coroutine.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,
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SOFTWARE.
*/
 
#pragma once
#include <functional>
#include <memory>
#include <utility>
 
#include "../core/csexc.h"
 
// clang-format off

#define cr_begin(type, ...)                                                    \
    int _state = 0;                                                            \
    return [=](__VA_ARGS__) mutable -> type {                                  \
        switch (_state) {                                                      \
        case 0:

#define cr_yield(value)                                                        \
        do {                                                                   \
            _state = __LINE__;                                                 \
            return value;                                                      \
        case __LINE__:;                                                        \
        } while (false)

#define cr_return(value)                                                       \
        do {                                                                   \
            _state = __LINE__;                                                 \
            return value;                                                      \
        case __LINE__:                                                         \
            throw console::StopIteration("StopIteration");                     \
        } while (false)

#define cr_throw(exception)                                                    \
        do {                                                                   \
            _state = __LINE__;                                                 \
            throw exception;                                                   \
        case __LINE__:                                                         \
            throw console::StopIteration("StopIteration");                     \
        } while (false)

#define cr_end                                                                 \
            _state = __LINE__;                                                 \
        case __LINE__:;                                                        \
            break;                                                             \
        }                                                                      \
        throw console::StopIteration("StopIteration");                         \
    }
 
// clang-format on
 
namespace console {
    template <class>
    class Coroutine;

    template <class Ret>
    class Coroutine<Ret()> {
        std::shared_ptr<std::function<Ret()>> coro;
        std::shared_ptr<Ret> ptr;
 
    public:
        template <class F>
        Coroutine(F f) :
            coro(std::make_shared<std::function<Ret()>>(std::move(f))) {}

        Ret operator()() { return (*coro)(); }

        using value_type = Ret;
        using difference_type = ptrdiff_t;
        using pointer = value_type *;
        using reference = value_type;
        using iterator_category = std::input_iterator_tag;

        value_type operator*() {
            if (!ptr) ++(*this);
            if (!ptr) throw StopIteration("StopIteration");
            return *ptr;
        }

        Coroutine &operator++() {
            try {
                if (ptr)
                    *ptr = (*coro)();
                else
                    ptr.reset(new Ret((*coro)()));
            } catch (const StopIteration &) {
                ptr.reset();
            }
            return *this;
        }

        Coroutine operator++(int) {
            Coroutine old = *this;
            ++(*this);
            return old;
        }

        bool operator==(const Coroutine &) {
            if (!ptr) ++(*this);
            return !ptr;
        }

        bool operator!=(const Coroutine &) {
            if (!ptr) ++(*this);
            return !!ptr;
        }

        Coroutine begin() { return *this; }
        Coroutine end() { return *this; }
    };

    template <class Ret>
    class Coroutine<Ret &()> {
        std::shared_ptr<std::function<Ret &()>> coro;
        Ret *ptr = nullptr;
 
    public:
        template <class F>
        Coroutine(F f) :
            coro(std::make_shared<std::function<Ret &()>>(std::move(f))) {}

        Ret &operator()() { return (*coro)(); }

        using value_type = Ret;
        using difference_type = ptrdiff_t;
        using pointer = Ret *;
        using reference = Ret &;
        using iterator_category = std::input_iterator_tag;

        reference operator*() {
            if (!ptr) ++(*this);
            if (!ptr) throw StopIteration("StopIteration");
            return *ptr;
        }

        Coroutine &operator++() {
            try {
                ptr = &(*coro)();
            } catch (const StopIteration &) {
                ptr = nullptr;
            }
            return *this;
        }

        Coroutine operator++(int) {
            Coroutine old = *this;
            ++(*this);
            return old;
        }

        bool operator==(const Coroutine &) {
            if (!ptr) ++(*this);
            return !ptr;
        }

        bool operator!=(const Coroutine &) {
            if (!ptr) ++(*this);
            return !!ptr;
        }

        Coroutine begin() { return *this; }
        Coroutine end() { return *this; }
    };

    template <class Ret, class... Args>
    class Coroutine<Ret(Args...)> {
        std::function<Ret(Args...)> coro;
 
    public:
        template <class F>
        Coroutine(F &&f) : coro(std::forward<F>(f)) {}

        template <class... Args_>
        Ret operator()(Args_ &&...args) {
            return coro(std::forward<Args_>(args)...);
        }
    };
}