module BABYLON {
    export class RayHelper {

        public ray: Nullable<Ray>;

        private _renderPoints: Vector3[];
        private _renderLine: Nullable<LinesMesh>;
        private _renderFunction: Nullable<() => void>;
        private _scene: Nullable<Scene>;

        private _updateToMeshFunction: Nullable<() => void>;
        private _attachedToMesh: Nullable<AbstractMesh>;
        private _meshSpaceDirection: Vector3;
        private _meshSpaceOrigin: Vector3;

        public static CreateAndShow(ray: Ray, scene: Scene, color: Color3): RayHelper {
            var helper = new RayHelper(ray);

            helper.show(scene, color);

            return helper;
        }

        constructor(ray: Ray) {
            this.ray = ray;
        }

        public show(scene: Scene, color?: Color3): void {

            if (!this._renderFunction && this.ray) {

                var ray = this.ray;

                this._renderFunction = this._render.bind(this);
                this._scene = scene;
                this._renderPoints = [ray.origin, ray.origin.add(ray.direction.scale(ray.length))];
                this._renderLine = Mesh.CreateLines("ray", this._renderPoints, scene, true);

                if (this._renderFunction) {
                    this._scene.registerBeforeRender(this._renderFunction);
                }
            }

            if (color && this._renderLine) {
                this._renderLine.color.copyFrom(color);
            }

        }

        public hide(): void {

            if (this._renderFunction && this._scene) {
                this._scene.unregisterBeforeRender(this._renderFunction);
                this._scene = null;
                this._renderFunction = null;
                if (this._renderLine) {
                    this._renderLine.dispose();
                    this._renderLine = null;
                }

                this._renderPoints = [];
            }

        }

        private _render(): void {

            var ray = this.ray;

            if (!ray) {
                return;
            }

            var point = this._renderPoints[1];
            var len = Math.min(ray.length, 1000000);

            point.copyFrom(ray.direction);
            point.scaleInPlace(len);
            point.addInPlace(ray.origin);

            Mesh.CreateLines("ray", this._renderPoints, this._scene, true, this._renderLine);

        }

        public attachToMesh(mesh: AbstractMesh, meshSpaceDirection?: Vector3, meshSpaceOrigin?: Vector3, length?: number): void {

            this._attachedToMesh = mesh;

            var ray = this.ray;

            if (!ray) {
                return;
            }

            if (!ray.direction) {
                ray.direction = Vector3.Zero();
            }

            if (!ray.origin) {
                ray.origin = Vector3.Zero();
            }

            if (length) {
                ray.length = length;
            }

            if (!meshSpaceOrigin) {
                meshSpaceOrigin = Vector3.Zero();
            }

            if (!meshSpaceDirection) {
                // -1 so that this will work with Mesh.lookAt
                meshSpaceDirection = new Vector3(0, 0, -1);
            }

            if (!this._meshSpaceDirection) {
                this._meshSpaceDirection = meshSpaceDirection.clone();
                this._meshSpaceOrigin = meshSpaceOrigin.clone();
            } else {
                this._meshSpaceDirection.copyFrom(meshSpaceDirection);
                this._meshSpaceOrigin.copyFrom(meshSpaceOrigin);
            }

            if (!this._updateToMeshFunction) {
                this._updateToMeshFunction = (<() => void>this._updateToMesh.bind(this));
                this._attachedToMesh.getScene().registerBeforeRender(this._updateToMeshFunction);
            }

            this._updateToMesh();

        }

        public detachFromMesh(): void {

            if (this._attachedToMesh) {
                if (this._updateToMeshFunction) {
                    this._attachedToMesh.getScene().unregisterBeforeRender(this._updateToMeshFunction);
                }
                this._attachedToMesh = null;
                this._updateToMeshFunction = null;
            }

        }

        private _updateToMesh(): void {

            var ray = this.ray;

            if (!this._attachedToMesh || !ray) {
                return;
            }

            if (this._attachedToMesh._isDisposed) {
                this.detachFromMesh();
                return;
            }

            this._attachedToMesh.getDirectionToRef(this._meshSpaceDirection, ray.direction);
            Vector3.TransformCoordinatesToRef(this._meshSpaceOrigin, this._attachedToMesh.getWorldMatrix(), ray.origin);

        }

        public dispose(): void {

            this.hide();
            this.detachFromMesh();
            this.ray = null;

        }

    }
}