import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.scene.text.*;
import javafx.scene.canvas.*;
import javafx.scene.paint.Color;
import javafx.animation.AnimationTimer;

/**
 * This program displays 25 copies of a message, and it runs
 * an animation in which the strings move around on the screen.
 * The color, position, and velocity of each message is selected 
 * at random when the program first starts, and there is a button that
 * the user can click to reinitialize all the random values.
 */
public class RandomStringsWithArray extends Application {

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

    //----------------------------------------------
    
    private final static String MESSAGE = "Hello JavaFX"; 

    private Font[] fonts;  // The five fonts.

    private Canvas canvas;  // The canvas on which the strings are drawn.
    
    private StringData[] stringData;  // Holds all information needed
                                      // to draw the strings.

    private static class StringData {  // Info needed to draw one string.
        double x,y;    // location of the string
        double dx,dy;  // velocity of the string, in pixels per second
        Color color;   // color of the string
        Font font;     // the font that is used to draw the string
    }
    

    public void start( Stage stage ) {

        fonts= new Font[] {
                Font.font("Times New Roman", FontWeight.BOLD, 20),
                Font.font("Arial", FontWeight.BOLD, FontPosture .ITALIC, 28),
                Font.font("Verdana", 32),
                Font.font(40),
                Font.font("Times New Roman", FontWeight.BOLD, FontPosture .ITALIC, 60)
        };

        canvas = new Canvas(500,300);
        createStringData();
        draw();  // draw content of canvas the first time.

        Button redraw = new Button("Restart!");
        redraw.setOnAction( e -> createStringData() );
             // When the button is clicked, the string data is re-initialized.
             // There is no need to call draw() because the animation that
             // runs continually will redraw the canvas in the next frame.

        StackPane bottom = new StackPane(redraw);
        bottom.setStyle("-fx-background-color: gray; -fx-padding:5px;" + 
                " -fx-border-color:black; -fx-border-width: 2px 0 0 0");
        BorderPane root = new BorderPane(canvas);
        root.setBottom(bottom);
        root.setStyle("-fx-border-color:black; -fx-border-width: 2px");

        stage.setScene( new Scene(root, Color.BLACK) );
        stage.setTitle("Random Strings");
        stage.setResizable(false);
        stage.show();
        
        AnimationTimer timer = new AnimationTimer() {
               // The timer will run continually.  In each frame, all the strings
               // will be moved, and the canvas will be redrawn.
            long previousTime;
            public void handle(long time) {
                if (previousTime > 0) {
                       // Time since previous call to handle is (time - previousTime),
                       // in nanoseconds.  Dividing by 1e9 converts nanoseconds to seconds.
                       // The first time handle() is called, previousTime is 0 and the
                       // update is not done.
                    updateStringData( (time - previousTime)/1e9 );
                }
                draw();
                previousTime = time;
            }
        };
        timer.start();
    }
    
    
    /**
     * Creates an array of 25 StringData objects and fills it with
     * randomly generated data for each of the 25 strings.  This is
     * called in the start() method and when the user clicks the
     * "Restart!" button.
     */
    private void createStringData() {
        stringData = new StringData[25];
        for (int i = 0; i < 25; i++) {
            stringData[i] = new StringData();
            stringData[i].x = canvas.getWidth() * Math.random();
            stringData[i].y = canvas.getHeight() * Math.random();
            stringData[i].dx = 50 + 150*Math.random(); // 50 to 200 pixels per second
            if (Math.random() < 0.5) // 50% chance that dx is negative
                stringData[i].dx = -stringData[i].dx;
            stringData[i].dy = 50 + 150*Math.random();
            if (Math.random() < 0.5) // 50% chance that dy is negative
                stringData[i].dy = -stringData[i].dy;
            stringData[i].color = Color.hsb( 360*Math.random(), 1.0, 1.0 );
            stringData[i].font = fonts[ (int)(5*Math.random()) ];
        }
    }

    
    /**
     * Update the data for the 25 strings by moving each string, where the
     * distance moved depends on the velocity.  If a string moves too far
     * off the canvas, move it to the opposite side of the canvas.
     * (To make sure a string has moved all the way off the canvas to the
     * left, wait until data.x reaches -400 before moving it to the
     * right of the canvas. 
     * @param deltaTimeInSeconds time that has elapsed since the previous
     *          call to updateStringData, measured in seconds.
     */
    private void updateStringData(double deltaTimeInSeconds) {
        for ( StringData data : stringData ) {
            data.x += data.dx * deltaTimeInSeconds;
            data.y += data.dy * deltaTimeInSeconds;
            if (data.x < -400)
                data.x = canvas.getWidth();
            if (data.x > canvas.getWidth()+10)
                data.x = -400;
            if (data.y < -10)
                data.y = canvas.getHeight() + 70;
            if (data.y > canvas.getHeight() + 80)
                data.y = -10;
        }
    }

    /**
     * The draw() method is responsible for drawing the content of the canvas.
     * It draws 25 copies of the message string, using a random color, font, and
     * position for each string.
     */
    private void draw() {

        GraphicsContext g = canvas.getGraphicsContext2D();

        double width = canvas.getWidth();
        double height = canvas.getHeight();

        g.setFill( Color.WHITE );  // fill with white background
        g.fillRect(0, 0, width, height);

        for ( StringData data : stringData ) {

            // Draw one string, using the properties in one of the
            // StringData objects from the array.

            g.setFill( data.color );
            g.setFont( data.font);
            g.fillText(MESSAGE, data.x, data.y);
            g.setStroke(Color.BLACK);
            g.strokeText(MESSAGE, data.x, data.y);

        } // end for

    } // end draw()


}  // end class RandomStringsWithArray