/********************************************************************\
  * BitlBee -- An IRC to other IM-networks gateway                     *
  *                                                                    *
  * Copyright 2002-2006 Wilmer van der Gaast and others                *
  \********************************************************************/

/*
 * Event handling (using libevent)
 */

/*
  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 with
  the Debian GNU/Linux distribution in /usr/share/common-licenses/GPL;
  if not, write to the Free Software Foundation, Inc., 51 Franklin St.,
  Fifth Floor, Boston, MA  02110-1301  USA
*/

#define BITLBEE_CORE
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/time.h>
#include <event.h>
#include "proxy.h"

static void b_main_restart();
static guint id_next = 1; /* Next ID to be allocated to an event handler. */
static guint id_cur = 0; /* Event ID that we're currently handling. */
static guint id_dead; /* Set to 1 if b_event_remove removes id_cur. */
static GHashTable *id_hash;
static int quitting = 0; /* Prepare to quit, stop handling events. */

/* Since libevent doesn't handle two event handlers for one fd-condition
   very well (which happens sometimes when BitlBee changes event handlers
   for a combination), let's buid some indexes so we can delete them here
   already, just in time. */
static GHashTable *read_hash;
static GHashTable *write_hash;

struct event_base *leh;
struct event_base *old_leh;

struct b_event_data {
	guint id;
	struct event evinfo;
	gint timeout;
	b_event_handler function;
	void *data;
	guint flags;
};

void b_main_init()
{
	if (leh != NULL) {
		/* Clean up the hash tables? */

		b_main_restart();
		old_leh = leh;
	}

	leh = event_init();

	id_hash = g_hash_table_new(g_int_hash, g_int_equal);
	read_hash = g_hash_table_new(g_int_hash, g_int_equal);
	write_hash = g_hash_table_new(g_int_hash, g_int_equal);
}

void b_main_run()
{
	/* This while loop is necessary to exit the event loop and start a
	   different one (necessary for ForkDaemon mode). */
	while (event_base_dispatch(leh) == 0 && !quitting) {
		if (old_leh != NULL) {
			/* For some reason this just isn't allowed...
			   Possibly a bug in older versions, will see later.
			event_base_free( old_leh ); */
			old_leh = NULL;
		}

		event_debug("New event loop.\n");
	}
}

static void b_main_restart()
{
	struct timeval tv;

	memset(&tv, 0, sizeof(struct timeval));
	event_base_loopexit(leh, &tv);

	event_debug("b_main_restart()\n");
}

void b_main_quit()
{
	/* Tell b_main_run() that it shouldn't restart the loop. Also,
	   libevent sometimes generates events before really quitting,
	   we want to stop them. */
	quitting = 1;

	b_main_restart();
}

static void b_event_passthrough(int fd, short event, void *data)
{
	struct b_event_data *b_ev = data;
	b_input_condition cond = 0;
	gboolean st;

	if (fd >= 0) {
		if (event & EV_READ) {
			cond |= B_EV_IO_READ;
		}
		if (event & EV_WRITE) {
			cond |= B_EV_IO_WRITE;
		}
	}

	event_debug("b_event_passthrough( %d, %d, 0x%x ) (%d)\n", fd, event, (int) data, b_ev->id);

	/* Since the called function might cancel this handler already
	   (which free()s b_ev), we have to remember the ID here. */
	id_cur = b_ev->id;
	id_dead = 0;

	if (quitting) {
		b_event_remove(id_cur);
		return;
	}

	st = b_ev->function(b_ev->data, fd, cond);
	if (id_dead) {
		/* This event was killed already, don't touch it! */
		return;
	} else if (!st && !(b_ev->flags & B_EV_FLAG_FORCE_REPEAT)) {
		event_debug("Handler returned FALSE: ");
		b_event_remove(id_cur);
	} else if (fd == -1) {
		/* fd == -1 means it was a timer. These can't be auto-repeated
		   so it has to be recreated every time. */
		struct timeval tv;

		tv.tv_sec = b_ev->timeout / 1000;
		tv.tv_usec = (b_ev->timeout % 1000) * 1000;

		evtimer_add(&b_ev->evinfo, &tv);
	}
}

gint b_input_add(gint fd, b_input_condition condition, b_event_handler function, gpointer data)
{
	struct b_event_data *b_ev;

