Follow.as

package com.aberustudios.cloneinfiltration.effects
{
    import flash.geom.Point;
    import flash.geom.Rectangle;

    import net.flashpunk.Entity;
    import net.flashpunk.FP;

    public class Follow
    {
        public var x:Number;
        public var y:Number;

        public var target:Entity;
        public var within:Rectangle;
        public var speed:Number;

        public function Follow(target:Entity, within:Rectangle, speed:Number = 10)
        {
            setView(target, within, speed);
        }

        public function setView(target:Entity, within:Rectangle, speed:Number = 10, teleport:Boolean = true):void
        {
            this.target = target;
            this.within = within;
            this.speed = speed;

            if(teleport) this.teleport();
        }

        public function teleport():void
        {
            x = target.x - FP.halfWidth;
            y = target.y - FP.halfHeight;

            stayWithin();
        }

        public function update():void
        {
            var distance:Number = FP.distance(target.x - FP.halfWidth, target.y - FP.halfHeight, x, y);
            var movementSpeed:Number = distance / speed;

            FP.stepTowards(this, target.x - FP.halfWidth, target.y - FP.halfHeight, movementSpeed);

            stayWithin();

            FP.camera.x = int(x);
            FP.camera.y = int(y);
        }

        protected function stayWithin():void
        {
            if(x < within.x) x = within.x;
            if(x + FP.width > within.x + within.width) x = within.x + within.width - FP.width;

            if(y < within.y) y = within.y;
            if(y + FP.height > within.y + within.height) y = within.y + within.height - FP.height;
        }
    }
}