#define _POSIX_SOURCE
#include <signal.h>
#include <glib.h>

static GPtrArray *signal_infos = NULL;

typedef struct _GUnixSignalInfo {
	guint source_id;
	GMainContext *context;
	gboolean triggered;
	gint signum;
} GUnixSignalInfo;

typedef struct _GUnixSignalSource {
	GSource source;
	GUnixSignalInfo *info;
} GUnixSignalSource;

static inline GUnixSignalInfo* get_signal_info(guint index)
{
	return (GUnixSignalInfo*)g_ptr_array_index(signal_infos, index);
}

static void handler(gint signum) {
	g_assert(signal_infos != NULL);
	for (guint i = 0; i < signal_infos->len; ++i)
		if (get_signal_info(i)->signum == signum)
			get_signal_info(i)->triggered = TRUE;
	sigaction(signum, &(struct sigaction){handler}, NULL);
}

static gboolean check(GSource *source)
{
	GUnixSignalSource *signal_source = (GUnixSignalSource*) source;
	return signal_source->info->triggered;
}

static gboolean prepare(GSource *source, gint *timeout_)
{
	GUnixSignalSource *signal_source = (GUnixSignalSource*) source;
	if (signal_source->info->context == NULL) {
		g_main_context_ref(signal_source->info->context = g_source_get_context(source));
		signal_source->info->source_id = g_source_get_id(source);
	}

	*timeout_ = -1;
	return signal_source->info->triggered;
}

static gboolean dispatch(GSource *source, GSourceFunc callback, gpointer user_data)
{
	GUnixSignalSource *signal_source = (GUnixSignalSource*) source;
	signal_source->info->triggered = FALSE;
	return callback(user_data) ? TRUE : FALSE;
}
static void finalize(GSource *source)
{
	GUnixSignalSource *signal_source = (GUnixSignalSource*) source;
	sigaction(signal_source->info->signum, &(struct sigaction){NULL}, NULL);
	g_main_context_unref(signal_source->info->context);
	g_ptr_array_remove_fast(signal_infos, signal_source->info);
	if (signal_infos->len == 0)
		signal_infos = (GPtrArray*) g_ptr_array_free(signal_infos, TRUE);
	g_free(signal_source->info);

}
static GSourceFuncs SourceFuncs = 
{
	.prepare  = prepare,
	.check    = check,
	.dispatch = dispatch,
	.finalize = finalize,
	.closure_callback = NULL, .closure_marshal = NULL
};

static void g_unix_signal_source_init(GSource *source, gint signum)
{
	GUnixSignalSource *signal_source = (GUnixSignalSource *) source;
	signal_source->info = g_new(GUnixSignalInfo, 1);
	signal_source->info->triggered = FALSE;
	signal_source->info->signum    = signum;
	signal_source->info->context   = NULL;

	if (signal_infos == NULL)
		signal_infos = g_ptr_array_new();
	g_ptr_array_add(signal_infos, signal_source->info);
}

GSource *g_unix_signal_source_new(gint signum)
{
	GSource *source = g_source_new(&SourceFuncs, sizeof(GUnixSignalSource));
	g_unix_signal_source_init(source, signum);
	sigaction(signum, &(struct sigaction){handler}, NULL);
	return source;
}

guint g_unix_signal_add_full(gint priority, gint signum, GSourceFunc function, gpointer data, GDestroyNotify notify)
{
	g_return_val_if_fail(function != NULL, 0);
	GSource *source = g_unix_signal_source_new(signum);
	if (priority != G_PRIORITY_DEFAULT)
		g_source_set_priority (source, priority);
	g_source_set_callback(source, function, data, notify);
	guint id = g_source_attach(source, NULL);
	g_source_unref(source);
	return id;
}

guint g_unix_signal_add(gint signum, GSourceFunc function, gpointer data)
{
	return g_unix_signal_add_full(G_PRIORITY_DEFAULT, signum, function, data, NULL);
}