DSI Tween

module DSI_Tween

  def self.linear(t, b, c, d)
    return b + c * (t/d.to_f)
	end

  def self.easeInOutQuart(t, b, c, d)
    if (t/=d/2.0) < 1
      return c/2*t*t*t*t + b
    end
		return -c/2 * ((t-=2)*t*t*t - 2) + b
	end

end

class Scene_Base

  alias_method(:dsi_tween_update, :update)

  def tween(obj, params, duration, &callback)
    @tween_objects ||= []
    tween_obj = {}
    tween_obj[:target] = obj
    tween_obj[:params] = []
    params.each do |data|
      begin_value = eval("tween_obj[:target].#{data[0].to_s}")
      change = data[1] - begin_value
      obj = [data[0].to_s, begin_value, change]
      tween_obj[:params] << obj
    end
    tween_obj[:duration] = duration
    tween_obj[:timer] = 0
    tween_obj[:callback] = callback if callback
    @tween_objects << tween_obj
    tween_obj[:easing] = :easeInOutQuart
    return tween_obj
  end

  def update
    dsi_tween_update
    update_tween_objects
  end

  def update_tween_objects
    return unless @tween_objects
    new_tweens = []
    @tween_objects.each do |tween_object|
      target = tween_object[:target]
      params = tween_object[:params]
      duration = tween_object[:duration]
      if tween_object[:timer] < duration
        params.each do |data|
          case tween_object[:easing]
          when :easeInOutQuart
            new_value = DSI_Tween.easeInOutQuart(tween_object[:timer], data[1], data[2], duration)
          when :linear
            new_value = DSI_Tween.linear(tween_object[:timer], data[1], data[2], duration)
          end
          eval("target.#{data[0]} = new_value")
        end
        tween_object[:timer] += 1
        new_tweens << tween_object
      else
        tween_object[:callback].call() if tween_object[:callback]
      end
    end
    @tween_objects = new_tweens
  end

end