#include "library.h"

double distance_between(const double x1, const double y1, const double x2, const double y2)
{ return sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2)); }

void main()
{ print("Width of field: ");
  const double width = read_double();
  print("Speed of boy: ");
  const double boyspeed = read_double();
  print("Speed of bull: ");
  const double bullspeed = read_double();
  print("Initial position of bull:\n  x: ");
  const double bullx0 = read_double();
  print("  y: ");
  const double bully0 = read_double();
  print("Position of tree:\n  x: ");
  const double treex = read_double();
  print("  y: ");
  const double treey = read_double();

  /*  
      I found that these figures provide for an exciting contest...

      width      = 700
      boyspeed   = 2
      bullspeed  = 2.8
      bullx0     = 300 for one result, 500 for the other.
      bully0     = 0
      treex      = 500
      treey      = 500

      P.S. This is a multi-line comment that I have never shown you before
  */

  MakeWindow(1000, width);
  PenColor(0.0, 1.0, 0.0);   // green
  PenWidth(10);
  DrawPointAt(treex, width-treey);
  PenColor(1.0, 1.0, 1.0);   // white
  PenWidth(7);
  DrawPointAt(treex, width-treey);

  PenWidth(2);

  const double time_increment=0.002, close_enough=1;
  double time_now=0.0;
  double bullx=bullx0, bully=bully0, boyx=0, boyy=width;

  while (distance_between(bullx, bully, boyx, boyy)>close_enough &&
         distance_between(boyx, boyy, treex, treey)>close_enough)

  { const double initbullx=bullx, initbully=bully, initboyx=boyx, initboyy=boyy;

    const double boy_tree_direction = atan2(treex-boyx, treey-boyy);
    boyx += boyspeed*sin(boy_tree_direction)*time_increment;
    boyy += boyspeed*cos(boy_tree_direction)*time_increment;

    const double bull_boy_direction = atan2(boyx-bullx, boyy-bully);
    bullx += bullspeed*sin(bull_boy_direction)*time_increment;
    bully += bullspeed*cos(bull_boy_direction)*time_increment;

    PenColor(0.0, 0.0, 1.0);    // blue
    MoveTo(initboyx, width-initboyy);
    DrawLineTo(boyx, width-boyy);

    PenColor(1.0, 0.0, 0.0);    // red
    MoveTo(initbullx, width-initbully);
    DrawLineTo(bullx, width-bully);

    time_now += time_increment; }

  MoveTo(treex+10, width-(treey-10));
  SetFontSize(24);
  SetFontFace("Arial");
  SetFontAttributes(FONT_BOLD);
  PenWidth(10);
  if (distance_between(boyx, boyy, treex, treey)<=close_enough)
  { PenColor(0.0, 0.0, 1.0);
    WriteText("The boy is safely in the tree");
    DrawPointAt(treex, width-treey); }
  else
  { PenColor(1.0, 0.0, 0.0);
    WriteText("The bull ate the boy");
    DrawPointAt(boyx, width-boyy); } }