#include <string.h>

 #include <errno.h>

 #include <stdio.h>

 #include <signal.h>

 #include <stdlib.h>

 #include <event2/bufferevent.h>

 #include <event2/buffer.h>

 #include <event2/listener.h>

 #include <event2/util.h>

 #include <event2/event.h>

 #include <sys/socket.h>

 #include <sys/un.h>

 #include <unistd.h>

 static const char MESSAGE[] = "Hello, World!\n";

 static const char PATH[] = "./roura";

 static void listener_cb(evutil_socket_t, short, void *);

 static void conn_read_cb(struct bufferevent *, void *);

 static void conn_write_cb(struct bufferevent *, void *);

 static void conn_event_cb(struct bufferevent *, short, void *);

 static void signal_cb(evutil_socket_t, short, void *);

 static void print_socket_info(int);

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

 	struct event_base *base;

 	evutil_socket_t listener;

 	struct event *listener_event;

 	struct event *signal_event;

 	struct sockaddr_un sun;

 	setvbuf(stdout, NULL, _IONBF, 0);

 	base = event_base_new();

 	if (!base) {

 		fprintf(stderr, "Could not initialize libevent!\n");

 		return 1;

 	}

 	memset(&sun, 0, sizeof (sun));

 	sun.sun_family = AF_UNIX;

 	strcpy(sun.sun_path, PATH);

 	listener = socket(AF_UNIX, SOCK_STREAM, 0);

 	evutil_make_socket_nonblocking(listener);

 	if (bind(listener, (struct sockaddr*) &sun, sizeof (sun)) < 0) {

 		fprintf(stderr, "Could not create domain socket: %s!\n", PATH);

 		return 1;

 	}

 	if (listen(listener, 16) < 0) {

 		fprintf(stderr, "Could not listen\n");

 		return 1;

 	}

 	// identifikátor serverového soketu (v současnosti číslo FD)

 	printf("Nasloucháme: sun_path = %s → socketId = %d\n", sun.sun_path, listener);

 	listener_event = event_new(base, listener, EV_READ | EV_PERSIST, listener_cb, (void*) base);

 	if (!listener_event) {

 		fprintf(stderr, "Could not do event_new\n");

 		return 1;

 	}

 	event_add(listener_event, NULL);

 	signal_event = evsignal_new(base, SIGINT, signal_cb, (void *) base);

 	if (!signal_event || event_add(signal_event, NULL) < 0) {

 		fprintf(stderr, "Could not create/add a signal event!\n");

 		return 1;

 	}

 	event_base_dispatch(base);

 	event_free(listener_event);

 	event_free(signal_event);

 	event_base_free(base);

 	// smažeme soket na disku / soubor -- jinak by program příště spadl na bind()

 	// TODO: co když soket někdo přesune a místo něj dá jiný soubor?

 	unlink(PATH);

 	printf("done\n");

 	return 0;

 }

 static void listener_cb(evutil_socket_t listener, short event, void *user_data) {

 	struct event_base *base = (event_base *) user_data;

 	struct bufferevent *bev;

 	struct sockaddr_storage ss;

 	socklen_t slen = sizeof (ss);

 	int fd = accept(listener, (struct sockaddr*) &ss, &slen);

 	if (fd < 0) {

 		fprintf(stderr, "Unable to accept(): %d", fd);

 		return;

 	} else if (fd > FD_SETSIZE) {

 		// FD_SETSIZE = 1024 -- Proč? Co když bude spojení víc?

 		fprintf(stderr, "fd (%d) > FD_SETSIZE (%d)", fd, FD_SETSIZE);

 		close(fd);

 		return;

 	}

 	evutil_make_socket_nonblocking(fd);

 	print_socket_info(fd);

 	bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);

 	if (!bev) {

 		fprintf(stderr, "Error constructing bufferevent!");

 		event_base_loopbreak(base);

 		return;

 	}

 	// identifikátor navázaného spojení (v současnosti číslo FD)

 	int * connectionId = (int*) malloc(sizeof (fd));

 	*connectionId = fd;

 	bufferevent_setcb(bev, conn_read_cb, conn_write_cb, conn_event_cb, (void*) connectionId);

 	bufferevent_enable(bev, EV_READ | EV_WRITE);

 	printf("někdo se k nám připojil! socketId = %d → connectionId = %d / bev = %p\n", listener, *connectionId, bev);

 	bufferevent_write(bev, MESSAGE, strlen(MESSAGE));

 }

 static void conn_read_cb(struct bufferevent *bev, void *user_data) {

 	printf("conn_read_cb: connectionId = %d\n", *((int*) user_data));

 	/* This callback is invoked when there is data to read on bev. */

 	struct evbuffer *input = bufferevent_get_input(bev);

 	struct evbuffer *output = bufferevent_get_output(bev);

 	struct event_base *base = bufferevent_get_base(bev);

 	size_t len = evbuffer_get_length(input);

 	char *data = (char*) malloc(len);

 	evbuffer_copyout(input, data, len);

 	printf("we got some data: %s\n", data);

 	if (memcmp(data, "exit\n", len) == 0) {

 		struct timeval delay = {2, 123};

 		printf("Klient říká, že máme končit; ukončuji program během %ld sekund a %ld mikrosekund.\n", delay.tv_sec, delay.tv_usec);

 		event_base_loopexit(base, &delay);

 	}

 	evbuffer_add(output, "echo: ", 6);

 	/* Copy all the data from the input buffer to the output buffer. */

 	evbuffer_add_buffer(output, input);

 	free(data);

 }

 static void conn_write_cb(struct bufferevent *bev, void *user_data) {

 	printf("conn_write_cb: connectionId = %d\n", *((int*) user_data));

 	struct evbuffer *output = bufferevent_get_output(bev);

 	if (evbuffer_get_length(output) == 0) {

 		printf("flushed answer / %p\n", bev);

 		/* nebudeme ukončovat spojení

 		bufferevent_free(bev);

 		 */

 	}

 }

 static void conn_event_cb(struct bufferevent *bev, short events, void *user_data) {

 	int connectionId = *((int*) user_data);

 	printf("conn_event_cb: connectionId = %d\n", connectionId);

 	if (events & BEV_EVENT_EOF) {

 		printf("Connection closed: connectionId = %d\n", connectionId);

 	} else if (events & BEV_EVENT_ERROR) {

 		printf("Got an error on the connectionId = %d: %s\n", connectionId, strerror(errno));

 	}

 	// None of the other events can happen here, since we haven't enabled timeouts

 	bufferevent_free(bev);

 	free(user_data);

 }

 static void signal_cb(evutil_socket_t sig, short events, void *user_data) {

 	struct event_base *base = (event_base *) user_data;

 	struct timeval delay = {2, 123};

 	printf("Zachycen SIGINT (Ctrl+C); ukončuji program během %ld sekund a %ld mikrosekund.\n", delay.tv_sec, delay.tv_usec);

 	event_base_loopexit(base, &delay);

 }

 static void print_socket_info(int fd) {

 	struct ucred cr;

 	unsigned int cl = sizeof (cr);

 	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cr, &cl) == 0) {

 		printf("připojený klient: pid=%d, uid=%d, gid=%d\n", cr.pid, cr.uid, cr.gid);

 	}

 }