// Copyright 2010 The Walk Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build windows

package lib

import (
	"syscall"
	"unsafe"

	"github.com/lxn/win"
)

var (
	registeredWindowClasses = make(map[string]bool)
	defaultWndProcPtr       = syscall.NewCallback(defaultWndProc)
)

// MustRegisterWindowClass registers the specified window class.
//
// MustRegisterWindowClass must be called once for every window type that is not
// based on any system provided control, before calling InitChildWidget or
// InitWidget. Calling MustRegisterWindowClass twice with the same className
// results in a panic.
func MustRegisterWindowClass(className string) {
	MustRegisterWindowClassWithWndProcPtr(className, defaultWndProcPtr)
}

func MustRegisterWindowClassWithStyle(className string, style uint32) {
	MustRegisterWindowClassWithWndProcPtrAndStyle(className, defaultWndProcPtr, style)
}

func MustRegisterWindowClassWithWndProcPtr(className string, wndProcPtr uintptr) {
	MustRegisterWindowClassWithWndProcPtrAndStyle(className, wndProcPtr, 0)
}

func MustRegisterWindowClassWithWndProcPtrAndStyle(className string, wndProcPtr uintptr, style uint32) {
	if registeredWindowClasses[className] {
		panic("window class already registered")
	}

	hInst := win.GetModuleHandle(nil)
	if hInst == 0 {
		panic("GetModuleHandle")
	}

	hIcon := win.LoadIcon(hInst, win.MAKEINTRESOURCE(7)) // rsrc uses 7 for app icon
	if hIcon == 0 {
		hIcon = win.LoadIcon(0, win.MAKEINTRESOURCE(win.IDI_APPLICATION))
	}
	if hIcon == 0 {
		panic("LoadIcon")
	}

	hCursor := win.LoadCursor(0, win.MAKEINTRESOURCE(win.IDC_ARROW))
	if hCursor == 0 {
		panic("LoadCursor")
	}

	var wc win.WNDCLASSEX
	wc.CbSize = uint32(unsafe.Sizeof(wc))
	wc.LpfnWndProc = wndProcPtr
	wc.HInstance = hInst
	wc.HIcon = hIcon
	wc.HCursor = hCursor
	wc.HbrBackground = win.COLOR_BTNFACE + 1
	wc.LpszClassName = syscall.StringToUTF16Ptr(className)
	wc.Style = style

	if atom := win.RegisterClassEx(&wc); atom == 0 {
		panic("RegisterClassEx")
	}
	registeredWindowClasses[className] = true
}

func defaultWndProc(hwnd win.HWND, msg uint32, wParam, lParam uintptr) (result uintptr) {
	return win.DefWindowProc(hwnd, msg, wParam, lParam)
}