/*
 ioloop.c : I/O loop

    Copyright (c) 2002 Timo Sirainen

    Permission is hereby granted, free of charge, to any person obtaining
    a copy of this software and associated documentation files (the
    "Software"), to deal in the Software without restriction, including
    without limitation the rights to use, copy, modify, merge, publish,
    distribute, sublicense, and/or sell copies of the Software, and to
    permit persons to whom the Software is furnished to do so, subject to
    the following conditions:

    The above copyright notice and this permission notice shall be
    included in all copies or substantial portions of the Software.

    THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
    OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
    MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
    IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
    CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
    TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
    SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/

/* FIXME: inserting io is slow if there's lots of them. I should add a linked
   list of priorities pointing to first item in the list with the priority. */

#include "lib.h"
#include "ioloop-internal.h"

#undef timercmp
#define timercmp(tvp, uvp) \
	((tvp)->tv_sec > (uvp)->tv_sec || \
	 ((tvp)->tv_sec == (uvp)->tv_sec && \
	  (tvp)->tv_usec > (uvp)->tv_usec))

time_t ioloop_time = 0;
struct timeval ioloop_timeval;
struct timezone ioloop_timezone;

static struct ioloop *current_ioloop = NULL;

static void update_highest_fd(struct ioloop *ioloop)
{
        struct io *io;
	int max_highest_fd;

        max_highest_fd = ioloop->highest_fd-1;
	ioloop->highest_fd = -1;

	for (io = ioloop->ios; io != NULL; io = io->next) {
		if (!io->destroyed && io->fd > ioloop->highest_fd) {
			ioloop->highest_fd = io->fd;

			if (ioloop->highest_fd == max_highest_fd)
                                break;
		}
	}
}

static void io_list_insert(struct ioloop *ioloop, struct io *io)
{
	struct io *prev, *next;

        prev = NULL;
	for (next = ioloop->ios; next != NULL; next = next->next) {
		if (next->priority >= io->priority)
                        break;
                prev = next;
	}

	if (prev == NULL)
                ioloop->ios = io;
	else {
		io->prev = prev;
                prev->next = io;
	}

	if (next != NULL) {
		io->next = next;
		next->prev = io;
	}
}

struct io *io_add(int fd, int condition, io_callback_t *callback, void *data)
{
	return io_add_priority(fd, IO_PRIORITY_DEFAULT,
			       condition, callback, data);
}

struct io *io_add_priority(int fd, int priority, int condition,
			   io_callback_t *callback, void *context)
{
	struct io *io;

	i_assert(fd >= 0);
	i_assert(callback != NULL);

	io = p_new(current_ioloop->pool, struct io, 1);
	io->fd = fd;
	io->priority = priority;
        io->condition = condition;

	io->callback = callback;
        io->context = context;

	if (io->fd > current_ioloop->highest_fd)
                current_ioloop->highest_fd = io->fd;

        io_loop_handle_add(current_ioloop, io->fd, io->condition);
	io_list_insert(current_ioloop, io);

	return io;
}

void io_remove(struct io *io)
{
	i_assert(io != NULL);
	i_assert(io->fd >= 0);
	i_assert(io->fd <= current_ioloop->highest_fd);

        /* notify the real I/O handler */
	io_loop_handle_remove(current_ioloop, io->fd, io->condition);

        /* check if we removed the highest fd */
	if (io->fd == current_ioloop->highest_fd)
                update_highest_fd(current_ioloop);

	io->destroyed = TRUE;
	io->fd = -1;
}

void io_destroy(struct ioloop *ioloop, struct io *io)
{
        /* remove from list */
	if (io->prev == NULL)
                ioloop->ios = io->next;
	else
		io->prev->next = io->next;

	if (io->next != NULL)
		io->next->prev = io->prev;

	p_free(ioloop->pool, io);
}

static void timeout_list_insert(struct ioloop *ioloop, struct timeout *timeout)
{
	struct timeout **t;
        struct timeval *next_run;

        next_run = &timeout->next_run;
	for (t = &ioloop->timeouts; *t != NULL; t = &(*t)->next) {
		if (timercmp(&(*t)->next_run, next_run))
                        break;
	}

        timeout->next = *t;
        *t = timeout;
}

static void timeout_update_next(struct timeout *timeout, struct timeval *tv_now)
{
	if (tv_now == NULL) {
		if (gettimeofday(&timeout->next_run, NULL) < 0)
			i_fatal("gettimeofday(): %m");
	} else {
                timeout->next_run.tv_sec = tv_now->tv_sec;
                timeout->next_run.tv_usec = tv_now->tv_usec;
	}

