#pragma once

#include <asio/basic_datagram_socket.hpp>
#include <asio/basic_seq_packet_socket.hpp>
#include <asio/basic_stream_socket.hpp>
#include <asio/bind_executor.hpp>
#include <asio/compose.hpp>
#include <asio/deferred.hpp>
#include <asio/ip/tcp.hpp>
#include <asio/ip/udp.hpp>
#include <asio/local/datagram_protocol.hpp>
#include <asio/local/seq_packet_protocol.hpp>
#include <asio/local/stream_protocol.hpp>
#include <asio/read.hpp>
#include <asio/read_until.hpp>
#include <asio/steady_timer.hpp>
#include <asio/strand.hpp>
#include <asio/streambuf.hpp>
#include <asio/use_awaitable.hpp>
#include <asio/use_future.hpp>
#include <asio/write.hpp>

#include <functional>
#include <queue>

#ifdef USE_OPENSSL_WITH_ASIO

#include <asio/ssl.hpp>
#include <asio/ssl/stream.hpp>

#endif


#include "../../common/adc_traits.h"
#include "../adc_net_concepts.h"
#include "../adc_netproto.h"


namespace adc::impl
{

// typedef for ASIO streambuf iterators
using asio_streambuff_iter_t = asio::buffers_iterator<asio::streambuf::const_buffers_type>;

// ASIO match condition result typedef
using asio_matchcond_result_t = std::pair<asio_streambuff_iter_t, bool>;

template <typename T>
concept adc_asio_transport_proto_c =
    std::derived_from<T, asio::ip::tcp> || std::derived_from<T, asio::ip::udp> ||
    std::derived_from<T, asio::local::seq_packet_protocol> || std::derived_from<T, asio::local::stream_protocol> ||
    std::derived_from<T, asio::local::datagram_protocol>;


template <typename T>
concept adc_asio_stream_transport_proto_c =
    std::derived_from<T, asio::ip::tcp> || std::derived_from<T, asio::local::stream_protocol>;


template <typename T>
concept adc_asio_is_future = requires {
    // [](std::type_identity<asio::use_future_t<>>) {}(std::type_identity<std::remove_cvref_t<T>>());
    []<typename AllocatorT>(std::type_identity<asio::use_future_t<AllocatorT>>) {
    }(std::type_identity<std::remove_cvref_t<T>>{});
};

template <typename T>
concept adc_asio_is_awaitable = requires {
    []<typename ExecutorT>(std::type_identity<asio::use_awaitable_t<ExecutorT>>) {
    }(std::type_identity<std::remove_cvref_t<T>>{});
};


template <typename T>
concept adc_asio_special_comp_token_c =
    adc_asio_is_future<T> || adc_asio_is_awaitable<T> || std::same_as<std::remove_cvref_t<T>, asio::deferred_t>;


// class adc_asio_async_call_ctx_t
// {
// };


// template <typename T, typename SignatureT = void>
// concept adc_completion_token_c =
//     std::same_as<T, adc_asio_async_call_ctx_t> ||
//     (traits::adc_is_callable<T> &&
//      std::conditional_t<std::same_as<SignatureT, void>,
//                         std::true_type,
//                         std::bool_constant<asio::completion_token_for<T, SignatureT>>>::value);



template <adc_asio_transport_proto_c TRANSPORT_PROTOT,
          interfaces::adc_netsession_proto_c<std::string_view> SESSION_PROTOT,
          traits::adc_output_char_range RMSGT =
              std::vector<char>>  // used only for inner storing of message byte sequence
class AdcNetServiceASIOBase : public SESSION_PROTOT
{
public:
    // typedefs to satisfy 'adc_netservice_c' concept
    typedef std::string_view netservice_ident_t;

    typedef std::vector<char> send_msg_t;  // in general, only one of several possible
    typedef RMSGT recv_msg_t;  // in general, only one of several possible (see class template arguments declaration)
    typedef traits::adc_common_duration_t timeout_t;
    using endpoint_t = typename TRANSPORT_PROTOT::endpoint;

