#include "library.h"

bool close(double a, double b)
{ return fabs(a-b) < 0.1; }

bool close(double x1, double y1, double x2, double y2)
{ return close(x1, x2) && close(y1, y2); }

double direction_from_a_to_b(double ax, double ay, double bx, double by)
{ return atan2(bx-ax, ay-by); }

void main()
{ double field_w=500, field_h=400, edge=100;
  double tree_x=400, tree_y=200;
  double bull_x=500, bull_y=150;
  double boy_x=100, boy_y=500;
  double bull_spd=3, boy_spd=2, delta_t=0.003;
  bool is_boy_safe = false;
  double total_time = 0.0;

  make_window(field_w+2*edge, field_h+2*edge);
  set_pen_color(color::green);
  fill_rectangle(edge, edge, field_w, field_h);
  set_pen_color(color::brown);
  set_pen_width(10);
  draw_point(tree_x, tree_y);
  set_pen_width(2);

      // this creates a new variable called "output".
      // ofstream is a type just like int or double or bool.
      // it represents a stream of text being output to a file.
  ofstream output("data.txt");
      // that caused a file on disc called "data.txt" to be created.
      // from now on, output << can be used just like cout <<, but
      // it will add things to the file instead of displaying them
      // in the text window.

  while (true)
  { total_time += delta_t;
    output << "time " << total_time << ": ";
        // the boy runs straight to the tree:
        // work out the direction he runs
    double ang = direction_from_a_to_b(boy_x, boy_y, tree_x, tree_y);
        // work out how far he runs in 0.1 seconds
    double dist = boy_spd * delta_t;
        // work out where he will be 0.1 seconds later
    double boy_new_x = boy_x + dist * sin(ang);
    double boy_new_y = boy_y - dist * cos(ang);
        // draw a line showing these few inches of progress
    set_pen_color(color::blue);
    move_to(boy_x, boy_y);
    draw_to(boy_new_x, boy_new_y);
        // has he reached the tree yet?
    if (close(boy_new_x, boy_new_y, tree_x, tree_y))
    { write_string("Boy Safe!");
      is_boy_safe = true; }

// Now we have to do exactly the same calculations for the bull
// running towards the bull.
// Lots of repeated code, very bad programming style. We must
// design a function to do it.

    ang = direction_from_a_to_b(bull_x, bull_y, boy_x, boy_y);
    dist = bull_spd * delta_t;
    double bull_new_x = bull_x + dist * sin(ang);
    double bull_new_y = bull_y - dist * cos(ang);
    set_pen_color(color::red);
    move_to(bull_x, bull_y);
    draw_to(bull_new_x, bull_new_y);
    if (close(bull_new_x, bull_new_y, boy_new_x, boy_new_y))
    { if (! is_boy_safe)
        write_string("Boy Eaten!");
      break; }

    boy_x = boy_new_x;
    boy_y = boy_new_y;
    bull_x = bull_new_x;
    bull_y = bull_new_y;
    output << "boy at (" << boy_x << ", " << boy_y << "), ";
    output << "bull at (" << bull_x << ", " << bull_y << ")\n"; }
  cout << "Finished\n"; }