#include <time.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <signal.h>

#include <nanomsg/nn.h>
#include <nanomsg/bus.h>
#include <nanomsg/ws.h>

#define MAX_LINE 1024

#define S(n) (1000000000 * ((long) n))
#define MS(n) (1000000 * ((long) n))

#define SENTINEL_TIMEOUT (MS(1500))
#define SENTINEL_DELAY (MS(200))

int timespec_diff_gt(struct timespec *before, struct timespec *after, long ns)
{
	/* be careful not to overflow the long... */
	long ss = ns / S(1) + 1;
	long ss_diff = after->tv_sec - before->tv_sec;
	if (ss_diff > ss)
		return 1;
	long ns_diff = ss_diff * S(1) + (after->tv_nsec - before->tv_nsec);
	return ns_diff > ns;
}

int killed = 0;
void handle_signal(int sig_num)
{
	killed = 1;
}


int main (int argc, char **argv)
{
	char *endpoint = "ws://norns.local:5555";
	int exit = 0;
	int s = 0;

	signal(SIGINT, handle_signal);
	signal(SIGTERM, handle_signal);

	/* Configure the websocket endpoint. */
	if (argc > 2 ||
	    (argc == 2 &&
	     (!strcmp(argv[1], "--help")
	      || !strcmp(argv[1], "-h")))) {
		fprintf(stderr,
			"Get a lua or supercollider shell on a norns.\n"
			"Usage: %s [ws://norns.local:5555]\n",
			argv[0]);
		goto error;
	}
	if (argc == 2) endpoint = argv[1];

	/* connect to the norns; use text, like it expects. */
	if ((s = nn_socket(AF_SP, NN_BUS)) < 0) {
		fprintf(stderr, "Can't create socket: %m\n");
		goto error;
	}
	if (nn_connect(s, endpoint) < 0) {
		fprintf(stderr, "Can't connect to %s: %m\n", endpoint);
		goto error;
	}
	if (nn_setsockopt(s,
			  NN_WS,
			  NN_WS_MSG_TYPE,
			  &(int) {NN_WS_MSG_TYPE_TEXT},
			  sizeof(int)) < 0) {
		fprintf(stderr, "Couldn't switch to text mode: %m\n");
		goto error;
	}

	/* since nanomsg has its own poll framework, we'll read to this
	   buffer in a nonblocking way until we get a newline. */
	size_t line_n = 0;
	char line[MAX_LINE + 1] = {0};
	
	int fl = 0;
	if ((fl = fcntl(STDIN_FILENO, F_GETFL)) < 0) {
		fprintf(stderr, "Couldn't read stdin fd flags: %m\n");
		goto error;
	}
	if (fcntl(STDIN_FILENO, F_SETFL, fl | O_NONBLOCK)) {
		fprintf(stderr, "Couldn't set stdin non-blocking: %m\n");
		goto error;
	}

	/* NN_BUS doesn't guarantee delivery, unfortunately.
	   in practice on a LAN this means that the first couple of
	   messages are dropped while the connection is being set up.
	   this seems strange to me (it seems like you'd have to go
	   out of your way to drop messages in a websocket handler?)
	   and I'm not sure this is the right fit for norns, but that's
	   how it is.

	   we partially solve this issue by sending an empty comment
	   -- as a sentinel -- repeatedly until we get the corresponding
	   <ok>.
	*/
	int received = 0;
	struct timespec began = {0};
	if (clock_gettime(CLOCK_MONOTONIC, &began)) {
		fprintf(stderr, "Can't use the clock? %m\n");
		goto error;
	}
	struct timespec sent_sentinel = {0};

	/* we'll also wait for one message after EOF... */
	int sent_last = 0;

	struct nn_pollfd poll_s = { .fd = s, .events = NN_POLLIN | NN_POLLOUT };
	while (!killed) {
		switch (nn_poll(&poll_s, 1, 1000)) {
		case -1:
			fprintf(stderr, "error polling: %m\n");
			goto error;
		case 0:
			fprintf(stderr, "# timeout...\n");
			break;
		case 1:
			/* If we can read, echo out the message (unless it's the
			   response to the sentinel, which we handle differently). */
			if (poll_s.revents & NN_POLLIN) {
				char *buf = NULL;
				size_t n = 0;
				if ((n = nn_recv(s, &buf, NN_MSG, 0)) < 0) {
					fprintf(stderr, "Couldn't receive: %m\n");
					goto error;
				}
				/* swallow the first <ok> */
				if (!received && !strncmp(buf, "<ok>\n\n", n)) {
					fprintf(stderr, "# it lives!\n");
				} else {
					/* strip final newline, if there are two... */
					if (n >= 2 && buf[n - 1] == '\n' && buf[n - 2] == '\n')
						n -= 1;
					if (write(STDOUT_FILENO, buf, n) < n) {
						fprintf(stderr, "Couldn't write: %m\n");
						goto error;
					}
					if (sent_last)
						goto finish;
				}
				nn_freemsg(buf);
				received = 1;
			}
			/* If we can write, see if there's a full line. */
			if (poll_s.revents & NN_POLLOUT) {
				if (!received) {
					struct timespec now = {0};
					if (clock_gettime(CLOCK_MONOTONIC, &now)) {
						fprintf(stderr, "Can't use the clock? %m\n");
						goto error;
					}
					/* if we've been waiting on sentinel response and
					   haven't gotten anything, time out. */
					if (timespec_diff_gt(&began, &now, SENTINEL_TIMEOUT)) {
						fprintf(stderr,
							"# timed out.\n"
							"# are you sure there's something "
							"listening at %s?\n",
							endpoint);
						goto error;
					}
					/* only do this once every SENTINEL_DELAY... */
					if (!timespec_diff_gt(&sent_sentinel,
							      &now,
							      SENTINEL_DELAY))
						break;
					memcpy(&sent_sentinel, &now, sizeof(struct timespec));
					
					/* send the sentinel comment */
					if (nn_send(s, "--\n", 3, 0) != 3) {
						fprintf(stderr, "Couldn't send: %m\n");
						goto error;
					}
				} else {
					int n = 0;
					if ((n = read(STDIN_FILENO,
						      &line[line_n],
						      MAX_LINE - line_n)) < 0) {
						if (errno != EAGAIN) {
							fprintf(stderr, "Can't read: %m\n");
							goto error;
						}
					}
					if (n == 0) sent_last = 1;
					/* treat EAGAIN as "read 0" */
					if (n < 1) n = 0;
					line_n += n;
					if (line_n >= 1 && line[line_n - 1] == '\n') {
						if ((nn_send(s, line, line_n, 0)) != line_n) {
							fprintf(stderr, "Can't send: %m\n");
							goto error;
						}
						line_n = 0;
					}
					if (line_n == MAX_LINE) {
						fprintf(stderr, "Line too long :(.\n");
						goto error;
					}
				}
			}
			break;
		}
	}
	goto finish;
error:
	exit = 1;
finish:
	if (s > 0) nn_close(s);
	return exit;
}