//go:build windows

package filelock

import (
	"errors"
	"os"

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

func tryLockFile(path string) (func(), error) {
	return tryLockFileMode(path, ModeExclusive)
}

func tryLockFileMode(path string, mode Mode) (func(), error) {
	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o600)
	if err != nil {
		if errors.Is(err, windows.ERROR_SHARING_VIOLATION) {
			return nil, ErrHeld
		}
		return nil, err
	}
	handle := windows.Handle(f.Fd())
	var overlapped windows.Overlapped
	flags := uint32(windows.LOCKFILE_EXCLUSIVE_LOCK | windows.LOCKFILE_FAIL_IMMEDIATELY)
	if mode == ModeShared {
		flags = uint32(windows.LOCKFILE_FAIL_IMMEDIATELY)
	}
	if err := windows.LockFileEx(handle, flags, 0, 1, 0, &overlapped); err != nil {
		_ = f.Close()
		if errors.Is(err, windows.ERROR_LOCK_VIOLATION) || errors.Is(err, windows.ERROR_SHARING_VIOLATION) {
			return nil, ErrHeld
		}
		return nil, err
	}
	return func() {
		_ = windows.UnlockFileEx(handle, 0, 1, 0, &overlapped)
		_ = f.Close()
	}, nil
}