Function flatten

3rd/json/include/nlohmann/json.hpp:9222–9272

! @param[in] reference_string the reference string to the current value @param[in] value the value to consider @param[in,out] result the result object to insert values to @note Empty objects or arrays are flattened to `null`. */

    @note Empty objects or arrays are flattened to `null`.
    */
    static void flatten(const std::string& reference_string,
                        const BasicJsonType& value,
                        BasicJsonType& result)
    {
        switch (value.m_type)
        {
            case detail::value_t::array:
            {
                if (value.m_value.array->empty())
                {
                    // flatten empty array as null
                    result[reference_string] = nullptr;
                }
                else
                {
                    // iterate array and use index as reference string
                    for (std::size_t i = 0; i < value.m_value.array->size(); ++i)
                    {
                        flatten(reference_string + "/" + std::to_string(i),
                                value.m_value.array->operator[](i), result);
                    }
                }
                break;
            }

            case detail::value_t::object:
            {
                if (value.m_value.object->empty())
                {
                    // flatten empty object as null
                    result[reference_string] = nullptr;
                }
                else
                {
                    // iterate object and use keys as reference string
                    for (const auto& element : *value.m_value.object)
                    {
                        flatten(reference_string + "/" + escape(element.first), element.second, result);
                    }
                }
                break;
            }

            default:
            {
                // add primitive value with its reference string
                result[reference_string] = value;
                break;
            }
        }
    }

    /*!
    @param[in] value  flattened JSON