/** Alternative Relativity: Doppler Effect Demonstrator 
    by Robert John Morton UK-YE572246C
    (Belo Horizonte-MG 27 September 2006, 02 May 2012) */

// THE WAVES DISPLAY PANEL


import javax.swing.*;   //library of swing widgets
import java.awt.*;      //for graphics operations (GUI)


class wpanel extends JPanel {
   private int 
      X = 5,       //initial position of source
      mp = 16,     //size of the wave objects references array
      ds = 0,      //default mode selection
      wi = 0,      //wave instance index
      SH = 0,      //image shift delay subcounter
      sh = -600;   //image shift variable

   private boolean cf = true;   //true means new mode selected
   private Image H;             //off-screen image
   private Graphics h;          //graphics reference variable

   //for references to instances of the wave class
   private wave MP[] = new wave[mp];

   wpanel(Image H, Graphics h, int ds) {      // CONSTRUCTOR
      this.H = H; this.h = h; this.ds = ds;

      /* Set the default mode for the applet (classical or alternative)
         and the quick calculation sine values for the wave class. */

      wave.sineValues(); wave.setMode(ds);
   }


   public void atualizar() {   // UPDATE THE DISPLAY

      if(cf) changeMode();   //if a new mode has been selected

      // mini loop to do only 4 waves per pass (CPU loading)
      for(int q = 0; q < 4; q++) {

         wave r = MP[wi];   //create a reference to this wave instance

         if (r != null) {   //if this wave is still alive (not yet faded out)

            r.atualizar(h);   //update this wave's position
            if(r.getmh())     //if it is time to launch the following wave

               /* then; if a new wave has not yet been launched, continue
                  traversing the image; else if the wave has now faded
                  out, kill its wave object. */

               if(!r.getnl()) imageTraverse(r); 
               else if(r.getah()) MP[wi] = null;
         }
         // If wave index has been incremented to its maximum, show image.
         if(++wi >= mp) showImage();

      }   //end of for-loop
   }


   private void changeMode() {
      cf = false;                 //cancel the mode change flag
      h.setColor(Color.black);    //set graphics fields's background colour
      h.fillRect(0,0,1200,191);   //wipe the graphics field's display area

      for(int i = 0; i < mp; i++) MP[i] = null;   //kill all wave objects

      /* If applet is in "classical relativity" mode, set start position and
         shift the off-screen image; otherwise set the corresponding values
         for the "alternative relativity" mode. */

      if(ds == 0) { X = 200; sh = -250; } else { X = 500; sh = -600; }

      MP[0] = new wave(X);   //spawn a new wave object (generate a new one)
      wi = 0;                //reinitialize the wave instance index
   }


   private void imageTraverse(wave r) {

      int k = wi;   //create a temporary cyclic index variable

      for(int j = 0; j < mp; j++) {    //for all possible wave objects

         // cycle round back to the start of the references array
         if (++k >= mp) k = 0;

         if (MP[k] == null) {   //if no live wave exists in this element

            if(ds == 0)   //if applet is in "classical relativity" mode...

               /* If the light-source has not yet reached its destination,
                  shift it another 10 pixels to the right; otherwise, set
                  it back to its extreme left position (off-screen) and
                  trigger the start of a new traverse of the light source. */

               if(X < 1195) X += 10; else { X = 250; cf = true; }

            /* Spawn a new wave object, signal that this has been done then
               break out of the search 'for' loop. */

            MP[k] = new wave(X); r.setnl(); break;
         }

      }   //end of 'for all possible wave objects'
   }


   private void showImage() {

      wi = 0;   //reset wave index back to zero

      /* If the applet is operating in its "alternative relativity" mode
         AND the delay sub-counter has exceeded its upper limit, reset it
         back to zero ... */

      if(ds == 1 && SH++ > 1) {
         SH = 0;

         /* then, if the image has shifted its maximum distance to the
            right, set it back to its extreme left position again and
            trigger the start of new traverse of the light source. */

         if(sh++ > 95) { sh = -600; cf = true; }
      }
   }


   // draw graphics image onto the visible panel
   public void paint(Graphics g) { g.drawImage(H, sh, 0, null); }

   void setCF(boolean cf) {this.cf = cf;}
   void setDS(int ds) {this.ds = ds;}
}