/*
   MovingBallsWithMouseFX.java Copyright (c) Kari Laitinen

   http://www.naturalprogramming.com/

   2014-12-13 File created.
   2015-10-11 Last modification.


   This program is a Java FX 8 application that shows three
   balls on the screen. It is possible to move the balls with
   the mouse.

   The balls are objects of a class that is derived from the
   standard class Circle.

   Ball objects are contained in a Group object that is put as
   the root node of the Scene of the application.

*/


import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.input.MouseEvent;

import javafx.scene.* ;

import javafx.scene.layout.* ;
import javafx.stage.Stage;
import javafx.geometry.* ; // Point2D

import javafx.scene.paint.Color;

import javafx.scene.shape.Circle ;

import javafx.collections.* ; // ObservableList etc.

class Ball extends Circle
{
   public Ball( double given_center_point_x,
                double given_center_point_y,
                double given_radius,
                Color  given_color )
   {
      super( given_center_point_x, given_center_point_y, given_radius, given_color ) ;

      setStroke( Color.BLACK ) ;
      setStrokeWidth( 2 ) ;
   }

   public void activate_ball()
   {
      setStrokeWidth( 6 ) ;
   }

   public void deactivate_ball()
   {
      setStrokeWidth( 2 ) ;
   }

   public void  move_this_ball( double movement_in_direction_x,
                                double movement_in_direction_y )
   {
      setCenterX( getCenterX()  +  movement_in_direction_x ) ;
      setCenterY( getCenterY()  +  movement_in_direction_y ) ;
   }

}

public class MovingBallsWithMouseFX extends Application
{
   static final int SCENE_WIDTH  = 800 ;
   static final int SCENE_HEIGHT = 600 ;

   boolean ball_movement_going_on = false ;

   double previous_cursor_position_x, previous_cursor_position_y ;

   Group group_for_balls = new Group() ;


   private void set_mouse_activities_for_balls()
   {
      // The following 'foreach' loop specifies, for each Ball object,
      // the activities to be performed when mouse events take place
      // on the balls.

      for ( Node child_in_list : group_for_balls.getChildren() )
      {
         Ball ball_in_list = (Ball) child_in_list ;

         ball_in_list.setOnMousePressed( ( MouseEvent event ) ->
         {
            if ( ball_movement_going_on == false )
            {
               ball_in_list.activate_ball() ;
               previous_cursor_position_x = event.getSceneX() ;
               previous_cursor_position_y = event.getSceneY() ;
               ball_movement_going_on = true ;
            }
         } ) ;

         ball_in_list.setOnMouseDragged( ( MouseEvent event ) ->
         {
            if ( ball_movement_going_on == true )
            {
               double mouse_movement_x  =  event.getSceneX()
                                          -  previous_cursor_position_x ;
      
               double mouse_movement_y  =  event.getSceneY() 
                                         -  previous_cursor_position_y ;
      
               previous_cursor_position_x  =  event.getSceneX() ;
               previous_cursor_position_y  =  event.getSceneY() ;
 
               ball_in_list.move_this_ball( mouse_movement_x, 
                                            mouse_movement_y ) ;

            }
         } ) ;

         ball_in_list.setOnMouseReleased( ( MouseEvent event ) ->
         {
            if ( ball_movement_going_on == true )
            {
               ball_in_list.deactivate_ball() ;
               ball_movement_going_on = false ;
            }
         } ) ;
      }
   }

   public void start( Stage stage )
   {

      group_for_balls.getChildren().add(
           new Ball( SCENE_WIDTH / 4, SCENE_HEIGHT / 2, 64, Color.RED ) ) ;


      group_for_balls.getChildren().add(
           new Ball( SCENE_WIDTH / 2, SCENE_HEIGHT / 2, 64, Color.GREEN ) ) ;


      group_for_balls.getChildren().add(
           new Ball( SCENE_WIDTH * 3 / 4, SCENE_HEIGHT / 2, 64, Color.BLUE ) ) ;


      // Now the Ball objects are stored as 'children' of the Group.
      // The following method call specifies what will happen when
      // the balls are operated with the mouse.

      set_mouse_activities_for_balls() ;


      Scene scene = new Scene( group_for_balls, SCENE_WIDTH, SCENE_HEIGHT ) ;

      scene.setFill( Color.LIGHTYELLOW ) ;

      stage.setTitle( "MovingBallsWithMouseFX.java" ) ;
      stage.setScene( scene ) ;
      stage.show();
   }


   public static void main( String[] command_line_parameters )
   {
      launch( command_line_parameters ) ;
   }
}

/* NOTES:

The following links were useful when this program was developed:

https://docs.oracle.com/javase/8/javafx/api/javafx/scene/shape/Circle.html
https://docs.oracle.com/javase/8/javafx/api/javafx/scene/Group.html

*/