/*************************************************************************************

   Extended WPF Toolkit

   Copyright (C) 2007-2013 Xceed Software Inc.

   This program is provided to you under the terms of the Microsoft Public
   License (Ms-PL) as published at http://wpftoolkit.codeplex.com/license 

   For more features, controls, and fast professional support,
   pick up the Plus Edition at http://xceed.com/wpf_toolkit

   Stay informed: follow @datagrid on Twitter or Like http://facebook.com/datagrids

  ***********************************************************************************/

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Windows.Input;
using System.Windows.Interop;
using System.Windows;
using System.Diagnostics;
using Xceed.Wpf.AvalonDock.Layout;
using System.Windows.Media;
using System.Windows.Threading;

namespace Xceed.Wpf.AvalonDock.Controls
{
    internal static class FocusElementManager
    {
        #region Focus Management
        static List<DockingManager> _managers = new List<DockingManager>();
        internal static void SetupFocusManagement(DockingManager manager)
        {
            if (_managers.Count == 0)
            {
                //InputManager.Current.EnterMenuMode += new EventHandler(InputManager_EnterMenuMode);
                //InputManager.Current.LeaveMenuMode += new EventHandler(InputManager_LeaveMenuMode);
                _windowHandler = new WindowHookHandler();
                _windowHandler.FocusChanged += new EventHandler<FocusChangeEventArgs>(WindowFocusChanging);
                //_windowHandler.Activate += new EventHandler<WindowActivateEventArgs>(WindowActivating);
                _windowHandler.Attach();

                if (Application.Current != null)
                    Application.Current.Exit += new ExitEventHandler(Current_Exit);
            }

            manager.PreviewGotKeyboardFocus += new KeyboardFocusChangedEventHandler(manager_PreviewGotKeyboardFocus);
            _managers.Add(manager);
        }

        internal static void FinalizeFocusManagement(DockingManager manager)
        {
            manager.PreviewGotKeyboardFocus -= new KeyboardFocusChangedEventHandler(manager_PreviewGotKeyboardFocus);
            _managers.Remove(manager);

            if (_managers.Count == 0)
            {
                //InputManager.Current.EnterMenuMode -= new EventHandler(InputManager_EnterMenuMode);
                //InputManager.Current.LeaveMenuMode -= new EventHandler(InputManager_LeaveMenuMode);
                if (_windowHandler != null)
                {
                    _windowHandler.FocusChanged -= new EventHandler<FocusChangeEventArgs>(WindowFocusChanging);
                    //_windowHandler.Activate -= new EventHandler<WindowActivateEventArgs>(WindowActivating);
                    _windowHandler.Detach();
                    _windowHandler = null;
                }
            }

        }

        private static void Current_Exit(object sender, ExitEventArgs e)
        {
            Application.Current.Exit -= new ExitEventHandler(Current_Exit);
            if (_windowHandler != null)
            {
                _windowHandler.FocusChanged -= new EventHandler<FocusChangeEventArgs>(WindowFocusChanging);
                //_windowHandler.Activate -= new EventHandler<WindowActivateEventArgs>(WindowActivating);
                _windowHandler.Detach();
                _windowHandler = null;
            }
        }

        static void manager_PreviewGotKeyboardFocus(object sender, KeyboardFocusChangedEventArgs e)
        {
            var focusedElement = e.NewFocus as Visual;
            if (focusedElement != null &&
                !(focusedElement is LayoutAnchorableTabItem || focusedElement is LayoutDocumentTabItem))
              //Avoid tracking focus for elements like this
            {
                var parentAnchorable = focusedElement.FindVisualAncestor<LayoutAnchorableControl>();
                if (parentAnchorable != null)
                {
                    _modelFocusedElement[parentAnchorable.Model] = e.NewFocus;
                }
                else
                {
                    var parentDocument = focusedElement.FindVisualAncestor<LayoutDocumentControl>();
                    if (parentDocument != null)
                    {
                        _modelFocusedElement[parentDocument.Model] = e.NewFocus;
                    }
                }
            }
        }

        static FullWeakDictionary<ILayoutElement, IInputElement> _modelFocusedElement = new FullWeakDictionary<ILayoutElement, IInputElement>();
        static WeakDictionary<ILayoutElement, IntPtr> _modelFocusedWindowHandle = new WeakDictionary<ILayoutElement, IntPtr>();

        /// <summary>
        /// Get the input element that was focused before user left the layout element
        /// </summary>
        /// <param name="model">Element to look for</param>
        /// <returns>Input element </returns>
        internal static IInputElement GetLastFocusedElement(ILayoutElement model)
        {
            IInputElement objectWithFocus;
            if (_modelFocusedElement.GetValue(model, out objectWithFocus))
                return objectWithFocus;

            return null;
        }


        /// <summary>
        /// Get the last window handle focused before user left the element passed as argument
        /// </summary>
        /// <param name="model"></param>
        /// <returns></returns>
        internal static IntPtr GetLastWindowHandle(ILayoutElement model)
        {
            IntPtr handleWithFocus;
            if (_modelFocusedWindowHandle.GetValue(model, out handleWithFocus))
                return handleWithFocus;

            return IntPtr.Zero;
        }
        static WeakReference _lastFocusedElement;

