/*
 * FLINT PARTICLE SYSTEM
 * .....................
 * 
 * Author: Richard Lord
 * Copyright (c) Richard Lord 2008-2010
 * http://flintparticles.org
 * 
 * 
 * Licence Agreement
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

package org.flintparticles.twoD.actions 
{
	import org.flintparticles.common.actions.ActionBase;
	import org.flintparticles.common.emitters.Emitter;
	import org.flintparticles.common.particles.Particle;
	import org.flintparticles.twoD.particles.Particle2D;
	
	import flash.display.DisplayObject;	

	/**
	 * The TurnTowardsMouse action causes the particle to constantly adjust its direction
	 * so that it travels towards the mouse pointer.
	 */

	public class TurnTowardsMouse extends ActionBase
	{
		private var _power:Number;
		private var _renderer:DisplayObject;
		
		/**
		 * The constructor creates a TurnTowardsMouse action for use by an emitter. 
		 * To add a TurnTowardsMouse to all particles created by an emitter, use the
		 * emitter's addAction method.
		 * 
		 * @see org.flintparticles.common.emitters.Emitter#addAction()
		 * 
		 * @param power The strength of the turn action. Higher values produce a sharper turn.
		 * @param renderer The display object whose coordinate system the mouse position is 
		 * converted to. This is usually the renderer for the particle system created by the emitter.
		 */
		public function TurnTowardsMouse( power:Number = 0, renderer:DisplayObject = null )
		{
			this.power = power;
			this.renderer = renderer;
		}
		
		/**
		 * The strength of the turn action. Higher values produce a sharper turn.
		 */
		public function get power():Number
		{
			return _power;
		}
		public function set power( value:Number ):void
		{
			_power = value;
		}

		/**
		 * The display object whose coordinate system the mouse position is converted to. This
		 * is usually the renderer for the particle system created by the emitter.
		 */
		public function get renderer():DisplayObject
		{
			return _renderer;
		}
		public function set renderer( value:DisplayObject ):void
		{
			_renderer = value;
		}
		
		/**
		 * Calculates the direction to the mouse and turns the particle towards 
		 * this direction.
		 * 
		 * <p>This method is called by the emitter and need not be called by the 
		 * user.</p>
		 * 
		 * @param emitter The Emitter that created the particle.
		 * @param particle The particle to be updated.
		 * @param time The duration of the frame - used for time based updates.
		 * 
		 * @see org.flintparticles.common.actions.Action#update()
		 */
		override public function update( emitter:Emitter, particle:Particle, time:Number ):void
		{
			var p:Particle2D = Particle2D( particle );
			var turnLeft:Boolean = ( ( p.y - _renderer.mouseY ) * p.velX + ( _renderer.mouseX - p.x ) * p.velY > 0 );
			var newAngle:Number;
			if ( turnLeft )
			{
				newAngle = Math.atan2( p.velY, p.velX ) - _power * time;
				
			}
			else
			{
				newAngle = Math.atan2( p.velY, p.velX ) + _power * time;
			}
			var len:Number = Math.sqrt( p.velX * p.velX + p.velY * p.velY );
			p.velX = len * Math.cos( newAngle );
			p.velY = len * Math.sin( newAngle );
			var overturned:Boolean = ( ( p.y - _renderer.mouseY ) * p.velX + ( _renderer.mouseX - p.x ) * p.velY > 0 ) != turnLeft;
			if( overturned )
			{
				var dx:Number = _renderer.mouseX - p.x;
				var dy:Number = _renderer.mouseY - p.y;
				var factor:Number = len / Math.sqrt( dx * dx + dy * dy );
				p.velX = dx * factor;
				p.velY = dy * factor;
			}
		}
	}
}
