#include <string>
#include <curses.h>
#include <unistd.h> // usleep

struct Object {
	int x, y; // center
	int width, height; // full, not half
	double scale;

	int Left()   const { return x - (width  / 2.0) * scale; }
	int Right()  const { return x + (width  / 2.0) * scale; }
	int Top()    const { return y - (height / 2.0) * scale; }
	int Bottom() const { return y + (height / 2.0) * scale; }
};

bool InBounds(Object bounds, Object object);

int main(int argc, char *argv[])
{
	WINDOW * mainwin;
	// Initialize ncurses
	if ( (mainwin = initscr()) == NULL ) {
		fprintf(stderr, "Error initialising ncurses.\n");
		exit(EXIT_FAILURE);
	}

	Object screen;
	screen.x = 20;
	screen.width = 20;
	screen.y = 13;
	screen.height = 6;
	screen.scale = 1.0;

	const Object initial_screen = screen;

	Object object;
	object.x = 3;
	object.width = 5;
	object.y = 6;
	object.height = 4;
	object.scale = 1.0;

	const Object initial_object = object;

	double scale_multiplier = 0.2;

	while(true)
	{
		screen = initial_screen;
		object = initial_object;

		object.scale *= scale_multiplier;
		scale_multiplier *= 2;

		// NOTE: This causes it to pause on each resize when it is immediately covered.
		//       To avoid this, move this initialization outside of the "while(true)" loop.
		bool covered_last_frame = false;

		const int num_rows = 14;
		for(auto r = 0; r < num_rows; ++r)
		{
			const int num_columns = 40;
			for(auto c = 0; c < num_columns; ++c)
			{
				// DRAW
				clear();
				int left;
				left = screen.Left();
				if(left < 0)
					left = 0;
				// NOTE: +1 to account for full width
				std::string scr(screen.Right() - left + 1, '+');
				for(auto row = screen.Top(); row <= screen.Bottom(); ++row)
					mvaddstr(row, left, scr.c_str());

				left = object.Left();
				if(left < 0)
					left = 0;
				// NOTE: +1 to account for full width
				std::string obj(object.Right() - left + 1, '*');
				for(auto row = object.Top(); row <= object.Bottom(); ++row)
					mvaddstr(row, left, obj.c_str());

				bool covered = InBounds(screen, object);

				mvaddstr(1, 1, covered ? "Covered: YES" : "Covered: NO");

				refresh();

				// When there is a change in "covered" status, freeze to show it:
				if(covered != covered_last_frame)
					usleep(300000); // 3/10 sec
				else
					usleep(5000); // quick (adjust to your PC's performance)

				covered_last_frame = covered;

				++object.x;
			}
			++object.y;
			object.x -= num_columns;
		}
	}

	// destroy ncurses
	delwin(mainwin);
	endwin();
	refresh();

	return 0;
}

bool InBounds(Object bounds, Object object)
{
	if(object.Right() < bounds.Left()
	   || object.Left() > bounds.Right()
	   || object.Bottom() < bounds.Top()
	   || object.Top() > bounds.Bottom())
		return false;
	return true;
}