package ari

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

type LockFile struct {
	path string
	file *os.File
}

func AcquireLock(path string) (*LockFile, error) {
	file, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		return nil, err
	}
	if err := syscall.Flock(int(file.Fd()), syscall.LOCK_EX|syscall.LOCK_NB); err != nil {
		_ = file.Close()
		return nil, fmt.Errorf("ARI events listener lock is already held: %s", path)
	}
	_, _ = file.WriteString(fmt.Sprintf("%d\n", os.Getpid()))
	return &LockFile{path: path, file: file}, nil
}

func (l *LockFile) Release() error {
	if l == nil || l.file == nil {
		return nil
	}
	_ = syscall.Flock(int(l.file.Fd()), syscall.LOCK_UN)
	return l.file.Close()
}