#include "library.h"  

const double off_x = 50, off_y = 50, timestep = 0.0033;

struct actor
{ double xpos, ypos, speed, reach;
  string yell;
  int color, size; };

void draw(actor a)
{ set_pen_color(a.color);
  set_pen_width(a.size);
  draw_point(a.xpos, a.ypos); }

void init_draw(double fw, double fl,
               actor tr, actor bu, actor bo)
{ set_pen_color(0.8, 1.0, 0.8);
  fill_rectangle(off_x, off_y, fl, fw);
  set_pen_color(color::dark_green);
  set_pen_width(50);
  draw_point(tr.xpos, tr.ypos);
  draw(tr);
  draw(bu);
  draw(bo); }

void init(actor & a, double x, double y, double sp, double r,
          string ye, int c)
{ a.xpos = x;
  a.ypos = y;
  a.speed = sp;
  a.reach = r;
  a.yell = ye;
  a.color = c;
  a.size = 3; }

double direction(actor from, actor to)
{ return atan2(to.xpos-from.xpos, to.ypos-from.ypos); }

double Distance(actor a, actor b)
{ return sqrt((a.xpos-b.xpos)*(a.xpos-b.xpos) +
              (a.ypos-b.ypos)*(a.ypos-b.ypos)); }

void move_towards(actor & mover, actor destiny)
{ double dir = direction(mover, destiny);
  double step_x = mover.speed * timestep * sin(dir);
  double step_y = mover.speed * timestep * cos(dir);
  move_to(mover.xpos, mover.ypos);
  set_pen_color(mover.color);
  mover.xpos += step_x;
  mover.ypos += step_y;
  draw_to(mover.xpos, mover.ypos); }

bool update(actor & mover, actor dest)
  // return true if mover reaches destination
{ move_towards(mover, dest);
  if (Distance(mover, dest) < mover.reach)
  { write_string(mover.yell);
    return true; }
  return false; }

void main()
{ double fieldw = 500,
         fieldl = 800;
  actor boy, bull, tree, dinosaur;
  init(tree, off_x + fieldl - 100, off_y + 150,    0.0, 0, "", color::brown);
  init(bull, off_x + 50,           off_y + 0,      1.2, 1, "Boy Eaten!", color::red);
  init(boy,  off_x + fieldl - 100, off_y + fieldw, 0.5, 1, "Ha ha stupid bull.", color::blue);
  init(dinosaur, off_x,            off_y + fieldw, 1.0, 1, "Graaaaah!", color::black);
  tree.size = 5;

  make_window(fieldl+2*off_x, fieldw+2*off_y);
  init_draw(fieldw, fieldl, tree, bull, boy);

  while (true)
  { if (update(dinosaur, bull))
      break;
    if (update(boy, tree))
      break;
    if (update(bull, boy))
      break; } }