setting.h

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#pragma once
 
#include <string_view>
 
#include "cppfig/traits.h"
#include "cppfig/validator.h"
 
namespace cppfig {
 
template <typename S>
concept IsSetting = requires {
    { S::path } -> std::convertible_to<std::string_view>;
    typename S::value_type;
    { S::default_value() } -> std::same_as<typename S::value_type>;
} && Configurable<typename S::value_type>;
 
template <typename S>
concept HasEnvOverride = IsSetting<S> && requires {
    { S::env_override } -> std::convertible_to<std::string_view>;
};
 
template <typename S>
concept HasValidator = IsSetting<S> && requires {
    { S::validator() } -> std::same_as<Validator<typename S::value_type>>;
};
 
template <IsSetting S>
constexpr auto GetEnvOverride() -> std::string_view
{
    if constexpr (HasEnvOverride<S>) {
        return S::env_override;
    }
    else {
        return "";
    }
}
 
template <IsSetting S>
auto GetSettingValidator() -> Validator<typename S::value_type>
{
    if constexpr (HasValidator<S>) {
        return S::validator();
    }
    else {
        return AlwaysValid<typename S::value_type>();
    }
}
 
}  // namespace cppfig