DeltaElementsMixin.h

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#pragma once
#include "BaseSetDefaultTraits.h"
#include "catapult/utils/traits/StlTraits.h"
#include <unordered_set>
 
namespace catapult { namespace deltaset {
 
    template<typename TSetDelta>
    class DeltaElementsMixin {
    private:
        // region value accessors
 
        template<typename TSet, bool IsMap = utils::traits::is_map_v<TSet>>
        struct ValueAccessorT {
            using ValueType = typename TSet::value_type;
 
            static const ValueType* GetPointer(const typename TSet::value_type& value) {
                return &value;
            }
        };
 
        template<typename TSet>
        struct ValueAccessorT<TSet, true> { // map specialization
            using ValueType = typename TSet::value_type::second_type;
 
            static const ValueType* GetPointer(const typename TSet::value_type& pair) {
                return &pair.second;
            }
        };
 
        // endregion
 
    private:
        // use MemorySetType for detection because it is always stl (memory) container
        using ValueAccessor = ValueAccessorT<typename TSetDelta::MemorySetType>;
        using ValueType = typename ValueAccessor::ValueType;
        using PointerContainer = std::unordered_set<const ValueType*>;
 
    public:
        explicit DeltaElementsMixin(const TSetDelta& setDelta) : m_setDelta(setDelta)
        {}
 
    public:
        PointerContainer addedElements() const {
            return CollectAllPointers(m_setDelta.deltas().Added);
        }
 
        PointerContainer modifiedElements() const {
            return CollectAllPointers(m_setDelta.deltas().Copied);
        }
 
        PointerContainer removedElements() const {
            return CollectAllPointers(m_setDelta.deltas().Removed);
        }
 
    private:
        template<typename TSource>
        static PointerContainer CollectAllPointers(const TSource& source) {
            PointerContainer dest;
            for (const auto& value : source)
                dest.insert(ValueAccessor::GetPointer(value));
 
            return dest;
        }
 
    private:
        const TSetDelta& m_setDelta;
    };
}}