/***************************************************************************

  gbx_watch.c

  (c) 2000-2012 Benoît Minisini <gambas@users.sourceforge.net>

  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, 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., 51 Franklin Street, Fifth Floor, Boston,
  MA 02110-1301, USA.

***************************************************************************/

#define __GBX_WATCH_C

#include "gb_common.h"
#include "gb_error.h"

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

#include "gb_array.h"
#include "gbx_exec.h"
#include "gbx_event.h"
#include "gbx_date.h"
#include "gbx_c_timer.h"
#include "gbx_watch.h"

//#define DEBUG_TIMER 1
//#define DEBUG_WATCH 1

static fd_set read_fd;
static fd_set write_fd;

static WATCH_CALLBACK *watch_callback = NULL;
//static short *watch_index = NULL;

static int max_fd = 0;

static WATCH_TIMER *_timers = NULL;

static int _do_not_really_delete_callback = 0;
static bool _must_delete_callback = FALSE;

#ifdef DEBUG_TIMER
double _debug_time;
static double time_to_double(const struct timeval *t)
{
	return (double)t->tv_sec + t->tv_usec / 1E6 - _debug_time;
}
#endif

static void time_add(struct timeval *t1, const struct timeval *t2)
{
	t1->tv_sec += t2->tv_sec;
	t1->tv_usec += t2->tv_usec;
	if (t1->tv_usec > 1000000)
	{
		t1->tv_usec -= 1000000;
		t1->tv_sec++;
	}
}

static void time_sub(struct timeval *t1, const struct timeval *t2)
{
	t1->tv_sec -= t2->tv_sec;
	t1->tv_usec -= t2->tv_usec;
	if (t1->tv_usec < 0)
	{
		t1->tv_usec += 1000000;
		t1->tv_sec--;
	}
}

#define time_comp(t1, t2, op) ((t1)->tv_sec op (t2)->tv_sec || ((t1)->tv_sec == (t2)->tv_sec && (t1)->tv_usec op (t2)->tv_usec))
#define time_lower_than(t1, t2) time_comp(t1, t2, <)

static void time_from_ms(struct timeval *t, int ms)
{
	t->tv_sec = ms / 1000;
	t->tv_usec = (ms % 1000) * 1000;
}

static struct timeval *time_now(void)
{
	static struct timeval current;

	gettimeofday(&current, NULL);
	if (current.tv_usec < 0 || current.tv_usec >= 1000000)
		fprintf(stderr, "gettimeofday: tv_usec = %ld!\n", current.tv_usec);
	return &current;
}


static void add_timer(GB_TIMER *timer, const struct timeval *timeout)
{
	int i;
	WATCH_TIMER *wt;

	for (i = 0; i < ARRAY_count(_timers); i++)
	{
		//if (_timers[i].timeout > timeout)
		if (time_lower_than(timeout, &_timers[i].timeout))
			break;
	}

	wt = ARRAY_insert(&_timers, i);
	wt->timer = timer;
	wt->timeout = *timeout;

	#ifdef DEBUG_TIMER
	fprintf(stderr, "add_timer: %p at %i: %g\n", timer, i, time_to_double(timeout));
	#endif
}

static int find_timer(GB_TIMER *timer)
{
	int i;

	for (i = 0; i < ARRAY_count(_timers); i++)
	{
		if (_timers[i].timer == timer)
			return i;
	}
	
	return (-1);
}

static void remove_timer(GB_TIMER *timer)
{
	int i = find_timer(timer);

	if (i >= 0)
	{
		ARRAY_remove(&_timers, i)
		#ifdef DEBUG_TIMER
		fprintf(stderr, "remove_timer: %p at %i\n", timer, i);
		#endif
	}
}

double WATCH_get_timeout(GB_TIMER *timer)
{
	int i = find_timer(timer);

	if (i < 0)
		return 0.0;
	else
		return DATE_to_double(&_timers[i].timeout, TRUE);
}

static void raise_timers()
{
	struct timeval timeout;
	struct timeval delay;
	struct timeval *now;
	GB_TIMER *timer;

	now = time_now();

	while (ARRAY_count(_timers))
	{
		timeout = _timers[0].timeout;
		if (time_lower_than(now, &timeout))
			return;

		timer = _timers[0].timer;

