simplex3d.engine.util.Reassignable.scala Maven / Gradle / Ivy

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/*
 * Simplex3dEngine - Core Module
 * Copyright (C) 2012, Aleksey Nikiforov
 *
 * This file is part of Simplex3dEngine.
 *
 * Simplex3dEngine is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * Simplex3dEngine is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see .
 */

package simplex3d.engine.util

import simplex3d.math.types._


final class Reassignable[T <: Accessible] private[engine] () {
  
  //*** PropertyContext Code ******************************************************************************************
  
  protected final var propertyContext: PropertyContext = _
  
  private[engine] final def register(context: PropertyContext) {
    if (context == null) throw new NullPointerException
    if (this.propertyContext != null && (this.propertyContext ne context)) throw new IllegalStateException(
      "Reassignable can register PropertyContext only once."
    )
    this.propertyContext = context
  }
  
  private[engine] final def unregister() {
    throw new UnsupportedOperationException("Reassignable cannot unregister PropertyContexts.")
  }
  
  
  //*** Property Code *************************************************************************************************
  
  private[this] final var value: T = _
  protected final var changed = true // Initialize as changed.
  
  private[engine] def hasDataChanges = changed
  private[engine] def clearDataChanges() { changed = false }
  private[engine] def signalDataChanges() { changed = true }
  
  
  final def get: T = if (value == null) throw new NoSuchElementException else value
  final def isDefined = (value != null)
  
  final def undefine() {
    if (isDefined) {
      if (propertyContext != null) propertyContext.signalStructuralChanges()
      changed = true
      value match { case d: PropertyContextDependent => d.unregister(); case _ => /* ignore */ }
      value = null.asInstanceOf[T]
    }
  }
  
  final def update: T = {
    if (!isDefined) throw new NoSuchElementException
    changed = true
    value
  }
  
  private final def init(value: T) {
    this.value = value
    value match { case d: PropertyContextDependent => d.register(propertyContext); case _ => /* ignore */ }
    changed = true
  }
  
  final def :=(t: T) {
    if (isDefined && (value.getClass eq t.getClass)) {
      val stable = value
      stable := t.asInstanceOf[stable.Read]
    }
    else {
      value match { case d: PropertyContextDependent => d.unregister(); case _ => /* ignore */ }
      value = t.mutableCopy.asInstanceOf[T]
      value match { case d: PropertyContextDependent => d.register(propertyContext); case _ => /* ignore */ }
      if (propertyContext != null) propertyContext.signalStructuralChanges()
    }
    changed = true
  }
  
  final def :=(p: Reassignable[T]) {
    if (p.isDefined) this := p.get else undefine()
  }
  
  final override def toString :String = {
    "Reassignable(" + (if (isDefined) get.toString else "undefined" ) + ")"
  }
}

object Reassignable {
  def optional[T <: Accessible]() :Reassignable[T] = {
    new Reassignable[T]()
  }
}