/** Air Navigation Waypoint Intercept Demonstrator
    by Robert J Morton UK-YE572246C 21 Oct 1997 */

/*  Plots the encounter on a 350 by 200 colour raster which is displayed 
    by the applet class WayPtApp.class */

import java.awt.Color;

class wpcolour {  // Waypoint Colour Array

  double
    π = Math.PI,     // the circular constant
    two_π = π + π,
    half_π = π / 2;

  int
    XW = 330,  // x-width: horizontal width of tracking area
    YH = 200;  // y-height: vertical height of tracking area

  Color
    BGC,                // background colour of track area
    ATC = Color.white,  // aircraft track colour
    SRC,                // selected radial colour
    GCC,                // green circle colour
    RCC,                // red circle colour
    C[][];              // to store the picture so far

  wpcolour() {                            // CONSTRUCTOR
    C = new Color[XW][YH];                // create the tracking area array
    GCC = new java.awt.Color(0,255,72);   // bright green for circle
    RCC = new java.awt.Color(255,0,72);   // bright red for circle
    BGC = new java.awt.Color(0,0,160);    // browny-green for axes
    SRC = new java.awt.Color(0,192,192);  // cyan for selected radial
  } 


  // DRAW THE APPROACH CONSTRUCTS ON THE DISPLAY RASTER
  void InitC(aircraft ac, waypoint wp, double OSR) {
    int i, j;

    // Set all pixels in the tracking square to the background colour.
    for(i = 0 ; i < XW ; i++)
      for(j = 0 ; j < YH ; j++)
        C[i][j] = BGC;

    /* DRAW THE RED AND GREEN GUDE CIRCLES

    The radius of the right-hand guide circle
    perpendicular to the selected radial line. */

    double
      a = OSR + half_π,

      /* The co-ordinates of the centre of the right-hand guide
      circle expressed as displacements from the waypoint. */

      xr = ac.r * Math.sin(a),
      yr = ac.r * Math.cos(a);

    /* The radius of the left-hand guide circle
    perpendicular to the selected radial line. */

    a = OSR - half_π;

    /* The co-ordinates of the centre of the left-hand guide
    circle expressed as displacements from the waypoint. */

    double
      xl = ac.r * Math.sin(a),
      yl = ac.r * Math.cos(a),
      x, y;  // local working variables for use within the 'for' loops

    // For every degree round a guide circle...
    for(a = 0; a <= two_π; a += .017453292) {

      /* Compute the absolute co-ordinates of one point
      on a generic guide circle centred on the waypoint. */

      x = wp.X + ac.r * Math.sin(a);
      y = wp.Y + ac.r * Math.cos(a);

      /* Compute the pixel position appropriately biased
      for the right-hand circle and set it green. Do the
      same for the left-hand circle and set it red. */

      C[(int)(xr + x)][(int)(yr + y)] = GCC;
      C[(int)(xl + x)][(int)(yl + y)] = RCC;
    }

    // DRAW THE SELECTED RADIAL LINE IN THE APPROPRIATE COLOUR
    for(i = 0 ; i < wp.R ; i++) {
      x = i * Math.sin(OSR); y = i * Math.cos(OSR); 
      C[(int)(x + wp.X)][(int)(y + wp.Y)] = SRC;
    }

    // Draw the waypoint as a small white square ...
    int
      I = (int)wp.X,
      J = (int)wp.Y;

    for(i = I - 2 ; i < I + 3 ; i++)
      for(j = J - 2 ; j < J + 3 ; j++)
        C[i][j] = ATC;

    // ... rounded off at the corners to make it into a circular blob.
    C[I - 2][J - 2] = BGC; C[I + 2][J + 2] = BGC;
    C[I - 2][J + 2] = BGC; C[I + 2][J - 2] = BGC;


    // DRAW THE LITTLE NORTH ARROW
    I = 30; J = 150;

    for(i = -10 ; i < 11 ; i++) C[I + i][J] = Color.white;
    for(j = -20 ; j < 21 ; j++) C[I][J + j] = Color.white;

    for(i = -3 ; i < 0 ; i++) {
      C[I + i][J + 20 + i] = Color.white;
      C[I - i][J + 20 + i] = Color.white;
    }
    for(j = -2 ; j < 3 ; j++) C[I - 2][J + 25 + j] = Color.white;
    for(j = -2 ; j < 3 ; j++) C[I + 2][J + 25 + j] = Color.white;
    for(j = -1 ; j < 2 ; j++) C[I - j][J + 25 + j] = Color.white;
  }

  // Plot the air4craft's current position on the tracking display raster.
  void PlotPosn(aircraft ac) { C[(int)ac.x][(int)ac.y] = ATC; }
}