#include "library.h"

const int fieldw = 500, fieldh = 400, offset = 25;
const double deltat = 0.1;

struct Actor
{ double x, y, speed, reach;
  int colour;
  string success; };

Actor Create(double ix, double iy, double ispeed, int icolour, double ireach, string isuccess)
{ Actor a;
  a.x = ix;
  a.y = iy;
  a.speed = ispeed;
  a.colour = icolour;
  a.reach = ireach;
  a.success = isuccess;
  return a; }

void draw_field()
{ set_pen_color(color::black);
  move_to(offset, offset);
  draw_to(fieldw + offset, offset);
  draw_to(fieldw + offset, fieldh + offset);
  draw_to(offset, fieldh + offset);
  draw_to(offset, offset); }

void draw_actor(Actor a)
{ move_to(offset + a.x, offset + a.y);
  set_pen_color(a.colour);
  draw_point(); }

void move_towards(Actor & mover, Actor target)
{ double alpha = atan2(target.x - mover.x, target.y - mover.y);
  double dx = mover.speed * deltat * sin(alpha);
  double dy = mover.speed * deltat * cos(alpha);
  mover.y += dy;
  mover.x += dx; }

bool close_enough(Actor a, Actor b)
{ double dist = sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
  if (dist < a.reach)
    return true;
  return false; }

void succeed(Actor a)
{ set_pen_color(a.colour);
  move_to(a.x - 10, a.y - 10);
  write_string(a.success); }

void main()
{ make_window(fieldw + 2 * offset, fieldh + 2 * offset);
  set_pen_width(3);
  Actor bull, boy, tree, dinosaur;
  bull = Create(offset + 250, offset + 50, 5, color::red, 3, "Boy eaten");
  boy = Create(offset + 200, offset + fieldh - 50, 3, color::blue, 1.5, "Boy safe");
  tree = Create(offset + fieldw - 50, offset + fieldh / 2, 0, color::green, 0, "");
  dinosaur = Create(offset + fieldw, offset, 3, color::purple, 6, "Graaah!");

  draw_field();
  draw_actor(bull);
  draw_actor(boy);
  draw_actor(tree);
  draw_actor(dinosaur);

  while (true)
  { sleep(0.1 * deltat / 10);

    move_towards(bull, boy);
    move_towards(boy, tree);
    move_towards(dinosaur, bull);

    draw_actor(bull);
    if (close_enough(bull, boy))
    { succeed(bull);
      break; }

    draw_actor(boy);
    if (close_enough(boy, tree))
    { succeed(boy);
      break; }

    draw_actor(dinosaur);
    if (close_enough(dinosaur, bull))
    { succeed(dinosaur);
      break; }

    draw_actor(tree); } }