#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
#include <malloc.h>
#include <string.h>
#include <limits.h>
#include <sys/time.h>
#include <time.h>

#include "list.h"
#include "glib-ectomy.h"

struct timeout {
	guint id;
	guint interval;
	struct timeval expiration;
	gpointer data;
	GSourceFunc function;
};

struct _GIOChannel {
	int fd;
	gboolean close_on_unref;
};

struct _GMainContext {
	guint next_id;
	glong next_timeout;

	struct slist *timeouts;
	struct slist *proc_timeouts;
	gboolean timeout_lock;

	struct slist *watches;
	struct slist *proc_watches;
	gboolean watch_lock;
};

struct _GMainLoop {
	gboolean is_running;
	GMainContext *context;
};

GIOError g_io_channel_read(GIOChannel *channel, gchar *buf, gsize count, gsize *bytes_read)
{
	int fd = channel->fd;
	gssize result;

	/* At least according to the Debian manpage for read */
	if (count > SSIZE_MAX)
		count = SSIZE_MAX;

retry:
	result = read (fd, buf, count);

	if (result < 0) {
		*bytes_read = 0;

		switch (errno) {
#ifdef EINTR
		case EINTR:
			goto retry;
#endif
#ifdef EAGAIN
		case EAGAIN:
			return G_IO_STATUS_AGAIN;
#endif
		default:
			return G_IO_STATUS_ERROR;
		}
	}

	*bytes_read = result;

	return (result > 0) ? G_IO_STATUS_NORMAL : G_IO_STATUS_EOF;
}

void g_io_channel_close(GIOChannel *channel)
{
	if (!channel)
		return;

	close(channel->fd);
	channel->fd = -1;
}

void g_io_channel_unref(GIOChannel *channel)
{
	if (!channel)
		return;

	if (channel->close_on_unref && channel->fd >= 0)
		g_io_channel_close(channel);

	free(channel);
}

GIOChannel *g_io_channel_unix_new(int fd)
{
	GIOChannel *channel;

	channel = malloc(sizeof(GIOChannel));
	if (!channel)
		return NULL;

	memset(channel, 0, sizeof(GIOChannel));

	channel->fd = fd;

	return channel;
}

void g_io_channel_set_close_on_unref(GIOChannel *channel, gboolean do_close)
{
	channel->close_on_unref = do_close;
}

gint g_io_channel_unix_get_fd(GIOChannel *channel)
{
	return channel->fd;
}

struct watch {
	guint id;
	GIOChannel *channel;
	gint priority;
	GIOCondition condition;
	short *revents;
	GIOFunc func;
	gpointer user_data;
	GDestroyNotify destroy;
};

static GMainContext *default_context = NULL;

static void watch_free(struct watch *watch)
{
	if (watch->destroy)
		watch->destroy(watch->user_data);
	free(watch);
}

static GMainContext *g_main_context_default()
{
	if (default_context)
		return default_context;

	default_context = malloc(sizeof(GMainContext));
	if (!default_context)
		return NULL;

	memset(default_context, 0, sizeof(GMainContext));

	default_context->next_timeout = -1;
	default_context->next_id = 1;

	return default_context;
}

void g_io_remove_watch(guint id)
{
	GMainContext *context = g_main_context_default();
	struct slist *l;
	struct watch *w;

	if (!context)
		return;

	for (l = context->watches; l != NULL; l = l->next) {
		w = l->data;	

		if (w->id != id)
			continue;

		context->watches = slist_remove(context->watches, w);
		watch_free(w);

		return;
	}

	for (l = context->proc_watches; l != NULL; l = l->next) {
		w = l->data;	

		if (w->id != id)
			continue;

		context->proc_watches = slist_remove(context->proc_watches, w);
		watch_free(w);

		return;
	}
}

guint g_io_add_watch_full(GIOChannel *channel, gint priority,
				GIOCondition condition, GIOFunc func,
				gpointer user_data, GDestroyNotify notify)
{
	struct watch *watch;
	GMainContext *context = g_main_context_default();

	if (!context)
		return 0;
       
	watch = malloc(sizeof(struct watch));
	if (!watch)
		return 0;

	watch->id = context->next_id++;
	watch->channel = channel;
	watch->priority = priority;
	watch->condition = condition;
	watch->func = func;
	watch->user_data = user_data;
	watch->destroy = notify;

	if (context->watch_lock)
		context->proc_watches = slist_prepend(context->proc_watches, watch);
	else
		context->watches = slist_prepend(context->watches, watch);

	return watch->id;
}

guint g_io_add_watch(GIOChannel *channel, GIOCondition condition,
					GIOFunc func, gpointer user_data)
{
	return g_io_add_watch_full(channel, 0, condition,
						func, user_data, NULL);
}

GMainLoop *g_main_loop_new(GMainContext *context, gboolean is_running)
{
	GMainLoop *ml;

	if (!context)
		context = g_main_context_default();

	if (!context)
		return NULL;

	ml = malloc(sizeof(GMainLoop));
	if (!ml)
		return NULL;

	memset(ml, 0, sizeof(GMainLoop));

	ml->context = context;
	ml->is_running = is_running;

	return ml;
}

static void timeout_handlers_prepare(GMainContext *context)
{
	struct slist *l;
	struct timeval tv;
	glong msec, timeout = LONG_MAX;

	gettimeofday(&tv, NULL);

	for (l = context->timeouts; l != NULL; l = l->next) {
		struct timeout *t = l->data;

