// Author: Gockner, Simon
// Created: 2021-04-06
// Copyright(c) 2021 SimonG. All Rights Reserved.

using System;
using System.Collections.Generic;
using System.Drawing;
using Avalonia;
using Avalonia.Controls;
using Avalonia.Platform;
using Lib.NotifyIcon.Windows.Native;
using Lib.NotifyIcon.Windows.Native.Types;
using Point = Lib.NotifyIcon.Windows.Native.Types.Point;

namespace Lib.NotifyIcon.Windows
{
    public class NotifyIcon : INotifyIcon
    {
        private static int _nextUId;
        
        private readonly NotifyIconHelperWindow _helperWindow;
        private readonly int _uId;
        
        private bool _doubleClick;
        private bool _iconAdded;
        private Icon _icon;
        
        private string _iconPath = "";
        private string _toolTipText = "";
        private bool _visible;
        
        /// <summary>
        /// Creates a new <see cref="NotifyIcon"/> instance and sets up some required resources
        /// </summary>
        public NotifyIcon()
        {
            _uId = ++_nextUId;
            _helperWindow = new NotifyIconHelperWindow(this);
        }

        ~NotifyIcon() => UpdateIcon(true);

        /// <summary>
        /// Gets or sets the path for the notify icon
        /// </summary>
        public string IconPath
        {
            get => _iconPath;
            set
            {
                _iconPath = value;
                
                IAssetLoader assetLoader = AvaloniaLocator.Current.GetService<IAssetLoader>();
                _icon = new Icon(assetLoader.Open(new Uri(_iconPath)));
                
                UpdateIcon();
            }
        }
        
        /// <summary>
        /// Gets or sets the tooltip text for the notify icon
        /// </summary>
        public string ToolTipText 
        {
            get => _toolTipText;
            set
            {
                _toolTipText = value;
                UpdateIcon();
            }
        }
        
        /// <summary>
        /// Gets or sets the context menu for the notify icon
        /// </summary>
        public ContextMenu ContextMenu { get; set; }
        
        /// <summary>
        /// Gets or sets if the notify icon is visible in the taskbar notification area or not
        /// </summary>
        public bool Visible
        {
            get => _visible;
            set
            {
                _visible = value;
                UpdateIcon();
            }
        }
        
        /// <summary>
        /// Removes the notify icon from the taskbar notification area
        /// </summary>
        public void Remove() => UpdateIcon(true);

        /// <summary>
        /// Handles the NotifyIcon-specific window messages sent by the notification icon
        /// </summary>
        public void WndProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam)
        {
            //We only care about tray icon messages
            if (msg != (uint) CustomWindowsMessage.WmTrayMouse)
                return;

            //Determine the type of message and call the matching event handlers
            switch (lParam.ToInt32())
            {
                case (int) WindowsMessage.WmLButtonUp:
                {
                    if (!_doubleClick) 
                        Click?.Invoke(this, new EventArgs());
                    
                    _doubleClick = false;
                    break;
                }
                case (int) WindowsMessage.WmLButtonDblClk:
                {
                    DoubleClick?.Invoke(this, new EventArgs());
                    _doubleClick = true;
                    break;
                }
                case (int) WindowsMessage.WmRButtonUp:
                {
                    EventArgs e = new EventArgs();
                    RightClick?.Invoke(this, e);
                    ShowContextMenu();
                    break;
                }
            }
        }
        
        /// <summary>
        /// Shows, hides or removes the notify icon based on the set properties and parameters
        /// </summary>
        /// <param name="remove">If set to true, the notify icon will be removed</param>
        private void UpdateIcon(bool remove = false)
        {
            NotifyIconData iconData = new()
            {
                hWnd = _helperWindow.Handle,
                uID = _uId,
                uFlags = NIF.Tip | NIF.Message,
                uCallbackMessage = (int) CustomWindowsMessage.WmTrayMouse,
                hIcon = IntPtr.Zero,
                szTip = ToolTipText
            };

            if (!remove && _icon != null && Visible)
            {
                iconData.uFlags |= NIF.Icon;
                iconData.hIcon = _icon.Handle;

                if (!_iconAdded)
                {
                    WindowApi.Shell_NotifyIcon(NIM.Add, iconData);
                    _iconAdded = true;
                }
                else
                    WindowApi.Shell_NotifyIcon(NIM.Modify, iconData);
            }
            else
            {
                WindowApi.Shell_NotifyIcon(NIM.Delete, iconData);
                _iconAdded = false;
            }
        }
        
        /// <summary>
        /// If available, displays the notification icon's context menu
        /// </summary>
        private void ShowContextMenu()
        {
            if (ContextMenu == null)
                return;
            
            // Since we can't use the Avalonia ContextMenu directly due to shortcomings
            // regrading its positioning, we'll create a native context menu instead. 
            // This dictionary will map the menu item IDs which we'll need for the native 
            // menu to the MenuItems of the provided Avalonia ContextMenu.
            Dictionary<uint, MenuItem> contextItemLookup = new();

            // Create a native (Win32) popup menu as the notify icon's context menu.
            IntPtr popupMenu = WindowApi.CreatePopupMenu();

            uint i = 1;
            foreach (var item in ContextMenu.Items)
            {
                if (item is MenuItem menuItem)
                {
                    // Add items to the native context menu by simply reusing
                    // the information provided within the Avalonia ContextMenu.
                    WindowApi.AppendMenu(popupMenu, MenuFlags.MfString, i, (string) menuItem.Header);

                    // Add the mapping so that we can find the selected item later
                    contextItemLookup.Add(i, menuItem);
                }
                else if (item is Separator)
                    WindowApi.AppendMenu(popupMenu, MenuFlags.MfSeparator, i, null);

                i++;
            }

            // To display a context menu for a notification icon, the current window 
            // must be the foreground window before the application calls TrackPopupMenu 
            // or TrackPopupMenuEx. Otherwise, the menu will not disappear when the user 
            // clicks outside of the menu or the window that created the menu (if it is 
            // visible). If the current window is a child window, you must set the 
            // (top-level) parent window as the foreground window.
            WindowApi.SetForegroundWindow(_helperWindow.Handle);

            // Get the mouse cursor position
            WindowApi.GetCursorPos(out Point pt);

            // Now display the context menu and block until we get a result
            uint commandId = WindowApi.TrackPopupMenuEx(popupMenu, 
                UFlags.TpmBottomAlign | UFlags.TpmRightAlign | UFlags.TpmNoNotify | UFlags.TpmReturnCmd,
                pt.X, pt.Y, _helperWindow.Handle, IntPtr.Zero);

            // If we have a result, execute the corresponding command
            if (commandId != 0)
                contextItemLookup[commandId].Command?.Execute(null);
        }

        public event EventHandler<EventArgs> Click;
        public event EventHandler<EventArgs> DoubleClick;
        public event EventHandler<EventArgs> RightClick;
    }
}