//go:build windows

package main

import (
	"errors"
	"unsafe"

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

const instanceMutexName = `Local\GoWallpaper-4F831CA6-6890-4D95-91A3-A819D7F29718`

func acquireSingleInstance() (windows.Handle, bool, error) {
	name, err := windows.UTF16PtrFromString(instanceMutexName)
	if err != nil {
		return 0, false, err
	}
	handle, err := windows.CreateMutex(nil, false, name)
	if errors.Is(err, windows.ERROR_ALREADY_EXISTS) {
		return handle, true, nil
	}
	if err != nil {
		return 0, false, err
	}
	return handle, false, nil
}

func showNativeMessage(title, message string) {
	titlePtr, _ := windows.UTF16PtrFromString(title)
	messagePtr, _ := windows.UTF16PtrFromString(message)
	procMessageBoxW := user32.NewProc("MessageBoxW")
	procMessageBoxW.Call(
		0,
		uintptr(unsafe.Pointer(messagePtr)),
		uintptr(unsafe.Pointer(titlePtr)),
		0x00000040,
	)
}