//go:build linux

package update

import (
	domain "RenewCMS/internal/domain/update"
	"errors"
	"io"
	"io/fs"
	"os"
	"path/filepath"
	"syscall"
)

const (
	privateTempDirPrefix = "renewcms-update-"
	readNoFollowFlags    = os.O_RDONLY | syscall.O_NOFOLLOW | syscall.O_NONBLOCK
	createNoFollowFlags  = os.O_WRONLY | os.O_CREATE | os.O_EXCL | syscall.O_NOFOLLOW
	directoryFlags       = os.O_RDONLY | syscall.O_NOFOLLOW | syscall.O_DIRECTORY
)

var errNotRegularFile = errors.New("not a regular file")

type NoFollowFilesystem struct{}

var _ domain.HelperFilesystem = &NoFollowFilesystem{}

func NewNoFollowFilesystem() *NoFollowFilesystem {
	return &NoFollowFilesystem{}
}

func (f *NoFollowFilesystem) Lstat(path string) (domain.FileInfo, error) {
	info, err := os.Lstat(path)
	if err != nil {
		return domain.FileInfo{}, err
	}
	mode := info.Mode()
	return domain.FileInfo{
		IsSymlink: mode&fs.ModeSymlink != 0,
		IsDir:     mode.IsDir(),
		IsRegular: mode.IsRegular(),
	}, nil
}

func (f *NoFollowFilesystem) ReadFile(path string) ([]byte, error) {
	file, err := openRegularNoFollow(path)
	if err != nil {
		return nil, err
	}
	defer file.Close()
	return io.ReadAll(file)
}

func (f *NoFollowFilesystem) CreateExclusive(path string, content []byte, mode uint32) error {
	file, err := os.OpenFile(path, createNoFollowFlags, fs.FileMode(mode))
	if err != nil {
		return err
	}
	if _, err := file.Write(content); err != nil {
		file.Close()
		return err
	}
	return finishWrite(file, mode)
}

func (f *NoFollowFilesystem) Copy(source string, destination string, mode uint32) error {
	input, err := openRegularNoFollow(source)
	if err != nil {
		return err
	}
	defer input.Close()
	output, err := os.OpenFile(destination, createNoFollowFlags, fs.FileMode(mode))
	if err != nil {
		return err
	}
	if _, err := io.Copy(output, input); err != nil {
		output.Close()
		return err
	}
	return finishWrite(output, mode)
}

func (f *NoFollowFilesystem) Rename(oldPath string, newPath string) error {
	return os.Rename(oldPath, newPath)
}

func (f *NoFollowFilesystem) Remove(path string) error {
	return os.Remove(path)
}

func (f *NoFollowFilesystem) RemoveAll(path string) error {
	info, err := os.Lstat(path)
	if errors.Is(err, fs.ErrNotExist) {
		return nil
	}
	if err != nil {
		return err
	}
	if !info.IsDir() {
		return os.Remove(path)
	}
	names, err := readDirectoryNames(path)
	if err != nil {
		return err
	}
	for _, name := range names {
		if err := f.RemoveAll(filepath.Join(path, name)); err != nil {
			return err
		}
	}
	return os.Remove(path)
}

func (f *NoFollowFilesystem) Chmod(path string, mode uint32) error {
	file, err := os.OpenFile(path, readNoFollowFlags, 0)
	if err != nil {
		return err
	}
	defer file.Close()
	return file.Chmod(fs.FileMode(mode))
}

func (f *NoFollowFilesystem) MakePrivateTempDir() (string, error) {
	return os.MkdirTemp("", privateTempDirPrefix)
}

func openRegularNoFollow(path string) (*os.File, error) {
	file, err := os.OpenFile(path, readNoFollowFlags, 0)
	if err != nil {
		return nil, err
	}
	info, err := file.Stat()
	if err != nil {
		file.Close()
		return nil, err
	}
	if !info.Mode().IsRegular() {
		file.Close()
		return nil, errNotRegularFile
	}
	return file, nil
}

func finishWrite(file *os.File, mode uint32) error {
	if err := file.Chmod(fs.FileMode(mode)); err != nil {
		file.Close()
		return err
	}
	if err := file.Sync(); err != nil {
		file.Close()
		return err
	}
	return file.Close()
}

func readDirectoryNames(path string) ([]string, error) {
	directory, err := os.OpenFile(path, directoryFlags, 0)
	if err != nil {
		return nil, err
	}
	defer directory.Close()
	return directory.Readdirnames(-1)
}