#include "defs.h"
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <err.h>
#include <errno.h>
#include <unistd.h>

#include "proc.h"
#include "dirinfo.h"
#include <fuse.h>
#include <fuse_log.h>
#include "filter.h"

struct tagfs_private_data
{
	struct dirinfo mntdir;
	struct dirinfo fsdir;
	struct dirinfo tagdir;
	struct dirinfo filterdir;
};

#define TAGFS_DATA ((struct tagfs_private_data*)fuse_get_context()->private_data)

int
tagfs_op_open(const char* path, struct fuse_file_info* fi) 
{
	fuse_log(FUSE_LOG_DEBUG, "open(%s)\n", path);

	if (*path == '\0')
		return -EACCES;

	int fd;
	
	if ((fd = openat(TAGFS_DATA->mntdir.fd, path + 1, fi->flags)) == -1)
		return -errno;

	fi->fh = fd;

	return 0;
}

int
tagfs_op_create(const char* path, mode_t mode, struct fuse_file_info* fi)
{
	fuse_log(FUSE_LOG_DEBUG, "create(%s)\n", path);

	int fd = -1;
	int flags = O_CREAT|O_RDWR;
	
	if (strrchr(path, '/') == path) {
		fd = openat(TAGFS_DATA->mntdir.fd, path + 1, flags, mode);
	}
	else if (strncmp(path, "/" TAGFS_FILTER_DIR, sizeof("/" TAGFS_FILTER_DIR) - 1) == 0) {
		const char* p = strrchr(path, '/');
		fd = openat(TAGFS_DATA->filterdir.fd, p + 1, flags, 0644);
	}

	if (fd == -1)
		return -1;

	fi->fh = fd;
	
	return 0;
}

int
tagfs_op_rename(const char* oldpath, const char* newpath, unsigned int flags)
{
	(void) flags;

	return renameat(TAGFS_DATA->mntdir.fd, oldpath + 1, TAGFS_DATA->mntdir.fd, newpath + 1);
}

int
tagfs_op_mkdir(const char* path, mode_t mode)
{
	fuse_log(FUSE_LOG_DEBUG, "mkdir(%s)\n", path);
	
	if (strncmp(path, "/" TAGFS_TAG_DIR, sizeof("/" TAGFS_TAG_DIR) - 1) != 0)
		return -1;

	const char* p = strrchr(path, '/');
	return mkdirat(TAGFS_DATA->tagdir.fd, p + 1, mode);
}

int
tagfs_op_rmdir(const char* path)
{
	fuse_log(FUSE_LOG_DEBUG, "rmdir(%s)\n", path);
	
	if (strncmp(path, "/" TAGFS_TAG_DIR, sizeof("/" TAGFS_TAG_DIR) - 1) != 0)
		return -1;

	const char* p = strrchr(path, '/');
	return unlinkat(TAGFS_DATA->tagdir.fd, p + 1, AT_REMOVEDIR);
}

int
tagfs_op_release(const char* path, struct fuse_file_info* fi)
{
	fuse_log(FUSE_LOG_DEBUG, "release(%s)\n", path);

	if (fi) 
		close(fi->fh);

	return 0;
}

int
tagfs_op_read(const char* path, char* buf, size_t size, off_t off, struct fuse_file_info* fi)
{
	fuse_log(FUSE_LOG_DEBUG, "read(%s)\n", path);

	ssize_t r = pread(fi->fh, buf, size, off);
	
	return r;
}

int
tagfs_op_write(const char* path, const char* buf, size_t size, off_t off, struct fuse_file_info* fi)
{
	fuse_log(FUSE_LOG_DEBUG, "write(%s)\n", path);

	ssize_t r = pwrite(fi->fh, buf, size, off);
	
	return r;
}

void
remove_from_tags(const char* name)
{
	rewinddir(TAGFS_DATA->tagdir.dp);

	struct dirent* tagent;
	while ((tagent = readdir(TAGFS_DATA->tagdir.dp))) {
		int fd = openat(TAGFS_DATA->tagdir.fd, tagent->d_name, O_DIRECTORY|O_RDONLY);
		if (fd == -1)
			continue;