    // typedefs for completion tokens (callbacks, required by 'adc_netservice_c' concept)
    typedef std::function<void(std::error_code)> async_accept_callback_t;
    typedef std::function<void(std::error_code)> async_connect_callback_t;
    typedef std::function<void(std::error_code)> async_send_callback_t;
    typedef std::function<void(std::error_code, RMSGT)> async_receive_callback_t;


    // typedefs from transport protocol
    using socket_t = typename TRANSPORT_PROTOT::socket;
    using acceptor_t =
        std::conditional_t<std::derived_from<socket_t, asio::basic_datagram_socket<typename socket_t::protocol_type>>,
                           std::nullptr_t,  // there is no acceptor
                           typename TRANSPORT_PROTOT::acceptor>;



    // to satisfy 'adc_netservice_c' concept
    class async_call_ctx_t
    {
        std::function<void(std::error_code)> _errc_comp_token;
        std::function<void(std::error_code, RMSGT)> _errc_msg_comp_token;

    public:
        async_call_ctx_t() = default;

        async_call_ctx_t(async_call_ctx_t&) = default;
        async_call_ctx_t(async_call_ctx_t&&) = default;
        async_call_ctx_t(const async_call_ctx_t&) = default;

        template <asio::completion_token_for<void(std::error_code)> TokenT>
        async_call_ctx_t(TokenT&& token)
        {
            _errc_comp_token = std::forward<TokenT>(token);
        }

        template <asio::completion_token_for<void(std::error_code, RMSGT)> TokenT>
        async_call_ctx_t(TokenT&& token)
        {
            _errc_msg_comp_token = std::forward<TokenT>(token);
        }

        template <asio::completion_token_for<void(std::error_code)> TokenT>
        async_call_ctx_t& operator=(TokenT&& token)
        {
            _errc_comp_token = std::forward<TokenT>(token);
            return *this;
        }

        template <asio::completion_token_for<void(std::error_code, RMSGT)> TokenT>
        async_call_ctx_t& operator=(TokenT&& token)
        {
            _errc_msg_comp_token = std::forward<TokenT>(token);
            return *this;
        }

        auto operator()(std::error_code ec)
        {
            return _errc_comp_token(std::move(ec));
        }

        auto operator()(std::error_code ec, RMSGT msg)
        {
            return _errc_msg_comp_token(std::move(ec), std::move(msg));
        }

        template <asio::completion_token_for<void(std::error_code)> TokenT>
        operator TokenT() const
        {
            return _errc_comp_token;
        }

        template <asio::completion_token_for<void(std::error_code, RMSGT)> TokenT>
        operator TokenT() const
        {
            return _errc_msg_comp_token;
        }
    };


    static constexpr std::chrono::duration DEFAULT_ACCEPT_TIMEOUT = std::chrono::seconds::max();
    static constexpr std::chrono::duration DEFAULT_CONNECT_TIMEOUT = std::chrono::seconds(10);
    static constexpr std::chrono::duration DEFAULT_SEND_TIMEOUT = std::chrono::seconds(5);
    static constexpr std::chrono::duration DEFAULT_RECEIVE_TIMEOUT = std::chrono::seconds(5);

    AdcNetServiceASIOBase(asio::io_context& ctx)
        : SESSION_PROTOT(),
          _ioContext(ctx),
          _receiveStrand(_ioContext),
          _receiveQueue(),
          _acceptor(_ioContext),
          _socket(_ioContext)
    {
    }


    AdcNetServiceASIOBase(socket_t socket)
        : SESSION_PROTOT(),
          _ioContext(socket.get_executor()),
          _receiveStrand(_ioContext),
          _receiveQueue(),
          _socket(std::move(socket))
    {
    }


    AdcNetServiceASIOBase(AdcNetServiceASIOBase&& other)
        : _ioContext(other._ioContext),
          _receiveStrand(std::move(other._receiveStrand)),
          _receiveQueue(std::move(_receiveQueue)),
          _acceptor(std::move(other._acceptor)),
          _socket(std::move(other._socket)),
          _streamBuffer()
    {
        auto bytes = asio::buffer_copy(_streamBuffer.prepare(other._streamBuffer.size()), other._streamBuffer.data());
        _streamBuffer.commit(bytes);
    };

