// https://github.com/cdown/clipnotify

#define _DEFAULT_SOURCE
#include <X11/Xatom.h>
#include <X11/Xlib.h>
#include <X11/extensions/Xfixes.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

static enum selections {
	NONE = 0,
	SELECTION_CLIPBOARD = (1 << 0),
	SELECTION_PRIMARY = (1 << 1),
	SELECTION_SECONDARY = (1 << 2)
} selections = NONE;

static int loop;

int main(int argc, char *argv[]) {
	static const char *usage =
		"%s: Notify by exiting on clipboard events.\n\n"
		"  -l    Instead of exiting, print a newline when a new selection is available.\n"
		"  -s    The selection to use. Available selections:\n"
		"        clipboard, primary, secondary\n"
		"        The default is to monitor clipboard and primary.\n";
	Display *disp;
	Window root;
	Atom clip;
	XEvent evt;
	int opt;

	while ((opt = getopt(argc, argv, "hs:l")) != -1) {
		switch (opt) {
			case 'h':
				printf(usage, argv[0]);
				return EXIT_SUCCESS;
			case 'l':
				loop = 1;
				break;
			case 's': {
				char *token = strtok(optarg, ",");
				while (token != NULL) {
					if (strcmp(token, "clipboard") == 0) {
						selections |= SELECTION_CLIPBOARD;
					} else if (strcmp(token, "primary") == 0) {
						selections |= SELECTION_PRIMARY;
					} else if (strcmp(token, "secondary") == 0) {
						selections |= SELECTION_SECONDARY;
					} else {
						fprintf(stderr, "Unknown selection '%s'\n", token);
						return EXIT_FAILURE;
					}
					token = strtok(NULL, ",");
				}
				break;
			}
			default:
				fprintf(stderr, usage, argv[0]);
				return EXIT_FAILURE;
		}
	}

	disp = XOpenDisplay(NULL);
	if (!disp) {
		fprintf(stderr, "Can't open X display\n");
		return EXIT_FAILURE;
	}

	root = DefaultRootWindow(disp);

	clip = XInternAtom(disp, "CLIPBOARD", False);

	/* <= 1.0.2 backwards compatibility */
	if (!selections)
		selections = SELECTION_CLIPBOARD | SELECTION_PRIMARY;

	if (selections & SELECTION_CLIPBOARD)
		XFixesSelectSelectionInput(disp, root, clip,
								   XFixesSetSelectionOwnerNotifyMask);
	if (selections & SELECTION_PRIMARY)
		XFixesSelectSelectionInput(disp, root, XA_PRIMARY,
								   XFixesSetSelectionOwnerNotifyMask);
	if (selections & SELECTION_SECONDARY)
		XFixesSelectSelectionInput(disp, root, XA_SECONDARY,
								   XFixesSetSelectionOwnerNotifyMask);

	if (loop) {
		(void)setvbuf(stdout, NULL, _IONBF, 0);
		do {
			XNextEvent(disp, &evt);

		for (unsigned int i = 0; i < 2; i += 1) {
			printf("%c", 0);
			fflush(stdout);
			usleep(50000);
		}
		} while (1);
	} else {
		XNextEvent(disp, &evt);
	}
	XCloseDisplay(disp);
}