " + x)
    case other => println("we have another property: " + other.name + " -> " + other.value)
  }
}

val bgcolor : Color = props2 collectFirst { case BackgroundColor(c) => c } getOrElse Color()

println("background color is " + bgcolor)