HaxePunk/HaxePunk

package haxepunk.tweens.motion;

import haxepunk.utils.Ease.EaseFunction;
import haxepunk.math.MathUtil;

/**
 * Determines a circular motion.
 */
class CircularMotion extends Motion
{
    /**
     * The current position on the circle.
     */
    public var angle(default, null):Float = 0;

    /**
     * The circumference of the current circle motion.
     */
    public var circumference(get, never):Float;
    function get_circumference():Float return _radius * _CIRC;

    /**
     * Starts moving along a circle.
     * @param    centerX        X position of the circle's center.
     * @param    centerY        Y position of the circle's center.
     * @param    radius        Radius of the circle.
     * @param    angle        Starting position on the circle.
     * @param    clockwise    If the motion is clockwise.
     * @param    duration    Duration of the movement.
     * @param    ease        Optional easer function.
     */
    public function setMotion(centerX:Float, centerY:Float, radius:Float, angle:Float, clockwise:Bool, duration:Float, ?ease:EaseFunction)
    {
        _centerX = centerX;
        _centerY = centerY;
        _radius = radius;
        this.angle = _angleStart = angle * MathUtil.RAD;
        _angleFinish = _CIRC * (clockwise ? 1 : -1);
        _target = duration;
        _ease = ease;
        start();
    }

    /**
     * Starts moving along a circle at the speed.
     * @param    centerX        X position of the circle's center.
     * @param    centerY        Y position of the circle's center.
     * @param    radius        Radius of the circle.
     * @param    angle        Starting position on the circle.
     * @param    clockwise    If the motion is clockwise.
     * @param    speed        Speed of the movement.
     * @param    ease        Optional easer function.
     */
    public function setMotionSpeed(centerX:Float, centerY:Float, radius:Float, angle:Float, clockwise:Bool, speed:Float, ?ease:EaseFunction)
    {
        _centerX = centerX;
        _centerY = centerY;
        _radius = radius;
        this.angle = _angleStart = angle * MathUtil.RAD;
        _angleFinish = _CIRC * (clockwise ? 1 : -1);
        _target = (_radius * _CIRC) / speed;
        _ease = ease;
        start();
    }

    /** @private Updates the Tween. */
    @:dox(hide)
    override function updateInternal()
    {
        angle = _angleStart + _angleFinish * _t;
        x = _centerX + Math.cos(angle) * _radius;
        y = _centerY + Math.sin(angle) * _radius;
    }

    // Circle information.
    var _centerX:Float = 0;
    var _centerY:Float = 0;
    var _radius:Float = 0;
    var _angleStart:Float = 0;
    var _angleFinish:Float = 0;

    static var _CIRC(get, never):Float;
    static inline function get__CIRC():Float return Math.PI * 2;
}