//go:build windows

package main

import (
	"bytes"
	_ "embed"
	"encoding/binary"
	"os"
	"path/filepath"
	"syscall"
	"unsafe"
)

//go:embed panel_icon.png
var panelIconPNG []byte

func setWindowIcon(windowPtr unsafe.Pointer) {
	hwnd := uintptr(windowPtr)
	if hwnd == 0 {
		return
	}

	// Write a temp ICO file (Windows LoadImage needs a file path)
	icoData := wrapPNG(panelIconPNG, 64, 64)
	icoPath := filepath.Join(os.TempDir(), "syncwarden-panel.ico")
	if err := os.WriteFile(icoPath, icoData, 0644); err != nil {
		return
	}

	user32 := syscall.NewLazyDLL("user32.dll")
	loadImage := user32.NewProc("LoadImageW")
	sendMessage := user32.NewProc("SendMessageW")

	pathW, _ := syscall.UTF16PtrFromString(icoPath)

	const (
		imageIcon      = 1
		lrLoadFromFile = 0x0010
		wmSetIcon      = 0x0080
		iconBig        = 1
		iconSmall      = 0
	)

	hBig, _, _ := loadImage.Call(0, uintptr(unsafe.Pointer(pathW)), imageIcon, 32, 32, lrLoadFromFile)
	if hBig != 0 {
		sendMessage.Call(hwnd, wmSetIcon, iconBig, hBig)
	}

	hSmall, _, _ := loadImage.Call(0, uintptr(unsafe.Pointer(pathW)), imageIcon, 16, 16, lrLoadFromFile)
	if hSmall != 0 {
		sendMessage.Call(hwnd, wmSetIcon, iconSmall, hSmall)
	}
}

func wrapPNG(pngData []byte, width, height int) []byte {
	const headerSize = 6
	const entrySize = 16
	imageOffset := headerSize + entrySize

	buf := new(bytes.Buffer)
	binary.Write(buf, binary.LittleEndian, uint16(0))
	binary.Write(buf, binary.LittleEndian, uint16(1))
	binary.Write(buf, binary.LittleEndian, uint16(1))

	w := byte(width)
	if width >= 256 {
		w = 0
	}
	h := byte(height)
	if height >= 256 {
		h = 0
	}
	buf.WriteByte(w)
	buf.WriteByte(h)
	buf.WriteByte(0)
	buf.WriteByte(0)
	binary.Write(buf, binary.LittleEndian, uint16(1))
	binary.Write(buf, binary.LittleEndian, uint16(32))
	binary.Write(buf, binary.LittleEndian, uint32(len(pngData)))
	binary.Write(buf, binary.LittleEndian, uint32(imageOffset))

	buf.Write(pngData)
	return buf.Bytes()
}