TypedElementMetaData.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include <type_traits>
#include "CoreMinimal.h"
#include "Containers/ArrayView.h"
#include "Containers/Map.h"
#include "Misc/EnumClassFlags.h"
#include "Misc/TVariant.h"
#include "Templates/Tuple.h"
#include "UObject/WeakObjectPtr.h"
 
class UScriptStruct;
 
namespace UE::Editor::DataStorage
{
    struct FQueryDescription;
 
    inline static const FName IsEditableName(TEXT("IsEditable"));
    inline static const FName IsConstName(TEXT("IsConst"));
 
    using MetaDataType = TVariant<bool, uint64, int64, double, FString>;
    using MetaDataTypeView = TVariant<FEmptyVariantState, bool, uint64, int64, double, const FString*>;
 
    class FMetaDataEntryView final
    {
    public:
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView();
        TYPEDELEMENTFRAMEWORK_API explicit FMetaDataEntryView(const MetaDataType& MetaData);
        TYPEDELEMENTFRAMEWORK_API explicit FMetaDataEntryView(const FString& MetaDataString);
        template<typename T>
        explicit FMetaDataEntryView(T&& MetaDataValue);
 
        TYPEDELEMENTFRAMEWORK_API bool IsSet() const;
        template<typename T>
        bool IsType() const;
        template<typename T>
        const T* TryGetExact() const;
 
    private:
        MetaDataTypeView DataView;
    };
 
    class FMetaDataBase
    {
    public:
        template<typename T>
        bool AddImmutableData(FName Name, T&& Value);
        template<typename T>
        void AddOrSetMutableData(FName Name, T&& Value);
 
        TYPEDELEMENTFRAMEWORK_API virtual FMetaDataEntryView Find(FName Name) const;
 
        TYPEDELEMENTFRAMEWORK_API virtual void Shrink();
        
        TYPEDELEMENTFRAMEWORK_API virtual bool IsEmpty() const;
 
    protected:
        FMetaDataBase() = default;
        virtual ~FMetaDataBase() = default;
 
        TMap<FName, MetaDataType> ImmutableData;
        TMap<FName, MetaDataType> MutableData;
    };
 
    class FMetaData final : public FMetaDataBase {};
 
    class FColumnMetaData final : public FMetaDataBase
    {
    public:
        enum class EFlags
        {
            None = 0,
            IsMutable = 1 << 0
        };
 
        FColumnMetaData() = default;
        TYPEDELEMENTFRAMEWORK_API FColumnMetaData(const UScriptStruct* InColumnType, EFlags InFlags);
 
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView Find(FName Name) const override;
        
        TYPEDELEMENTFRAMEWORK_API bool IsEmpty() const override;
 
    private:
        const UScriptStruct* ColumnType{ nullptr };
        EFlags Flags = EFlags::None;
    };
 
    class FMetaDataView
    {
    public:
        virtual ~FMetaDataView() = default;
 
        TYPEDELEMENTFRAMEWORK_API virtual FMetaDataEntryView FindGeneric(FName AttributeName) const;
        TYPEDELEMENTFRAMEWORK_API virtual FMetaDataEntryView FindForColumn(
            TWeakObjectPtr<const UScriptStruct> Column, FName AttributeName) const;
        template<typename Column>
        FMetaDataEntryView FindForColumn(FName AttributeName) const;
    };
 
    class FQueryMetaDataView final : public FMetaDataView
    {
    public:
        ~FQueryMetaDataView() override = default;
 
        TYPEDELEMENTFRAMEWORK_API explicit FQueryMetaDataView(const FQueryDescription& InQuery);
        
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindGeneric(FName AttributeName) const override;
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindForColumn(
            TWeakObjectPtr<const UScriptStruct> Column, FName AttributeName) const override;
 
    private:
        const FQueryDescription& Query;
    };
 
    class FColumnsMetaDataView final : public FMetaDataView
    {
    public:
        ~FColumnsMetaDataView() override = default;
 
        TYPEDELEMENTFRAMEWORK_API explicit FColumnsMetaDataView(TConstArrayView<TWeakObjectPtr<const UScriptStruct>> InColumns);
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindForColumn(
            TWeakObjectPtr<const UScriptStruct> Column, FName AttributeName) const override;
 
    private:
        TConstArrayView<TWeakObjectPtr<const UScriptStruct>> Columns;
    };
 
    class FGenericMetaDataView final : public FMetaDataView
    {
    public:
        ~FGenericMetaDataView() override = default;
 
        TYPEDELEMENTFRAMEWORK_API explicit FGenericMetaDataView(const FMetaData& InMetaData);
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindGeneric(FName AttributeName) const override;
 
    private:
        const FMetaData& MetaData;
    };
 
    class FForwardingMetaDataView final : public FMetaDataView
    {
    public:
        ~FForwardingMetaDataView() override = default;
 
        TYPEDELEMENTFRAMEWORK_API explicit FForwardingMetaDataView(const FMetaDataView& InView);
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindGeneric(FName AttributeName) const override;
        TYPEDELEMENTFRAMEWORK_API FMetaDataEntryView FindForColumn(
            TWeakObjectPtr<const UScriptStruct> Column, FName AttributeName) const override;
 
    private:
        const FMetaDataView& View;
    };
 
    template<typename... ViewTypes>
    class FComboMetaDataView final : public FMetaDataView
    {
    public:
        FComboMetaDataView(const ViewTypes&... InViews);
        FComboMetaDataView(ViewTypes&&... InViews);
 
        template<typename NextViewType>
        FComboMetaDataView<ViewTypes..., NextViewType> Next(NextViewType&& NextView);
 
        FMetaDataEntryView FindGeneric(FName AttributeName) const override;
        FMetaDataEntryView FindForColumn(TWeakObjectPtr<const UScriptStruct> Column, FName AttributeName) const;
 
        TTuple<ViewTypes...> Views;
    };
 
} // UE::Editor::DataStorage
 
#include "Elements/Framework/TypedElementMetaData.inl"