// Copyright Epic Games, Inc. All Rights Reserved.

#pragma once

#include "Slate/SObjectWidget.h"
#include "Blueprint/IUserObjectListEntry.h"
#include "Types/ReflectionMetadata.h"
#include "Widgets/Views/STableRow.h"
#include "Widgets/Views/STableViewBase.h"
#include "Widgets/Text/STextBlock.h"
#include "Widgets/Views/SListView.h"

class IObjectTableRow : public ITableRow
{
public:
	virtual UListViewBase* GetOwningListView() const = 0;
	virtual UUserWidget* GetUserWidget() const = 0;

	static TSharedPtr<const IObjectTableRow> ObjectRowFromUserWidget(const UUserWidget* RowUserWidget)
	{
		TWeakPtr<const IObjectTableRow>* ObjectRow = ObjectRowsByUserWidget.Find(RowUserWidget);
		if (ObjectRow && ObjectRow->IsValid())
		{
			return ObjectRow->Pin();
		}
		return nullptr;
	}

protected:
	// Intentionally being a bit nontraditional here - we track associations between UserWidget rows and their underlying IObjectTableRow.
	// This allows us to mirror the ITableRow API very easily on IUserListEntry without requiring rote setting/getting of row states on every UMG subclass.
	UMG_API static TMap<TWeakObjectPtr<const UUserWidget>, TWeakPtr<const IObjectTableRow>> ObjectRowsByUserWidget;
};

DECLARE_DELEGATE_OneParam(FOnRowHovered, UUserWidget&);

class UListViewBase;

/** 
 * It's an SObjectWidget! It's an ITableRow! It does it all!
 *
 * By using UUserWidget::TakeDerivedWidget<T>(), this class allows UMG to fully leverage the robust Slate list view widgets.
 * The major gain from this is item virtualization, which is an even bigger deal when unnecessary widgets come with a boatload of additional UObject allocations.
 * 
 * The owning UUserWidget is expected to implement the IUserListItem UInterface, which allows the row widget to respond to various list-related events.
 *
 * Note: Much of the implementation here matches STableRow<T> exactly, so refer there if looking for additional information.
 */
template <typename ItemType>
class SObjectTableRow : public SObjectWidget, public IObjectTableRow
{
public:
	SLATE_BEGIN_ARGS(SObjectTableRow<ItemType>)
		:_bAllowDragging(true)
	{}
		SLATE_ARGUMENT(bool, bAllowDragging)
		SLATE_DEFAULT_SLOT(FArguments, Content)
		SLATE_EVENT(FOnRowHovered, OnHovered)
		SLATE_EVENT(FOnRowHovered, OnUnhovered)
	SLATE_END_ARGS()

public:
	void Construct(const FArguments& InArgs, const TSharedRef<STableViewBase>& InOwnerTableView, UUserWidget& InWidgetObject, UListViewBase* InOwnerListView = nullptr)
	{
		TSharedPtr<SWidget> ContentWidget;

		if (ensureMsgf(InWidgetObject.Implements<UUserListEntry>(), TEXT("Any UserWidget generated as a table row must implement the IUserListEntry interface")))
		{
			ObjectRowsByUserWidget.Add(&InWidgetObject, SharedThis(this));

			OwnerListView = InOwnerListView;
			OwnerTablePtr = StaticCastSharedRef<SListView<ItemType>>(InOwnerTableView);

			bAllowDragging = InArgs._bAllowDragging;
			OnHovered = InArgs._OnHovered;
			OnUnhovered = InArgs._OnUnhovered;
			ContentWidget = InArgs._Content.Widget;
		}
		else
		{
			ContentWidget = SNew(STextBlock)
				.Text(NSLOCTEXT("SObjectTableRow", "InvalidWidgetClass", "Any UserWidget generated as a table row must implement the IUserListEntry interface"));
		}

		SObjectWidget::Construct(
			SObjectWidget::FArguments()
			.Content()
			[
				ContentWidget.ToSharedRef()
			], &InWidgetObject);

