// Author: Gockner, Simon
// Created: 2021-04-07
// Copyright(c) 2021 SimonG. All Rights Reserved.

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;
using Lib.NotifyIcon.Windows.Native.Types;

namespace Lib.NotifyIcon.Windows.Native
{
    internal abstract class NativeWindow
    {
        private const uint WS_POPUP = 0x80000000;
        
        // ReSharper disable once PrivateFieldCanBeConvertedToLocalVariable
        private readonly WindowApi.WndProc _wndProc; //We need to store the window proc as a field so that it doesn't get garbage collected away
        
        private readonly string _className = "NativeHelperWindow" + Guid.NewGuid();

        /// <summary>
        /// The window handle of the underlying native window
        /// </summary>
        public IntPtr Handle { get; }

        /// <summary>
        /// Creates a new native (Win32) helper window for receiving window messages
        /// </summary>
        protected NativeWindow()
        {
            _wndProc = WndProc;

            WndClassEx wndClassEx = new()
            {
                cbSize = Marshal.SizeOf<WndClassEx>(),
                lpfnWndProc = _wndProc,
                hInstance = WindowApi.GetModuleHandle(null),
                lpszClassName = _className
            };

            ushort atom = WindowApi.RegisterClassEx(ref wndClassEx);

            if (atom == 0)
                throw new Win32Exception();

            Handle = WindowApi.CreateWindowEx(0, atom, null, WS_POPUP, 0, 0, 0, 0, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero, IntPtr.Zero);

            if (Handle == IntPtr.Zero)
                throw new Win32Exception();
        }

        /// <summary>
        /// Destructs the object and destroys the native window
        /// </summary>
        ~NativeWindow()
        {
            if (Handle != IntPtr.Zero)
                WindowApi.PostMessage(Handle, (uint) WindowsMessage.WmDestroy, IntPtr.Zero, IntPtr.Zero);
        }

        /// <summary>
        /// This function will receive all the system window messages relevant to our window
        /// </summary>
        protected virtual IntPtr WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
        {
            switch (msg)
            {
                case (uint) WindowsMessage.WmClose:
                {
                    WindowApi.DestroyWindow(hWnd);
                    break;
                }
                case (uint) WindowsMessage.WmDestroy:
                {
                    WindowApi.PostQuitMessage(0);
                    break;
                }
                default:
                    return WindowApi.DefWindowProc(hWnd, msg, wParam, lParam);
            }
            
            return IntPtr.Zero;
        }
    }
}