/** Air Navigation Waypoint Intercept Demonstrator 
    by Robert J Morton 21 Oct 1997 */

/*  A demonstrator applet for the Waypoint Encounter class: NavEncPG.class
    which in turn uses the classes: Aircraft.class and Waypoint.class */

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

public class wpapplet extends JPanel implements Runnable {

  private int
    XE,            // horizontal extent of window and JFrame.
    YE,            // vertical extent of window and JFrame.
    SelRad = -44,  // Selected Radial in angular degrees
    XM = 190,      // x margin between left edge and start of tracking area
    fh,            // font height (height of a line of text)
    fa,            // font ascent (height of letters above base line)
    nw,            // width in pixels of longest field name
    vw,            // width in pixels of standard value string
    NY,            // top margin for start of text
    VY,            // start height of first numeric value
    vy,            // start height of first numeric value
    X = 520,       // window and image buffer dimensions
    Y = 200;       // window and image buffer dimensions

  private int[] 
    OldVal = {  // values from previous pass of update()
      999,999,999,999,999,999,999
    };

  private long 
    tf = 50,  // inter-plot time frame (milliseconds)
    t;        // system time at which a new plot will be due to begin

  private String  // Field names
    Names[] = { 
      "WAYPOINT ENCOUNTER","","Waypoint Name","","Selected Radial",
      "Aircraft Bearing","Radial Deviation","","Station Bearing",
      "Steering Offset","Required Heading","","Distance"
    },
    Zeros[] = {
      "","0","00","000"  // leading zeros for displaying numeric values
    };

  private Color 
    TFC = Color.white;  // text foreground colour

  private Font  // set font for text in this applet
    font = new Font("Dialog",Font.PLAIN,12);

  private FontMetrics
    fm;  // reference to font's dimensions etc.

  private BufferedImage
    I = null;  // reference for an off-screen image buffer

  private Graphics2D 
    gi = null;  // graphics context for the off-screen image

  private Thread T;     // declare a program thread reference 
  private aircraft ac;  // reference to an aircraft object
  private waypoint wp;  // reference to a waypoint object
  private wpencpg  en;  // reference to an encounter object
  private wpcolour ca;  // reference to a colour array object


  public wpapplet(int XE, int YE) {
    this.XE = XE;          // horizontal [X] dimension of the JPanel
    this.YE = YE;          // vertical [Y] dimension of the JPanel
    setBounds(0,0,XE,YE);  // the JPanel fills the whole of the JFrame area
    setLayout(null);       // JPanel has free-form layout [for graph]

    I = new BufferedImage(X,Y,BufferedImage.TYPE_INT_RGB);
    gi = I.createGraphics();
    gi.setColor(Color.black);  // set background colour for off-screen image
    gi.fillRect(0,0,X,Y);      // paint background colour of off-screen image

    ac = new aircraft();  // create an aircraft object
    wp = new waypoint();  // create a waypoint object
    en = new wpencpg();   // create an encounter object
    ca = new wpcolour();  // create a colour array object

    fm = getFontMetrics(font);  // get the dimensions etc for this font
    fh = fm.getHeight();        // get the full height of a line of text
    fh = 14;                    // Netscape Navigator problem
    fa = fm.getAscent();        // get the font's ascent (ht above baseline)
    fa = 10;                    // Netscape Navigator problem

    // width of the longest field name + 10pixels
    nw = fm.stringWidth(Names[10]) + 20; 

    // width of numeric value readout string
    vw = fm.stringWidth("000+");

    NY = 5;                // top 'margin' for text
    VY = NY+fh+fh+fh+fh;   // starting height of first numeric field
    T = new Thread(this);  // by creating the thread object
    T.start();             // and starting it running by

    // Set system time at which the first plot time-frame will end
    t = System.currentTimeMillis() + tf;
  }


  private void reset(){         // PAINT THE SUPERSTRUCTURE FOR A NEW RUN
    gi.setColor(Color.black);   // set background colour for the text area
    gi.fillRect(0,0,XM,ca.YH);  // clear the text area
    gi.setFont(font);           // activate the chosen font
    gi.setColor(Color.white);   // set colour for displaying text
    int y = NY;                 // vertical start position for text

    for(int i = 0; i < 13; i++) {           // display the field names
      gi.drawString(Names[i],10,y += fh);   // show a field name
      if(i == 2)
        gi.drawString(wp.N,nw,y);  // show the waypoint name
    }
    for(y = 0; y < ca.YH; y++) {  // for each line of pixels of tracking area

      int X = 0;  // starting dot of next single-colour stretch of line
      int x = 0;  // to find next pixel in current line of different colour 