		// Register an active timer, not an OnTick to determine if item selection changed.
		// If we use OnTick, it will be potentially stomped by DisableNativeTick, when the
		// SObjectTableRow is used to wrap the UUserWidget construction.
		RegisterActiveTimer(0.f, FWidgetActiveTimerDelegate::CreateSP(this, &SObjectTableRow::DetectItemSelectionChanged));
	}

	virtual ~SObjectTableRow()
	{
		// Remove the association between this widget and its user widget
		ObjectRowsByUserWidget.Remove(WidgetObject);
	}

	virtual UUserWidget* GetUserWidget() const
	{
		return WidgetObject;
	}

	virtual UListViewBase* GetOwningListView() const
	{
		if (OwnerListView.IsValid())
		{
			return OwnerListView.Get();
		}
		return nullptr;
	}

	EActiveTimerReturnType DetectItemSelectionChanged(double InCurrentTime, float InDeltaTime)
	{
		DetectItemSelectionChanged();
		return EActiveTimerReturnType::Continue;
	}

	virtual void NotifyItemExpansionChanged(bool bIsExpanded)
	{
		if (WidgetObject)
		{
			IUserListEntry::UpdateItemExpansion(*WidgetObject, bIsExpanded);
		}
	}

	//~ ITableRow interface
	virtual void InitializeRow() override final
	{
		// ObjectRows can be generated in the widget designer with dummy data, which we want to ignore
		if (WidgetObject && !WidgetObject->IsDesignTime())
		{
			InitializeObjectRow();
		}
	}

	virtual void ResetRow() override final
	{
		if (WidgetObject && !WidgetObject->IsDesignTime())
		{
			ResetObjectRow();
		}
	}

	virtual TSharedRef<SWidget> AsWidget() override
	{
		return SharedThis(this);
	}
	virtual void SetIndexInList(int32 InIndexInList) override
	{
		IndexInList = InIndexInList;
	}
	virtual int32 GetIndexInList() override
	{
		return IndexInList;
	}
	virtual TSharedPtr<SWidget> GetContent() override
	{
		return ChildSlot.GetChildAt(0);
	}
	virtual int32 GetIndentLevel() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		return OwnerTable ? OwnerTable->Private_GetNestingDepth(IndexInList) : 0;
	}
	virtual int32 DoesItemHaveChildren() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		return OwnerTable ? OwnerTable->Private_DoesItemHaveChildren(IndexInList) : 0;
	}
	virtual void Private_OnExpanderArrowShiftClicked() override
	{
		/* Intentionally blank - far too specific to be a valid game UI interaction */
	}
	virtual ESelectionMode::Type GetSelectionMode() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		return OwnerTable ? OwnerTable->Private_GetSelectionMode() : ESelectionMode::None;
	}
	virtual FVector2D GetRowSizeForColumn(const FName& InColumnName) const override
	{
		return FVector2D::ZeroVector;
	}

	virtual bool IsItemExpanded() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
		if (MyItemPtr)
		{
			return OwnerTable->Private_IsItemExpanded(*MyItemPtr);
		}

		return false;
	}

	virtual void ToggleExpansion() override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		if (OwnerTable && OwnerTable->Private_DoesItemHaveChildren(IndexInList))
		{
			if (const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = GetItemForThis(OwnerTable.ToSharedRef()))
			{
				OwnerTable->Private_SetItemExpansion(*MyItemPtr, !OwnerTable->Private_IsItemExpanded(*MyItemPtr));
			}
		}
	}

	virtual bool IsItemSelected() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
		if (MyItemPtr)
		{
			return OwnerTable->Private_IsItemSelected(*MyItemPtr);
		}

		return false;
	}

	virtual TBitArray<> GetWiresNeededByDepth() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		return OwnerTable ? OwnerTable->Private_GetWiresNeededByDepth(IndexInList) : TBitArray<>();
	}

	virtual bool IsLastChild() const override
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		return OwnerTable ? OwnerTable->Private_IsLastChild(IndexInList) : true;
	}

