using Windows.Win32.Foundation;
using UIAutomationClient;
using System.Diagnostics;

namespace TheXamlGuy.TaskbarGroup.Core
{

    public class TaskbarButtonMonitor : ITaskbarButtonMonitor
    {
        private readonly IDispatcherTimer dispatcherTimer;
        private readonly IDispatcherTimerFactory dispatcherTimerFactory;
        private readonly ITaskbarList taskbarList;
        private readonly IMessenger messenger;
        private readonly IServiceFactory serviceFactory;
        private readonly IDisposer disposer;
        private readonly Dictionary<string, TaskbarButton> taskbarButtons = new();
        private Rect? taskbarRectCache;
        private IUIAutomationCondition? taskListCondition;
        private IUIAutomationElement? taskListElement;
        private IntPtr taskListHandle;

        public TaskbarButtonMonitor(ITaskbarList taskbarList,
            IMessenger messenger, 
            IDispatcherTimerFactory dispatcherTimerFactory,
            IServiceFactory serviceFactory,
            IDisposer disposer)
        {
            this.taskbarList = taskbarList;
            this.messenger = messenger;
            this.dispatcherTimerFactory = dispatcherTimerFactory;
            this.serviceFactory = serviceFactory;
            this.disposer = disposer;

            disposer.Add(this, dispatcherTimer = dispatcherTimerFactory.Create(OnDispatcher, TimeSpan.FromMilliseconds(500)));
        }

        public void Initialize()
        {
            var clientUIAutomation = new CUIAutomation();
            taskListCondition = clientUIAutomation.CreateTrueCondition();

            taskListHandle = taskbarList.GetHandle();
            taskListElement = clientUIAutomation.ElementFromHandle(taskListHandle);

            if (WindowHelper.TryGetBounds(taskListHandle, out var rect))
            {
                taskbarRectCache = rect;
            }

            dispatcherTimer.Start();
            UpdateTaskbarButtons();
        }

        private bool CheckDirtyTaskbarRegion()
        {
            if (WindowHelper.TryGetBounds(taskListHandle, out var rect))
            {
                if (taskbarRectCache?.Width != rect.Width || taskbarRectCache?.Height != rect.Height)
                {
                    taskbarRectCache = rect;
                    return true;
                }
            }

            return false;
        }

        private Dictionary<string, tagRECT> FindTaskbarButtons()
        {
            var taskElements = taskListElement?.FindAll(TreeScope.TreeScope_Descendants | TreeScope.TreeScope_Children, taskListCondition);

            var buttons = new Dictionary<string, tagRECT>();
            if (taskElements is not null)
            {
                for (var index = 0; index <= taskElements.Length - 1; index++)
                {
                    var taskUIElement = taskElements.GetElement(index);
                    var name = taskUIElement.CurrentName;
                    var rect = taskUIElement.CurrentBoundingRectangle;

                    buttons.Add(name, rect);
                }
            }

            return buttons;
        }

        private void OnDispatcher()
        {
            dispatcherTimer.Stop();

            if (CheckDirtyTaskbarRegion())
            {
                UpdateTaskbarButtons();
            }

            dispatcherTimer.Start();
        }

        private void UpdateTaskbarButtons()
        {
            if (taskListElement is null)
            {
                return;
            }

            var buttons = FindTaskbarButtons();

            foreach (var buttonToRemove in taskbarButtons.Where(taskbarButton => !buttons.ContainsKey(taskbarButton.Key)))
            {
                var key = buttonToRemove.Key;
                var button = buttonToRemove.Value;

                Debug.WriteLine($"{key} button removed");

                taskbarButtons.Remove(key);
                messenger.Send(new TaskbarButtonRemoved(button));

                button.Dispose();
            }

            foreach (var button in buttons)
            {
                var name = button.Key;
                var bounds = button.Value;

                var rect = new Rect(bounds.left,
                    bounds.top,
                    bounds.right - bounds.left,
                    bounds.bottom - bounds.top);

                if (taskbarButtons.TryGetValue(name, out var taskbarButton))
                {
                    Debug.WriteLine($"{name} button updated");

                    taskbarButtons[name].Rect = rect;
                    messenger.Send(new TaskbarButtonUpdated(taskbarButtons[name]));
                }
                else
                {
                    Debug.WriteLine($"{name} button added");

                    taskbarButtons.Add(name, serviceFactory.Create<TaskbarButton>(name, rect));
                    messenger.Send(new TaskbarButtonCreated(taskbarButtons[name]));
                }
            }
        }
    }
}