import javax.swing.*;
import java.awt.*;


public class Letter extends JFrame { 
    static int sn = 0; // last used serial number 
    
    String text = " ";  //default text of Letter
    int fontSize = 120; //default fontsize of text in pixel height
    int step = 10; 
    
    LetterPanel panel;
    
    /********** Constructors *********/ 
   
    // creates a blank Letter 
    public Letter() {
        this(" ");
    }
    
    //creates a Letter with text s
    //at the top left of the screen, with newer Letters shifted farther to the right
    public Letter(String s) {
        this.panel = new LetterPanel(this);
        this.add(this.panel);
        if (s!=null && s.length()>0) {
            text = s.substring(0,1);
        }
        this.setSize(120,150);
        this.setTitle("#"+sn++);
        this.setLocation(10*sn, 10);
        this.setVisible(true);
    }
    
    //creates a Letter with text c
    public Letter(char c) {
        this(String.valueOf( c ));
    }
    
    //changes the text to t
    public void setText(String t) {
        if (t!=null) { text = t; }
        this.repaint();
    }
    
    //ditto 
    public void setText(char c) {
        this.setText(String.valueOf( c ));
    }
    
    //redraws the Letter, called by the windowing system
    //text is vertically more or less centered, horizontally it is not 
 /*   public void paint(Graphics g) {
        //super.paint(g);
        int bar = 10;           // height of title bar (Mac OS); estimation
        int h = getHeight() - bar; 
        Font font = new Font(
            g.getFont().getFontName(), Font.BOLD, fontSize
        );
        g.setFont(font);
        g.drawString(text, 25, (h+fontSize)/2 - 10);
    }*/
    
    //changes (sets) the background color 
    public void setColor(Color c) {
        this.panel.setBackground(c);
    }
    
    //changes (sets) the fontsize to a height of fs pixels 
    public void setFontSize(int fs) {
        this.fontSize = fs;
        this.repaint();
    }
    
    //centers the Letter on the screen
    public void center() {
        Dimension screen = Toolkit.getDefaultToolkit().getScreenSize();
        int a = screen.width;
        int b = this.getWidth();
        int x = (a-b)/2;
        //int x = (screen.getWidth() - this.getWidth())/2;
        int y = screen.height/2 - this.getHeight()/2;
        this.setLocation(x, y);
    }
    
    /* methods to move the Letter on the screen */
    
    // move dx pixels to the right and dy down; negative arguments move left resp. up
    public void moveRel(int dx, int dy) {
        Point here = this.getLocationOnScreen();
        this.setLocation(here.x + dx, here.y + dy);
    }
    
    // four methods that move step pixels to the right, left, down, up
    public void moveRight() {
        this.moveRel(step,0);
    }

    public void moveLeft() {
        this.moveRel(-step,0);
    }

    public void moveDown() {
        this.moveRel(0,step);
    }

    public void moveUp() {
        this.moveRel(0,-step);
    }
    
    // move Letter to an absolute position on the screen
    public void moveAbs(int x, int y) {
        this.setLocation(x,y);
    }
    
    //pause execution for ms milliseconds
    public static void pause(long ms) {
        try { 
            Thread.sleep(ms); 
        } catch (InterruptedException e) {
            System.err.println(e); 
        }
    }
    
    //pause execution for sec seconds           
    public static void pause(double sec) {
        pause((long) sec*1000);
    }
    
    // only for testing purposes
    public static void main(String[] ar) {
        Letter x = new Letter("X");
        x.pause(0.5);
        x.setColor(Color.pink);
        x.pause(1.0);
        x.setColor(Color.green);   
    }
}

class LetterPanel extends JPanel {
  Letter letter;
  
  LetterPanel(Letter let) {
      this.letter = let;
  }
  
    //redraws the Letter, called by the windowing system
    //text is vertically more or less centered, horizontally it is not 
    public void paint(Graphics g) {
        super.paintComponent(g);
        int bar = 10;           // height of title bar (Mac OS); estimation
        int h = getHeight() - bar; 
        Font font = new Font(
            g.getFont().getFontName(), Font.BOLD, letter.fontSize
        );
        g.setFont(font);
        g.drawString(letter.text, 25, (h+letter.fontSize)/2 - 10);
    }
 
}