//go:build windows

package common

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

// LockFileEx's exclusive byte-range lock is released by Windows if either
// process exits. The shared lock file coordinates SDK and game server saves.
func lockPersistentFile() (func(), error) {
	file, err := os.OpenFile("persistent.lock", os.O_CREATE|os.O_RDWR, 0600)
	if err != nil {
		return nil, err
	}
	dll := syscall.NewLazyDLL("kernel32.dll")
	lock := dll.NewProc("LockFileEx")
	unlock := dll.NewProc("UnlockFileEx")
	overlapped := new(syscall.Overlapped)
	const lockfileExclusiveLock = 2 // Win32 LOCKFILE_EXCLUSIVE_LOCK.
	ok, _, callErr := lock.Call(file.Fd(), lockfileExclusiveLock, 0, 1, 0, uintptr(unsafe.Pointer(overlapped)))
	if ok == 0 {
		file.Close()
		return nil, fmt.Errorf("lock persistent: %w", callErr)
	}
	return func() { unlock.Call(file.Fd(), 0, 1, 0, uintptr(unsafe.Pointer(overlapped))); file.Close() }, nil
}