//go:build windows

package main

import (
	"errors"
	"fmt"
	"path/filepath"
	"unsafe"

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

const (
	spiSetDesktopWallpaper = 0x0014
	spifUpdateINIFile      = 0x0001
	spifSendChange         = 0x0002
)

var (
	user32                    = windows.NewLazySystemDLL("user32.dll")
	procSystemParametersInfoW = user32.NewProc("SystemParametersInfoW")
)

func validWallpaperStyle(style string) bool {
	switch style {
	case "keep", "fill", "fit", "stretch", "tile", "center", "span":
		return true
	default:
		return false
	}
}

func setWallpaper(path, style string) error {
	absPath, err := filepath.Abs(path)
	if err != nil {
		return err
	}
	if style != "keep" {
		if err := setWallpaperStyle(style); err != nil {
			return err
		}
	}
	pathPtr, err := windows.UTF16PtrFromString(absPath)
	if err != nil {
		return err
	}
	r1, _, callErr := procSystemParametersInfoW.Call(
		spiSetDesktopWallpaper,
		0,
		uintptr(unsafe.Pointer(pathPtr)),
		spifUpdateINIFile|spifSendChange,
	)
	if r1 == 0 {
		if callErr != nil && !errors.Is(callErr, windows.ERROR_SUCCESS) {
			return fmt.Errorf("调用 Windows 壁纸接口: %w", callErr)
		}
		return errors.New("Windows 拒绝设置壁纸")
	}
	return nil
}

func setWallpaperStyle(style string) error {
	values := map[string][2]string{
		"fill":    {"10", "0"},
		"fit":     {"6", "0"},
		"stretch": {"2", "0"},
		"tile":    {"0", "1"},
		"center":  {"0", "0"},
		"span":    {"22", "0"},
	}
	value, ok := values[style]
	if !ok {
		return fmt.Errorf("不支持的壁纸显示方式: %s", style)
	}
	key, err := registry.OpenKey(registry.CURRENT_USER, `Control Panel\Desktop`, registry.SET_VALUE)
	if err != nil {
		return fmt.Errorf("打开壁纸设置: %w", err)
	}
	defer key.Close()
	if err := key.SetStringValue("WallpaperStyle", value[0]); err != nil {
		return fmt.Errorf("设置壁纸样式: %w", err)
	}
	if err := key.SetStringValue("TileWallpaper", value[1]); err != nil {
		return fmt.Errorf("设置壁纸平铺方式: %w", err)
	}
	return nil
}