#define FUSE_USE_VERSION 30

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>

#include <fuse.h>

#include <udisks/udisks.h>

static GMainLoop *main_loop;
static GThread *sub_thread;
static UDisksClient *client;

static GHashTable *mounts;
G_LOCK_DEFINE_STATIC(mounts);

static void udisks_changed(UDisksClient *client, gpointer user_data)
{
	GDBusObjectManager *manager = udisks_client_get_object_manager(client);
	GList *objs = g_dbus_object_manager_get_objects(manager);

	G_LOCK(mounts);

	g_debug("udisks changed");

	g_hash_table_remove_all(mounts);

	for (GList *l = objs; l; l = g_list_next(l)) {
		UDisksObject *obj = UDISKS_OBJECT(l->data);
		UDisksFilesystem *filesys = udisks_object_get_filesystem(obj);
		UDisksBlock *block = udisks_object_get_block(obj);
		if (block && filesys) {
			const gchar *name = udisks_block_get_id_label(block);
			if (!name || strlen(name) == 0) {
				name = udisks_block_get_id_uuid(block);
			}

			const gchar * const * mpoints = udisks_filesystem_get_mount_points(filesys);
			const gchar * mountpoint = mpoints && mpoints[0] ? mpoints[0] : NULL;

			if (name && mountpoint) {
				g_debug("%s -> %s", name, mountpoint);
				g_hash_table_insert(mounts, g_strdup(name), g_strdup(mountpoint));
			}
		}
		if (filesys) g_object_unref(filesys);
		if (block) g_object_unref(block);
	}

	G_UNLOCK(mounts);

	g_list_free_full(objs, g_object_unref);
}

static gpointer sub_thread_main(gpointer user_data)
{
	GError *error = NULL;

	client = udisks_client_new_sync(NULL, &error);
	if (!client) {
		g_printerr("Could not connect to UDisks2 service: %s", error->message);
		g_error_free(error);
	}

	g_signal_connect(client, "changed",
	                 G_CALLBACK(udisks_changed), NULL);

	udisks_changed(client, NULL);

	g_main_loop_run(main_loop);

	return NULL;
}

static void * volumesfs_init(struct fuse_conn_info *conn)
{
	main_loop = g_main_loop_new(NULL, FALSE);

	mounts = g_hash_table_new_full(g_str_hash, g_str_equal, g_free, g_free);

	sub_thread = g_thread_new("volumesfs-sub-thread", sub_thread_main, NULL);

	return NULL;
}

static void volumesfs_destroy(void *user_data)
{
	g_main_loop_quit(main_loop);

	g_thread_join(sub_thread);

	g_object_unref(client);
	g_hash_table_destroy(mounts);
	g_main_loop_unref(main_loop);
}

static int volumesfs_getattr(const char *path, struct stat *stbuf)
{
	if (strcmp(path, "/") == 0) {
		stbuf->st_mode = S_IFDIR | 0755;
		stbuf->st_nlink = 2;
	} else {
		G_LOCK(mounts);
		gboolean mount_exists = g_hash_table_lookup(mounts, path + 1) != NULL;
		G_UNLOCK(mounts);

		if (mount_exists) {
			stbuf->st_mode = S_IFLNK | 0444;
			stbuf->st_nlink = 1;
		} else {
			return -ENOENT;
		}
	}
	return 0;
}

static int volumesfs_readdir(const char *path, void *buf, fuse_fill_dir_t filler,
                            off_t offset, struct fuse_file_info *fi)
{
	if (strcmp(path, "/") != 0) {
		return -ENOENT;
	}

	G_LOCK(mounts);

	(void) offset;
	(void) fi;

	filler(buf, ".", NULL, 0);
	filler(buf, "..", NULL, 0);

	GHashTableIter iter;
	gchar *name;
	g_hash_table_iter_init(&iter, mounts);
	while (g_hash_table_iter_next(&iter, (void**)&name, NULL)) {
		filler(buf, name, NULL, 0);
	}

	G_UNLOCK(mounts);

	return 0;
}

static int volumesfs_readlink(const char *path, char *buf, size_t size)
{
	if (strcmp(path, "/") == 0) {
		return -EINVAL;
	}
	if (size == 0) {
		return -EINVAL;
	}

	G_LOCK(mounts);
	gboolean mount_exists;
	gchar *mountpoint = g_hash_table_lookup(mounts, path + 1);
	if (mountpoint) {
		g_strlcpy(buf, mountpoint, size);
		mount_exists = TRUE;
	} else {
		mount_exists = FALSE;
	}
	G_UNLOCK(mounts);

	if (mount_exists) {
		return 0;
	} else {
		return -ENOENT;
	}
}

static struct fuse_operations volumesfs_oper = {
	.init = volumesfs_init,
	.destroy = volumesfs_destroy,
	.getattr = volumesfs_getattr,
	.readdir = volumesfs_readdir,
	.readlink = volumesfs_readlink
};

int main(int argc, char *argv[])
{
	return fuse_main(argc, argv, &volumesfs_oper, NULL);
}