#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <xcb/xcb.h>

#define MKASPECT(w, h) { (double)w/h, #w ":" #h }

/* Table of common monitor aspect ratios.  Add to this as necessary. */
static struct aspect {
	double ratio;
	char *name;
} aspects[] = {
	MKASPECT(16, 10),
	MKASPECT(16, 9),
	MKASPECT(8, 3),
	MKASPECT(5, 4),
	MKASPECT(4, 3)
};

/*
 * Get the xcb screen structure for the specified screen, or NULL if it doesn't
 * exist.
 */
static xcb_screen_t *getscreen(xcb_connection_t *c, int screen)
{
	xcb_screen_iterator_t iter;

	iter = xcb_setup_roots_iterator(xcb_get_setup(c));
	while (iter.rem) {
		if (screen == 0)
			return iter.data;
		screen--;
		xcb_screen_next(&iter);
	}

	return NULL;
}

char *testaspect(xcb_screen_t *screen)
{
	unsigned int w = screen->width_in_millimeters;
	unsigned int h = screen->height_in_millimeters;

	double ratio = (double)w/h;
	double diff = 0;
	char *best = NULL;
	int i;

	for (i = 0; i < (sizeof aspects / sizeof aspects[0]); i++) {
		if (!best || fabs(aspects[i].ratio - ratio) < diff) {
			best = aspects[i].name;
			diff = fabs(aspects[i].ratio - ratio);
		}
	}

	return best;
}

int main(int argc, char **argv)
{
	xcb_connection_t *display;
	xcb_screen_t     *screen;
	char *dpynam = NULL;
	int screen_num;

	if (argc > 2 && strcmp(argv[1], "-display") == 0)
		dpynam = argv[2];
	
	display = xcb_connect(dpynam, &screen_num);
	if (xcb_connection_has_error(display)) {
		fprintf(stderr, "Failed to open display.\n");
		xcb_disconnect(display);
		return EXIT_FAILURE;
	}

	screen = getscreen(display, screen_num);
	if (!screen) {
		fprintf(stderr, "Invalid screen number.\n");
		xcb_disconnect(display);
		return EXIT_FAILURE;
	}

	printf("%s\n", testaspect(screen));

	xcb_disconnect(display);
	return EXIT_SUCCESS;
}