/**
 A **CubicBezierCurve** is a {{#crossLink "Curve"}}{{/crossLink}} along which a 3D position can be animated.
 
 ## Overview
 
 <ul>
 <li>As shown in the diagram below, a CubicBezierCurve is defined by four control points.</li>
 <li>You can sample a {{#crossLink "CubicBezierCurve/point:property"}}{{/crossLink}} and a {{#crossLink "CubicBezierCurve/tangent:property"}}{{/crossLink}}
 vector on a CubicBezierCurve for any given value of {{#crossLink "CubicBezierCurve/t:property"}}{{/crossLink}} in the range [0..1].</li>
 <li>When you set {{#crossLink "CubicBezierCurve/t:property"}}{{/crossLink}} on a CubicBezierCurve, its
 {{#crossLink "CubicBezierCurve/point:property"}}{{/crossLink}} and {{#crossLink "CubicBezierCurve/tangent:property"}}{{/crossLink}} properties
 will update accordingly.</li>
 <li>To build a complex path, you can combine an unlimited combination of CubicBezierCurves,
 {{#crossLink "QuadraticBezierCurve"}}QuadraticBezierCurves{{/crossLink}} and {{#crossLink "SplineCurve"}}SplineCurves{{/crossLink}}
 into a {{#crossLink "Path"}}{{/crossLink}}.</li>
 </ul>
 
 <img style="border:1px solid;" src="https://upload.wikimedia.org/wikipedia/commons/thumb/d/db/B%C3%A9zier_3_big.gif/240px-B%C3%A9zier_3_big.gif"/><br>
 *[Cubic Bezier Curve from WikiPedia](https://en.wikipedia.org/wiki/B%C3%A9zier_curve)*
 
 ## Examples
 
 <ul>
 <li>[CubicBezierCurve example](../../examples/#animation_curves_cubicBezier)</li>
 </ul>
 
 ## Usage
 
 #### Animation along a CubicBezierCurve
 
 Let's create a CubicBezierCurve, subscribe to updates on its {{#crossLink "CubicBezierCurve/point:property"}}{{/crossLink}},
 {{#crossLink "Curve/tangent:property"}}{{/crossLink}} and {{#crossLink "Curve/t:property"}}{{/crossLink}} properties,
 then vary its {{#crossLink "CubicBezierCurve/t:property"}}{{/crossLink}}
 property over time:
 
 ````javascript
 var curve = new xeogl.CubicBezierCurve({
     v0: [-10, 0, 0],
     v1: [-5, 15, 0],
     v2: [20, 15, 0],
     v3: [10, 0, 0]
 });
 
 curve.on("point", function(point) {
     this.log("curve.point=" + JSON.stringify(point));
 });
 
 curve.on("tangent", function(tangent) {
     this.log("curve.tangent=" + JSON.stringify(tangent));
 });
 
 curve.on("t", function(t) {
     this.log("curve.t=" + t);
 });
 
 curve.scene.on("tick", function(e) {
     curve.t = (e.time - e.startTime) * 0.01;
 });
 ````
 
 #### Randomly sampling points
 
 Use CubicBezierCurve's {{#crossLink "CubicBezierCurve/getPoint:method"}}{{/crossLink}} and
 {{#crossLink "Curve/getTangent:method"}}{{/crossLink}} methods to sample the point and vector
 at a given **t**:
 
 ````javascript
 curve.scene.on("tick", function(e) {
 
     var t = (e.time - e.startTime) * 0.01;
 
     var point = curve.getPoint(t);
     var tangent = curve.getTangent(t);
 
     this.log("t=" + t + ", point=" + JSON.stringify(point) + ", tangent=" + JSON.stringify(tangent));
 });
 ````
 
 #### Sampling multiple points
 
 Use CubicBezierCurve's {{#crossLink "Curve/getPoints:method"}}{{/crossLink}} method to sample a list of equidistant points
 along it. In the snippet below, we'll build a {{#crossLink "Geometry"}}{{/crossLink}} that renders a line along the
 curve.  Note that we need to flatten the points array for consumption by the {{#crossLink "Geometry"}}{{/crossLink}}.
 
 ````javascript
 var geometry = new xeogl.Geometry({
     positions: xeogl.math.flatten(curve.getPoints(50))
 });
 ````
 
 @class CubicBezierCurve
 @module xeogl
 @submodule curves
 @constructor
 @param [scene] {Scene} Parent {{#crossLink "Scene"}}Scene{{/crossLink}}.
 @param [cfg] {*} Configuration
 @param [cfg.id] {String} Optional ID, unique among all components in the parent {{#crossLink "Scene"}}Scene{{/crossLink}}, generated automatically when omitted.
 @param [cfg.meta] {String:Object} Optional map of user-defined metadata to attach to this CubicBezierCurve.
 @param [cfg.v0=[0,0,0]] The starting point.
 @param [cfg.v1=[0,0,0]] The first control point.
 @param [cfg.v2=[0,0,0]] The middle control point.
 @param [cfg.v3=[0,0,0]] The ending point.
 @param [cfg.t=0] Current position on this CubicBezierCurve, in range between 0..1.
 @extends Curve
 */
xeogl.CubicBezierCurve = class xeoglCubicBezierCurve extends xeogl.Curve {
 
    init(cfg) {
        super.init(cfg);
        this.v0 = cfg.v0;
        this.v1 = cfg.v1;
        this.v2 = cfg.v2;
        this.v3 = cfg.v3;
        this.t = cfg.t;
    }
 
    /**
     Starting point on this CubicBezierCurve.
 