	//~ ITableRow interface

	//~ SWidget interface
	virtual bool SupportsKeyboardFocus() const override
	{
		return true;
	}

	virtual void OnMouseEnter(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
	{
		SObjectWidget::OnMouseEnter(MyGeometry, MouseEvent);
		if (WidgetObject && OnHovered.IsBound())
		{
			OnHovered.ExecuteIfBound(*WidgetObject);
		}
	}

	virtual void OnMouseLeave(const FPointerEvent& MouseEvent) override
	{
		SObjectWidget::OnMouseLeave(MouseEvent);
		if (WidgetObject && OnUnhovered.IsBound())
		{
			OnUnhovered.ExecuteIfBound(*WidgetObject);
		}
	}

	virtual FReply OnMouseButtonDoubleClick(const FGeometry& InMyGeometry, const FPointerEvent& InMouseEvent) override
	{
		if (InMouseEvent.GetEffectingButton() == EKeys::LeftMouseButton)
		{
			TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
			const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
			if (MyItemPtr)
			{
				OwnerTable->Private_OnItemDoubleClicked(*MyItemPtr);
				return FReply::Handled();
			}
		}
		return FReply::Unhandled();
	}

	virtual FReply OnTouchStarted(const FGeometry& MyGeometry, const FPointerEvent& InTouchEvent) override
	{
		//TODO: FReply Reply = SObjectWidget::OnTouchStarted(MyGeometry, InTouchEvent);
		bProcessingSelectionTouch = true;

		return FReply::Handled()
			.DetectDrag(SharedThis(this), EKeys::LeftMouseButton);
	}

	virtual FReply OnTouchEnded(const FGeometry& MyGeometry, const FPointerEvent& InTouchEvent) override
	{
		FReply Reply = SObjectWidget::OnTouchEnded(MyGeometry, InTouchEvent);

		if (bProcessingSelectionTouch)
		{
			bProcessingSelectionTouch = false;
			TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
			const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
			if (MyItemPtr)
			{
				if (IsItemSelectable())
				{
					ESelectionMode::Type SelectionMode = GetSelectionMode();
					if (SelectionMode != ESelectionMode::None)
					{
						const bool bIsSelected = OwnerTable->Private_IsItemSelected(*MyItemPtr);
						if (!bIsSelected)
						{
							if (SelectionMode != ESelectionMode::Multi)
							{
								OwnerTable->Private_ClearSelection();
							}
							OwnerTable->Private_SetItemSelection(*MyItemPtr, true, true);
							OwnerTable->Private_SignalSelectionChanged(ESelectInfo::OnMouseClick);

							Reply = FReply::Handled();
						}
						else if (SelectionMode == ESelectionMode::SingleToggle || SelectionMode == ESelectionMode::Multi)
						{
							OwnerTable->Private_SetItemSelection(*MyItemPtr, true, true);
							OwnerTable->Private_SignalSelectionChanged(ESelectInfo::OnMouseClick);

							Reply = FReply::Handled();
						}
					}
				}

				if (OwnerTable->Private_OnItemClicked(*MyItemPtr))
				{
					Reply = FReply::Handled();
				}
			}
		}

		return Reply;
	}

	virtual FReply OnDragDetected(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
	{
		if (bAllowDragging)
		{
			TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();

			if (bProcessingSelectionTouch)
			{
				bProcessingSelectionTouch = false;
				return OwnerTable ? FReply::Handled().CaptureMouse(OwnerTable->AsWidget()) : FReply::Unhandled();
			}
			//@todo DanH TableRow: does this potentially trigger twice? If not, why does an unhandled drag detection result in not calling mouse up?
			else if (HasMouseCapture() && bChangedSelectionOnMouseDown)
			{
				if (OwnerTable)
				{
					OwnerTable->Private_SignalSelectionChanged(ESelectInfo::OnMouseClick);
				}
			}

			return SObjectWidget::OnDragDetected(MyGeometry, MouseEvent);
		}

		bProcessingSelectionTouch = false;
		return FReply::Unhandled();
	}

	virtual FReply OnMouseButtonDown(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
	{
		bChangedSelectionOnMouseDown = false;