        /// <summary>
        /// Given a layout element tries to set the focus of the keyword where it was before user moved to another element
        /// </summary>
        /// <param name="model"></param>
        internal static void SetFocusOnLastElement(ILayoutElement model)
        {
            bool focused = false;
            IInputElement objectToFocus;
            if (_modelFocusedElement.GetValue(model, out objectToFocus))
            {
                focused = objectToFocus == Keyboard.Focus(objectToFocus);
            }

            IntPtr handleToFocus;
            if (_modelFocusedWindowHandle.GetValue(model, out handleToFocus))
                focused = IntPtr.Zero != Win32Helper.SetFocus(handleToFocus);

            Trace.WriteLine( string.Format( "SetFocusOnLastElement(focused={0}, model={1}, element={2})", focused, model, handleToFocus == IntPtr.Zero ? ( objectToFocus == null ? "" : objectToFocus.ToString() ) : handleToFocus.ToString() ) );

            if (focused)
            {
                _lastFocusedElement = new WeakReference(model);
            }

        }

        static WindowHookHandler _windowHandler = null;

        static void WindowFocusChanging(object sender, FocusChangeEventArgs e)
        {
            foreach (var manager in _managers)
            {
                var hostContainingFocusedHandle = manager.FindLogicalChildren<HwndHost>().FirstOrDefault(hw => Win32Helper.IsChild(hw.Handle, e.GotFocusWinHandle));

                if (hostContainingFocusedHandle != null)
                {
                    var parentAnchorable = hostContainingFocusedHandle.FindVisualAncestor<LayoutAnchorableControl>();
                    if (parentAnchorable != null)
                    {
                        _modelFocusedWindowHandle[parentAnchorable.Model] = e.GotFocusWinHandle;
                        if (parentAnchorable.Model != null)
                            parentAnchorable.Model.IsActive = true;
                    }
                    else
                    {
                        var parentDocument = hostContainingFocusedHandle.FindVisualAncestor<LayoutDocumentControl>();
                        if (parentDocument != null)
                        {
                            _modelFocusedWindowHandle[parentDocument.Model] = e.GotFocusWinHandle;
                            if (parentDocument.Model != null)
                                parentDocument.Model.IsActive = true;
                        }
                    }
                }


            }
        }

        static DispatcherOperation _setFocusAsyncOperation;

        static void WindowActivating(object sender, WindowActivateEventArgs e)
        {
            Trace.WriteLine("WindowActivating");

            if (Keyboard.FocusedElement == null && 
                _lastFocusedElement != null && 
                _lastFocusedElement.IsAlive)
            {
                var elementToSetFocus = _lastFocusedElement.Target as ILayoutElement;
                if (elementToSetFocus != null)
                {
                    var manager = elementToSetFocus.Root.Manager;
                    if (manager == null)
                        return;

                    IntPtr parentHwnd;
                    if (!manager.GetParentWindowHandle(out parentHwnd))
                        return;

                    if (e.HwndActivating != parentHwnd)
                        return;

                    _setFocusAsyncOperation = Dispatcher.CurrentDispatcher.BeginInvoke(new Action(() =>
                    {
                        try
                        {
                            SetFocusOnLastElement(elementToSetFocus);
                        }
                        finally
                        {
                            _setFocusAsyncOperation = null;
                        }
                    }), DispatcherPriority.Background);
                }
            }
        }


        static WeakReference _lastFocusedElementBeforeEnterMenuMode = null;
        static void InputManager_EnterMenuMode(object sender, EventArgs e)
        {
            if (Keyboard.FocusedElement == null)
                return;

            var lastfocusDepObj = Keyboard.FocusedElement as DependencyObject;
            if (lastfocusDepObj.FindLogicalAncestor<DockingManager>() == null)
            {
                _lastFocusedElementBeforeEnterMenuMode = null;
                return;
            }

            _lastFocusedElementBeforeEnterMenuMode = new WeakReference(Keyboard.FocusedElement);
        }
        static void InputManager_LeaveMenuMode(object sender, EventArgs e)
        {
            if (_lastFocusedElementBeforeEnterMenuMode != null &&
                _lastFocusedElementBeforeEnterMenuMode.IsAlive)
            {
                var lastFocusedInputElement = _lastFocusedElementBeforeEnterMenuMode.GetValueOrDefault<UIElement>();
                if (lastFocusedInputElement != null)
                {
                    if (lastFocusedInputElement != Keyboard.Focus(lastFocusedInputElement))
                        Debug.WriteLine("Unable to activate the element");
                }
            }
        }

        #endregion

    }
}