/***************************************************************************
 *   Copyright (C) 10/2006 by Olaf Rempel                                  *
 *   razzor@kopf-tisch.de                                                  *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the                         *
 *   Free Software Foundation, Inc.,                                       *
 *   59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.             *
 ***************************************************************************/
#include <stdlib.h>
#include <unistd.h>
#include <string.h>

#include <sys/time.h>
#include <sys/types.h>

#include "list.h"
#include "logging.h"

#include "event.h"

#define FD_TYPE		(FD_READ | FD_WRITE | FD_EXCEPT)
#define FD_NEW		0x10
#define FD_DELETE	0x20

static LIST_HEAD(fd_list);
static LIST_HEAD(timeout_list);

struct fd_entry {
	struct list_head list;
	int fd;
	int flags;
	int (*callback)(int fd, void *privdata);
	void *privdata;
};

struct timeout_entry {
	struct list_head list;
	struct timeval timeout;
	struct timeval nextrun;
	int (*callback)(void *privdata);
	void *privdata;
};

int event_add_fd(int fd, int type, int (*callback)(int fd, void *privdata), void *privdata)
{
	if (fd < 0 || fd > FD_SETSIZE || type == 0)
		return -1;

	struct fd_entry *entry;
	entry = malloc(sizeof(struct fd_entry));
	if (entry == NULL) {
		log_print(LOG_ERROR, "event_add_fd(): out of memory");
		return -1;
	}

	entry->fd = fd;
	entry->flags = (type & FD_TYPE) | FD_NEW;
	entry->callback = callback;
	entry->privdata = privdata;

	list_add_tail(&entry->list, &fd_list);
	return 0;
}

int event_remove_fd(int fd)
{
	struct fd_entry *entry, *tmp;
	list_for_each_entry_safe(entry, tmp, &fd_list, list) {
		if (entry->fd == fd) {
			entry->flags |= FD_DELETE;
			return 0;
		}
	}
	return -1;
}

static void calc_nextrun(struct timeval *timeout, struct timeval *nextrun)
{
	struct timeval now;
	gettimeofday(&now, NULL);

	nextrun->tv_usec = now.tv_usec + timeout->tv_usec;
	nextrun->tv_sec = now.tv_sec + timeout->tv_sec;

	if (nextrun->tv_usec >= 1000000) {
		nextrun->tv_usec -= 1000000;
		nextrun->tv_sec++;
	}
}

static void calc_timeout(struct timeval *timeout, struct timeval *nextrun)
{
	struct timeval now;
	gettimeofday(&now, NULL);

	timeout->tv_usec = nextrun->tv_usec - now.tv_usec;
	timeout->tv_sec = nextrun->tv_sec - now.tv_sec;

	if (timeout->tv_usec < 0) {
		timeout->tv_usec += 1000000;
		timeout->tv_sec--;
	}
}

static void schedule_nextrun(struct timeout_entry *entry)
{
	struct timeout_entry *search;

	list_for_each_entry(search, &timeout_list, list) {
		if (search->nextrun.tv_sec > entry->nextrun.tv_sec) {
			list_add_tail(&entry->list, &search->list);
			return;

		} else if (search->nextrun.tv_sec == entry->nextrun.tv_sec &&
			   search->nextrun.tv_usec > entry->nextrun.tv_usec) {
				list_add_tail(&entry->list, &search->list);
				return;
		}
	}
	list_add_tail(&entry->list, &timeout_list);
}

int event_add_timeout(struct timeval *timeout, int (*callback)(void *privdata), void *privdata)
{
	struct timeout_entry *entry;
	entry = malloc(sizeof(struct timeout_entry));
	if (entry == NULL) {
		log_print(LOG_ERROR, "event_add_timeout(): out of memory");
		return -1;
	}

	memcpy(&entry->timeout, timeout, sizeof(entry->timeout));
	entry->callback = callback;
	entry->privdata = privdata;

	calc_nextrun(&entry->timeout, &entry->nextrun);
	schedule_nextrun(entry);
	return 0;
}

