/**
     * Listen to keyboard events to control the camera.
     * @see http://doc.babylonjs.com/how_to/customizing_camera_inputs
     */
    export class FlyCameraKeyboardInput implements ICameraInput<FlyCamera> {
        /**
         * Defines the camera the input is attached to.
         */
        public camera: FlyCamera;

        /**
         * The list of keyboard keys used to control the forward move of the camera.
         */
        @serialize()
        public keysForward = [87];

        /**
         * The list of keyboard keys used to control the backward move of the camera.
         */
        @serialize()
        public keysBackward = [83];

        /**
         * The list of keyboard keys used to control the forward move of the camera.
         */
        @serialize()
        public keysUp = [69];

        /**
         * The list of keyboard keys used to control the backward move of the camera.
         */
        @serialize()
        public keysDown = [81];

        /**
         * The list of keyboard keys used to control the right strafe move of the camera.
         */
        @serialize()
        public keysRight = [68];

        /**
         * The list of keyboard keys used to control the left strafe move of the camera.
         */
        @serialize()
        public keysLeft = [65];

        private _keys = new Array<number>();
        private _onCanvasBlurObserver: Nullable<Observer<Engine>>;
        private _onKeyboardObserver: Nullable<Observer<KeyboardInfo>>;
        private _engine: Engine;
        private _scene: Scene;

        /**
         * Attach the input controls to a specific dom element to get the input from.
         * @param element Defines the element the controls should be listened from
         * @param noPreventDefault Defines whether event caught by the controls should call preventdefault() (https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault)
         */
        public attachControl(element: HTMLElement, noPreventDefault?: boolean): void {
            if (this._onCanvasBlurObserver) {
                return;
            }

            this._scene = this.camera.getScene();
            this._engine = this._scene.getEngine();

            this._onCanvasBlurObserver = this._engine.onCanvasBlurObservable.add(() => {
                this._keys = [];
            });

            this._onKeyboardObserver = this._scene.onKeyboardObservable.add((info) => {
                let evt = info.event;

                if (info.type === KeyboardEventTypes.KEYDOWN) {
                    if (this.keysForward.indexOf(evt.keyCode) !== -1 ||
                        this.keysBackward.indexOf(evt.keyCode) !== -1 ||
                        this.keysUp.indexOf(evt.keyCode) !== -1 ||
                        this.keysDown.indexOf(evt.keyCode) !== -1 ||
                        this.keysLeft.indexOf(evt.keyCode) !== -1 ||
                        this.keysRight.indexOf(evt.keyCode) !== -1) {
                        var index = this._keys.indexOf(evt.keyCode);

                        if (index === -1) {
                            this._keys.push(evt.keyCode);
                        }
                        if (!noPreventDefault) {
                            evt.preventDefault();
                        }
                    }
                } else {
                    if (this.keysForward.indexOf(evt.keyCode) !== -1 ||
                        this.keysBackward.indexOf(evt.keyCode) !== -1 ||
                        this.keysUp.indexOf(evt.keyCode) !== -1 ||
                        this.keysDown.indexOf(evt.keyCode) !== -1 ||
                        this.keysLeft.indexOf(evt.keyCode) !== -1 ||
                        this.keysRight.indexOf(evt.keyCode) !== -1) {
                        var index = this._keys.indexOf(evt.keyCode);

                        if (index >= 0) {
                            this._keys.splice(index, 1);
                        }
                        if (!noPreventDefault) {
                            evt.preventDefault();
                        }
                    }
                }
            });
        }

        /**
         * Detach the current controls from the specified dom element.
         * @param element Defines the element to stop listening the inputs from
         */
        public detachControl(element: Nullable<HTMLElement>): void {
            if (this._scene) {
                if (this._onKeyboardObserver) {
                    this._scene.onKeyboardObservable.remove(this._onKeyboardObserver);
                }

                if (this._onCanvasBlurObserver) {
                    this._engine.onCanvasBlurObservable.remove(this._onCanvasBlurObserver);
                }
                this._onKeyboardObserver = null;
                this._onCanvasBlurObserver = null;
            }
            this._keys = [];
        }

        /**
         * Gets the class name of the current intput.
         * @returns the class name
         */
        public getClassName(): string {
            return "FlyCameraKeyboardInput";
        }

        /** @hidden */
        public _onLostFocus(e: FocusEvent): void {
            this._keys = [];
        }

        /**
         * Get the friendly name associated with the input class.
         * @returns the input friendly name
         */
        public getSimpleName(): string {
            return "keyboard";
        }

        /**
         * Update the current camera state depending on the inputs that have been used this frame.
         * This is a dynamically created lambda to avoid the performance penalty of looping for inputs in the render loop.
         */
        public checkInputs(): void {
            if (this._onKeyboardObserver) {
                var camera = this.camera;
                // Keyboard
                for (var index = 0; index < this._keys.length; index++) {
                    var keyCode = this._keys[index];
                    var speed = camera._computeLocalCameraSpeed();

                    if (this.keysForward.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(0, 0, speed);
                    } else
                    if (this.keysBackward.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(0, 0, -speed);
                    } else
                    if (this.keysUp.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(0, speed, 0);
                    } else
                    if (this.keysDown.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(0, -speed, 0);
                    } else
                    if (this.keysRight.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(speed, 0, 0);
                    } else
                    if (this.keysLeft.indexOf(keyCode) !== -1) {
                      camera._localDirection.copyFromFloats(-speed, 0, 0);
                    }

                    if (camera.getScene().useRightHandedSystem) {
                        camera._localDirection.z *= -1;
                    }

                    camera.getViewMatrix().invertToRef(camera._cameraTransformMatrix);
                    Vector3.TransformNormalToRef(camera._localDirection, camera._cameraTransformMatrix, camera._transformedDirection);
                    camera.cameraDirection.addInPlace(camera._transformedDirection);
                }
            }
        }
    }

    (<any>CameraInputTypes)["FlyCameraKeyboardInput"] = FlyCameraKeyboardInput;