/*
 * event.h
 */

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2009 Maksim Yevmenkin <m_evmenkin@yahoo.com>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */


/*
 * Hack to provide libevent (see devel/libevent port) like API.
 * Should be removed if FreeBSD ever decides to import libevent into base.
 */

#include <sys/select.h>
#include <sys/time.h>
#include <sys/queue.h>
#include <assert.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>
#include <syslog.h>

#include "event.h"
#define L2CAP_SOCKET_CHECKED
#include "btpand.h"

#define         __event_link(ev) \
do { \
                TAILQ_INSERT_TAIL(&pending, ev, next); \
                ev->flags |= EV_PENDING; \
} while (0)

static void     tv_add(struct timeval *, struct timeval const *);
static void     tv_sub(struct timeval *, struct timeval const *);
static int      tv_cmp(struct timeval const *, struct timeval const *);
static int      __event_dispatch(void);
static void     __event_add_current(struct event *);
static void     __event_del_current(struct event *);


static TAILQ_HEAD(, event)      pending;
static TAILQ_HEAD(, event)      current;

void
event_init(void)
{
        TAILQ_INIT(&pending);
}

int
event_dispatch(void)
{
        while (__event_dispatch() == 0)
                ;

        return (-1);
}

static int
__event_dispatch(void)
{
        fd_set                  r, w;
        int                     nfd;
        struct event            *ev;
        struct timeval          now, timeout, t;

        FD_ZERO(&r);
        FD_ZERO(&w);

        nfd = 0;

        gettimeofday(&now, NULL);

        timeout.tv_sec = 10;    /* arbitrary */
        timeout.tv_usec = 0;

        TAILQ_INIT(&current);

        /*
         * Build fd_set's
         */

        event_log_debug("%s: building fd set...", __func__);

        while (!TAILQ_EMPTY(&pending)) {
                ev = TAILQ_FIRST(&pending);
                event_del(ev);

                if (ev->flags & EV_HAS_TIMEOUT) {
                        if (tv_cmp(&now, &ev->expire) >= 0)
                                t.tv_sec = t.tv_usec = 0;
                        else {
                                t = ev->expire;
                                tv_sub(&t, &now);
                        }

                        if (tv_cmp(&t, &timeout) < 0)
                                timeout = t;
                }

                if (ev->fd >= 0) {
                        if (ev->flags & EV_READ) {
                                FD_SET(ev->fd, &r);
                                nfd = (nfd > ev->fd) ? nfd : ev->fd;
                        }

                        if (ev->flags & EV_WRITE) {
                                FD_SET(ev->fd, &w);
                                nfd = (nfd > ev->fd) ? nfd : ev->fd;
                        }
                }

                __event_add_current(ev);
        }

        event_log_debug("%s: waiting for events...", __func__);

        nfd = select(nfd + 1, &r, &w, NULL, &timeout);
        if (nfd < 0)
                return (-1);

        /*
         * Process current pending
         */

        event_log_debug("%s: processing events...", __func__);

        gettimeofday(&now, NULL);

        while (!TAILQ_EMPTY(&current)) {
                ev = TAILQ_FIRST(&current);
                __event_del_current(ev);

                /* check if fd is ready for reading/writing */
                if (nfd > 0 && ev->fd >= 0) {
                        if (FD_ISSET(ev->fd, &r) || FD_ISSET(ev->fd, &w)) {
                                if (ev->flags & EV_PERSIST) {
                                        if (ev->flags & EV_HAS_TIMEOUT)
                                                event_add(ev, &ev->timeout);
                                        else
                                                event_add(ev, NULL);
                                }

                                nfd --;

                                event_log_debug("%s: calling %p(%d, %p), " \
                                        "ev=%p", __func__, ev->cb, ev->fd,
                                        ev->cbarg, ev);

                                (ev->cb)(ev->fd,
                                        (ev->flags & (EV_READ|EV_WRITE)),
                                        ev->cbarg);

                                continue;
                        }
                }

                /* if event has no timeout - just requeue */
                if ((ev->flags & EV_HAS_TIMEOUT) == 0) {
                        event_add(ev, NULL);
                        continue;
                }

                /* check if event has expired */
                if (tv_cmp(&now, &ev->expire) >= 0) {
                        if (ev->flags & EV_PERSIST) 
                                event_add(ev, &ev->timeout);

                        event_log_debug("%s: calling %p(%d, %p), ev=%p",
                                __func__, ev->cb, ev->fd, ev->cbarg, ev);

                        (ev->cb)(ev->fd,
                                (ev->flags & (EV_READ|EV_WRITE)),
                                ev->cbarg);

                        continue;
                }

                assert((ev->flags & (EV_PENDING|EV_CURRENT)) == 0);
                __event_link(ev);
        }

        return (0);
}

void
__event_set(struct event *ev, int fd, short flags,
        void (*cb)(int, short, void *), void *cbarg)
{
        ev->fd = fd;
        ev->flags = flags;
        ev->cb = cb;
        ev->cbarg = cbarg;
}

int
__event_add(struct event *ev, const struct timeval *timeout)
{
        assert((ev->flags & (EV_PENDING|EV_CURRENT)) == 0);

        if (timeout != NULL) {
                gettimeofday(&ev->expire, NULL);
                tv_add(&ev->expire, timeout);
                ev->timeout = *timeout;
                ev->flags |= EV_HAS_TIMEOUT;
        } else
                ev->flags &= ~EV_HAS_TIMEOUT;

        __event_link(ev);

        return (0);
}

int
__event_del(struct event *ev)
{
        assert((ev->flags & EV_CURRENT) == 0);

        if ((ev->flags & EV_PENDING) != 0) {
                TAILQ_REMOVE(&pending, ev, next);
                ev->flags &= ~EV_PENDING;
        }

        return (0);
}

static void
__event_add_current(struct event *ev)
{
        assert((ev->flags & (EV_PENDING|EV_CURRENT)) == 0);

        TAILQ_INSERT_TAIL(&current, ev, next);
        ev->flags |= EV_CURRENT;
}

static void
__event_del_current(struct event *ev)
{
        assert((ev->flags & (EV_CURRENT|EV_PENDING)) == EV_CURRENT);

        TAILQ_REMOVE(&current, ev, next);
        ev->flags &= ~EV_CURRENT;
}

static void
tv_add(struct timeval *a, struct timeval const *b)
{
        a->tv_sec += b->tv_sec;
        a->tv_usec += b->tv_usec;

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

static void
tv_sub(struct timeval *a, struct timeval const *b)
{
        if (a->tv_usec < b->tv_usec) {
                a->tv_usec += 1000000;
                a->tv_sec -= 1;
        }

        a->tv_usec -= b->tv_usec;
        a->tv_sec -= b->tv_sec;
}

static int
tv_cmp(struct timeval const *a, struct timeval const *b)
{
        if (a->tv_sec > b->tv_sec)
                return (1);

        if (a->tv_sec < b->tv_sec)
                return (-1);

        if (a->tv_usec > b->tv_usec)
                return (1);

        if (a->tv_usec < b->tv_usec)
                return (-1);

        return (0);
}