		FReply Reply = SObjectWidget::OnMouseButtonDown(MyGeometry, MouseEvent);
		if (!Reply.IsEventHandled())
		{
			TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
			if (OwnerTable)
			{
				const ESelectionMode::Type SelectionMode = GetSelectionMode();
				if (MouseEvent.GetEffectingButton() == EKeys::LeftMouseButton && SelectionMode != ESelectionMode::None)
				{
					if (IsItemSelectable())
					{
						const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = GetItemForThis(OwnerTable.ToSharedRef());
						// New selections are handled on mouse down, deselection is handled on mouse up
						if (MyItemPtr)
						{
							const ItemType& MyItem = *MyItemPtr;
							if (!OwnerTable->Private_IsItemSelected(MyItem))
							{
								if (SelectionMode != ESelectionMode::Multi)
								{
									OwnerTable->Private_ClearSelection();
								}
								OwnerTable->Private_SetItemSelection(MyItem, true, true);
								bChangedSelectionOnMouseDown = true;
							}
						}

						Reply = FReply::Handled()
							.DetectDrag(SharedThis(this), EKeys::LeftMouseButton)
							.CaptureMouse(SharedThis(this));

						// Set focus back to the owning widget if the item is invalid somehow or its not selectable or can be navigated to
						if (!MyItemPtr || !OwnerTable->Private_IsItemSelectableOrNavigable(*MyItemPtr))
						{
							Reply.SetUserFocus(OwnerTable->AsWidget(), EFocusCause::Mouse);
						}
					}
				}
			}
		}
		
		return Reply;
	}

	virtual FReply OnMouseButtonUp(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
	{
		FReply Reply = SObjectWidget::OnMouseButtonUp(MyGeometry, MouseEvent);

		if (!Reply.IsEventHandled())
		{
			TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
			const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
			if (MyItemPtr)
			{
				const ESelectionMode::Type SelectionMode = GetSelectionMode();
				if (MouseEvent.GetEffectingButton() == EKeys::LeftMouseButton && HasMouseCapture())
				{
					bool bSignalSelectionChanged = bChangedSelectionOnMouseDown;
					// Don't change selection on mouse up if it already changed on mouse down
					if (!bChangedSelectionOnMouseDown && IsItemSelectable() && MyGeometry.IsUnderLocation(MouseEvent.GetScreenSpacePosition()))
					{
						if (SelectionMode == ESelectionMode::SingleToggle)
						{
							OwnerTable->Private_ClearSelection();
							bSignalSelectionChanged = true;
						}
						else if (SelectionMode == ESelectionMode::Multi &&
							OwnerTable->Private_GetNumSelectedItems() > 1 &&
							OwnerTable->Private_IsItemSelected(*MyItemPtr))
						{
							// Releasing mouse over one of the multiple selected items - leave this one as the sole selected item
							OwnerTable->Private_ClearSelection();
							OwnerTable->Private_SetItemSelection(*MyItemPtr, true, true);
							bSignalSelectionChanged = true;
						}
					}

					if (bSignalSelectionChanged)
					{
						OwnerTable->Private_SignalSelectionChanged(ESelectInfo::OnMouseClick);
						Reply = FReply::Handled();
					}

					if (OwnerTable->Private_OnItemClicked(*MyItemPtr))
					{
						Reply = FReply::Handled();
					}

					Reply = Reply.ReleaseMouseCapture();
				}
				else if (SelectionMode != ESelectionMode::None && MouseEvent.GetEffectingButton() == EKeys::RightMouseButton)
				{
					// Ignore the right click release if it was being used for scrolling
					TSharedPtr<STableViewBase> OwnerTableViewBase = StaticCastSharedPtr<SListView<ItemType>>(OwnerTable);
					if (!OwnerTableViewBase->IsRightClickScrolling())
					{
						if (IsItemSelectable() && !OwnerTable->Private_IsItemSelected(*MyItemPtr))
						{
							// If this item isn't selected, it becomes the sole selected item. Otherwise we leave selection untouched.
							OwnerTable->Private_ClearSelection();
							OwnerTable->Private_SetItemSelection(*MyItemPtr, true, true);
							OwnerTable->Private_SignalSelectionChanged(ESelectInfo::OnMouseClick);
						}

