package goutils

import (
	"fmt"
	"os"
	"syscall"
)

type FileLock struct {
	dir string
	f   *os.File
}

func NewFileLock(dir string) *FileLock {
	return &FileLock{
		dir: dir,
	}
}

func (l *FileLock) Lock() error {
	f, err := os.Open(l.dir)
	if err != nil {
		return err
	}

	l.f = f
	err = syscall.Flock(int(f.Fd()), syscall.LOCK_EX|syscall.LOCK_NB)
	if err != nil {
		return fmt.Errorf("cannot flock directory %s - %s", l.dir, err)
	}

	return nil
}

func (l *FileLock) Unlock() error {
	defer func() {
		if err := l.f.Close(); err != nil {
			fmt.Println(err)
		}
	}()
	return syscall.Flock(int(l.f.Fd()), syscall.LOCK_UN)
}