		/* calculate the remainning time */
		msec = (t->expiration.tv_sec - tv.tv_sec) * 1000 +
				(t->expiration.tv_usec - tv.tv_usec) / 1000;
		if (msec < 0)
			msec = 0;

		timeout = MIN_TIMEOUT(timeout, msec);
	}

	/* set to min value found or NO timeout */
	context->next_timeout = (timeout != LONG_MAX ? timeout : -1);
}

static int ptr_cmp(const void *t1, const void *t2)
{
	return t1 - t2;
}

static void timeout_handlers_check(GMainContext *context)
{
	struct timeval tv;

	gettimeofday(&tv, NULL);

	context->timeout_lock = TRUE;

	while (context->timeouts) {
		struct timeout *t = context->timeouts->data;
		glong secs, msecs;
		gboolean ret;

		if (timercmp(&tv, &t->expiration, <)) {
			context->timeouts = slist_remove(context->timeouts, t);
			context->proc_timeouts = slist_append(context->proc_timeouts, t);
			continue;
		}

		ret = t->function(t->data);

		/* Check if the handler was removed/freed by the callback
		 * function */
		if (!slist_find(context->timeouts, t, ptr_cmp))
			continue;

		context->timeouts = slist_remove(context->timeouts, t);

		if (!ret) {
			free(t);
			continue;
		}

		/* update the next expiration time */
		secs = t->interval / 1000;
		msecs = t->interval - secs * 1000;

		t->expiration.tv_sec = tv.tv_sec + secs;
		t->expiration.tv_usec = tv.tv_usec + msecs * 1000;
		if (t->expiration.tv_usec >= 1000000) {
			t->expiration.tv_usec -= 1000000;
			t->expiration.tv_sec++;
		}

		context->proc_timeouts = slist_append(context->proc_timeouts, t);
	}

	context->timeouts = context->proc_timeouts;
	context->proc_timeouts = NULL;
	context->timeout_lock = FALSE;
}

void g_main_loop_run(GMainLoop *loop)
{
	int open_max = sysconf(_SC_OPEN_MAX);
	struct pollfd *ufds;
	GMainContext *context = loop->context;

	ufds = malloc(open_max * sizeof(struct pollfd));
	if (!ufds)
		return;

	loop->is_running = TRUE;

	while (loop->is_running) {
		int nfds;
		struct slist *l;
		struct watch *w;

		for (nfds = 0, l = context->watches; l != NULL; l = l->next, nfds++) {
			w = l->data;
			ufds[nfds].fd = w->channel->fd;
			ufds[nfds].events = w->condition;
			ufds[nfds].revents = 0;
			w->revents = &ufds[nfds].revents;
		}

		/* calculate the next timeout */
		timeout_handlers_prepare(context);

		if (poll(ufds, nfds, context->next_timeout) < 0)
			continue;

		context->watch_lock = TRUE;

		while (context->watches) {
			gboolean ret;

			w = context->watches->data;

			if (!*w->revents) {
				context->watches = slist_remove(context->watches, w);
				context->proc_watches = slist_append(context->proc_watches, w);
				continue;
			}

			ret = w->func(w->channel, *w->revents, w->user_data);

			/* Check if the watch was removed/freed by the callback
			 * function */
			if (!slist_find(context->watches, w, ptr_cmp))
				continue;

			context->watches = slist_remove(context->watches, w);

			if (!ret) {
				watch_free(w);
				continue;
			}

			context->proc_watches = slist_append(context->proc_watches, w);
		}

		context->watches = context->proc_watches;
		context->proc_watches = NULL;
		context->watch_lock = FALSE;

		/* check expired timers */
		timeout_handlers_check(loop->context);
	}

	free(ufds);
}

void g_main_loop_quit(GMainLoop *loop)
{
	loop->is_running = FALSE;
}

void g_main_loop_unref(GMainLoop *loop)
{
	if (!loop->context)
		return;

	slist_foreach(loop->context->watches, (slist_func_t)watch_free, NULL);
	slist_free(loop->context->watches);

	slist_foreach(loop->context->timeouts, (slist_func_t)free, NULL);
	slist_free(loop->context->timeouts);

	free(loop->context);
	loop->context = NULL;
}

guint g_timeout_add(guint interval, GSourceFunc function, gpointer data)
{
	GMainContext *context = g_main_context_default();
	struct timeval tv;
	guint secs;
	guint msecs;
	struct timeout *t;

	if (!context || !function)
		return 0;

	t = malloc(sizeof(*t));

	if (!t)
		return 0;

	memset(t, 0, sizeof(*t));
	t->interval = interval;
	t->function = function;
	t->data = data;

	gettimeofday(&tv, NULL);

	secs = interval /1000;
	msecs = interval - secs * 1000;

	t->expiration.tv_sec = tv.tv_sec + secs;
	t->expiration.tv_usec = tv.tv_usec + msecs * 1000;

	if (t->expiration.tv_usec >= 1000000) {
		t->expiration.tv_usec -= 1000000;
		t->expiration.tv_sec++;
	}

	/* attach the timeout the default context */
	t->id = context->next_id++;

	if (context->timeout_lock)
		context->proc_timeouts = slist_prepend(context->proc_timeouts, t);
	else
		context->timeouts = slist_prepend(context->timeouts, t);

	return t->id;
}

gint g_timeout_remove(const guint id)
{
	GMainContext *context = g_main_context_default();
	struct slist *l;
	struct timeout *t;

	if (!context)
		return -1;

	l = context->timeouts;

	while (l) {
		t = l->data;
		l = l->next;

		if (t->id != id)
			continue;

		context->timeouts = slist_remove(context->timeouts, t);
		free(t);

		return 0;
	}

	l = context->proc_timeouts;

	while (l) {
		t = l->data;
		l = l->next;

		if (t->id != id)
			continue;

		context->proc_timeouts = slist_remove(context->proc_timeouts, t);
		free(t);

		return 0;
	}

	return -1;
}