Monadic-ScalaFX-Demo/src/main/scala/nova/monadic_sfx/util/History.scala

package nova.monadic_sfx.util

class MutHistory[T](initValue: T) {
  private var _values = Vector(initValue)
  def values = _values
  private var _sp = 0
  def sp = _sp

  // def current = if (ints.isEmpty) None else Some(ints(sp))
  def current = _values(_sp)

  def push(v: T) = {
    if (_sp < _values.length - 1) {
      _values = _values.splitAt(_sp)._1
      _values = _values :+ v
    } else {
      _values = _values :+ v
      _sp = _values.length - 1
    }
  }

  def forward() = {
    if (!_values.isEmpty && _sp < _values.length - 1) _sp += 1
  }

  def backward() = {
    if (_sp > 0) {
      _sp -= 1
    }
  }
}