		#ifdef DEBUG_TIMER
		fprintf(stderr, "raise_timers: %p has been triggered! now = %.7f timeout = %.7f\n", timer, time_to_double(now), time_to_double(&timeout));
		#endif

		time_from_ms(&delay, timer->delay);
		time_add(&timeout, &delay);

		if (time_lower_than(&timeout, now))
		{
			timeout = *now;
			time_add(&timeout, &delay);
		}

		remove_timer(timer);
		add_timer(timer, &timeout);

		CTIMER_raise(timer);
	}
}


static bool get_timeout(const struct timeval *wait, struct timeval *tv)
{
	struct timeval timeout;
	struct timeval *now;

	if (ARRAY_count(_timers) == 0 && !wait)
		return TRUE;

	now = time_now();

	#ifdef DEBUG_TIMER
	fprintf(stderr, "get_timeout: now = %.7g timeout = %.7g\n", time_to_double(now), time_to_double(&_timers[0].timeout));
	#endif

	if (ARRAY_count(_timers) == 0)
		timeout = *wait;
	else
	{
		timeout = _timers[0].timeout;
		if (wait && time_lower_than(wait, &timeout))
			timeout = *wait;
	}

	time_sub(&timeout, now);

	// HZ = 100 on Linux. If a timer must be triggered in less than 10 ms, then
	// we do a busy wait instead of calling the system.

	if (timeout.tv_sec == 0 && timeout.tv_usec < (1000000 / 100))
	{
		#ifdef DEBUG_TIMER
		fprintf(stderr, "busy loop\n");
		#endif
		// busy loop!
		time_add(&timeout, now);
		for(;;)
		{
			now = time_now();
			if (!time_lower_than(now, &timeout))
				break;
		}
		timeout.tv_sec = 0;
		timeout.tv_usec = 0;
	}
	else if (timeout.tv_sec < 0)
	{
		#ifdef DEBUG_TIMER
		fprintf(stderr, "timeout < 0: %ld %ld\n", timeout.tv_sec, timeout.tv_usec);
		#endif
		timeout.tv_sec = 0;
		timeout.tv_usec = 0;
	}

	*tv = timeout;

	#ifdef DEBUG_TIMER
	fprintf(stderr, "timeout: %.7f %ld %ld\n", timeout.tv_sec + timeout.tv_usec / 1E6, tv->tv_sec, tv->tv_usec);
	#endif
	return FALSE;
}


void WATCH_init(void)
{
	FD_ZERO(&read_fd);
	FD_ZERO(&write_fd);

	ARRAY_create(&watch_callback);
	//ARRAY_create(&watch_index);
	ARRAY_create(&_timers);

	#ifdef DEBUG_TIMER
	DATE_timer(&_debug_time, FALSE);
	#endif
}


void WATCH_exit(void)
{
	ARRAY_delete(&watch_callback);
	//ARRAY_delete(&watch_index);
	ARRAY_delete(&_timers);
}


static void watch_fd(int fd, int flag, bool watch)
{
	#if DEBUG_WATCH
	fprintf(stderr, "watch_fd: %d for %s: %s\n", fd, flag == WATCH_READ ? "read" : "write", watch ? "set" : "clear");
	#endif

	if (flag == WATCH_READ)
	{
		if (watch)
			FD_SET(fd, &read_fd);
		else
			FD_CLR(fd, &read_fd);
	}
	else if (flag == WATCH_WRITE)
	{
		if (watch)
			FD_SET(fd, &write_fd);
		else
			FD_CLR(fd, &write_fd);
	}
}


static int watch_find_callback(int fd)
{
	int i;

	for (i = 0; i < ARRAY_count(watch_callback); i++)
	{
		if (watch_callback[i].fd == fd)
			return i;
	}

	return -1;
}


static int find_max_fd(void)
{
	int i;
	int max = -1;

	for (i = 0; i < ARRAY_count(watch_callback); i++)
	{
		if (watch_callback[i].fd > max)
			max = watch_callback[i].fd;
	}

	return max;
}

/*static void ensure_watch_index(int fd)
{
	int i;
	int count = ARRAY_count(watch_index);
	
	//fprintf(stderr, "ensure_watch_index: %d (%d)\n", fd, count);
	
	if (fd < count)
		return;
	
	ARRAY_add_many(&watch_index, fd - count + 1);
	for (i = count; i <= fd; i++)
		watch_index[i] = -1;
}*/

static WATCH_CALLBACK *watch_create_callback(int fd)
{
	int pos;
	WATCH_CALLBACK *wcb;