		DIR* dp = fdopendir(fd);
		struct dirent* ent;
		while ((ent = readdir(dp))) {
			if (strcmp(name, ent->d_name) == 0)
				unlinkat(fd, ent->d_name, 0);
		}

		closedir(dp);
		close(fd);
	}
}

int
tagfs_op_unlink(const char* path)
{
	fuse_log(FUSE_LOG_DEBUG, "unlink(%s)\n", path);

	if (strrchr(path, '/') == path) {
		remove_from_tags(path + 1);
	}

	unlinkat(TAGFS_DATA->mntdir.fd, path + 1, 0);

	return 0;
}

void
fill_readdir(struct dirinfo* dir, void* buf, fuse_fill_dir_t filler, int skip_dirs)
{
	rewinddir(dir->dp);

	struct dirent* ent;
	while ((ent = readdir(dir->dp))) {
		struct stat stbuf;

		if (fstatat(dir->fd, ent->d_name, &stbuf, 0) == 0 && skip_dirs) {
			if ((stbuf.st_mode & S_IFDIR) == S_IFDIR)
				continue;
		}

		filler(buf, ent->d_name, &stbuf, 0, 0);
	}
}

/* Removes filter files for dead processes, run at access and readdir */
void
remove_dead_filters(void)
{
	DIR* dp = TAGFS_DATA->filterdir.dp;
	rewinddir(dp);
	
	struct dirent* ent;
	while ((ent = readdir(dp))) {
		char* end;
		int pid = strtol(ent->d_name, &end, 10);

		if (end && *end == 0 && !is_pid_alive(pid)) {
			unlinkat(TAGFS_DATA->filterdir.fd, ent->d_name, 0);
		}
	}
}

int
open_process_filter(unsigned pid)
{
	char path[PATH_MAX];
	snprintf(path, sizeof path, "%u", pid);

	return openat(TAGFS_DATA->filterdir.fd, path, O_RDONLY);
}

int
fill_readdir_filtered(int filterfd, void* buf, fuse_fill_dir_t filler)
{
	struct filter filter = { 0 };
	
	if (!load_filter_tags(filterfd, &filter)) {
		fuse_log(FUSE_LOG_DEBUG, "load_tags failed\n");
		filter_free(&filter);
		return 0;
	}

	if (!load_filter_files(&filter, &TAGFS_DATA->tagdir)) {
		fuse_log(FUSE_LOG_DEBUG, "load_files failed\n");
		filter_free(&filter);
		return 0;
	}

	int include_count = filter_include_count(&filter);
	int exclude_count = filter_exclude_count(&filter);

	if (include_count > 0) {
		for (size_t i = 0; i < filter.files.included.len; ++i) {
			fuse_log(FUSE_LOG_DEBUG, "- %s\n", filter.files.included.ptr[i]);

			if (filter.files.included.in[i] != include_count)
				continue;

			int skip = 0;
			for (size_t j = 0; j < filter.files.excluded.len; ++j) {
				skip = strcmp(filter.files.included.ptr[i], filter.files.excluded.ptr[j]) == 0;
			}

			if (skip)
				continue;

			filler(buf, filter.files.included.ptr[i], NULL, 0, 0);
		}
	}
	else if (exclude_count > 0) {
		int fd = TAGFS_DATA->mntdir.fd;
		DIR* dp = TAGFS_DATA->mntdir.dp;
		rewinddir(dp);
		struct dirent* ent;
		while ((ent = readdir(dp))) {
			struct stat stbuf;
			if (fstatat(fd, ent->d_name, &stbuf, 0) == 0 && (stbuf.st_mode & S_IFDIR) == S_IFDIR)
				continue;
			
			int skip = 0;
			for (size_t i = 0; i < filter.files.excluded.len; ++i) {
				if ((skip = strcmp(ent->d_name, filter.files.excluded.ptr[i]) == 0))
					break;
			}

			if (skip)
				continue;

			filler(buf, ent->d_name, NULL, 0, 0);
		}
	}

	filter_free(&filter);

	return 1;
}

int
tagfs_op_readdir(const char* path, void* buf, fuse_fill_dir_t filler, off_t off, struct fuse_file_info* fi, enum fuse_readdir_flags flags)
{
	fuse_log(FUSE_LOG_DEBUG, "readdir(%s)\n", path);
	
	remove_dead_filters();
	
	if (strcmp(path, "/") == 0)
	{
		unsigned pid = fuse_get_context()->pid;
		int fd = open_process_filter(pid);

		while (fd == -1 && pid != 1) {
			pid = proc_get_ppid(pid);
			fd = open_process_filter(pid);
		}

		if (fd == -1) {
			filler(buf, TAGFS_DIR, NULL, 0, 0);
			fill_readdir(&TAGFS_DATA->mntdir, buf, filler, 1);
		}
		else {
			filler(buf, TAGFS_DIR, NULL, 0, 0);
			if (!fill_readdir_filtered(fd, buf, filler))
				close(fd);
		}
	}
	else if (strcmp(path, "/" TAGFS_DIR) == 0)
	{
		fill_readdir(&TAGFS_DATA->fsdir, buf, filler, 0);
	}
	else if (strcmp(path, "/" TAGFS_TAG_DIR) == 0)
	{
		fill_readdir(&TAGFS_DATA->tagdir, buf, filler, 0);
	}
	else if (strncmp(path, "/" TAGFS_TAG_DIR, sizeof("/" TAGFS_TAG_DIR) - 1) == 0)
	{
		const char* rpath = strrchr(path, '/') + 1;
		int fd = openat(TAGFS_DATA->tagdir.fd, rpath, O_DIRECTORY|O_RDONLY);
		if (fd == -1)
			return -1;