	event_debug("b_input_add( %d, %d, 0x%x, 0x%x ) ", fd, condition, function, data);

	if ((condition & B_EV_IO_READ  && (b_ev = g_hash_table_lookup(read_hash,  &fd))) ||
	    (condition & B_EV_IO_WRITE && (b_ev = g_hash_table_lookup(write_hash, &fd)))) {
		/* We'll stick with this libevent entry, but give it a new BitlBee id. */
		g_hash_table_remove(id_hash, &b_ev->id);

		event_debug("(replacing old handler (id = %d)) = %d\n", b_ev->id, id_next);

		b_ev->id = id_next++;
		b_ev->function = function;
		b_ev->data = data;
	} else {
		GIOCondition out_cond;

		event_debug("(new) = %d\n", id_next);

		b_ev = g_new0(struct b_event_data, 1);
		b_ev->id = id_next++;
		b_ev->function = function;
		b_ev->data = data;

		out_cond = EV_PERSIST;
		if (condition & B_EV_IO_READ) {
			out_cond |= EV_READ;
		}
		if (condition & B_EV_IO_WRITE) {
			out_cond |= EV_WRITE;
		}

		event_set(&b_ev->evinfo, fd, out_cond, b_event_passthrough, b_ev);
		event_add(&b_ev->evinfo, NULL);

		if (out_cond & EV_READ) {
			g_hash_table_insert(read_hash, &b_ev->evinfo.ev_fd, b_ev);
		}
		if (out_cond & EV_WRITE) {
			g_hash_table_insert(write_hash, &b_ev->evinfo.ev_fd, b_ev);
		}
	}

	b_ev->flags = condition;
	g_hash_table_insert(id_hash, &b_ev->id, b_ev);
	return b_ev->id;
}

/* TODO: Persistence for timers! */
gint b_timeout_add(gint timeout, b_event_handler function, gpointer data)
{
	struct b_event_data *b_ev = g_new0(struct b_event_data, 1);
	struct timeval tv;

	b_ev->id = id_next++;
	b_ev->timeout = timeout;
	b_ev->function = function;
	b_ev->data = data;

	tv.tv_sec = timeout / 1000;
	tv.tv_usec = (timeout % 1000) * 1000;

	evtimer_set(&b_ev->evinfo, b_event_passthrough, b_ev);
	evtimer_add(&b_ev->evinfo, &tv);

	event_debug("b_timeout_add( %d, 0x%x, 0x%x ) = %d\n", timeout, function, data, b_ev->id);

	g_hash_table_insert(id_hash, &b_ev->id, b_ev);

	return b_ev->id;
}

void b_event_remove(gint id)
{
	struct b_event_data *b_ev = g_hash_table_lookup(id_hash, &id);

	event_debug("b_event_remove( %d )\n", id);
	if (b_ev) {
		if (id == id_cur) {
			id_dead = TRUE;
		}

		g_hash_table_remove(id_hash, &b_ev->id);
		if (b_ev->evinfo.ev_fd >= 0) {
			if (b_ev->evinfo.ev_events & EV_READ) {
				g_hash_table_remove(read_hash, &b_ev->evinfo.ev_fd);
			}
			if (b_ev->evinfo.ev_events & EV_WRITE) {
				g_hash_table_remove(write_hash, &b_ev->evinfo.ev_fd);
			}
		}

		event_del(&b_ev->evinfo);
		g_free(b_ev);
	} else {
		event_debug("Already removed?\n");
	}
}

void closesocket(int fd)
{
	struct b_event_data *b_ev;

	/* Since epoll() (the main reason we use libevent) automatically removes sockets from
	   the epoll() list when a socket gets closed and some modules have a habit of
	   closing sockets before removing event handlers, our and libevent's administration
	   get a little bit messed up. So this little function will remove the handlers
	   properly before closing a socket. */

	if ((b_ev = g_hash_table_lookup(read_hash, &fd))) {
		event_debug("Warning: fd %d still had a read event handler when shutting down.\n", fd);
		b_event_remove(b_ev->id);
	}
	if ((b_ev = g_hash_table_lookup(write_hash, &fd))) {
		event_debug("Warning: fd %d still had a write event handler when shutting down.\n", fd);
		b_event_remove(b_ev->id);
	}

	close(fd);
}