/** Alternative Relativity: Doppler Effect Demonstrator 
  * author: Robert John Morton
  * location: Belo Horizonte-MG
  * date: 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

  private wave MP[] = new wave[mp];  // for refs to instances of wave class
  private String QS = "YE572246C";   // merging code

  wpanel(Image H, Graphics h, int ds) {
    this.H = H;
    this.h = h;
    this.ds = ds;
    wave.sineValues();  // set up quick calc sine values for the wave class
    wave.setMode(ds);   // set default mode (classical or alternative)
  }

  public void atualizar() {  // UPDATE THE DISPLAY
    if(cf) changeMode();     // if a new mode has been selected

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

      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 spawn the following wave...

          if(!r.getnl())       // if new wave has not yet been launched
            imageTraverse(r);  // move the image forward
          else if (r.getah())  // else (if the wave has now faded out)
            MP[wi] = null;     // kill its wave object
      }

      // if wave index has been incremented to its maximum
      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(ds == 0) {  // if app is in "classical relativity" mode...
      X = 200;     // set start position 
      sh = -250;   // shift the off-screen image
    } else {       // otherwise it must be "alternative relativity" mode
      X = 560;     // set start position
      sh = -600;   // shift the off-screen image
    }
    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
      if (++k >= mp)               // if reached end of reference array
        k = 0;                     // cycle back to its beginning again
      if (MP[k] == null) {         // if no live wave exists in this element
        if(ds == 0)                // if 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;}

          MP[k] = new wave(X);  // spawn a new wave object
          r.setnl();            // signal that new launch has been done
          break;                // stop seach for an element with a null ref
        }
     }  // end of 'for all possible wave objects'
  }


  private void showImage() {
    wi = 0;              // reset wave index back to zero
    if(ds != 1) return;  // exit if not in "alternative relativity" mode

    if(SH++ > 1) {  // if the delay sub-counter has exceeded its upper limit
      SH = 0;       // reset it back to zero

      /* 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++ > -10){  // sh limit was 95
        cf = true;     // mode change used to clear image & reset wave array
      }
    }
  }


  // 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;}
}