		DIR* dp = fdopendir(fd);
		struct dirinfo dir = { fd, dp, (struct stat){0} };
		fill_readdir(&dir, buf, filler, 0);

		closedir(dp);
		close(fd);
	}
	else if (strcmp(path, "/" TAGFS_FILTER_DIR) == 0)
	{
		fill_readdir(&TAGFS_DATA->filterdir, buf, filler, 0);
	}

	return 0;
}

int
tagfs_op_readlink(const char* path, char* buf, size_t length)
{
	fuse_log(FUSE_LOG_DEBUG, "readlink(%s)\n", path);

	if (strncmp(path, "/" TAGFS_TAG_DIR, sizeof("/" TAGFS_TAG_DIR) - 1) != 0)
		return -1;

	const char* rpath = &path[sizeof("/" TAGFS_TAG_DIR)];
	fuse_log(FUSE_LOG_DEBUG, "- rpath(%s)\n", rpath);

	readlinkat(TAGFS_DATA->tagdir.fd, rpath, buf, length);

	return 0; 
}

int
tagfs_op_symlink(const char* target, const char* path)
{
	fuse_log(FUSE_LOG_DEBUG, "symlink(%s, %s)\n", target, path);

	if (strncmp(path, "/" TAGFS_TAG_DIR, sizeof("/" TAGFS_TAG_DIR) - 1) != 0)
		return -1;

	const char* rpath = &path[sizeof("/" TAGFS_TAG_DIR)];
	symlinkat(target, TAGFS_DATA->tagdir.fd, rpath);

	return 0;
}

int
tagfs_op_getattr(const char* path, struct stat* st, struct fuse_file_info* fi)
{
	fuse_log(FUSE_LOG_DEBUG, "getattr(%s)\n", path);

	if (strcmp(path, "/") == 0) {
		*st = TAGFS_DATA->mntdir.stat;
		return 0;
	}

	struct stat stbuf;
	if (fstatat(TAGFS_DATA->mntdir.fd, path + 1, &stbuf, 0) == -1)
		return -errno;

	*st = stbuf;

	return 0;
}

int
tagfs_op_access(const char* path, int mask)
{
	fuse_log(FUSE_LOG_DEBUG, "access(%s)\n", path);

	if (strcmp(path, "/") == 0) {
		return faccessat(TAGFS_DATA->mntdir.fd, ".", mask, 0);
		
	}
	
	return faccessat(TAGFS_DATA->mntdir.fd, path + 1, mask, 0);
}

void
init_tagfs_dir(int dirfd)
{
	mode_t mode = 0774;
	mkdirat(dirfd, TAGFS_DIR, mode);
	mkdirat(dirfd, TAGFS_TAG_DIR, mode);
	mkdirat(dirfd, TAGFS_FILTER_DIR, mode);
}

int
main(int argc, char** argv)
{
	struct fuse_operations tagfs_ops = {
		.open    = tagfs_op_open,
		.release = tagfs_op_release,
		.read    = tagfs_op_read,
		.write   = tagfs_op_write,
		.create  = tagfs_op_create,
		.rename  = tagfs_op_rename,
		.mkdir   = tagfs_op_mkdir,
		.rmdir   = tagfs_op_rmdir,
		.unlink  = tagfs_op_unlink,
		.readdir = tagfs_op_readdir,
		.readlink= tagfs_op_readlink,
		.symlink = tagfs_op_symlink,
		/*.chmod   = tagfs_op_chmod,
		.chown   = tagfs_op_chown,*/
		.access  = tagfs_op_access,
		.getattr = tagfs_op_getattr,
	};
	
	const char* mntpoint = argv[argc - 1];
	struct tagfs_private_data data;

	if (!open_dirinfo(mntpoint, &data.mntdir))
		err(1, "open_dirinfo(mntpoint)");

	init_tagfs_dir(data.mntdir.fd);

	if (!openat_dirinfo(data.mntdir.fd, TAGFS_DIR, &data.fsdir))
		err(1, "openat_dirinfo(fsdir)");

	if (!openat_dirinfo(data.mntdir.fd, TAGFS_TAG_DIR, &data.tagdir))
		err(1, "openat_dirinfo(tagdir)");

	if (!openat_dirinfo(data.mntdir.fd, TAGFS_FILTER_DIR, &data.filterdir))
		err(1, "openat_dirinfo(filterdir)");

	// FIXME: check if mount point is availeble, otherwise exit
	fuse_main(argc, argv, &tagfs_ops, &data);

	return 0;
}