#include <string.h>

#include <errno.h>

#include <stdio.h>

#include <signal.h>

#include <stdlib.h>

#include <string>

#include <regex>

#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>

using namespace std;

static const string HELLO_MESSAGE("Hello, World!\n");

static const string SOCKET_PATH("./roura");

static const string COMMAND_EXIT("exit\n");

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);

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

	printf("%4s %8s\n", "*", "STARTED");

	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) {

		printf("%4s %8s %s\n", "*", "ERROR", "unable to initialize libevent");

		return 1;

	}

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

	sun.sun_family = AF_UNIX;

	strcpy(sun.sun_path, SOCKET_PATH.c_str());

	listener = socket(AF_UNIX, SOCK_STREAM, 0);

	evutil_make_socket_nonblocking(listener);

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

		printf("%4s %8s %s: %s\n", "*", "ERROR", "unable to create domain socket:", SOCKET_PATH.c_str());

		return 1;

	}

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

		printf("%4s %8s %s\n", "*", "ERROR", "unable to listen");

		return 1;

	}

	// identifikátor serverového soketu (v současnosti číslo FD)

	printf("%4s %8s listening at: sun_path = %s → socketId = %d\n", "*", "SOCKET", sun.sun_path, listener);

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

	if (!listener_event) {

		printf("%4s %8s %s\n", "*", "ERROR", "unable to do event_new()");

		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) {

		printf("%4s %8s %s\n", "*", "ERROR", "unable to create/add a signal event");

		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(SOCKET_PATH.c_str());

	printf("%4s %8s\n", "*", "FINISHED");

	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);

	// identifikátor navázaného spojení (v současnosti číslo FD)

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

	*connectionId = fd;

	if (fd < 0) {

		printf("%4d %8s %s\n", *connectionId, "ERROR", "unable to accept()");

		return;

	} else if (fd > FD_SETSIZE) {

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

		printf("%4d %8s fd (%d) > FD_SETSIZE (%d)\n", *connectionId, "ERROR", fd, FD_SETSIZE);

		close(fd);

		return;

	}

	evutil_make_socket_nonblocking(fd);

	bev = bufferevent_socket_new(base, fd, BEV_OPT_CLOSE_ON_FREE);

	if (!bev) {

		printf("%4d %8s %s\n", *connectionId, "ERROR", "constructing bufferevent");

		event_base_loopbreak(base);

		return;

	}

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

	bufferevent_enable(bev, EV_READ | EV_WRITE);

	printf("%4d %8s somebody has connected: socketId = %d → connectionId = %d\n", *connectionId, "CONN", listener, *connectionId);

	print_socket_info(*connectionId, fd);

	bufferevent_write(bev, HELLO_MESSAGE.c_str(), strlen(HELLO_MESSAGE.c_str()));

}

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

	int connectionId = *((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 + 1);

	data[len] = 0; // as a string must be terminated by \0 

	evbuffer_copyout(input, data, len);

	//TODO: there might already be \0 in the byte stream, only the part before the first \0 will be formatted as a string

	string dataFormated(data);

	dataFormated = regex_replace(dataFormated, regex("\\n"), "\\n");

	printf("%4d %8s '%s'\n", connectionId, "IN", dataFormated.c_str());

	if (COMMAND_EXIT.compare(data) == 0) {

		struct timeval delay = {2, 123};

		printf("%4d %8s client asks us to terminate; finishing in %ld sesonds and %ld microseconds\n", connectionId, "EXIT", 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) {

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

	struct evbuffer *output = bufferevent_get_output(bev);

	if (evbuffer_get_length(output) == 0) {

		printf("%4d %8s\n", connectionId, "FLUSH");

		/* nebudeme ukončovat spojení

		bufferevent_free(bev);

		 */

	} else {

		// FIXME: sem to nikdy nepřijde

		size_t len = evbuffer_get_length(output);

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

		evbuffer_copyout(output, data, len);

		printf("%4d %8s '%s'\n", connectionId, "OUT", data);

		free(data);

	}

}

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

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

	if (events & BEV_EVENT_EOF) {

		printf("%4d %8s\n", connectionId, "CLOSE");

	} else if (events & BEV_EVENT_ERROR) {

		printf("%4d %8s %s\n", connectionId, "ERROR", strerror(errno));

	} else {

		printf("%4d %8s\n", connectionId, "OTHER");

		// 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("\n%4s %8s got SIGINT (Ctrl+C); finishing in %ld sesonds and %ld microseconds\n", "*", "SIGNAL", delay.tv_sec, delay.tv_usec);

	event_base_loopexit(base, &delay);

}

static void print_socket_info(int connectionId, int fd) {

	struct ucred cr;

	unsigned int cl = sizeof (cr);

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

		printf("%4d %8s client identification: pid=%d, uid=%d, gid=%d\n", connectionId, "CONN", cr.pid, cr.uid, cr.gid);

	}

}