//go:build !windows

package store

import (
	"errors"
	"os"
	"syscall"
)

func acquireInstanceLock(path string) (func() error, error) {
	if err := ensurePrivateFile(path); err != nil {
		return nil, err
	}
	file, err := os.OpenFile(path, os.O_RDWR, 0)
	if err != nil {
		return nil, err
	}
	if err := syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		_ = file.Close()
		if errors.Is(err, syscall.EWOULDBLOCK) {
			return nil, ErrAlreadyOpen
		}
		return nil, err
	}
	return func() error {
		unlockErr := syscall.Flock(int(file.Fd()), syscall.LOCK_UN)
		closeErr := file.Close()
		if unlockErr != nil {
			return unlockErr
		}
		return closeErr
	}, nil
}