Steady.as

/*
 * FLINT PARTICLE SYSTEM
 * .....................
 * 
 * Author: Richard Lord
 * Copyright (c) Richard Lord 2008-2011
 * 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.common.counters
{
	import org.flintparticles.common.emitters.Emitter;		

	/**
	 * The Steady counter causes the emitter to emit particles continuously
	 * at a steady rate. It can be used to simulate any continuous particle
	 * stream.
	 */
	public class Steady implements Counter
	{
		private var _timeToNext:Number;
		private var _rate:Number;
		private var _rateInv:Number;
		private var _running:Boolean;
		
		/**
		 * The constructor creates a Steady counter for use by an emitter. To
		 * add a Steady counter to an emitter use the emitter's counter property.
		 * 
		 * @param rate The number of particles to emit per second.
		 * 
		 * @see org.flintparticles.common.emitter.Emitter.counter
		 */
		public function Steady( rate:Number = 0 )
		{
			_running = false;
			this.rate = rate;
		}
		
		/**
		 * Stops the emitter from emitting particles
		 */
		public function stop():void
		{
			_running = false;
		}
		
		/**
		 * Resumes the emitter emitting particles after a stop
		 */
		public function resume():void
		{
			_running = true;
		}
		
		/**
		 * The number of particles to emit per second.
		 */
		public function get rate():Number
		{
			return _rate;
		}
		public function set rate( value:Number ):void
		{
			if( !value || value < 0 )
			{
				value = 0;
			}
			if( _rate != value )
			{
				if( _rate && value )
				{
					var timePassed:Number = _rateInv - _timeToNext;
					_rate = value;
					_rateInv = value ? 1 / value : Number.MAX_VALUE;
					_timeToNext = Math.max( _rateInv - timePassed, 0 );
				}
				else
				{
					_rate = value;
					_rateInv = value ? 1 / value : Number.MAX_VALUE;
					_timeToNext = _rateInv;
				}
			}
		}
		
		/**
		 * Initilizes the counter. Returns 0 to indicate that the emitter should 
		 * emit no particles when it starts.
		 * 
		 * <p>This method is called within the emitter's start method 
		 * and need not be called by the user.</p>
		 * 
		 * @param emitter The emitter.
		 * @return 0
		 * 
		 * @see org.flintparticles.common.counters.Counter#startEmitter()
		 */
		public function startEmitter( emitter:Emitter ):uint
		{
			_running = true;
			_timeToNext = _rateInv;
			return 0;
		}
		
		/**
		 * Uses the time, rateMin and rateMax to calculate how many
		 * particles the emitter should emit now.
		 * 
		 * <p>This method is called within the emitter's update loop and need not
		 * be called by the user.</p>
		 * 
		 * @param emitter The emitter.
		 * @param time The time, in seconds, since the previous call to this method.
		 * @return the number of particles the emitter should create.
		 * 
		 * @see org.flintparticles.common.counters.Counter#updateEmitter()
		 */
		public function updateEmitter( emitter:Emitter, time:Number ):uint
		{
			if( !_running )
			{
				return 0;
			}
			var count:uint = 0;
			_timeToNext -= time;
			while( _timeToNext <= 0 )
			{
				++count;
				_timeToNext += _rateInv;
			}
			return count;
		}

		/**
		 * Indicates if the counter has emitted all its particles. For this counter
		 * this will always be false.
		 */
		public function get complete():Boolean
		{
			return false;
		}
		
		/**
		 * Indicates if the counter is currently emitting particles
		 */
		public function get running():Boolean
		{
			return _running;
		}
	}
}