command_line_switch.h

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#ifndef OOKII_COMMAND_LINE_SWITCH_H_
#define OOKII_COMMAND_LINE_SWITCH_H_
 
#pragma once
 
#include <ostream>
#include "format_helper.h"
#include "value_description.h"
 
namespace ookii
{
    template<typename CharType, typename Traits, typename Alloc>
    struct lexical_convert<bool, CharType, Traits, Alloc>
    {
        static std::optional<bool> from_string(std::basic_string_view<CharType, Traits> value, const std::locale & = {})
        {
            constexpr auto true_value = literal_cast<CharType>("true");
            constexpr auto true_alt_value = literal_cast<CharType>("1");
            constexpr auto false_value = literal_cast<CharType>("false");
            constexpr auto false_alt_value = literal_cast<CharType>("0");
 
            if (string_equal_case_insensitive<CharType, Traits>(value, true_value.data()) ||
                value == true_alt_value.data())
            {
                return {true};
            }
            else if (string_equal_case_insensitive<CharType, Traits>(value, false_value.data()) ||
                value == false_alt_value.data())
            {
                return {false};
            }
            else
            {
                return {};
            }
        }
    };
 
    namespace details
    {
        template<typename T>
        struct is_switch : public std::false_type {};
 
        template<>
        struct is_switch<bool> : public std::true_type {};
 
        template<>
        struct is_switch<std::optional<bool>> : public std::true_type {};
    }
}
 
#endif