sync_generator_adapter.h

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#ifndef C6A6302D_1533_460C_84B8_A465FEABCAF6
#define C6A6302D_1533_460C_84B8_A465FEABCAF6

 
#include <cstddef>
#include <iterator>
#include <ranges>
#include <utility>
 
#include "async_generator.h"
#include "eager_task.h"
 
namespace wwa::coro {

template<typename Result>
class [[nodiscard]] sync_generator_adapter : public std::ranges::view_interface<sync_generator_adapter<Result>> {
public:
    struct iterator {
        using iterator_concept = std::input_iterator_tag;

        using difference_type = std::ptrdiff_t;


        iterator() noexcept : m_op(nullptr) {}

        explicit iterator(const async_generator<Result>::iterator::advance_op& op) : m_op(std::move(op))
        {
            this->advance();
        }

        ~iterator() = default;

        iterator(const iterator& other) noexcept = default;

        iterator(iterator&& other) noexcept = default;

        iterator& operator=(const iterator& other) noexcept = default;

        iterator& operator=(iterator&& other) noexcept = default;

        iterator& operator++() { return this->advance(); }

        void operator++(int) { this->operator++(); }

        async_generator<Result>::iterator::reference operator*() const { return *this->m_it; }

        bool operator==(const iterator& other) const noexcept { return this->m_it == other.m_it; }
 
    private:
        async_generator<Result>::iterator::advance_op m_op;  
        async_generator<Result>::iterator m_it{nullptr};     

        iterator& advance()
        {
            [](iterator* self) -> eager_task { self->m_it = co_await self->m_op; }(this);
            return *this;
        }
    };

    explicit sync_generator_adapter(async_generator<Result> gen) noexcept : m_gen(std::move(gen)) {}

    sync_generator_adapter(sync_generator_adapter&& other) noexcept = default;

    ~sync_generator_adapter() = default;

    sync_generator_adapter(const sync_generator_adapter&)            = delete;
    sync_generator_adapter& operator=(const sync_generator_adapter&) = delete;
    sync_generator_adapter& operator=(sync_generator_adapter&&)      = delete;

    iterator begin() { return iterator(this->m_gen.begin()); }

    iterator end() noexcept { return {}; }
 
private:
    async_generator<Result> m_gen;  
};


template<typename Result>
sync_generator_adapter(async_generator<Result>) -> sync_generator_adapter<Result>;
 
}  // namespace wwa::coro
 
#endif /* C6A6302D_1533_460C_84B8_A465FEABCAF6 */