int event_loop(void)
{
	fd_set *fdsets = malloc(sizeof(fd_set) * 3);
	if (fdsets == NULL) {
		log_print(LOG_ERROR, "event_loop(): out of memory");
		return -1;
	}

	while (1) {
		fd_set *readfds = NULL, *writefds = NULL, *exceptfds = NULL;
		struct fd_entry *entry, *tmp;
		list_for_each_entry_safe(entry, tmp, &fd_list, list) {
			entry->flags &= ~FD_NEW;

			if (entry->flags & FD_DELETE) {
				log_print(LOG_DEBUG, "event_loop: delete FD: %d (%p/%p)", entry->fd, entry->callback, entry->privdata);
				list_del(&entry->list);
				free(entry);

			} else if ((entry->flags & FD_READ) != 0) {
				if (readfds == NULL) {
					readfds = &fdsets[0];
					FD_ZERO(readfds);
				}
				log_print(LOG_DEBUG, "event_loop: read FD: %d (%p/%p)", entry->fd, entry->callback, entry->privdata);
				FD_SET(entry->fd, readfds);

			} else if ((entry->flags & FD_WRITE) != 0) {
				if (writefds == NULL) {
					writefds = &fdsets[1];
					FD_ZERO(writefds);
				}
				log_print(LOG_DEBUG, "event_loop: write FD: %d (%p/%p)", entry->fd, entry->callback, entry->privdata);
				FD_SET(entry->fd, writefds);

			} else if ((entry->flags & FD_EXCEPT) != 0) {
				if (exceptfds == NULL) {
					exceptfds = &fdsets[2];
					FD_ZERO(exceptfds);
				}
				log_print(LOG_DEBUG, "event_loop: except FD: %d (%p/%p)", entry->fd, entry->callback, entry->privdata);
				FD_SET(entry->fd, exceptfds);
			}
		}

		struct timeval timeout, *timeout_p = NULL;
		if (!list_empty(&timeout_list)) {
			struct timeout_entry *entry, *tmp;
			list_for_each_entry_safe(entry, tmp, &timeout_list, list) {

				calc_timeout(&timeout, &entry->nextrun);
				if (timeout.tv_sec >= 0 && timeout.tv_usec > 0) {
					timeout_p = &timeout;
					break;
				}

				// delayed timeout, exec NOW!
				list_del(&entry->list);
				int ret = entry->callback(entry->privdata);
				if (ret == 0) {
					calc_nextrun(&entry->timeout, &entry->nextrun);
					schedule_nextrun(entry);

				} else {
					free(entry);
				}
			}
		}

		log_print(LOG_DEBUG, "");

		int i = select(FD_SETSIZE, readfds, writefds, exceptfds, timeout_p);
		if (i < 0) {
			/* On error, -1 is returned, and errno is set
			 * appropriately; the sets and timeout become
			 * undefined, so do not rely on their contents
			 * after an error.
			 */
			continue;

		} else if (i == 0 && !list_empty(&timeout_list)) {
			struct timeout_entry *entry;
			entry = list_entry(timeout_list.next, typeof(*entry), list);
			list_del(&entry->list);

			int ret = entry->callback(entry->privdata);
			if (ret == 0) {
				calc_nextrun(&entry->timeout, &entry->nextrun);
				schedule_nextrun(entry);

			} else {
				free(entry);
			}

		} else {
			list_for_each_entry(entry, &fd_list, list) {
				if ((entry->flags & FD_NEW) != 0) {
					continue;

				} else if ((entry->flags & FD_READ) != 0) {
					if (!FD_ISSET(entry->fd, readfds))
						continue;

				} else if ((entry->flags & FD_WRITE) != 0) {
					if (!FD_ISSET(entry->fd, writefds))
						continue;

				} else if ((entry->flags & FD_EXCEPT) != 0) {
					if (!FD_ISSET(entry->fd, exceptfds))
						continue;
				}

				if (entry->callback(entry->fd, entry->privdata) != 0)
					entry->flags |= FD_DELETE;
			}
		}
	}
	free(fdsets);
}