#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <time.h>
#include <unistd.h>

#include <cairo/cairo.h>
#include <cairo/cairo-xcb.h>
#include <xcb/xcb.h>
#include <xcb/present.h>
#include <xcb/xfixes.h>
#include <xcb/randr.h>

/************************************************************************************************************/
/* _ ********************************************************************************************************/
/************************************************************************************************************/

static void _draw        (void);
static void _init_cairo  (void);
static void _init_xcb    (void);
static void _reset       (void);
static void _run         (void);

/************************************************************************************************************/
/************************************************************************************************************/
/************************************************************************************************************/

static uint32_t _opt_frame_divider = 1;
static int _opt_async = 0;

static xcb_connection_t    *_x_con = NULL;
static xcb_screen_t        *_x_scr = NULL;
static xcb_visualtype_t    *_x_vis = NULL;
static xcb_special_event_t *_x_sev = NULL;
static xcb_window_t         _x_win = 0;
static xcb_pixmap_t         _x_pix = 0;

static cairo_surface_t *_c_srf = NULL;
static cairo_t         *_c_ctx = NULL;

static int _speed1 = 60;
static int _speed2 = 5;

static double _pos1 = 0;
static double _inc1 = 1;

static double _pos2 = 0;
static double _inc2 = 1;

static long _t_full  = 0;
static long _t_paint = 0;
static long _t_xsync = 0;

static double _fps    = 0;
static long   _total  = 0;

static uint32_t stamp = 0;

/************************************************************************************************************/
/************************************************************************************************************/
/************************************************************************************************************/

int
main(int argc, char **argv)
{
	/* options */

	int opt;
	while ((opt = getopt(argc, argv, "al:")) != -1) {
		switch (opt) {

			case 'a':
				_opt_async = 1;
				break;

			case 'l':
				_opt_frame_divider = (unsigned int)atoi(optarg);
				break;
		}
	}

	/* program */

	_init_xcb();
	_init_cairo();
	_run();
	_reset();

	return 0;
}

/************************************************************************************************************/
/* _ ********************************************************************************************************/
/************************************************************************************************************/

static void
_draw(void)
{
	/* background */

	cairo_set_source_rgb(_c_ctx, 0.1, 0.1, 0.1);
	cairo_rectangle(_c_ctx, 0, 0, 700, 700);
	cairo_fill(_c_ctx);

	/* big square */

	double adv1 = (double)(_speed1 * _t_full) / 1000000.0;
	_pos1 += adv1 * _inc1;
	while (_pos1 > 600.0 || _pos1 < 0.0) {
		if (_pos1 > 600.0) {
			_inc1 = -1;
			 adv1 = _pos1 - 600;
			_pos1 = 600;
		} else {
			_inc1 = 1;
			 adv1 = -_pos1;
			_pos1 = 0;
		}
		_pos1 += adv1 * _inc1;
	}

	cairo_set_source_rgb(_c_ctx, 0.8, 0.8, 0.8);
	cairo_rectangle(_c_ctx, _pos1, _pos1, 100, 100);
	cairo_fill(_c_ctx);

	/* small square */

	double adv2 = (double)(_speed2 * _t_full) / 1000000.0;
	_pos2 += adv2 * _inc2;
	while (_pos2 > 80.0 || _pos2 < 0.0) {
		if (_pos2 > 80.0) {
			_inc2 = -1;
			 adv2 = _pos2 - 80;
			_pos2 = 80;
		} else {
			_inc2 = 1;
			 adv2 = -_pos2;
			_pos2 = 0;
		}
		_pos2 += adv2 * _inc2;
	}

	cairo_set_source_rgb(_c_ctx, 0.3, 0.3, 0.3);
	cairo_rectangle(_c_ctx, _pos1 + 80 - _pos2, _pos1 + _pos2, 20, 20);
	cairo_fill(_c_ctx);

	/* counters */

	char str[128];
	cairo_set_source_rgb(_c_ctx, 1.0, 1.0, 1.0);

	sprintf(str, "fps : %f", _fps);
	cairo_move_to(_c_ctx, 25, 555);
	cairo_show_text(_c_ctx, str);

	sprintf(str, "frame time (µs) : %li", _t_full);
	cairo_move_to(_c_ctx, 25, 585);
	cairo_show_text(_c_ctx, str);

	sprintf(str, "paint time (µs) : %li", _t_paint);
	cairo_move_to(_c_ctx, 25, 615);
	cairo_show_text(_c_ctx, str);

	sprintf(str, "x sync time (µs) : %li", _t_xsync);
	cairo_move_to(_c_ctx, 25, 645);
	cairo_show_text(_c_ctx, str);

