json_support.h

#pragma once

#include <optional>
#include <string>
#include <tuple>
#include <nlohmann/json.hpp>

namespace Faunus {

using json = nlohmann::json;

json loadJSON(
    const std::string& filename); 

struct SingleUseJSON : public json
{
    explicit SingleUseJSON(const json&);
    [[nodiscard]] bool empty() const;
    [[nodiscard]] size_type count(const std::string&) const;
    [[nodiscard]] std::string dump(int = -1) const;
    [[nodiscard]] bool is_object() const;

    void clear();
    json at(const std::string&);
    json operator[](const std::string&);
    void erase(const std::string&);

    template <class T> T value(const std::string& key, const T& fallback)
    {
        return (count(key) > 0) ? at(key).get<T>() : fallback;
    }
};

double roundValue(double value,
                  int number_of_digits = 3); 
void roundJSON(json& j,
               int number_of_digits = 3); 
double getValueInfinity(
    const json& j,
    const std::string& key); 

std::tuple<const std::string&, const json&> jsonSingleItem(const json& j);

template <typename T> std::optional<T> get_optional(const json& j, std::string_view key)
{
    if (const auto it = j.find(key); it != j.end()) {
        return it->get<T>(); // may throw exception
    }
    return std::nullopt;
}

} // namespace Faunus