class FirstPersonControls {
 THREE.Object3D object;
 Vector3 target = new Vector3.zero();

 Element domElement;

 num movementSpeed = 1.0;
 num lookSpeed = 0.005;

 bool lookVertical = true;
 bool autoForward = false;
 // bool invertVertical = false;

 bool activeLook = true;

 bool heightSpeed = false;
 num heightCoef = 1.0;
 num heightMin = 0.0;
 num heightMax = 1.0;

 bool constrainVertical = false;
 num verticalMin = 0;
 num verticalMax = Math.PI;

 num autoSpeedFactor = 0.0;

 num mouseX = 0;
 num mouseY = 0;

 num lat = 0;
 num lon = 0;
 num phi = 0;
 num theta = 0;

 bool moveForward = false;
 bool moveBackward = false;
 bool moveLeft = false;
 bool moveRight = false;
 bool moveUp = false;
 bool moveDown = false;
 bool freeze = false;

 bool mouseDragOn = false;

 num viewHalfX = 0;
 num viewHalfY = 0;

 FirstPersonControls(this.object, [Element domElement]) {
   this.domElement = (domElement != null) ? domElement : document.body;

   if ( this.domElement != document.body ) {
     this.domElement.tabIndex = -1;
   }

   this.domElement.onContextMenu.listen((event) => event.preventDefault());

   this.domElement.onMouseMove.listen(this.onMouseMove);
   this.domElement.onMouseDown.listen(this.onMouseDown);
   this.domElement.onMouseUp.listen(this.onMouseUp);
   this.domElement.onKeyDown.listen(this.onKeyDown);
   this.domElement.onKeyUp.listen(this.onKeyUp);

   this.handleResize();
 }

  void handleResize() {
   if ( this.domElement == document.body ) {
     this.viewHalfX = window.innerWidth / 2;
     this.viewHalfY = window.innerHeight / 2;
   } else {
     this.viewHalfX = this.domElement.offsetWidth / 2;
     this.viewHalfY = this.domElement.offsetHeight / 2;
   }
 }

 void onMouseDown(event) {

   if ( this.domElement != document.body ) {
     this.domElement.focus();
   }

   event.preventDefault();
   event.stopPropagation();

   if ( this.activeLook ) {
     switch ( event.button ) {
       case 0: this.moveForward = true; break;
       case 2: this.moveBackward = true; break;
     }
   }

   this.mouseDragOn = true;
 }

 void onMouseUp(event) {
   event.preventDefault();
   event.stopPropagation();

   if ( this.activeLook ) {
     switch ( event.button ) {
       case 0: this.moveForward = false; break;
       case 2: this.moveBackward = false; break;
     }
   }
   this.mouseDragOn = false;
 }

 void onMouseMove(event) {
   if ( this.domElement == document.body ) {
     this.mouseX = event.page.x - this.viewHalfX;
     this.mouseY = event.page.y - this.viewHalfY;
   } else {
     this.mouseX = event.page.x - this.domElement.offsetLeft - this.viewHalfX;
     this.mouseY = event.page.y - this.domElement.offsetTop - this.viewHalfY;
   }
 }

 void onKeyDown(event) {

   //event.preventDefault();

   switch ( event.keyCode ) {
     case 38: /*up*/
     case 87: /*W*/ this.moveForward = true; break;

     case 37: /*left*/
     case 65: /*A*/ this.moveLeft = true; break;

     case 40: /*down*/
     case 83: /*S*/ this.moveBackward = true; break;

     case 39: /*right*/
     case 68: /*D*/ this.moveRight = true; break;

     case 82: /*R*/ this.moveUp = true; break;
     case 70: /*F*/ this.moveDown = true; break;

     case 81: /*Q*/ this.freeze = !this.freeze; break;
   }
 }

 void onKeyUp(event) {

   switch( event.keyCode ) {

     case 38: /*up*/
     case 87: /*W*/ this.moveForward = false; break;

     case 37: /*left*/
     case 65: /*A*/ this.moveLeft = false; break;

     case 40: /*down*/
     case 83: /*S*/ this.moveBackward = false; break;

     case 39: /*right*/
     case 68: /*D*/ this.moveRight = false; break;

     case 82: /*R*/ this.moveUp = false; break;
     case 70: /*F*/ this.moveDown = false; break;
   }
 }

 void update(delta) {
   var actualMoveSpeed = 0;
   var actualLookSpeed = 0;
   if ( this.freeze ) {

     return;

   } else {

     if ( this.heightSpeed ) {
       var y = THREEMath.clamp( this.object.position.y, this.heightMin, this.heightMax );
       var heightDelta = y - this.heightMin;

       this.autoSpeedFactor = delta * ( heightDelta * this.heightCoef );
     } else {
       this.autoSpeedFactor = 0.0;
     }

     actualMoveSpeed = delta * this.movementSpeed;

     if ( this.moveForward || ( this.autoForward && !this.moveBackward ) ) this.object.translateZ( - ( actualMoveSpeed + this.autoSpeedFactor ) );
     if ( this.moveBackward ) this.object.translateZ( actualMoveSpeed );

     if ( this.moveLeft ) this.object.translateX( - actualMoveSpeed );
     if ( this.moveRight ) this.object.translateX( actualMoveSpeed );

     if ( this.moveUp ) this.object.translateY( actualMoveSpeed );
     if ( this.moveDown ) this.object.translateY( - actualMoveSpeed );

     var actualLookSpeed = delta * this.lookSpeed;

     if ( !this.activeLook ) {

       actualLookSpeed = 0;

     }

     this.lon += this.mouseX * actualLookSpeed;
     if( this.lookVertical ) this.lat -= this.mouseY * actualLookSpeed; // * this.invertVertical?-1:1;

     this.lat = Math.max( - 85, Math.min( 85, this.lat ) );
     this.phi = ( 90 - this.lat ) * Math.PI / 180;
     this.theta = this.lon * Math.PI / 180;

     var targetPosition = this.target,
         position = this.object.position;

     targetPosition.x = position.x + 100 * Math.sin( this.phi ) * Math.cos( this.theta );
     targetPosition.y = position.y + 100 * Math.cos( this.phi );
     targetPosition.z = position.z + 100 * Math.sin( this.phi ) * Math.sin( this.theta );
   }

   var verticalLookRatio = 1;

   if ( this.constrainVertical ) {
     verticalLookRatio = Math.PI / ( this.verticalMax - this.verticalMin );
   }

   this.lon += this.mouseX * actualLookSpeed;
   if( this.lookVertical ) this.lat -= this.mouseY * actualLookSpeed * verticalLookRatio;

   this.lat = Math.max( - 85, Math.min( 85, this.lat ) );
   this.phi = ( 90 - this.lat ) * Math.PI / 180;

   this.theta = this.lon * Math.PI / 180;

   if ( this.constrainVertical ) {
     this.phi = THREEMath.mapLinear( this.phi, 0, Math.PI, this.verticalMin, this.verticalMax );
   }

   var targetPosition = this.target,
       position = this.object.position;

   targetPosition.x = position.x + 100 * Math.sin( this.phi ) * Math.cos( this.theta );
   targetPosition.y = position.y + 100 * Math.cos( this.phi );
   targetPosition.z = position.z + 100 * Math.sin( this.phi ) * Math.sin( this.theta );

   this.object.lookAt( targetPosition );
 }
}