GameLib.D3.ComponentLookAt = function(
    componentId,
    targetEntity,
    targetOffset
) {
    this.componentId = componentId || GameLib.D3.Tools.RandomId();
    this.parentEntity = null;

    // Todo: this should be executed somewhere in game-lib-z, so that we don't execute it on every construction of an object.
    GameLib.D3.Utils.Extend(GameLib.D3.ComponentLookAt, GameLib.D3.ComponentInterface);

    // todo: USE TARGET OFFSET.
    this.targetEntity = targetEntity;
    this.targetOffset = targetOffset || new GameLib.D3.Vector3(0, 0, 0);
};

///////////////////////// Methods to override //////////////////////////
GameLib.D3.ComponentLookAt.prototype.onUpdate = function(
    deltaTime,
    parentEntity
) {
    if(this.targetEntity) {
        var target = this.targetEntity.position;
        var lookAtMatrix = new THREE.Matrix4().lookAt(
            new THREE.Vector3(
                parentEntity.position.x,
                parentEntity.position.y,
                parentEntity.position.z
            ),
            new THREE.Vector3(
                target.x,
                target.y,
                target.z
            ),
            new THREE.Vector3(
                0,
                1,
                0
            )
        );

        var quaternion = new THREE.Quaternion().setFromRotationMatrix(lookAtMatrix);
        this.parentEntity.quaternion.x = quaternion.x;
        this.parentEntity.quaternion.y = quaternion.y;
        this.parentEntity.quaternion.z = quaternion.z;
        this.parentEntity.quaternion.w = quaternion.w;
    }
};