iso_639.hpp

// Copyright Take Vos 2021.
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt or copy at https://www.boost.org/LICENSE_1_0.txt)
 
#pragma once
 
#include <cctype>
#include "../assert.hpp"
#include "../strings.hpp"
 
namespace tt {
 
class iso_639 {
public:
    constexpr iso_639(iso_639 const &) noexcept = default;
    constexpr iso_639(iso_639 &&) noexcept = default;
    constexpr iso_639 &operator=(iso_639 const &) noexcept = default;
    constexpr iso_639 &operator=(iso_639 &&) noexcept = default;
 
    constexpr iso_639() noexcept : v0(0), v1(0), v2(0) {}
 
    constexpr iso_639(std::string_view str) noexcept
    {
        if (std::size(str) == 0) {
            _v0 = 0;
            _v1 = 0;
            _v2 = 0;
        } else if (std::size(str) == 2) {
            _v0 = to_lower(str[0]);
            _v1 = to_lower(str[1]);
            _v2 = 0;
        } else if (std::size(str) == 3) {
            _v0 = to_lower(str[0]);
            _v1 = to_lower(str[1]);
            _v2 = to_lower(str[2]);
        } else {
            tt_no_default();
        }
    }
 
    constexpr explicit operator bool () const noexcept
    {
        return _v0 == 0 and _v1 == 0 and _v2 == 0;
    }
 
    constexpr explicit operator std::string() const noexcept
    {
        auto r = std::string{};
        if (_v0 == 0) {
            return r;
        }
 
        r += _v0;
        if (_v1 == 0) {
            return r;
        }
 
        r += _v1;
        if (_v2 == 0) {
            return r;
        }
 
        r += _v2;
        return r;
    }
 
    [[nodiscard]] constexpr friend operator==(iso_639 const &lhs, iso_639 const &rhs) noexcept = default;
    [[nodiscard]] constexpr friend operator<=>(iso_639 const &lhs, iso_639 const &rhs) noexcept = default;
 
private:
    char _v0;
    char _v1;
    char _v2;
};
 
}