expected.hxx

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/*
 * Copyright (C) 2024-2026 David C. Manuelda (StormBytePP)
 *
 * This file is part of StormByte.
 *
 * StormByte original source is dual-licensed:
 *
 * 1. GNU Lesser General Public License v3.0 (or later)
 *    You may redistribute and/or modify this file under the terms of the
 *    GNU Lesser General Public License as published by the Free Software
 *    Foundation, either version 3 of the License, or (at your option)
 *    any later version.
 *
 * 2. Commercial license
 *    Alternatively, this file may be used under the terms of a commercial
 *    license agreement with the copyright holder
 *    (David C. Manuelda <StormByte@gmail.com>).
 *
 * Both licenses apply only to original StormByte source in this repository.
 * They do not cover other StormByte modules or any third-party material
 * shipped with this repository (including everything under thirdparty/),
 * which remains under its own license.
 *
 * Neither license grants any patent rights. Any patent licenses required
 * to use this software or third-party components must be obtained separately
 * from the patent holders.
 *
 * 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
 * version 3 along with StormByte. If not, see
 * <https://www.gnu.org/licenses/lgpl-3.0.html>.
 *
 * SPDX-License-Identifier: LGPL-3.0-or-later OR LicenseRef-StormByte-Commercial
 */
 
#pragma once
 
#include <StormByte/safe_pointers.hxx>
#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>>, Shared<E>>,
        std::expected<T, Shared<E>>
    >;
 
    template <typename E>
    auto Unexpected(Shared<E> error) {
        return std::unexpected<Shared<E>>(std::move(error));
    }
 
    template <typename E>
    auto Unexpected(std::shared_ptr<E>) = delete;
 
    template <typename E>
    requires (
        !requires { typename std::remove_cvref_t<E>::element_type; } ||
        !Type::SameAs<std::remove_cvref_t<E>, Shared<typename std::remove_cvref_t<E>::element_type>>
    )
    auto Unexpected(E&& error) {
        using Error = std::decay_t<E>;
        return std::unexpected<Shared<Error>>(
            Heap::MakeShared<Error>(std::forward<E>(error))
        );
    }
 
    template <typename Base, typename Derived>
    auto Unexpected(Derived&& error) -> std::unexpected<Shared<Base>>
    requires Type::DerivedFrom<std::decay_t<Derived>, Base> &&
        (!Type::SameAs<Base, std::decay_t<Derived>>)
    {
        using DerivedT = std::decay_t<Derived>;
        return std::unexpected<Shared<Base>>(
            Shared<Base>::template MakePointer<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<Shared<E>>(
            Heap::MakeShared<E>(std::move(formatted_message))
        );
    }
}