//go:build windows

package instance

import (
	"errors"

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

type windowsInstanceLock struct {
	handle windows.Handle
}

// tryAcquireInstanceLock 用共享模式为 0 的 CreateFile 独占锁文件：
// 已被占用的锁文件会返回 ERROR_SHARING_VIOLATION，此时调用方继续扫描下一个槽位。
func tryAcquireInstanceLock(path string) (instanceLock, bool, error) {
	handle, err := windows.CreateFile(
		windows.StringToUTF16Ptr(path),
		windows.GENERIC_READ|windows.GENERIC_WRITE,
		0,
		nil,
		windows.OPEN_ALWAYS,
		windows.FILE_ATTRIBUTE_NORMAL,
		0,
	)
	if err != nil {
		if errors.Is(err, windows.ERROR_SHARING_VIOLATION) || errors.Is(err, windows.ERROR_ACCESS_DENIED) {
			return nil, false, nil
		}
		return nil, false, err
	}
	return &windowsInstanceLock{handle: handle}, true, nil
}

func (l *windowsInstanceLock) Close() error {
	if l == nil || l.handle == windows.InvalidHandle {
		return nil
	}
	err := windows.CloseHandle(l.handle)
	l.handle = windows.InvalidHandle
	return err
}