	#if DEBUG_WATCH
	fprintf(stderr, "watch_create_callback: %d\n", fd);
	#endif

	pos = watch_find_callback(fd);
	if (pos < 0)
	{
		pos = ARRAY_count(watch_callback);
		wcb = ARRAY_add_void(&watch_callback);
		wcb->fd = fd;
	}
	else
		wcb = &watch_callback[pos];

	if (fd > max_fd)
		max_fd = fd;
		
	#if DEBUG_WATCH
	fprintf(stderr, "watch_create_callback: %d -> %d read = %p (%p) write = %p (%p)\n", fd, pos, wcb->callback_read, (void *)wcb->param_read, wcb->callback_write, (void *)wcb->param_write);
	#endif
	
	//ensure_watch_index(fd);
	//watch_index[fd] = pos;
	
	return wcb;
}


static void watch_delete_callback(int fd)
{
	WATCH_CALLBACK *wcb;
	int pos;
	
	#if DEBUG_WATCH
	fprintf(stderr, "watch_delete_callback: %d (%d)\n", fd, _do_not_really_delete_callback);
	#endif

	pos = watch_find_callback(fd);
	if (pos < 0)
		return;
	
	//watch_index[fd] = -1;
	
	wcb = &watch_callback[pos];
	wcb->fd = -1;
	watch_fd(fd, WATCH_READ, FALSE);
	watch_fd(fd, WATCH_WRITE, FALSE);
	max_fd = find_max_fd();
	
	if (_do_not_really_delete_callback)
	{
		_must_delete_callback = TRUE;
		return;
	}
		
	ARRAY_remove(&watch_callback, pos);
}


void WATCH_watch(int fd, int type, void *callback, intptr_t param)
{
	WATCH_CALLBACK *wcb;

	if (fd < 0 || fd > FD_SETSIZE)
	{
		if (type != WATCH_NONE)
			ERROR_warning("trying to watch fd #%d", fd);
		return;
	}

	if (type == WATCH_NONE)
		watch_delete_callback(fd);
	else
	{
		wcb = watch_create_callback(fd);
		if (type == WATCH_READ)
		{
			wcb->callback_read = callback;
			wcb->param_read = param;
		}
		else
		{
			wcb->callback_write = callback;
			wcb->param_write = param;
		}

		#if DEBUG_WATCH
		fprintf(stderr, "add watch: %d -> %d read = %p (%p) write = %p (%p)\n", fd, watch_find_callback(fd), wcb->callback_read, (void *)wcb->param_read, wcb->callback_write, (void *)wcb->param_write);
		#endif

		if (!wcb->callback_read && !wcb->callback_write)
			watch_delete_callback(fd);
		else
		{
			watch_fd(fd, WATCH_READ, wcb->callback_read != NULL);
			watch_fd(fd, WATCH_WRITE, wcb->callback_write != NULL);
		}
	}
}


static void raise_callback(fd_set *rfd, fd_set *wfd)
{
	int i;
	WATCH_CALLBACK wcb;

	_do_not_really_delete_callback++;

	#if DEBUG_WATCH
	fprintf(stderr, "raise_callback: max_fd = %d\n", max_fd);
	#endif
	for (i = 0; i < ARRAY_count(watch_callback); i++)
	{
		// We copy the callback structure, because the watch_callback array can change during the
		// execution of the callbacks.
		
		if (watch_callback[i].fd < 0)
			continue;
		
		wcb = watch_callback[i];

		#if DEBUG_WATCH
		fprintf(stderr, "raise_callback: [%d] fd = %d read = %p (%p) write = %p (%p)\n", i, wcb.fd, wcb.callback_read, (void *)wcb.param_read, wcb.callback_write, (void *)wcb.param_write);
		#endif
		
		if (FD_ISSET(wcb.fd, rfd))
		{
			if (wcb.callback_read)
			{
				#ifdef DEBUG_WATCH
				fprintf(stderr, "call read callback on fd %d\n", wcb.fd);
				#endif
				(*(wcb.callback_read))(wcb.fd, WATCH_READ, wcb.param_read);
			}
		}

		if (FD_ISSET(wcb.fd, wfd))
		{
			if (wcb.callback_write)
			{
				#ifdef DEBUG_WATCH
				fprintf(stderr, "call write callback on fd %d\n", wcb.fd);
				#endif
				(*(wcb.callback_write))(wcb.fd, WATCH_WRITE, wcb.param_write);
			}
		}
	}

