/* Copyright (c) 2002-2007 Timo Sirainen */

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

#include <unistd.h>

/* If time moves backwards more than this, kill ourself instead of sleeping. */
#define IOLOOP_MAX_TIME_BACKWARDS_SLEEP 5

#define timer_is_larger(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;

struct ioloop *current_ioloop = NULL;

#undef io_add
struct io *io_add(int fd, enum io_condition condition,
		  io_callback_t *callback, void *context)
{
	struct io_file *io;

	i_assert(fd >= 0);
	i_assert(callback != NULL);
	i_assert((condition & IO_NOTIFY) == 0);

	io = i_new(struct io_file, 1);
        io->io.condition = condition;
	io->io.callback = callback;
        io->io.context = context;
	io->refcount = 1;
	io->fd = fd;

	io_loop_handle_add(current_ioloop, io);

	if (current_ioloop->io_files != NULL) {
		current_ioloop->io_files->prev = io;
		io->next = current_ioloop->io_files;
	}
	current_ioloop->io_files = io;
	return &io->io;
}

static void io_file_unlink(struct io_file *io)
{
	if (io->prev != NULL)
		io->prev->next = io->next;
	else
		current_ioloop->io_files = io->next;

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

	/* if we got here from an I/O handler callback, make sure we
	   don't try to handle this one next. */
	if (current_ioloop->next_io_file == io)
		current_ioloop->next_io_file = io->next;
}

void io_remove(struct io **_io)
{
	struct io *io = *_io;

	*_io = NULL;

	/* make sure the callback doesn't get called anymore.
	   kqueue code relies on this. */
	io->callback = NULL;

	if ((io->condition & IO_NOTIFY) != 0)
		io_loop_notify_remove(current_ioloop, io);
	else {
		struct io_file *io_file = (struct io_file *)io;

		io_file_unlink(io_file);
		io_loop_handle_remove(current_ioloop, io_file);
	}
}

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 (timer_is_larger(&(*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;
	}
}

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

	timeout = i_new(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;
	*timeout = NULL;
}

int io_loop_get_wait_time(struct timeout *timeout, struct timeval *tv,
			  struct timeval *tv_now)
{
	if (timeout == NULL) {
		/* no timeouts. give it INT_MAX msecs. */
		tv->tv_sec = INT_MAX / 1000;
		tv->tv_usec = 0;
		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 *called_timeouts;
	struct timeval tv;
        unsigned int t_id;

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

	/* Don't bother comparing usecs. */
	if (ioloop_time > ioloop_timeval.tv_sec) {
		time_t diff = ioloop_time - ioloop_timeval.tv_sec;

		/* Note that this code is here only because this is the easiest
		   place to check for this. The I/O loop code itself could be
		   easily fixed to work with time moving backwards, but there's
		   really no point because there are a lot of other places
		   which may break in more or less bad ways, such as files'
		   timestamps moving backwards. */
		if (diff > IOLOOP_MAX_TIME_BACKWARDS_SLEEP) {
			i_fatal("Time just moved backwards by %ld seconds. "
				"This might cause a lot of problems, "
				"so I'll just kill myself now.", (long)diff);
		} else {
			i_error("Time just moved backwards by %ld seconds. "
				"I'll sleep now until we're back in present.",
				(long)diff);
			/* Sleep extra second to make sure usecs also grows. */
			diff++;

			while (diff > 0 && sleep(diff) != 0) {
				/* don't use sleep()'s return value, because
				   it could get us to a long loop in case
				   interrupts just keep coming */
				diff = ioloop_time - time(NULL) + 1;
			}

			/* Try again. */
			io_loop_handle_timeouts(ioloop);
		}
	}

	ioloop_time = ioloop_timeval.tv_sec;

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

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

		if (t->destroyed) {
			ioloop->timeouts = t->next;
			i_free(t);
			continue;
		}

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

			if (!t->run_now)
				break;
		}

		/* move timeout to called_timeouts list */
		ioloop->timeouts = t->next;
		t->next = called_timeouts;
		called_timeouts = t;

                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 in timeout handler %p",
				(void *)t->callback);
		}
	}

	/* move timeouts back to list so they get re-sorted again by next_run
	   time, or destroy them if timeout_remove() was called for them. */
	while (called_timeouts != NULL) {
		struct timeout *t = called_timeouts;

		if (t->destroyed) {
			called_timeouts = t->next;
			i_free(t);
		} else {
			called_timeouts = t->next;
			timeout_list_insert(current_ioloop, t);
		}
	}
#ifdef DEBUG
	if (ioloop->timeouts != NULL) {
		struct timeout *t;

		for (t = ioloop->timeouts; t->next != NULL; t = t->next) {
			if (timer_is_larger(&t->next_run, &t->next->next_run))
				i_panic("broken timeout list");
		}
	}
#endif
}

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;
}

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

struct ioloop *io_loop_create(void)
{
	struct ioloop *ioloop;

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

        ioloop = i_new(struct ioloop, 1);
	io_loop_handler_init(ioloop);

	ioloop->prev = current_ioloop;
        current_ioloop = ioloop;

        return ioloop;
}

void io_loop_destroy(struct ioloop **_ioloop)
{
        struct ioloop *ioloop = *_ioloop;

	*_ioloop = NULL;

	if (ioloop->notify_handler_context != NULL)
		io_loop_notify_handler_deinit(ioloop);

	while (ioloop->io_files != NULL) {
		struct io_file *io = ioloop->io_files;
		struct io *_io = &io->io;

		i_warning("I/O leak: %p (%d)", (void *)io->io.callback, io->fd);
		io_remove(&_io);
	}

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

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

	i_free(ioloop);
}