coroutines.h

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#ifndef ORIGINAL_COROUTINES_H
#define ORIGINAL_COROUTINES_H
#include "optional.h"
#include <coroutine>
#include <exception>
 
namespace original {
    class coroutine {
    public:
        template<typename TYPE>
        class generator {
        public:
            struct promise_type;
        private:
            using handle = std::coroutine_handle<promise_type>;  
 
            handle handle_;  
 
        public:
            struct promise_type {
                bool initial_staus = false;      
                alternative<TYPE> value_;        
                std::exception_ptr e_;           
 
                generator get_return_object();
 
                static std::suspend_always initial_suspend();
 
                static std::suspend_always final_suspend() noexcept;
 
                static void return_void();
 
                std::suspend_always yield_value(TYPE value);
 
                void unhandled_exception();
 
                void rethrow_if_exception() const;
            };
 
            class iterator {
                generator* gen_;  
                bool end_;        
 
                iterator();
 
                explicit iterator(generator* gen);
            public:
                friend coroutine;
 
                iterator& operator++();
 
                TYPE operator*();
 
                bool operator!=(const iterator& other) const;
 
                bool operator==(const iterator& other) const;
            };
 
            generator(const generator&) = delete;            
            generator& operator=(const generator&) = delete; 
 
            generator(generator&& other) noexcept;
 
            generator& operator=(generator&& other) noexcept;
 
            generator() = default;  
 
            explicit generator(handle h);
 
            iterator begin();
 
            static iterator end();
 
            [[nodiscard]] bool launched() const;
 
            [[nodiscard]] bool hasNext() const;
 
            [[nodiscard]] alternative<TYPE> peek() const;
 
            alternative<TYPE> next();
 
            ~generator();
        };
    };
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>
original::coroutine::generator<TYPE>::promise_type::get_return_object()
{
    return generator{handle::from_promise(*this)};
}
 
template <typename TYPE>
std::suspend_always original::coroutine::generator<TYPE>::promise_type::initial_suspend()
{
    return std::suspend_always{};
}
 
template <typename TYPE>
std::suspend_always original::coroutine::generator<TYPE>::promise_type::final_suspend() noexcept
{
    return std::suspend_always{};
}
 
template <typename TYPE>
void original::coroutine::generator<TYPE>::promise_type::return_void() {}
 
template <typename TYPE>
std::suspend_always original::coroutine::generator<TYPE>::promise_type::yield_value(TYPE value)
{
    if (!this->initial_staus) {
        this->initial_staus = true;
    }
    this->value_ = std::move(value);
    return std::suspend_always{};
}
 
template <typename TYPE>
void original::coroutine::generator<TYPE>::promise_type::unhandled_exception()
{
    this->e_ = std::current_exception();
}
 
template <typename TYPE>
void original::coroutine::generator<TYPE>::promise_type::rethrow_if_exception() const
{
    if (this->e_)
        std::rethrow_exception(this->e_);
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::iterator::iterator() : gen_(nullptr), end_(true) {}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::iterator::iterator(generator* gen) : gen_(gen), end_(false)
{
    if (!this->gen_) {
        this->end_ = true;
        return;
    }
    ++*this;
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::iterator&
original::coroutine::generator<TYPE>::iterator::operator++()
{
    if (this->end_)
        return *this;
    if (auto gen_next = this->gen_->next(); !gen_next) {
        this->end_ = true;
    }
    return *this;
}
 
template <typename TYPE>
TYPE original::coroutine::generator<TYPE>::iterator::operator*()
{
    if (this->end_)
        throw nullPointerError("Dereferencing end iterator");
    return *this->gen_->peek();
}
 
template <typename TYPE>
bool original::coroutine::generator<TYPE>::iterator::operator!=(const iterator& other) const
{
    return !(*this == other);
}
 
template <typename TYPE>
bool original::coroutine::generator<TYPE>::iterator::operator==(const iterator& other) const
{
    if (this->end_ && other.end_)
        return true;
    if (this->end_ != other.end_)
        return false;
    return this->gen_ == other.gen_;
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::generator(generator&& other) noexcept
{
    this->handle_ = other.handle_;
    other.handle_ = nullptr;
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>&
original::coroutine::generator<TYPE>::operator=(generator&& other) noexcept
{
    if (this == &other) {
        return *this;
    }
 
    if (this->handle_) {
        this->handle_.destroy();
    }
 
    this->handle_ = other.handle_;
    other.handle_ = nullptr;
    return *this;
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::generator(handle h) : handle_(std::move(h)) {}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::iterator
original::coroutine::generator<TYPE>::begin()
{
    return iterator{this};
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::iterator
original::coroutine::generator<TYPE>::end()
{
    return iterator{};
}
 
template <typename TYPE>
bool original::coroutine::generator<TYPE>::launched() const
{
    return this->handle_.promise().initial_staus;
}
 
template <typename TYPE>
bool original::coroutine::generator<TYPE>::hasNext() const
{
    return this->handle_ && !this->handle_.done();
}
 
template <typename TYPE>
original::alternative<TYPE> original::coroutine::generator<TYPE>::peek() const
{
    return this->handle_.promise().value_;
}
 
template <typename TYPE>
original::alternative<TYPE>
original::coroutine::generator<TYPE>::next()
{
    if (!this->hasNext())
        return alternative<TYPE>{};
 
    this->handle_.resume();
    this->handle_.promise().rethrow_if_exception();
 
    if (!this->hasNext())
        return alternative<TYPE>{};
 
    return this->handle_.promise().value_;
}
 
template <typename TYPE>
original::coroutine::generator<TYPE>::~generator()
{
    if (this->handle_)
        this->handle_.destroy();
}
 
#endif //ORIGINAL_COROUTINES_H