expected.hxx

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/*
 * Copyright (C) 2024-2026 David C. Manuelda (StormBytePP)
 *
 * This file is part of StormByte.
 *
 * StormByte is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License version 3
 * or later, as published by the Free Software Foundation.
 *
 * StormByte is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with StormByte. If not, see
 * <https://www.gnu.org/licenses/lgpl-3.0.html>.
 */
 
#pragma once
 
#include <StormByte/type_traits.hxx>
 
#include <expected>
#include <format>
#include <type_traits>
#include <memory>
#include <string>
 
namespace StormByte {
    template <typename T, class E>
    using Expected = std::conditional_t<
        Type::Reference<T>,
        std::expected<std::reference_wrapper<std::remove_reference_t<T>>, std::shared_ptr<E>>,
        std::expected<T, std::shared_ptr<E>>
    >;
 
    template <typename E>
    auto Unexpected(std::shared_ptr<E> error_ptr) {
        return std::unexpected<std::shared_ptr<E>>(std::move(error_ptr));
    }
 
    template <typename E>
    auto Unexpected(E&& error) {
        return std::unexpected<std::shared_ptr<std::decay_t<E>>>(
            std::make_shared<std::decay_t<E>>(std::forward<E>(error))
        );
    }
 
    template <typename Base, typename Derived>
    auto Unexpected(Derived&& error) -> std::unexpected<std::shared_ptr<Base>>
    requires std::is_base_of_v<Base, std::decay_t<Derived>> &&
        (!std::same_as<Base, std::decay_t<Derived>>)
    {
        using DerivedT = std::decay_t<Derived>;
        return std::unexpected<std::shared_ptr<Base>>(std::static_pointer_cast<Base>(std::make_shared<DerivedT>(std::forward<Derived>(error))));
    }
 
    template <typename E, typename... Args>
    auto Unexpected(const std::string& fmt, Args&&... args) {
        std::string formatted_message;
 
        if constexpr (sizeof...(Args) == 0) {
            formatted_message = fmt;
        } else {
            auto format_args = std::make_format_args(args...);
            formatted_message = std::vformat(fmt, format_args);
        }
 
        return std::unexpected<std::shared_ptr<E>>(
            std::make_shared<E>(std::move(formatted_message))
        );
    }
}