/*
 * Copyright (c) 2006, Stefan Walter
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *	 * Redistributions of source code must retain the above
 *	   copyright notice, this list of conditions and the
 *	   following disclaimer.
 *	 * Redistributions in binary form must reproduce the
 *	   above copyright notice, this list of conditions and
 *	   the following disclaimer in the documentation and/or
 *	   other materials provided with the distribution.
 *	 * The names of contributors to this software may not be
 *	   used to endorse or promote products derived from this
 *	   software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

#include "config.h"
#include "server-mainloop.h"

#include <sys/time.h>

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#ifdef HAVE_PTHREAD
#include <pthread.h>
#endif

typedef struct _socket_callback {
	int fd;
	server_socket_callback callback;
	void *arg;
	int closed;

	struct _socket_callback *next;
} socket_callback;

typedef struct _timer_callback {
	struct timeval at;
	struct timeval interval;
	server_timer_callback callback;
	void* arg;
	int closed;

	struct _timer_callback *next;
} timer_callback;

typedef struct _server_context {
	int stopped;
	fd_set read_fds;
	fd_set write_fds;
	int max_fd;
	int revision;
	socket_callback *callbacks;
	timer_callback *timers;
	int wakeup[2];
#ifdef HAVE_PTHREAD
	pthread_mutex_t mutex;
#endif
} server_context;

#ifdef HAVE_PTHREAD
#define LOCK() pthread_mutex_lock (&ctx.mutex)
#define UNLOCK() pthread_mutex_unlock (&ctx.mutex)
#else
#define LOCK()
#define UNLOCK()
#endif

/* Global context */
static server_context ctx;

static void
timeval_add(struct timeval *t1, struct timeval *t2)
{
	assert (t1->tv_usec < 1000000);
	assert (t2->tv_usec < 1000000);

	t1->tv_sec += t2->tv_sec;
	t1->tv_usec += t2->tv_usec;
	if (t1->tv_usec >= 1000000) {
		t1->tv_usec -= 1000000;
		t1->tv_sec += 1;
	}
}

static void
timeval_subtract (struct timeval *t1, struct timeval *t2)
{
	assert (t1->tv_usec < 1000000);
	assert (t2->tv_usec < 1000000);

	t1->tv_sec -= t2->tv_sec;
	if (t1->tv_usec < t2->tv_usec) {
		t1->tv_usec += 1000000;
		t1->tv_sec -= 1;
	}
	t1->tv_usec -= t2->tv_usec;
}

static int
timeval_compare(struct timeval *t1, struct timeval *t2)
{
	assert (t1->tv_usec < 1000000);
	assert (t2->tv_usec < 1000000);

	if (t1->tv_sec > t2->tv_sec)
		return 1;
	else if (t1->tv_sec < t2->tv_sec)
		return -1;
	else {
		if (t1->tv_usec > t2->tv_usec)
			return 1;
		else if (t1->tv_usec < t2->tv_usec)
			return -1;
		else
			return 0;
	}
}

#define timeval_empty(tv) \
	((tv)->tv_sec == 0 && (tv)->tv_usec == 0)

#define timeval_to_ms(tv) \
	((((uint64_t)(tv).tv_sec) * 1000L) + (((uint64_t)(tv).tv_usec) / 1000L))

#define timeval_dump(tv) \
	(fprintf(stderr, "{ %d:%d }", (uint)((tv).tv_sec), (uint)((tv).tv_usec / 1000)))

static int
add_timer (int ms, int oneshot, server_timer_callback callback, void *arg)
{
	struct timeval interval;
	timer_callback *cb;

	assert (ms || oneshot);
	assert (callback != NULL);

	interval.tv_sec = ms / 1000;
	interval.tv_usec = (ms % 1000) * 1000; /* into micro seconds */

	cb = (timer_callback*)calloc (1, sizeof (*cb));
	if(!cb) {
		errno = ENOMEM;
		return -1;
	}

	if (gettimeofday (&(cb->at), NULL) == -1) {
		free(cb);
		return -1;
	}

	timeval_add (&(cb->at), &interval);

	if (oneshot)
		memset (&(cb->interval), 0, sizeof (cb->interval));
	else
		memcpy (&(cb->interval), &interval, sizeof(cb->interval));

	cb->callback = callback;
	cb->arg = arg;

	cb->next = ctx.timers;
	ctx.timers = cb;
	++ctx.revision;
	server_wakeup ();

	return 0;
}

static void
remove_closed (void)
{
	timer_callback **tcb, *timcb;
	socket_callback **scb, *sockcb;

