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

#pragma once

#include "DragAndDrop/DecoratedDragDropOp.h"

/** Drag payload type - implement derived types using DRAG_DROP_OPERATOR_TYPE */
class IDragPayload
{
protected:
    /** Friendship required so we can access IsOfType without exposing it */
    friend class FMultipleDataDragOp;

    /** Check if this payload type is the same as the specified type ID */
    virtual bool IsOfTypeImpl(const FString& Type) const { return false; }
};

/** A drag/drop operation that contains multiple types of dragged data (payloads) */
class FMultipleDataDragOp: public FDecoratedDragDropOp
{
public:
    DRAG_DROP_OPERATOR_TYPE(FMultipleDataDragOp, FDecoratedDragDropOp)

    /** Add some more data to this operation's payload */
    void AddPayload(TUniquePtr<IDragPayload> InPayload)
    {
        Payload.Add(MoveTemp(InPayload));
    }

    /** Extract the specified data type from this operation */
    virtual const void* Extract(const FString& Type) const
    {
        for (const auto& Entry: Payload)
        {
            if (Entry->IsOfTypeImpl(T::GetTypeId()))
            {
                return Entry.Get();
            }
        }
        return FDecoratedDragDropOp::Extract(Type);
    }

protected:
    /** The data that we're dragging */
    TArray<TUniquePtr<IDragPayload>> Payload;
};