	_do_not_really_delete_callback--;
	
	if (!_do_not_really_delete_callback && _must_delete_callback)
	{
		i = 0;
		while (i < ARRAY_count(watch_callback))
		{
			if (watch_callback[i].fd < 0)
			{
				ARRAY_remove(&watch_callback, i);
			}
			else
				i++;
		}		
		_must_delete_callback = FALSE;
	}
}


static int do_select(fd_set *rfd, fd_set *wfd, struct timeval *timeout)
{
	int fd;

	for (fd = max_fd; fd >= 0; fd--)
	{
		if (FD_ISSET(fd, &read_fd) || FD_ISSET(fd, &write_fd))
			break;
	}

	if (fd < 0 && !timeout)
		return 0;

	max_fd = fd;

	*rfd = read_fd;
	*wfd = write_fd;

	return select(max_fd + 1, rfd, wfd, NULL, timeout);
}

static bool do_loop(struct timeval *wait)
{
	int ret;
	struct timeval tv;
	fd_set rfd, wfd;
	bool something_done = FALSE;

	if (EVENT_check_post())
		something_done = TRUE;

	#ifdef DEBUG_TIMER
	fprintf(stderr, "\ndo_loop: now = %.7g: select (%d)\n", time_to_double(time_now()), something_done);
	#endif

	if (get_timeout(wait, &tv))
		ret = do_select(&rfd, &wfd, NULL);
	else
	{
		ret = do_select(&rfd, &wfd, &tv);
		something_done = TRUE;
	}

	if (ret < 0 && errno != EINTR)
		THROW_SYSTEM(errno, NULL);
	
	#ifdef DEBUG_TIMER
	fprintf(stderr, "do_loop: now = %.7g: timers (%d)\n", time_to_double(time_now()), something_done);
	#endif

	raise_timers();

	#ifdef DEBUG_TIMER
	fprintf(stderr, "do_loop: now = %.7g: callbacks\n", time_to_double(time_now()));
	#endif

	if (ret > 0)
	{
		raise_callback(&rfd, &wfd);
		something_done = TRUE;
	}
	else if (ret < 0)
	{
		something_done = TRUE;
	}

	//if (EVENT_check_post())
	//	something_done = TRUE;

	return something_done;
}


bool WATCH_one_loop(int wait)
{
	struct timeval timeout;
	
	if (wait == 0)
		return do_loop(NULL);
	else
	{
		time_from_ms(&timeout, wait);
		return do_loop(&timeout);
	}
}

void WATCH_loop(void)
{
	while (do_loop(NULL));
}


void WATCH_wait(int wait)
{
	struct timeval *now;
	struct timeval timeout;

	if (wait == 0)
	{
		timeout.tv_sec = 0;
		timeout.tv_usec = 0;
		do_loop(&timeout);
	}
	else
	{
		now = time_now();
		time_from_ms(&timeout, wait);
		time_add(&timeout, now);

		for(;;)
		{
			now = time_now();
			if (time_lower_than(&timeout, now))
				break;
			do_loop(&timeout);
		}
	}
}

int WATCH_process(int fd_end, int fd_output)
{
	fd_set rfd;
	int ret, fd_max;

	fd_max = fd_end > fd_output ? fd_end : fd_output;

	for(;;)
	{
		FD_ZERO(&rfd);
		FD_SET(fd_end, &rfd);
		if (fd_output >= 0)
			FD_SET(fd_output, &rfd);

		ret = select(fd_max + 1, &rfd, NULL, NULL, NULL);

		if (ret > 0)
			break;
		if (errno != EINTR)
			break;
	}

	if (FD_ISSET(fd_end, &rfd))
		return fd_end;
	else if (FD_ISSET(fd_output, &rfd))
		return fd_output;
	else
		return -1;
}


void WATCH_timer(void *t, int on)
{
	GB_TIMER *timer = (GB_TIMER *)t;
	struct timeval timeout;

	if (on)
	{
		time_from_ms(&timeout, timer->delay);
		time_add(&timeout, time_now());
		add_timer(timer, &timeout);
		timer->id = (intptr_t)timer;
	}
	else
	{
		remove_timer(timer);
		timer->id = 0;
	}
}