#define _GNU_SOURCE   /* program_invocation_name */
#include <assert.h>   /* assert(3p) */
#include <errno.h>    /* program_invocation_name */
#include <error.h>    /* error(3gnu) */
#include <fcntl.h>    /* O_* flags to open(3p) */
#include <glob.h>     /* glob(3p), globfree(3p), GLOB_* */
#include <signal.h>   /* sigaction(3p) */
#include <stdbool.h>  /* bool */
#include <stdio.h>    /* dprintf(3p) */
#include <stdlib.h>   /* exit(3p), malloc(3p) */
#include <string.h>   /* strcmp(3p), strlen(3p), strcpy(3p) */
#include <sys/stat.h> /* open(3p) */
#include <unistd.h>   /* unlink(3p) */

char *rbar_globescape(const char *lit);

/* Main *************************************************************/

struct impl {
	int (*left_click)(void);
	int (*middle_click)(void);
	int (*right_click)(void);
	int (*scroll_up)(void);
	int (*scroll_down)(void);
	int (*update)(const char *tag);
} impl;

#define errusage(...) do { \
	error(6, 0, __VA_ARGS__); \
	usage(2); \
	exit(2); \
} while(0)

void usage(int fd) {
	dprintf(fd,
		"Usage: %1$s NN_LABEL\n"
		"   or: %1$s BTN_ID\n"
		"   or: %1$s -h\n",
		program_invocation_name);
}

void sigexit(int sig) {
	error(0, 0, "Caught signal: %d", sig);
	exit(0);
}

char *xrd_glob;
size_t xrd_glob_len;

void xrd_cleanup(void) {
	free(xrd_glob);
}

void xrd_setup(void) {
	char *xrd = getenv("XDG_RUNTIME_DIR");
	if (xrd == NULL || xrd[0] == '\0') {
		error(6, 0, "XDG_RUNTIME_DIR isn't set");
	}
	xrd_glob = rbar_globescape(xrd);
	xrd_glob_len = strlen(xrd_glob);
	atexit(xrd_cleanup);
}

int main(int argc, char *argv[]) {
	if (argc != 2) {
		errusage("exactly 1 argument expected, got %d", argc-1);
	}
	const char *arg = argv[1];

	if (strcmp(arg, "-h") == 0) {
		usage(1);
		exit(0);
	}

	struct sigaction sa = { 0 };
	sa.sa_handler = sigexit;
	sigaction(SIGHUP, &sa, NULL);
	sigaction(SIGINT, &sa, NULL);
	sigaction(SIGTERM, &sa, NULL);

	if ('1' <= arg[0] && arg[0] <= '5' && arg[1] == '\0') {
		int (*fn)(void) = NULL;
		switch (arg[0]) {
		case '1': fn = impl.left_click; break;
		case '2': fn = impl.middle_click; break;
		case '3': fn = impl.right_click; break;
		case '4': fn = impl.scroll_up; break;
		case '5': fn = impl.scroll_down; break;
		}
		xrd_setup();
		if (fn == NULL) {
			exit(0);
		} else {
			exit(fn());
		}
	}

	if ('0' <= arg[0] && arg[0] <= '9' &&
	    '0' <= arg[1] && arg[1] <= '9' &&
	    arg[2] == '_') {
		xrd_setup();
		if (impl.update == NULL) {
			exit(0);
		} else {
			exit(impl.update(arg));
		}
	}

	errusage("invalid argument: %s", arg);
}

/* Util *************************************************************/

#define RBAR_DIRGLOB "/wmii*/rbar"

char *rbar_globescape(const char *lit) {
	size_t len = 0;
	for (const char *a = lit; *a != '\0'; a++) {
		switch (*a) {
		case '\\': case '*': case '?': case '[':
			len++; /* fall through */
		default:
			len++;
		}
	}

	char *glob = malloc(len+1);
	if (!glob)
		error(1, errno, "rbar_globescape: malloc");

	// copy 'a' to 'b'
	char *b = glob;
	for (const char *a = lit; *a != '\0'; a++) {
		switch (*a) {
		case '\\': case '*': case '?': case '[':
			*(b++) = '\\'; /* fall through */
		default:
			*(b++) = *a;
		}
	}
	*b = '\0';

	return glob;
}

/* returns 0 or GLOB_NOMATCH */
bool rbar_write(const char *filename, const char *msg) {
	char *fullglob = alloca(xrd_glob_len+(sizeof RBAR_DIRGLOB));
	strcpy(fullglob, xrd_glob);
	strcpy(&fullglob[xrd_glob_len], RBAR_DIRGLOB);

	glob_t __attribute__((__cleanup__(globfree))) globbuf = { 0 };
	switch (glob(fullglob, GLOB_ONLYDIR|GLOB_NOSORT|GLOB_ERR, NULL, &globbuf)) {
	case GLOB_NOSPACE:
		error(1, ENOMEM, "rbar_write"); assert(0);
	case GLOB_ABORTED:
		error(1, errno, "rbar_write: glob"); assert(0);
	case GLOB_NOMATCH:
		return false;
	}

	const size_t filenamelen = strlen(filename);
	const size_t msglen = strlen(msg);
	for (size_t i = 0; i < globbuf.gl_pathc; i++) {
		const char *dirname = globbuf.gl_pathv[i];
		const size_t dirnamelen = strlen(dirname);
		char *fullname = alloca(dirnamelen+1+filenamelen+1);
		strcpy(fullname, dirname);
		fullname[dirnamelen] = '/';
		strcpy(&fullname[dirnamelen+1], filename);

		int fd = open(fullname, O_WRONLY|O_APPEND|O_CREAT, 0666);
		if (fd < 0) {
			error(0, errno, "open: %s", fullname);
			continue;
		}
		if (write(fd, msg, msglen) < (ssize_t)msglen)
			error(0, errno, "write: %s", fullname);
		close(fd);
	}
	return true;
}

void rbar_remove(const char *fileglob) {
	char *fullglob = alloca(xrd_glob_len+(sizeof RBAR_DIRGLOB)+strlen(fileglob)+1);
	strcpy(fullglob, xrd_glob);
	strcpy(&fullglob[xrd_glob_len], RBAR_DIRGLOB);
	fullglob[xrd_glob_len+(sizeof RBAR_DIRGLOB)-1] = '/';
	strcpy(&fullglob[xrd_glob_len+(sizeof RBAR_DIRGLOB)], fileglob);

	glob_t __attribute__((__cleanup__(globfree))) globbuf = { 0 };
	if (glob(fullglob, GLOB_NOSORT, NULL, &globbuf) != 0)
		return;
	for (size_t i = 0; i < globbuf.gl_pathc; i++) {
		unlink(globbuf.gl_pathv[i]);
	}
}