using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using ElmSharp;
using EToolbarItem = ElmSharp.ToolbarItem;
using EToolbarItemEventArgs = ElmSharp.ToolbarItemEventArgs;

using Xamarin.Forms.PlatformConfiguration.TizenSpecific;
using Xamarin.Forms.Internals;

namespace Xamarin.Forms.Platform.Tizen
{
	public class TabbedPageRenderer : VisualElementRenderer<TabbedPage>, IVisualElementRenderer
	{
		Box _outterLayout;
		Box _innerBox;
		Scroller _scroller;
		Toolbar _toolbar;
		Dictionary<EToolbarItem, Page> _itemToItemPage = new Dictionary<EToolbarItem, Page>();
		IReadOnlyCollection<Element> Pages => (Element as IElementController).LogicalChildren;

		public TabbedPageRenderer()
		{
			//Register for title change property
			RegisterPropertyHandler(TabbedPage.TitleProperty, UpdateTitle);
			//Register for current page change property
			RegisterPropertyHandler("CurrentPage", CurrentPageChanged);
		}

		protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
		{
			if (_toolbar == null)
			{
				//Create box that holds toolbar and selected content
				_outterLayout = new Box(Forms.Context.MainWindow)
				{
					AlignmentX = -1,
					AlignmentY = -1,
					WeightX = 1,
					WeightY = 1,
					IsHorizontal = false,
				};
				_outterLayout.Show();

				//Create toolbar that is placed inside the _outterLayout
				_toolbar = new Toolbar(Forms.Context.MainWindow)
				{
					AlignmentX = -1,
					WeightX = 1,
					SelectionMode = ToolbarSelectionMode.Always,
					Style = "tabbar_with_title"
				};
				_toolbar.Show();
				//Add callback for Toolbar item selection
				_toolbar.Selected += OnToolbarItemSelected;
				_outterLayout.PackEnd(_toolbar);

				_scroller = new Scroller(_outterLayout)
				{
					AlignmentX = -1,
					AlignmentY = -1,
					WeightX = 1,
					WeightY = 1,
					HorizontalPageScrollLimit = 1,
					ScrollBlock = ScrollBlock.Vertical,
					HorizontalScrollBarVisiblePolicy = ScrollBarVisiblePolicy.Invisible
				};
				_scroller.SetPageSize(1.0, 1.0);
				_scroller.PageScrolled += OnItemPageScrolled;
				_scroller.Resized += OnScrollerResized;

				_innerBox = new Box(Forms.Context.MainWindow)
				{
					AlignmentX = -1,
					AlignmentY = -1,
					WeightX = 1,
					WeightY = 1,
					IsHorizontal = true,
				};
				_scroller.SetContent(_innerBox);
				_scroller.Show();

				_outterLayout.PackEnd(_scroller);

				SetNativeControl(_outterLayout);
				UpdateTitle();
			}

			base.OnElementChanged(e);
		}

		void OnScrollerResized(object sender, System.EventArgs e)
		{
			foreach (var item in _itemToItemPage)
			{
				var nativeView = Platform.GetRenderer(item.Value).NativeView;
				nativeView.MinimumWidth = _scroller.Geometry.Width;
				nativeView.MinimumHeight = _scroller.Geometry.Height;
			}
			int index = Pages.IndexOf(_itemToItemPage[_toolbar.SelectedItem]);
			_scroller.ScrollTo(index, 0, true);
		}

		void OnItemPageScrolled(object sender, System.EventArgs e)
		{
			Page newPage = Element.GetPageByIndex(_scroller.HorizontalPageIndex);
			foreach (var pair in _itemToItemPage)
			{
				if (pair.Value == newPage)
				{
					pair.Key.IsSelected = true;
					return;
				}
			}

		}

		protected override void Dispose(bool disposing)
		{
			if (_outterLayout != null)
			{
				_outterLayout.Unrealize();
				_outterLayout = null;
			}
			if (_toolbar != null)
			{
				_toolbar.Selected -= OnToolbarItemSelected;
				_scroller.PageScrolled -= OnItemPageScrolled;

				_toolbar.Unrealize();
				_toolbar = null;
			}
			base.Dispose(disposing);
		}

		protected override void OnElementReady()
		{
			FillToolbarAndContents();
			base.OnElementReady();
		}

		protected override void UpdateThemeStyle()
		{
			var style = Element.OnThisPlatform().GetStyle();
			if (!string.IsNullOrEmpty(style))
			{
				_toolbar.Style = style;
				((IVisualElementController)Element).NativeSizeChanged();
			}
		}

		void UpdateTitle()
		{
			_toolbar.Text = Element.Title;
		}

		void UpdateTitle(Page page)
		{
			if (_itemToItemPage.ContainsValue(page))
			{
				var pair = _itemToItemPage.FirstOrDefault(x => x.Value == page);
				pair.Key.SetPartText(null, pair.Value.Title);
			}
		}

		void OnPageTitleChanged(object sender, PropertyChangedEventArgs e)
		{
			if (e.PropertyName == Page.TitleProperty.PropertyName)
			{
				UpdateTitle(sender as Page);
			}
		}

		void FillToolbarAndContents()
		{
			//add items to toolbar
			foreach (Page child in Pages)
			{
				EToolbarItem toolbarItem = _toolbar.Append(child.Title, string.IsNullOrEmpty(child.Icon) ? null : ResourcePath.GetPath(child.Icon));

				_itemToItemPage.Add(toolbarItem, child);

				var childContent = Platform.GetOrCreateRenderer(child).NativeView;
				_innerBox.PackEnd(childContent);

				if (Element.CurrentPage == child)
				{
					//select item on the toolbar and fill content
					toolbarItem.IsSelected = true;
				}
				child.PropertyChanged += OnPageTitleChanged;
			}
		}

		void OnToolbarItemSelected(object sender, EToolbarItemEventArgs e)
		{
			if (_toolbar.SelectedItem == null)
				return;

			var oldPage = Element.CurrentPage;
			var newPage = _itemToItemPage[_toolbar.SelectedItem];

			if (oldPage == newPage)
				return;

			oldPage?.SendDisappearing();

			Element.CurrentPage = newPage;
			newPage?.SendAppearing();

			int index = MultiPage<Page>.GetIndex(newPage);
			_scroller.ScrollTo(index, 0, true);
		}

		void CurrentPageChanged()
		{
			foreach (var pair in _itemToItemPage)
			{
				if (pair.Value == Element.CurrentPage)
				{
					pair.Key.IsSelected = true;
					return;
				}
			}
		}
	}
}