	/* we don't want microsecond accuracy or this function will be
	   called all the time - millisecond is more than enough */
	timeout->next_run.tv_usec -= timeout->next_run.tv_usec % 1000;

	timeout->next_run.tv_sec += timeout->msecs/1000;
	timeout->next_run.tv_usec += (timeout->msecs%1000)*1000;

	if (timeout->next_run.tv_usec > 1000000) {
                timeout->next_run.tv_sec++;
                timeout->next_run.tv_usec -= 1000000;
	}
}

struct timeout *timeout_add(int msecs, timeout_callback_t *callback,
			    void *context)
{
	struct timeout *timeout;

	timeout = p_new(current_ioloop->pool, struct timeout, 1);
        timeout->msecs = msecs;

	timeout->callback = callback;
	timeout->context = context;

	timeout_update_next(timeout, current_ioloop->running ?
			    NULL : &ioloop_timeval);
        timeout_list_insert(current_ioloop, timeout);
	return timeout;
}

void timeout_remove(struct timeout *timeout)
{
	i_assert(timeout != NULL);

	timeout->destroyed = TRUE;
}

void timeout_destroy(struct ioloop *ioloop, struct timeout *timeout)
{
	struct timeout **t;

	for (t = &ioloop->timeouts; *t != NULL; t = &(*t)->next) {
		if (*t == timeout)
			break;
	}
	*t = timeout->next;

        p_free(ioloop->pool, timeout);
}

int io_loop_get_wait_time(struct timeout *timeout, struct timeval *tv,
			  struct timeval *tv_now)
{
	if (timeout == NULL)
		return INT_MAX;

	if (tv_now == NULL) {
		if (gettimeofday(tv, NULL) < 0)
			i_fatal("gettimeofday(): %m");
	} else {
		tv->tv_sec = tv_now->tv_sec;
		tv->tv_usec = tv_now->tv_usec;
	}

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

	if (tv->tv_sec > 0 || (tv->tv_sec == 0 && tv->tv_usec > 0))
		return tv->tv_sec*1000 + tv->tv_usec/1000;

	/* no need to calculate the times again with this timeout */
        tv->tv_sec = tv->tv_usec = 0;
	timeout->run_now = TRUE;
        return 0;
}

void io_loop_handle_timeouts(struct ioloop *ioloop)
{
	struct timeout *t, *next;
	struct timeval tv;
        unsigned int t_id;

	if (gettimeofday(&ioloop_timeval, &ioloop_timezone) < 0)
		i_fatal("gettimeofday(): %m");
	ioloop_time = ioloop_timeval.tv_sec;

	if (ioloop->timeouts == NULL || !ioloop->timeouts->run_now)
		return;

	for (t = ioloop->timeouts; t != NULL; t = next) {
		next = t->next;

		if (t->destroyed) {
                        timeout_destroy(ioloop, t);
			continue;
		}

		if (!t->run_now) {
			io_loop_get_wait_time(t, &tv, &ioloop_timeval);

			if (!t->run_now)
				break;
		}

                t->run_now = FALSE;
                timeout_update_next(t, &ioloop_timeval);

                t_id = t_push();
		t->callback(t->context);
		if (t_pop() != t_id)
                        i_panic("Leaked a t_pop() call!");
	}
}

void io_loop_run(struct ioloop *ioloop)
{
        ioloop->running = TRUE;
	while (ioloop->running)
		io_loop_handler_run(ioloop);
}

void io_loop_stop(struct ioloop *ioloop)
{
        ioloop->running = FALSE;
}

void io_loop_set_running(struct ioloop *ioloop)
{
        ioloop->running = TRUE;
}

int io_loop_is_running(struct ioloop *ioloop)
{
        return ioloop->running;
}

struct ioloop *io_loop_create(pool_t pool)
{
	struct ioloop *ioloop;

	/* initialize time */
	if (gettimeofday(&ioloop_timeval, &ioloop_timezone) < 0)
		i_fatal("gettimeofday(): %m");
	ioloop_time = ioloop_timeval.tv_sec;

        ioloop = p_new(pool, struct ioloop, 1);
	pool_ref(pool);
	ioloop->pool = pool;
	ioloop->highest_fd = -1;

	io_loop_handler_init(ioloop);

	ioloop->prev = current_ioloop;
        current_ioloop = ioloop;

        return ioloop;
}

void io_loop_destroy(struct ioloop *ioloop)
{
	while (ioloop->ios != NULL) {
		struct io *io = ioloop->ios;

		if (!io->destroyed) {
			i_warning("I/O leak: %p (%d)",
				  (void *) io->callback, io->fd);
			io_remove(io);
		}
		io_destroy(ioloop, io);
	}

	while (ioloop->timeouts != NULL) {
		struct timeout *to = ioloop->timeouts;

		if (!to->destroyed) {
			i_warning("Timeout leak: %p", (void *) to->callback);
			timeout_remove(to);
		}
                timeout_destroy(ioloop, to);
	}

        io_loop_handler_deinit(ioloop);

        /* ->prev won't work unless loops are destroyed in create order */
        i_assert(ioloop == current_ioloop);
	current_ioloop = current_ioloop->prev;

	pool_unref(ioloop->pool);
}