result.h

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/*
Copyright (c) 2026 MrXie1109
 
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
 
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
 
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/
 
#pragma once
#include <cassert>
#include <cstring>
#include <new>
#include <type_traits>
#include <utility>
 
#include "../core/csexc.h"
 
#if __cplusplus >= 201703L
#include <optional>
#endif
 
namespace console {
    template <class T, class E>
    class Result {
        static_assert(
            !std::is_same<T, E>::value, "T and E cannot be the same type");

        static constexpr size_t buffer_size
            = sizeof(T) > sizeof(E) ? sizeof(T) : sizeof(E);
        static constexpr size_t buffer_align
            = alignof(T) > alignof(E) ? alignof(T) : alignof(E);

        alignas(buffer_align) mutable unsigned char buffer[buffer_size];
        bool is_ok_;

        T *get_ok_ptr() const { return reinterpret_cast<T *>(buffer); }
        E *get_err_ptr() const { return reinterpret_cast<E *>(buffer); }
 
    public:
        typedef T value_type;
        typedef E error_type;

        Result(const T &value) : is_ok_(true) { new (get_ok_ptr()) T(value); }

        Result(const E &error) : is_ok_(false) { new (get_err_ptr()) E(error); }

        Result(T &&value) : is_ok_(true) {
            new (get_ok_ptr()) T(std::move(value));
        }

        Result(E &&error) : is_ok_(false) {
            new (get_err_ptr()) E(std::move(error));
        }

        Result(const Result &other) : is_ok_(other.is_ok_) {
            if (is_ok_) {
                new (get_ok_ptr()) T(*other.get_ok_ptr());
            } else {
                new (get_err_ptr()) E(*other.get_err_ptr());
            }
        }

        Result(Result &&other) noexcept : is_ok_(other.is_ok_) {
            if (is_ok_)
                new (get_ok_ptr()) T(std::move(*other.get_ok_ptr()));
            else
                new (get_err_ptr()) E(std::move(*other.get_err_ptr()));
        }

        Result &operator=(const Result &other) {
            if (this != &other) Result(other).swap(*this);
            return *this;
        }

        Result &operator=(Result &&other) noexcept {
            if (this != &other) Result(std::move(other)).swap(*this);
            return *this;
        }

        ~Result() {
            if (is_ok_)
                get_ok_ptr()->~T();
            else
                get_err_ptr()->~E();
        }

        T ok() const & {
            assert(is_ok_ && "Called get_ok on error");
            return *get_ok_ptr();
        }

        E err() const & {
            assert(!is_ok_ && "Called get_err on success");
            return *get_err_ptr();
        }

        T ok() && {
            assert(is_ok_ && "Called get_ok on error");
            return std::move(*get_ok_ptr());
        }

        E err() && {
            assert(!is_ok_ && "Called get_err on success");
            return std::move(*get_err_ptr());
        }

        T unwrap() const {
            if (!is_ok_) throw ValueError("Called unwrap on error");
            return *get_ok_ptr();
        }

        T expect(const std::string &msg) const {
            if (!is_ok_) throw ValueError(msg);
            return *get_ok_ptr();
        }

        bool is_ok() const { return is_ok_; }

        bool is_err() const { return !is_ok_; }

        template <class F, class G>
        void visit(F &&f, G &&g) const {
            if (is_ok_)
                f(ok());
            else
                g(err());
        }

        template <class F>
        auto and_then(F &&f) const & -> Result< //
            typename std::decay<decltype(f(
                std::declval<T>()))>::type::value_type,
            E> {
            if (is_ok_) return f(*get_ok_ptr());
            return *get_err_ptr();
        }

        template <class F>
        auto and_then(F &&f) && -> Result< //
            typename std::decay<decltype(f(
                std::declval<T>()))>::type::value_type,
            E> {
            if (is_ok_) return f(std::move(*get_ok_ptr()));
            return std::move(*get_err_ptr());
        }

        template <class F>
        auto or_else(F &&f) const & -> Result<T,
            typename std::decay<decltype(f(
                std::declval<E>()))>::type::error_type> {
            if (is_ok_) return ok();
            return f(err());
        }

        template <class F>
        auto or_else(F &&f) && -> Result<T,
            typename std::decay<decltype(f(
                std::declval<E>()))>::type::error_type> {
            if (is_ok_) return std::move(*get_ok_ptr());
            return f(std::move(*get_err_ptr()));
        }

        void swap(Result &other) noexcept {
            if (this == &other) return;
            if (is_ok_ && other.is_ok_) {
                T temp              = std::move(*get_ok_ptr());
                *get_ok_ptr()       = std::move(*other.get_ok_ptr());
                *other.get_ok_ptr() = std::move(temp);
            } else if (!is_ok_ && !other.is_ok_) {
                E temp               = std::move(*get_err_ptr());
                *get_err_ptr()       = std::move(*other.get_err_ptr());
                *other.get_err_ptr() = std::move(temp);
            } else if (is_ok_) {
                T temp_t = std::move(*get_ok_ptr());
                get_ok_ptr()->~T();
                new (get_err_ptr()) E(std::move(*other.get_err_ptr()));
                other.get_err_ptr()->~E();
                new (other.get_ok_ptr()) T(std::move(temp_t));
            } else {
                E temp_e = std::move(*get_err_ptr());
                get_err_ptr()->~E();
                new (get_ok_ptr()) T(std::move(*other.get_ok_ptr()));
                other.get_ok_ptr()->~T();
                new (other.get_err_ptr()) E(std::move(temp_e));
            }
            std::swap(is_ok_, other.is_ok_);
        }

        friend void swap(Result &a, Result &b) noexcept { a.swap(b); }

        explicit operator bool() const { return is_ok_; }

        bool operator!() const { return !is_ok_; }

        const T &unwrap_or(const T &default_value) const & {
            return is_ok_ ? *get_ok_ptr() : default_value;
        }

        T unwrap_or(T &&default_value) && {
            return is_ok_ ? std::move(*get_ok_ptr()) : std::move(default_value);
        }

        template <class F>
        T unwrap_or_else(F &&fn) const & {
            return is_ok_ ? *get_ok_ptr() : fn();
        }

        template <class F>
        T unwrap_or_else(F &&fn) && {
            return is_ok_ ? std::move(*get_ok_ptr()) : fn();
        }

        const T *ok_ptr() const { return is_ok_ ? get_ok_ptr() : nullptr; }

        T *ok_ptr() { return is_ok_ ? get_ok_ptr() : nullptr; }

        const E *err_ptr() const { return !is_ok_ ? get_err_ptr() : nullptr; }

        E *err_ptr() { return !is_ok_ ? get_err_ptr() : nullptr; }

        bool operator==(const Result &other) const {
            if (is_ok_ != other.is_ok_) return false;
            if (is_ok_) return *get_ok_ptr() == *other.get_ok_ptr();
            return *get_err_ptr() == *other.get_err_ptr();
        }

        bool operator!=(const Result &other) const { return !(*this == other); }
 
#if __cplusplus >= 201703L
        std::optional<T> as_optional() const & {
            return is_ok_ ? std::optional<T>(*get_ok_ptr()) : std::nullopt;
        }

        std::optional<T> as_optional() && {
            return is_ok_ ? std::optional<T>(std::move(*get_ok_ptr()))
                          : std::nullopt;
        }
#endif
    };

}