//go:build !windows

package version

import (
	"errors"
	"fmt"
	"os"

	"golang.org/x/sys/unix"
)

func lockFile(file *os.File) error {
	return unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB)
}

func unlockFile(file *os.File) error {
	return unix.Flock(int(file.Fd()), unix.LOCK_UN)
}

func isLockContended(err error) bool {
	return errors.Is(err, unix.EWOULDBLOCK) || errors.Is(err, unix.EAGAIN)
}

// Locking the directory inode as well as the named file prevents another
// cooperating updater from bypassing the lock by unlinking and recreating the
// lock pathname while a transaction is active.
func openUpdateLockAnchor(directory string) (*os.File, error) {
	return os.Open(directory)
}

func releaseUpdateLockAnchor(anchor *os.File) error {
	if anchor == nil {
		return nil
	}
	unlockErr := unlockFile(anchor)
	closeErr := anchor.Close()
	if unlockErr != nil {
		return fmt.Errorf("unlock update directory anchor: %w", unlockErr)
	}
	if closeErr != nil {
		return fmt.Errorf("close update directory anchor: %w", closeErr)
	}
	return nil
}

func syncDirectory(path string) error {
	directory, err := os.Open(path)
	if err != nil {
		return err
	}
	defer directory.Close()
	return directory.Sync()
}