     Fires a {{#crossLink "CubicBezierCurve/v0:event"}}{{/crossLink}} event on change.
 
     @property v0
     @default [0.0, 0.0, 0.0]
     @type Float32Array
     */
    set v0(value) {
 
        /**
         * Fired whenever this CubicBezierCurve's
         * {{#crossLink "CubicBezierCurve/v0:property"}}{{/crossLink}} property changes.
         * @event v0
         * @param value The property's new value
         */
        this.fire("v0", this._v0 = value || xeogl.math.vec3([0, 0, 0]));
    }
 
    get v0() {
        return this._v0;
    }
 
    /**
     First control point on this CubicBezierCurve.
 
     Fires a {{#crossLink "CubicBezierCurve/v1:event"}}{{/crossLink}} event on change.
 
     @property v1
     @default [0.0, 0.0, 0.0]
     @type Float32Array
     */
    set v1(value) {
 
        /**
         * Fired whenever this CubicBezierCurve's
         * {{#crossLink "CubicBezierCurve/v1:property"}}{{/crossLink}} property changes.
         * @event v1
         * @param value The property's new value
         */
        this.fire("v1", this._v1 = value || xeogl.math.vec3([0, 0, 0]));
    }
 
    get v1() {
        return this._v1;
    }
 
    /**
     Second control point on this CubicBezierCurve.
 
     Fires a {{#crossLink "CubicBezierCurve/v2:event"}}{{/crossLink}} event on change.
 
     @property v2
     @default [0.0, 0.0, 0.0]
     @type Float32Array
     */
    set v2(value) {
 
        /**
         * Fired whenever this CubicBezierCurve's
         * {{#crossLink "CubicBezierCurve/v2:property"}}{{/crossLink}} property changes.
         * @event v2
         * @param value The property's new value
         */
        this.fire("v2", this._v2 = value || xeogl.math.vec3([0, 0, 0]));
    }
 
    get v2() {
        return this._v2;
    }
 
    /**
     End point on this CubicBezierCurve.
 
     Fires a {{#crossLink "CubicBezierCurve/v3:event"}}{{/crossLink}} event on change.
 
     @property v3
     @default [0.0, 0.0, 0.0]
     @type Float32Array
     */
    set v3(value) {
 
        /**
         * Fired whenever this CubicBezierCurve's
         * {{#crossLink "CubicBezierCurve/v3:property"}}{{/crossLink}} property changes.
         * @event v3
         * @param value The property's new value
         */
        this.fire("v3", this._v3 = value || xeogl.math.vec3([0, 0, 0]));
    }
 
    get v3() {
        return this._v3;
    }
 
    /**
     Current position of progress along this CubicBezierCurve.
 
     Automatically clamps to range [0..1].
 
     Fires a {{#crossLink "CubicBezierCurve/t:event"}}{{/crossLink}} event on change.
 
     @property t
     @default 0
     @type Number
     */
 
    set t(value) {
 
        value = value || 0;
 
        this._t = value < 0.0 ? 0.0 : (value > 1.0 ? 1.0 : value);
 
        /**
         * Fired whenever this CubicBezierCurve's
         * {{#crossLink "CubicBezierCurve/t:property"}}{{/crossLink}} property changes.
         * @event t
         * @param value The property's new value
         */
        this.fire("t", this._t);
    }
 
    get t() {
        return this._t;
    }
 
    /**
     Point on this CubicBezierCurve at position {{#crossLink "CubicBezierCurve/t:property"}}{{/crossLink}}.
 
     @property point
     @type {{Array of Number}}
     */
    get point() {
        return this.getPoint(this._t);
    }
 
    /**
     * Returns point on this CubicBezierCurve at the given position.
     * @method getPoint
     * @param {Number} t Position to get point at.
     * @returns {{Array of Number}}
     */
    getPoint(t) {
 
        var math = xeogl.math;
        var vector = math.vec3();
 
        vector[0] = math.b3(t, this._v0[0], this._v1[0], this._v2[0], this._v3[0]);
        vector[1] = math.b3(t, this._v0[1], this._v1[1], this._v2[1], this._v3[1]);
        vector[2] = math.b3(t, this._v0[2], this._v1[2], this._v2[2], this._v3[2]);
 
        return vector;
    }
 
    getJSON() {
        return {
            v0: this._v0,
            v1: this._v1,
            v2: this._v2,
            v3: this._v3,
            t: this._t
        };
    }
};