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

#pragma once

#include "CoreMinimal.h"
#include "InputCoreTypes.h"
#include "Widgets/DeclarativeSyntaxSupport.h"
#include "Input/Events.h"
#include "Input/Reply.h"
#include "Widgets/SCompoundWidget.h"
#include "Widgets/Views/STableRow.h"
#include "Widgets/Input/SSearchBox.h"

/** This is a container widget to help refocus to a listview widget from a searchbox or other text box widgets that are used in conjunction.
        Will refocus when the up or down arrows are pressed, and will commit a selection when enter is pressed regardless of where focus is. */
template <typename ListType>
class SListViewSelectorDropdownMenu: public SCompoundWidget
{
public:
    SLATE_BEGIN_ARGS(SListViewSelectorDropdownMenu)
    {}
    SLATE_DEFAULT_SLOT(FArguments, Content)
    SLATE_END_ARGS()
public:
    /**
     * @param InDefaultfocusWidget		The default widget to give focus to when the listview does not handle an action
     * @param InTargetListView			If the SListViewSelectorDropdownMenu is handling the KeyDown event, focus will be applied to the TargetListView for certain keys that it can handle
     */
    void Construct(const FArguments& InArgs, TSharedPtr<SSearchBox> InDefaultFocusWidget, TSharedPtr<SListView<ListType>> InTargetListView)
    {
        check(InTargetListView.IsValid());

        TargetListView     = InTargetListView;
        DefaultFocusWidget = InDefaultFocusWidget;

        if (DefaultFocusWidget.IsValid())
        {
            // We have some overrides for OnKeyDown handling of the SSearchBox to provide the seamless functionality
            InDefaultFocusWidget->SetOnKeyDownHandler(FOnKeyDown::CreateSP(this, &SListViewSelectorDropdownMenu<ListType>::OnKeyDown));
        }

        this->ChildSlot
            [InArgs._Content.Widget];
    }

    // SWidget interface
    virtual FReply OnKeyDown(const FGeometry& MyGeometry, const FKeyEvent& KeyEvent) override
    {
        TSharedPtr<SListView<ListType>> TargetListViewPtr = TargetListView.Pin();

        if (KeyEvent.GetKey() == EKeys::Up || KeyEvent.GetKey() == EKeys::Down)
        {
            // Deliver focus to the tree view, so the user can use the arrow keys to move through the items
            return TargetListViewPtr->OnKeyDown(FindChildGeometry(MyGeometry, TargetListViewPtr.ToSharedRef()), KeyEvent);
        }
        else if (KeyEvent.GetKey() == EKeys::Enter)
        {
            // If there is anything selected, re-select it "direct" so that the menu will act upon the selection
            if (TargetListViewPtr->GetNumItemsSelected() > 0)
            {
                TargetListViewPtr->SetSelection(TargetListViewPtr->GetSelectedItems()[0]);
            }
            return FReply::Handled();
        }
        else if (DefaultFocusWidget.IsValid())
        {
            TSharedPtr<SWidget> DefaultFocusWidgetPtr = DefaultFocusWidget.Pin();
            FReply Reply                              = DefaultFocusWidgetPtr->OnKeyDown(FindChildGeometry(MyGeometry, TargetListViewPtr.ToSharedRef()), KeyEvent);

            if (!DefaultFocusWidgetPtr->HasKeyboardFocus())
            {
                Reply.SetUserFocus(DefaultFocusWidgetPtr.ToSharedRef(), EFocusCause::OtherWidgetLostFocus);
            }
            return Reply;
        }
        return FReply::Unhandled();
    }
    // End of SWidget interface

private:
    /** The type tree view widget this is handling keyboard input for */
    TWeakPtr<SListView<ListType>> TargetListView;
    /** Widget to revert focus back to when this widget does not handle (or forward) a key input */
    TWeakPtr<SSearchBox> DefaultFocusWidget;
};