	sprintf(str, "total frames : %li", _total);
	cairo_move_to(_c_ctx, 25, 675);
	cairo_show_text(_c_ctx, str);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/

static void
_init_cairo(void)
{
	_c_srf = cairo_xcb_surface_create(_x_con, _x_pix, _x_vis, 700, 700);
	_c_ctx = cairo_create(_c_srf);

	cairo_set_font_size(_c_ctx, 20);
	cairo_select_font_face(_c_ctx, "Terminus", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);

	cairo_surface_flush(_c_srf);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/

static void
_init_xcb(void)
{
	/* connection */ 

	_x_con = xcb_connect(NULL, NULL);
	_x_scr = xcb_setup_roots_iterator(xcb_get_setup(_x_con)).data;

	xcb_visualtype_iterator_t x_vi;
	xcb_depth_iterator_t      x_di;

	x_di = xcb_screen_allowed_depths_iterator(_x_scr);
	for (; x_di.rem; xcb_depth_next(&x_di)) {
		x_vi = xcb_depth_visuals_iterator(x_di.data);
		for (; x_vi.rem; xcb_visualtype_next(&x_vi)) {
			if (_x_scr->root_visual == x_vi.data->visual_id) {
				_x_vis = x_vi.data;
				break;
			}
		}
	}

	/* window */ 

	uint32_t mask_vals[2]; 
	mask_vals[0] = _x_scr->black_pixel;
	mask_vals[1] = XCB_EVENT_MASK_EXPOSURE;

	_x_win = xcb_generate_id(_x_con);	                       
	xcb_create_window(
		_x_con,
		XCB_COPY_FROM_PARENT,
		_x_win,
		_x_scr->root,
		0, 0,
		700, 700,
		0,
		XCB_WINDOW_CLASS_INPUT_OUTPUT,
		_x_scr->root_visual,
		XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK,
		mask_vals);

		xcb_map_window(_x_con, _x_win);
		xcb_flush(_x_con);

	/* pixmap */

	_x_pix = xcb_generate_id(_x_con);
	xcb_create_pixmap(_x_con, _x_scr->root_depth, _x_pix, _x_win, 700, 700);

	/* present extension */

	uint32_t id = xcb_generate_id(_x_con);

	xcb_present_select_input(
		_x_con,
		id,
		_x_win,
		XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY);

	/* optional setup a special event queue for the present extension              */
	/* if not done present completion events can still be recoved from the regular */
	/* xcb_wait_for_event() queue                                                  */

	_x_sev = xcb_register_for_special_xge(_x_con, &xcb_present_id, id, &stamp);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/

static void
_reset(void)
{
	cairo_destroy(_c_ctx);
	cairo_surface_destroy(_c_srf);

	xcb_free_pixmap(_x_con, _x_pix);
	xcb_destroy_window(_x_con, _x_win);
	xcb_disconnect(_x_con);
}

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -*/

static void
_run(void)
{
	xcb_generic_event_t *ev = NULL;

	int   n = 0;
	long t1 = 0;
	long t2 = 0;
	long t3 = 0;

	struct timespec ts = {0};

	while (1) {

		_total++;

		clock_gettime(CLOCK_MONOTONIC, &ts);
		t1 = ts.tv_nsec / 1000 + ts.tv_sec * 1000000;

		_draw();

		clock_gettime(CLOCK_MONOTONIC, &ts);
		t2 = ts.tv_nsec / 1000 + ts.tv_sec * 1000000;

		xcb_present_pixmap(
			_x_con,
			_x_win,
			_x_pix,
			123456,
			XCB_XFIXES_REGION_NONE,
			XCB_XFIXES_REGION_NONE,
			0, 0,
			0,
			0,
			0,
			_opt_async ? XCB_PRESENT_OPTION_ASYNC : XCB_PRESENT_OPTION_NONE,
			0, _opt_frame_divider, 0,
			0,
			NULL);
		xcb_flush(_x_con);

		clock_gettime(CLOCK_MONOTONIC, &ts);
		t3 = ts.tv_nsec / 1000 + ts.tv_sec * 1000000;

		_t_paint = t2 - t1;
		_t_xsync = t3 - t2;

		ev = xcb_wait_for_special_event(_x_con, _x_sev);
		if (!ev) {
			printf("exiting\n");
			return;
		}

		free(ev);

		clock_gettime(CLOCK_MONOTONIC, &ts);
		_t_full = ts.tv_nsec / 1000 + ts.tv_sec * 1000000 - t1;
		_fps = 1000000.0 / (double)_t_full;
	}
}