package {
 import flash.display.Sprite;
 import flash.display.StageAlign;
 import flash.display.StageScaleMode;
 import flash.events.Event;
 import flash.geom.Point;

 public class animation_ch14_PlayBall extends Sprite
 {
  private var segments:Array;
  private var numSegments:uint = 6;
  private var gravity:Number = 0.5;
  private var bounce:Number = -0.9;
  private var ball:animation_ch14_Ball;
  
  public function animation_ch14_PlayBall()
  {
   init();
  }
//@ init(s)  
  private function init():void
  {
   stage.align = StageAlign.TOP_LEFT;
   stage.scaleMode = StageScaleMode.NO_SCALE;
   ball = new animation_ch14_Ball(20);
   ball.vx = 10;
   addChild(ball);
   segments = new Array();
   for(var i:uint = 0; i < numSegments; i++)
   {
    var segment:animation_ch14_Segment = new animation_ch14_Segment(50, 10);
    addChild(segment);
    segments.push(segment);
   }
   segment.x = stage.stageWidth / 2;
   segment.y = stage.stageHeight;
   addEventListener(Event.ENTER_FRAME, onEnterFrame);
  }
 //@ frame(s) 
  private function onEnterFrame(event:Event):void
  {
   moveBall();
   var target:Point = reach(segments[0], ball.x, ball.y);
   for(var i:uint = 1; i < numSegments; i++)
   {
    var segment:animation_ch14_Segment = segments[i];
    target = reach(segment, target.x, target.y);
   }
   for(i = numSegments - 1; i > 0; i--)
   {
    var segmentA:animation_ch14_Segment = segments[i];
    var segmentB:animation_ch14_Segment = segments[i - 1];
    position(segmentB, segmentA);
   }
   checkHit();
  }
 //@ reach 
  private function reach(segment:animation_ch14_Segment, xpos:Number, ypos:Number):Point
  {
   var dx:Number = xpos - segment.x;
   var dy:Number = ypos - segment.y;
   var angle:Number = Math.atan2(dy, dx);
   segment.rotation = angle * 180 / Math.PI;
   
   var w:Number = segment.getPin().x - segment.x;
   var h:Number = segment.getPin().y - segment.y;
   var tx:Number = xpos - w;
   var ty:Number = ypos - h;
   return new Point(tx, ty);
  }
 //@ position 
  private function position(segmentA:animation_ch14_Segment, segmentB:animation_ch14_Segment):void
  {
   segmentA.x = segmentB.getPin().x;
   segmentA.y = segmentB.getPin().y;
  }

//@ move(s)
  private function moveBall():void
  {
   ball.vy += gravity;
   ball.x += ball.vx;
   ball.y += ball.vy;
   if(ball.x + ball.radius > stage.stageWidth)
   {
    ball.x = stage.stageWidth - ball.radius;
    ball.vx *= bounce;
   }
   else if(ball.x - ball.radius < 0)
   {
    ball.x = ball.radius;
    ball.vx *= bounce;
   }
   if(ball.y + ball.radius > stage.stageHeight)
   {
    ball.y = stage.stageHeight - ball.radius;
    ball.vy *= bounce;
   }
   else if(ball.y - ball.radius < 0)
   {
    ball.y = ball.radius;
    ball.vy *= bounce;
   }
  }
//@ hit(s)?
  
  public function checkHit():void
  {
   var segment:animation_ch14_Segment = segments[0];
   var dx:Number = segment.getPin().x - ball.x;
   var dy:Number = segment.getPin().y - ball.y;
   var dist:Number = Math.sqrt(dx * dx + dy * dy);
   if(dist < ball.radius)
   {
    ball.vx += Math.random() * 2 - 1;
    ball.vy -= 1;
   }
  }
 }
}