Tween

/*
    CASA Lib for ActionScript 3.0
    Copyright (c) 2011, Aaron Clinger & Contributors of CASA Lib
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*/
package org.casalib.transitions {
    import flash.events.Event;
    import org.casalib.events.TweenEvent;
    import org.casalib.math.Percent;
    import org.casalib.process.Process;
    import org.casalib.time.EnterFrame;
    import org.casalib.time.FrameTimeStopwatch;
    
    [Event(name="start", type="org.casalib.events.TweenEvent")]
    [Event(name="stop", type="org.casalib.events.TweenEvent")]
    [Event(name="resume", type="org.casalib.events.TweenEvent")]
    [Event(name="update", type="org.casalib.events.TweenEvent")]
    [Event(name="complete", type="org.casalib.events.TweenEvent")]
    
    /**
        Simple and easily extendable tween/transition class.
        
        Advantages of using this tween class over others:
        

            
Does not include any tweening equations, only the equation(s) a user defines.
            
Using the built in events you are able to tween more than one value.
            
Ability to tween any value, not only DisplayObject properties.
            
Works with all easing equations that follow the current time, start position, end position, total time standard.
        
        
        @author Aaron Clinger
        @author Mike Creighton
        @version 09/06/09
        @example
            
                package {
                    import fl.motion.easing.Bounce;
                    import org.casalib.display.CasaMovieClip;
                    import org.casalib.events.TweenEvent;
                    import org.casalib.transitions.Tween;
                    
                    
                    public class MyExample extends CasaMovieClip {
                        protected var _tween:Tween;
                        
                        
                        public function MyExample() {
                            super();
                            
                            this._tween = new Tween(Bounce.easeOut, 0, 1, 2);
                            this._tween.addEventListener(TweenEvent.UPDATE, this._onTweenPosition);
                            this._tween.start();
                        }
                        
                        protected function _onTweenPosition(e:TweenEvent):void {
                            trace(e.position);
                        }
                    }
                }
            
            
            You can tween color by using {@link ColorUtil}'s {@link ColorUtil#interpolateColor interpolateColor} function:
            
                package {
                    import fl.motion.easing.Linear;
                    import flash.geom.ColorTransform;
                    import org.casalib.display.CasaMovieClip;
                    import org.casalib.display.CasaSprite;
                    import org.casalib.events.TweenEvent;
                    import org.casalib.transitions.Tween;
                    import org.casalib.util.ColorUtil;
                    
                    
                    public class MyExample extends CasaMovieClip {
                        protected var _box:CasaSprite;
                        protected var _finishColor:ColorTransform;
                        protected var _tween:Tween;
                        
                        
                        public function MyExample() {
                            super();
                            
                            this._box = new CasaSprite();
                            this._box.graphics.beginFill(0x0000FF);
                            this._box.graphics.drawRect(0, 0, 250, 250);
                            this._box.graphics.endFill();
                            
                            this.addChild(this._box);
                            
                            this._finishColor       = new ColorTransform();
                            this._finishColor.color = 0xFF0000;
                            
                            this._tween = new Tween(Linear.easeNone, 0, 1, 1);
                            this._tween.addEventListener(TweenEvent.UPDATE, this._onTweenPosition);
                            this._tween.start();
                        }
                        
                        protected function _onTweenPosition(e:TweenEvent):void {
                            this._box.transform.colorTransform = ColorUtil.interpolateColor(new ColorTransform(), this._finishColor, e.progress);
                        }
                    }
                }
            
            
            If you want to tween an item on a ellipse you can use the {@link Ellipse} class and its {@link Ellipse#getPointOfDegree getPointOfDegree} function:
            
                package {
                    import fl.motion.easing.Bounce;
                    import flash.geom.Point;
                    import org.casalib.display.CasaMovieClip;
                    import org.casalib.display.CasaSprite;
                    import org.casalib.events.TweenEvent;
                    import org.casalib.math.geom.Ellipse;
                    import org.casalib.transitions.Tween;
                    
                    
                    public class MyExample extends CasaMovieClip {
                        protected var _box:CasaSprite;
                        protected var _tween:Tween;
                        protected var _ellipse:Ellipse = new Ellipse(20, 50, 300, 200);
                        
                        
                        public function MyExample() {
                            super();
                            
                            this._box = new CasaSprite();
                            this._box.graphics.beginFill(0xFF00FF);
                            this._box.graphics.drawRect(0, 0, 25, 25);
                            this._box.graphics.endFill();
                            
                            this.addChild(this._box);
                            
                            this._tween = new Tween(Bounce.easeOut, 0, 360, 5);
                            this._tween.addEventListener(TweenEvent.UPDATE, this._onTweenPosition);
                            this._tween.start();
                        }
                        
                        protected function _onTweenPosition(e:TweenEvent):void {
                            var point:Point = this._ellipse.getPointOfDegree(e.position);
                            
                            this._box.x = point.x;
                            this._box.y = point.y;
                        }
                    }
                }
            
            
        @usageNote If you want to tween a property use {@link PropertyTween}.
        @see {@link PropertySetter}
    */
    public class Tween extends Process {
        protected var _hasInit:Boolean;
        protected var _equat:Function;
        protected var _frameFires:int;
        protected var _framePulse:EnterFrame;
        protected var _stopwatch:FrameTimeStopwatch;
        protected var _time:Number;
        protected var _useFrames:Boolean;
        protected var _begin:Number;
        protected var _currentPosition:Number;
        protected var _diff:Number;
        protected var _end:Number;
        
        
        /**
            Creates and defines a new Tween.
            