	for (tcb = &ctx.timers; *tcb; ) {
		timcb = *tcb;
		if (timcb->closed) {
			*tcb = timcb->next;
			free (timcb);
			continue;
		} else {
			tcb = &timcb->next;
		}
	}

	for (scb = &ctx.callbacks; *scb; ) {
		sockcb = *scb;
		if (sockcb->closed) {
			*scb = sockcb->next;
			free (sockcb);
			continue;
		} else {
			scb = &sockcb->next;
		}
	}
}

int
server_init (void)
{
	memset (&ctx, 0, sizeof (ctx));

	if (pipe (ctx.wakeup) < 0)
		return -1;

	FD_ZERO (&ctx.read_fds);
	FD_ZERO (&ctx.write_fds);

	/* The wakeup descriptor */
	FD_SET (ctx.wakeup[0], &ctx.read_fds);
	fcntl (ctx.wakeup[0], F_SETFL, fcntl (ctx.wakeup[0], F_GETFL, 0) | O_NONBLOCK);

	ctx.max_fd = ctx.wakeup[0] + 1;

	ctx.stopped = 1;
	ctx.callbacks = NULL;
	ctx.timers = NULL;


#ifdef HAVE_PTHREAD
	{
		int ret = pthread_mutex_init (&ctx.mutex, NULL);
		if (ret != 0) {
			errno = ret;
			close (ctx.wakeup[0]);
			close (ctx.wakeup[1]);
			return -1;
		}
	}
#endif

	return 0;
}

void
server_uninit (void)
{
	timer_callback *timcb;
	timer_callback *timn;
	socket_callback *sockcb;
	socket_callback *sockn;

	LOCK ();

	for(timcb = ctx.timers; timcb; timcb = timn) {
		timn = timcb->next;
		free (timcb);
	}

	ctx.timers = NULL;

	for(sockcb = ctx.callbacks; sockcb; sockcb = sockn) {
		sockn = sockcb->next;
		free (sockcb);
	}

	ctx.callbacks = NULL;

	UNLOCK ();

#ifdef HAVE_PTHREAD
	pthread_mutex_destroy (&ctx.mutex);
#endif
}

uint64_t
server_get_time (void)
{
	struct timeval tv;
	if (gettimeofday (&tv, NULL) == -1)
		return 0L;
	return timeval_to_ms (tv);
}

int
server_run (void)
{
	char buffer[16];
	struct timeval *timeout;
	struct timeval tv, current;
	timer_callback *timcb;
	socket_callback *sockcb;
	fd_set rfds, wfds;
	int r, revision, max_fd;
	int ret = 0;

	/* For doing lock safe callbacks */
	int type, fd;
	server_socket_callback scb;
	server_timer_callback tcb;
	void *arg;

	LOCK ();

	/* No watches have been set */
	assert (ctx.max_fd > -1);

	ctx.stopped = 0;
	ctx.revision = 0;

	while (!ctx.stopped)  {

		/* Drain the wakeup if necessary */
		while (read (ctx.wakeup[0], buffer, sizeof (buffer)) > 0);

		/* Watch for the various fds */
		memcpy (&rfds, &ctx.read_fds, sizeof (rfds));
		memcpy (&wfds, &ctx.write_fds, sizeof (wfds));

		/* Prepare for timers */
		timeout = NULL;
		if (gettimeofday (&current, NULL) == -1) {
			ret = -1;
			break;
		}

		/* Cycle through timers */
		for (timcb = ctx.timers; timcb; timcb = timcb->next) {
			assert (timcb->callback);

			if (timcb->closed)
				continue;

			/* Call any timers that have already passed */
			if (timeval_compare (&current, &timcb->at) >= 0) {

				/* Do a lock safe callback */
				tcb = timcb->callback;
				arg = timcb->arg;

				/* Convert to milliseconds, and make the call */
				UNLOCK ();
				r = (tcb) (timeval_to_ms (current), arg);
				LOCK ();

				/* Reset timer if so desired */
				if (r == 1 && !timeval_empty (&timcb->interval)) {
					timeval_add (&timcb->at, &timcb->interval);

					/* If the time has already passed, just use current time */
					if (timeval_compare (&(timcb->at), &current) <= 0)
						memcpy (&(timcb->at), &current, sizeof (timcb->at));

				/* Otherwise remove it. Either one shot, or returned 0 */
				} else {
					timcb->closed = 1;
					continue;
				}
			}