      Color c = ca.C[X][y];  // make colour of first dot the reference colour
      while(++x < ca.XW) {   // while not yet reached end of current line

        // if this dot is a different colour from the previous dot...
        if(c != ca.C[x][y]) {
          gi.setColor(c);  // set colour to colour of previous dot

          // draw a line from the start dot to the 'previous' dot
          gi.drawLine(XM + X,ca.YH - y - 1,XM + x - 1,ca.YH - y - 1);

          c = ca.C[X = x][y];  // make new reference colour that of this dot
        }
      }
      gi.setColor(c);  // set colour for final stretch of current line

      // draw the last stretch of the current line
      gi.drawLine(XM + X,ca.YH - y - 1,XM + x - 1,ca.YH - y - 1);
    }
    repaint();  // re-display the off-screen image
  }


  public void paint(Graphics g) {  // PAINT THE INITIAL IMAGE
    g.drawImage(I,10,15,null);  // draw from the off-screen image buffer
  }


  // DISPLAY A NUMERIC VALUE FOR A FIELD IN THE OFF-SCREEN IMAGE
  void ShowNum(Graphics g,double a,int n) {

    if(n < 6)           // if displaying an angle,
      a *= en.DegRad;   // convert IT from radians to degrees
    String sign = "+";  // means number to be displayed is positive

    if(a < 0) {    // If the number is negative,
      a = -a;      // reverse it
      sign = "-";  // and make it's sign a minus
    }
    int i = (int)a;    // convert it to an integer
    if((a -= i) > .5)  // and round it
      i++;
    vy += fh;  // advance downwards to new text line

    if(i != OldVal[n]) {  // if this value has changed since last update
      OldVal[n] = i;      // note this time's (changed) value for next time

      String s = String.valueOf(i);  // convert integer to a string
      i = 3 - s.length();            // Compute the number of 
      if(i < 0) i = 0;               // leading zeros needed.
      gi.setColor(Color.black);      // set text background colour
      gi.fillRect(nw,vy-fa,vw,fh);   // wipe numeric field's display area
      gi.setColor(Color.white);      // set text foreground colour

      gi.drawString(Zeros[i] + s + sign,nw,vy);  // display the string
    }
  }


  void advance(){  // ADVANCE THE AIRCRAFT ALONG THE TRACK
    int
      x = (int)(ac.x + XM),     // current 'window co-ordinates'
      y = (int)(ca.YH - ac.y);  // of aircraft

    gi.setColor(ca.ATC);   // set colour of aircraft track
    gi.drawLine(x,y,x,y);  // Draw the next bit of the aircraft track

    vy = VY;  // set the vertical start position of the first numeric field

    gi.setFont(font);       // activate the chosen font
    ShowNum(gi,en.OSR,0);   // display outbound selected radial
    ShowNum(gi,en.tBrg,1);  // display bearing of aircraft from waypoint

    // Display the aircraft's deviation from the selected outbound radial
    ShowNum(gi,en.RadDev,2);
    vy += fh;                 // miss a line
    ShowNum(gi,en.rBrg,3);    // display bearing of waypoint from aircraft
    ShowNum(gi,en.StrOff,4);  // display steering offset
    ShowNum(gi,en.ReqHdg,5);  // display required heading
    vy += fh;                 // miss a line
    double a = en.Dst; 
    if(en.approach)   // show distance 'to' as negative 
      a =- a;         // and 'from' as positive
    ShowNum(gi,a,6);  // display distance to/from waypoint
    repaint();        // re-display the off-screen image
  }


  public void run() {  // RUN THE WAYPOINT ENCOUNTER PROGRAM THREAD
    while(true) {      // permanent loop broken only by an external event

      if(en.outofRange(ac,wp)) {  // if aircraft has just passed out of range
        if((SelRad += 44) > 359)  // if selected radial has come full circle, 
          SelRad -= 360;          // then start over

        en.SetRadial(ac,wp,SelRad);  // set up the new selected radial
        ca.InitC(ac,wp,en.OSR);      // initialise the colour array
        reset();                     // begin a new fly-past of the waypoint
      } else 
        ca.PlotPosn(ac);  // plot aircraft's new position on display raster
      advance();          // advance the aircraft along its track

      // get time left in this plot's time frame
      long s = t - System.currentTimeMillis();

      if(s < 5) s = 5;  // in case machine isn't fast enough

      try{Thread.currentThread().sleep(s);}  // sleep for the time remaining
      catch(InterruptedException e) {}       // catch interrupt from GUI

      // Set the system time at which the next plot's time frame will end.
      t = System.currentTimeMillis() + tf;
    }
  }
}