using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Markup;
using System.Windows.Shapes;
using System.Windows.Threading;
using Tango.Core.Threading;

namespace Tango.Touch.Controls
{
    [ContentProperty(nameof(Content))]
    public class TouchVirtualizedContentReplaceControl : Control
    {
        private LightTouchScrollViewer _scrollViewer;
        private Border _innerBorder;
        private ActionTimer _updateTimer;
        private Point _location;
        private bool _loaded;
        private Image _replaceContent;
        private FrameworkElement _element;
        private INameScopeDictionary _parentNameScope;

        public DataTemplate Content
        {
            get { return (DataTemplate)GetValue(ContentProperty); }
            set { SetValue(ContentProperty, value); }
        }
        public static readonly DependencyProperty ContentProperty =
            DependencyProperty.Register("Content", typeof(DataTemplate), typeof(TouchVirtualizedContentReplaceControl), new PropertyMetadata(null));

        public bool CanMovePosition
        {
            get { return (bool)GetValue(CanMovePositionProperty); }
            set { SetValue(CanMovePositionProperty, value); }
        }
        public static readonly DependencyProperty CanMovePositionProperty =
            DependencyProperty.Register("CanMovePosition", typeof(bool), typeof(TouchVirtualizedContentReplaceControl), new PropertyMetadata(false));

        public LightTouchDataGrid DataGrid
        {
            get { return (LightTouchDataGrid)GetValue(DataGridProperty); }
            set { SetValue(DataGridProperty, value); }
        }
        public static readonly DependencyProperty DataGridProperty =
            DependencyProperty.Register("DataGrid", typeof(LightTouchDataGrid), typeof(TouchVirtualizedContentReplaceControl), new PropertyMetadata(null));

        public bool Disconnect
        {
            get { return (bool)GetValue(DisconnectProperty); }
            set { SetValue(DisconnectProperty, value); }
        }
        public static readonly DependencyProperty DisconnectProperty =
            DependencyProperty.Register("Disconnect", typeof(bool), typeof(TouchVirtualizedContentReplaceControl), new PropertyMetadata(true));

        static TouchVirtualizedContentReplaceControl()
        {
            DefaultStyleKeyProperty.OverrideMetadata(typeof(TouchVirtualizedContentReplaceControl), new FrameworkPropertyMetadata(typeof(TouchVirtualizedContentReplaceControl)));
        }

        public TouchVirtualizedContentReplaceControl()
        {
            _replaceContent = new Image();
            _updateTimer = new ActionTimer(TimeSpan.FromMilliseconds(100));
            Loaded += TouchVirtualizedContentControl_Loaded;
        }

        public override void OnApplyTemplate()
        {
            base.OnApplyTemplate();
            _innerBorder = GetTemplateChild("PART_innerBorder") as Border;
            _innerBorder.Child = _replaceContent;
        }

        private void TouchVirtualizedContentControl_Loaded(object sender, System.Windows.RoutedEventArgs e)
        {
            _scrollViewer = this.FindAncestor<LightTouchScrollViewer>();
            _scrollViewer.Scrolling += _scrollViewer_Scrolling;

            _parentNameScope = NameScope.GetNameScope(this.FindAncestor<UserControl>()) as INameScopeDictionary;

            if (DataGrid != null)
            {
                DataGrid.SortingChanged += DataGrid_SortingChanged;
                DataGrid.FilterChanged += DataGrid_FilterChanged;
            }

            _location = this.TranslatePoint(new Point(0, 0), _scrollViewer.GetContentGrid());

            _scrollViewer.GetContentGrid().SizeChanged += TouchVirtualizedContentControl_SizeChanged;

            ApplyVirtualization();
            _loaded = true;
        }

        private void DataGrid_FilterChanged(object sender, EventArgs e)
        {
            InvalidateVirtualization();
        }

        private void DataGrid_SortingChanged(object sender, EventArgs e)
        {
            InvalidateVirtualization();
        }

        private void TouchVirtualizedContentControl_SizeChanged(object sender, SizeChangedEventArgs e)
        {
            InvalidateVirtualization();
        }

        private void _scrollViewer_Scrolling(object sender, DoubleValueChangedEventArgs e)
        {
            if (_loaded)
            {
                ApplyVirtualization();
            }
        }

        private void InvalidateVirtualization()
        {
            _updateTimer.ResetReplace(() =>
            {
                Dispatcher.Invoke(new Action(() =>
                {
                    _location = this.TranslatePoint(new Point(0, 0), _scrollViewer.GetContentGrid());
                    ApplyVirtualization();
                }));
            });
        }

        private void ApplyVirtualization()
        {
            if (!Disconnect && _element != null)
            {
                _updateTimer.Dispose();
                return;
            }

            var _border_viewport = _scrollViewer.GetViewportBorder();

            if (CanMovePosition)
            {
                _location = this.TranslatePoint(new Point(0, 0), _scrollViewer.GetContentGrid());
            }

            Rect bounds = new Rect(_location.X, _location.Y, ActualWidth, ActualHeight);
            Rect rect = new Rect(0.0, _scrollViewer.GetScrollPosition(), _border_viewport.ActualWidth, _border_viewport.ActualHeight);

            if (_innerBorder != null)
            {
                if (bounds.IntersectsWith(rect))
                {
                    if (Disconnect || _element == null)
                    {
                        if (_innerBorder.Child == _replaceContent || _element == null)
                        {
                            _element = Content.LoadContent() as FrameworkElement;

                            if (_parentNameScope != null)
                            {
                                NameScope.SetNameScope(_element, _parentNameScope);
                            }

                            _innerBorder.Child = _element;
                            _innerBorder.Height = double.NaN;
                        }
                    }
                }
                else
                {
                    if (Disconnect)
                    {
                        if (_innerBorder.Child == _element)
                        {
                            double height = _element != null ? _element.ActualHeight : MinHeight;
                            _innerBorder.Child = _replaceContent;
                            _innerBorder.Height = height;
                        }
                    }
                }
            }
        }
    }
}