			/* Get soonest timer */
			if (!timeout || timeval_compare (&timcb->at, timeout) < 0)
				timeout = &timcb->at;
		}

		/* Convert to an offset */
		if (timeout) {
			memcpy (&tv, timeout, sizeof (tv));
			timeout = &tv;
			timeval_subtract (timeout, &current);
		}

		if (ctx.stopped)
			continue;

		remove_closed ();

		/* No callbacks? No use continuing */
		if (!ctx.callbacks && !ctx.timers)
			break;

		/* fprintf(stderr, "selecting with timeout: ");
		   timeval_dump(timeout);
		   fprintf(stderr, "\n"); */

		/* We can see if changes happen while in select */
		revision = ctx.revision;
		max_fd = ctx.max_fd;

		UNLOCK ();
		r = select (max_fd, &rfds, &wfds, NULL, timeout);
		LOCK ();

		if (r < 0) {
			/* Interrupted so try again, and possibly exit */
			if (errno == EINTR)
				continue;

			if (errno == EBADF) {
				if (ctx.revision != revision)
					continue;
				assert (0 && "bad file descriptor being watched");
			}

			/* Programmer errors */
			assert (errno != EINVAL);
			ret = -1;
			break;
		}

		/* Timeout, just jump to timeout processing */
		if(r == 0)
			continue;

		/* Process ready file descriptors */
		for (sockcb = ctx.callbacks; sockcb; sockcb = sockcb->next) {
			assert (sockcb->fd != -1);
			if (sockcb->closed)
				continue;

			/* Call any that are set */
			type = 0;
			if (FD_ISSET (sockcb->fd, &rfds))
				type = SERVER_READ;
			if (FD_ISSET (sockcb->fd, &wfds))
				type = SERVER_WRITE;

			/* Lock safe callback */
			if (type != 0) {
				scb = sockcb->callback;
				fd = sockcb->fd;
				arg = sockcb->arg;

				UNLOCK ();
					(scb) (fd, type, arg);
				LOCK ();
			}
		}
	}

	UNLOCK ();
	return ret;
}

void
server_wakeup (void)
{
	/*
	 * This can be called from within arbitrary
	 * locks, so be careful.
	 */
	int r = write (ctx.wakeup[1], "a", 1);
	fprintf (stderr, "wakeup: %d\n", r);
}

void
server_stop (void)
{
	/*
	 * This could be called from a signal handler,
	 * so it's not worth trying to lock.
	 */
	ctx.stopped = 1;
	server_wakeup ();
}

int
server_stopped (void)
{
	return ctx.stopped;
}

int
server_watch (int fd, int type, server_socket_callback callback, void *arg)
{
	socket_callback *cb;
	assert (type != 0);
	assert (fd != -1);
	assert (callback != NULL);

	cb = (socket_callback*)calloc (sizeof(*cb), 1);
	if(!cb) {
		errno = ENOMEM;
		return -1;
	}

	LOCK ();

	cb->fd = fd;
	cb->callback = callback;
	cb->arg = arg;

	cb->next = ctx.callbacks;
	ctx.callbacks = cb;

	if (type & SERVER_READ)
		FD_SET (fd, &ctx.read_fds);
	if (type & SERVER_WRITE)
		FD_SET (fd, &ctx.write_fds);

	if (fd >= ctx.max_fd)
		ctx.max_fd = fd + 1;

	++ctx.revision;
	server_wakeup ();

	UNLOCK ();

	return 0;
}

void
server_unwatch (int fd)
{
	socket_callback* cb;

	assert (fd != -1);

	LOCK ();

	FD_CLR (fd, &ctx.read_fds);
	FD_CLR (fd, &ctx.write_fds);

	if (!ctx.callbacks)
		goto done;

	/* First in list */;
	if (ctx.callbacks->fd == fd) {
		ctx.callbacks->closed = 1;
		goto done;
	}

	/* One ahead processing of rest */
	for (cb = ctx.callbacks; cb->next; cb = cb->next) {
		if (cb->next->fd == fd) {
			cb->next->closed = 1;
			goto done;
		}
	}

done:
	server_wakeup ();
	++ctx.revision;
	UNLOCK ();
}

int
server_timer (int ms, server_timer_callback callback, void *arg)
{
	int ret;

	LOCK ();
	ret = add_timer (ms, 0, callback, arg);
	UNLOCK ();

	return ret;
}

int
server_oneshot (int ms, server_timer_callback callback, void *arg)
{
	int ret;

	LOCK ();
	ret = add_timer (ms, 1, callback, arg);
	UNLOCK ();

	return ret;
}