list_change.hpp

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#pragma once
 
#include <cstddef>
#include <memory>
#include <utility>
#include <vector>
 
namespace aria {
 
enum class ListChangeKind { Insert, Remove, Replace, ItemChanged, Reset, Move };

template<typename T>
struct ListChange {
    using Snapshot = std::vector<std::shared_ptr<T>>;
    ListChangeKind kind;
    std::size_t index = 0;
    std::shared_ptr<T> item;
    std::size_t from_index = 0;
    std::shared_ptr<const Snapshot> snapshot = nullptr;
 
    static ListChange reset(Snapshot items) {
        return {ListChangeKind::Reset, 0, {}, 0,
                std::make_shared<const Snapshot>(std::move(items))};
    }
 
    static ListChange cleared() {
        static const auto empty = std::make_shared<const Snapshot>();
        return {ListChangeKind::Reset, 0, {}, 0, empty};
    }
};
 
} // namespace aria