/*
  -------------------------------------
  DESCRIPTION:
  -------------------------------------
  
  BezierTween class extends Macromedia's Tween class using Robert Penner's cubic bezier tween function
  
  -------------------------------------
  USAGE:
  -------------------------------------  
      
  function BezierTween(obj, prop, begin, finish, duration, useSeconds, a_val, b_val);    
  
  obj: reference - the object which the Tween targets
  prop: string - name of the property (in obj) that will be affected
  begin: number - the starting value of prop
  finish: number - the starting value of prop  
  duration: number - the length of time of the motion
  useSeconds: boolean - a flag specifying whether to use seconds instead of frames
  a_val = control point A's value
  b_val = control point B's value
  
  -------------------------------------
  EXAMPLE:
  -------------------------------------
  
  //Create a new FLA. Copy this Class file into same folder as FLA.
  //Create a movieclip on stage with name "mcClip".
  //Put this code in frame 1.
  
  import mx.transitions.*;
  import mx.transitions.easing.*;
  
  twnBezX = new BezierTween(mcClip, "_x", 0, 300, 30, false, 100, 400);
  twnBezY = new BezierTween(mcClip, "_y", 0, 300, 30, false, 400, 100);
    
  twnBezX._tl = this;
  
  twnBezX.onMotionFinished = function(){
    this._tl.tweenDone();
  }
  
  function tweenDone(){
    trace("tween done");
  }
  
  -------------------------------------
  CREDITS:
  -------------------------------------
  BezierTween Class by Felix Turner (www.airtightinteractive.com)
  Bezier Tween function by Robert Penner (www.robertpenner.com)
  Tween Class by Macromedia

*/

import mx.transitions.BroadcasterMX;
import mx.transitions.OnEnterFrameBeacon;
import mx.transitions.Tween;

class BezierTween extends Tween {

  public var point1:Number;
  public var point2:Number;
    
  
/////////////////////////////////////////////////////////////////////////

/* constructor for BezierTween class

  obj: reference - the object which the Tween targets
  prop: string - name of the property (in obj) that will be affected
  begin: number - the starting value of prop
  duration: number - the length of time of the motion; set to infinity if negative or omitted
  useSeconds: boolean - a flag specifying whether to use seconds instead of frames
*/
  function BezierTween (obj, prop, begin, finish, duration, useSeconds,point1,point2) {
    OnEnterFrameBeacon.init();
    if (!arguments.length) return;
    this.obj = obj;
    this.prop = prop;
    this.begin = begin;
    this.position = begin;
    this.duration = duration;
    this.point1 = point1;
    this.point2 = point2;
    this.useSeconds = useSeconds;
    this.func = tweenCubicBez;
    this.finish = finish;
    this._listeners = [];
    this.addListener (this);
    this.start();
  }
  
  function getPosition (t:Number):Number {
    if (t == undefined) t = this._time;
    return this.func (t, this.begin, this.change, this._duration,this.point1,this.point2);
  };
  
  
  // Cubic Bezier tween from b to b+c, influenced by p1 & p2
  // t: current time, b: beginning value, c: total change, d: duration
  // p1, p2: Bezier control point positions
  static function tweenCubicBez (t:Number, b:Number, c:Number, d:Number,p1:Number,p2:Number):Number {
    return ((t/=d)*t*c + 3*(1-t)*(t*(p2-b) + (1-t)*(p1-b)))*t + b;
  }

  
}