import java.awt.*;

public class RandomMosaicRandomWalk extends java.applet.Applet implements Runnable {

         /*
                   Applet shows a window full of randomly colored
                   squares.  A "disturbance" moves randomly around
                   in the window, randomly changing the color of
                   each square that it visits.  The program runs
                   in an infinite loop, and so will never end on its
                   own.
         */
                
   int ROWS = 10;    // number of rows of squares; can be reset by applet param named "rows"
   int COLUMNS = 20; // number of colums of squares; can be reset by applet param named "columns"

   int currentRow;       // row currently containing "disturbance"
   int currentColumn;    // column currently containing "disturbance"
   MosaicCanvas mosaic;  // the actual mosaic of colored squares

   Thread runner = null; // thread for running the moving disturbance animation
   
   public void init() {
      setLayout(new BorderLayout());
      String param;
      param = getParameter("rows");
      if (param != null) {
         try {
            ROWS = Integer.parseInt(param);
         }
         catch (NumberFormatException e) {
         }
      }
      param = getParameter("columns");
      if (param != null) {
         try {
            COLUMNS = Integer.parseInt(param);
         }
         catch (NumberFormatException e) {
         }
      }
      mosaic = new MosaicCanvas(ROWS,COLUMNS);
      add("Center",mosaic);
   }
   
   public void start() {
      if (runner == null) {
         runner = new Thread(this);
         runner.start();
      }
   }
   
   public void stop() {
      if (runner != null) {
         runner.stop();
         runner = null;
      }
   }
   
   public void run() {
      currentRow = ROWS / 2;
      currentColumn = COLUMNS / 2;
      fillWithRandomColors();
      while (true) {
         changeToRandomColor(currentRow,currentColumn);
         randomMove();
         try {
            Thread.sleep(25);
         }
         catch (InterruptedException e) {
         }
      }
   }
   
   void fillWithRandomColors() {
        // fill every square, in each row and column,
        // with a random color
        for (int row=0; row < ROWS; row++) {
           for (int column=0; column < COLUMNS; column++) {
              changeToRandomColor(row, column);  
           }
        }
   }  // end of fillWithRandomColors()
   
   void changeToRandomColor(int rowNum, int colNum) {
        // change the square in row number rowNum and
        // column number colNum to a random color.
        double red = Math.random();    // choose random levels in range
        double green = Math.random();  //     0.0 to 1.0 for red, green, 
        double blue = Math.random();   //     and blue color components
        mosaic.setColor(rowNum,colNum,red,green,blue);  
    }  // end of changeToRandomColor()
    
    void randomMove() {
        // randomly move the disturbance in one of
        // four possible directions: up, down, left, or right;
        // if this moves the disturbance outside the window,
        // then move it to the opposit edge of the window.
        int directionNum = (int)(4*Math.random());
             // direction num is randomly set to 0, 1, 2, or 3
        switch (directionNum) {
           case 0:  // move up 
              currentRow--;
              if (currentRow < 0)
                  currentRow = ROWS - 1;
              break;
           case 1:  // move right
              currentColumn++;
              if (currentColumn >= COLUMNS)
                currentColumn = 0;
              break; 
           case 2:  // move down
              currentRow ++;
              if (currentRow >= ROWS)
                  currentRow = 0;
              break;
           case 3:  
              currentColumn--;
              if (currentColumn < 0)
                  currentColumn = COLUMNS - 1;
              break; 
        }
    }  // end of randomMove()
    
} // end of class