            @param equat: The tween equation.
            @param startPos: The starting value of the transition.
            @param endPos: The ending value of the transition.
            @param duration: The length of time of the tween transition.
            @param useFrames: Indicates to use frames true, or seconds false in relation to the value specified in the duration parameter.
            @usageNote The function specified in the equation parameter must follow the (currentTime, startPosition, endPosition, totalTime) parameter standard.
        */
        public function Tween(equat:Function, startPos:Number, endPos:Number, duration:Number, useFrames:Boolean = false) {
            super();
            
            this.equation   = equat;
            this._begin     = this.position = startPos;
            this._end       = endPos;
            this._diff      = this._end - this._begin;
            this._useFrames = useFrames;
            this.duration   = duration;
            
            if (!this._useFrames)
                this._stopwatch = new FrameTimeStopwatch();
            
            this._framePulse = EnterFrame.getInstance();
        }
        
        /**
            Starts the transition from its starting position.
            
            @sends TweenEvent#START - Dispatched when transition starts.
        */
        override public function start():void {
            if (this._useFrames)
                this._frameFires = 0;
            else
                this._stopwatch.start();
            
            this._hasInit = true;
            this._framePulse.addEventListener(Event.ENTER_FRAME, this._onFrame, false, 0, true);
            
            super.start();
            
            var updateEvent:TweenEvent = new TweenEvent(TweenEvent.START);
            updateEvent.progress       = this.progress;
            updateEvent.position       = this.position;
            this.dispatchEvent(updateEvent);
            
            this._onFrame();
        }
        
        /**
            Stops the transition at its current position.
            
            @sends TweenEvent#STOP - Dispatched when transition is stopped.
        */
        override public function stop():void {
            if (!this.running || this.completed)
                return;
            
            if (!this._useFrames)
                this._stopwatch.stop();
            
            this._framePulse.removeEventListener(Event.ENTER_FRAME, this._onFrame);
            
            super.stop();
            
            var updateEvent:TweenEvent = new TweenEvent(TweenEvent.STOP);
            updateEvent.progress       = this.progress;
            updateEvent.position       = this.position;
            this.dispatchEvent(updateEvent);
        }
        
        /**
            Resumes the transition from {@link Tween#stop stopped} position.
            
            @sends TweenEvent#RESUME - Dispatched when transition is resumed.
        */
        public function resume():void {
            if (!this._hasInit)
                this.start();
            
            if (this.running || this.completed)
                return;
            
            if (!this._useFrames)
                this._stopwatch.resume();
            
            this._framePulse.addEventListener(Event.ENTER_FRAME, this._onFrame);
            
            super.start();
            
            var updateEvent:TweenEvent = new TweenEvent(TweenEvent.RESUME);
            updateEvent.progress       = this.progress;
            updateEvent.position       = this.position;
            this.dispatchEvent(updateEvent);
        }
        
        /**
            Transitions from the tween's current position to a new end position and duration.
            
            @param endPos: The ending value of the transition.
            @param duration: Length of time of the transition.
            @usageNote Will automatically start tween if currently stopped.
        */
        public function continueTo(endPos:Number, duration:Number):void {
            this._begin   = this.position;
            this._end     = endPos;
            this._diff    = this._end - this._begin;
            this.duration = duration;
            
            this.start();
        }
        
        /**
            The tween equation.
        */
        public function get equation():Function {
            return this._equat;
        }
        
        public function set equation(equat:Function):void {
            this._equat = equat;
        }
        
        /**
            The length of time of the tween transition.
        */
        public function get duration():Number {
            return (this._useFrames) ? this._time : this._time / 1000;
        }
        
        public function set duration(dur:Number):void {
            this._time = (this._useFrames) ? dur : dur * 1000;
        }
        
        /**
            The current position of the tween.
        */
        public function get position():Number {
            return this._currentPosition;
        }
        
        public function set position(pos:Number):void {
            this._currentPosition = pos;
        }
        
        /**
            The percent completed of the tween's duration.
        */
        public function get progress():Percent {
            return new Percent(this._timeProgress / this._time);
        }
        
        override public function destroy():void {
            super.destroy();
        }
        
        /**
            @sends TweenEvent#UPDATE - Dispatched as the transition progresses.
            @sends TweenEvent#COMPLETE - Dispatched when transition completes.
        */
        protected function _onFrame(e:Event = null):void {
            const timePos:Number   = this._timeProgress;
            const finished:Boolean = timePos == this._time;
            
            this.position = finished ? this._end : this.equation.apply(null, [timePos, this._begin, this._diff, this._time]);
            
            var updateEvent:TweenEvent = new TweenEvent(TweenEvent.UPDATE);
            updateEvent.progress       = this.progress;
            updateEvent.position       = this.position;
            this.dispatchEvent(updateEvent);
            
            if (finished) {
                if (!this._useFrames)
                    this._stopwatch.stop();
                
                this._framePulse.removeEventListener(Event.ENTER_FRAME, this._onFrame);
                
                this._complete();
                
                updateEvent          = new TweenEvent(TweenEvent.COMPLETE);
                updateEvent.progress = this.progress;
                updateEvent.position = this.position;
                this.dispatchEvent(updateEvent);
            }
        }
        
        protected function get _timeProgress():Number {
            var timeProgress:Number = (this._useFrames) ? ++this._frameFires : this._stopwatch.time;
            
            return (timeProgress > this._time) ? this._time : timeProgress;
        }
    }
}