						OwnerTable->Private_OnItemRightClicked(*MyItemPtr, MouseEvent);

						Reply = FReply::Handled();
					}
				}
			}
		}

		return Reply;
	}
	// ~SWidget interface

protected:
	virtual void InitializeObjectRow()
	{
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
		if (MyItemPtr)
		{
			InitObjectRowInternal(*WidgetObject, *MyItemPtr);

			// Unselectable items should never be selected
			if (!ensure(!OwnerTable->Private_IsItemSelected(*MyItemPtr) || IsItemSelectable()))
			{
				OwnerTable->Private_SetItemSelection(*MyItemPtr, false, false);
			}
		}
	}

	virtual void ResetObjectRow()
	{
		bIsAppearingSelected = false;
		if (WidgetObject)
		{
			IUserListEntry::ReleaseEntry(*WidgetObject);
		}
	}

	virtual void DetectItemSelectionChanged()
	{
		// List views were built assuming the use of attributes on rows to check on selection status, so there is no
		// clean way to inform individual rows of changes to the selection state of their current items.
		// Since event-based selection changes are only really needed in a game scenario, we (crudely) monitor it here to generate events.
		// If desired, per-item selection events could be added as a longer-term todo
		TSharedPtr<ITypedTableView<ItemType>> OwnerTable = OwnerTablePtr.Pin();
		const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable ? GetItemForThis(OwnerTable.ToSharedRef()) : nullptr;
		if (MyItemPtr)
		{
			if (bIsAppearingSelected != OwnerTable->Private_IsItemSelected(*MyItemPtr))
			{
				bIsAppearingSelected = !bIsAppearingSelected;
				OnItemSelectionChanged(bIsAppearingSelected);
			}
		}
	}

	virtual void OnItemSelectionChanged(bool bIsItemSelected)
	{
		if (WidgetObject)
		{
			IUserListEntry::UpdateItemSelection(*WidgetObject, bIsItemSelected);
		}
	}

	bool IsItemSelectable() const 
	{
		IUserListEntry* NativeListEntryImpl = Cast<IUserListEntry>(WidgetObject);
		return NativeListEntryImpl ? NativeListEntryImpl->IsListItemSelectable() : true;
	}

	const TObjectPtrWrapTypeOf<ItemType>* GetItemForThis(const TSharedRef<ITypedTableView<ItemType>>& OwnerTable) const
	{
		const TObjectPtrWrapTypeOf<ItemType>* MyItemPtr = OwnerTable->Private_ItemFromWidget(this);
		if (MyItemPtr)
		{
			return MyItemPtr;
		}
		else
		{
			checkf(OwnerTable->Private_IsPendingRefresh(), TEXT("We were unable to find the item for this widget. If it was removed from the source collection, the list should be pending a refresh. %s"), *FReflectionMetaData::GetWidgetPath(this, false, false));
		}

		return nullptr;
	}

	FOnRowHovered OnHovered;
	FOnRowHovered OnUnhovered;

	TWeakObjectPtr<UListViewBase> OwnerListView;
	TWeakPtr<ITypedTableView<ItemType>> OwnerTablePtr;

private:
	void InitObjectRowInternal(UUserWidget& ListEntryWidget, ItemType ListItemObject) {}
	
	int32 IndexInList = INDEX_NONE;
	bool bChangedSelectionOnMouseDown = false;
	bool bIsAppearingSelected = false;

	bool bProcessingSelectionTouch = false;

	/** Whether to allow dragging of this item */
	bool bAllowDragging;
};

template <>
inline void SObjectTableRow<UObject*>::InitObjectRowInternal(UUserWidget& ListEntryWidget, UObject* ListItemObject)
{
	if (ListEntryWidget.Implements<UUserObjectListEntry>())
	{
		IUserObjectListEntry::SetListItemObject(*WidgetObject, ListItemObject);
	}
}