    AdcNetServiceASIOBase(const AdcNetServiceASIOBase&) = delete;  // no copy constructor!

    virtual ~AdcNetServiceASIOBase() {}


    constexpr netservice_ident_t ident() const
    {
        return _ident;
    }


    /*    asynchronuos methods   */

    template <asio::completion_token_for<void(std::error_code)> TokenT,
              traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_ACCEPT_TIMEOUT)>
    auto asyncAccept(const endpoint_t& endpoint, TokenT&& token, const TimeoutT& timeout = DEFAULT_ACCEPT_TIMEOUT)
    {
        // no acceptor for UDP-sockets
        if constexpr (std::is_null_pointer_v<acceptor_t>) {
            static_assert(false, "INVALID TRANSPORT PROTOCOL TYPE!");
        }

        // auto acc = acceptor_t(_ioContext);

        // auto timer = getDeadlineTimer(acc, timeout);
        auto timer = getDeadlineTimer(_acceptor, timeout);

        return asio::async_compose<TokenT, void(std::error_code)>(
            // [acc = std::move(acc), timer = std::move(timer), start = true, &endpoint, this](
            [timer = std::move(timer), start = true, &endpoint, this](auto& self, std::error_code ec = {}) mutable {
                if (!ec) {
                    if (start) {
                        start = false;
                        try {
                            // acc = acceptor_t(_ioContext, endpoint);
                            if (!_acceptor.is_open() || (_acceptor.local_endpoint() != endpoint)) {
                                _acceptor = acceptor_t(_ioContext, endpoint);
                            }
                        } catch (std::system_error err) {
                            timer->cancel();
                            self.complete(err.code());
                            return;
                        }

                        // return acc.async_accept(_socket, std::move(self));
                        return _acceptor.async_accept(_socket, std::move(self));
                    }
                }

                if (isTimeout(timer, ec)) {
                    ec = std::make_error_code(std::errc::timed_out);
                } else {  // an error occured in async_connect
                    timer->cancel();
                }

                self.complete(ec);
            },
            token, _ioContext);
    }


    template <asio::completion_token_for<void(std::error_code)> TokenT,
              traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_CONNECT_TIMEOUT)>
    auto asyncConnect(const endpoint_t& endpoint, TokenT&& token, const TimeoutT& timeout = DEFAULT_CONNECT_TIMEOUT)
    {
        auto timer = getDeadlineTimer(_socket, timeout);

        return asio::async_compose<TokenT, void(asio::error_code)>(
            [start = true, endpoint, timer = std::move(timer), this](auto& self, asio::error_code ec = {}) mutable {
                if (!ec) {
                    if (start) {
                        start = false;
                        return _socket.async_connect(endpoint, std::move(self));
                    }
                }

                if (isTimeout(timer, ec)) {
                    ec = std::make_error_code(std::errc::timed_out);
                } else {  // an error occured in async_connect
                    timer->cancel();
                }

                self.complete(ec);
            },
            token, _socket);
    }


    template <traits::adc_input_char_range MessageT,
              asio::completion_token_for<void(std::error_code ec)> TokenT,
              traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_SEND_TIMEOUT)>
    auto asyncSend(const MessageT& msg, TokenT&& token, const TimeoutT& timeout = DEFAULT_SEND_TIMEOUT)
    {
        // create buffer sequence of sending session protocol representation of the input message
        std::vector<asio::const_buffer> buff_seq;
        std::ranges::for_each(this->toProto(msg), [&buff_seq](const auto& el) { buff_seq.emplace_back(el); });

        auto timer = getDeadlineTimer(_socket, timeout);

        return asio::async_compose<TokenT, void(asio::error_code)>(
            [start = true, buff_seq = std::move(buff_seq), timer = std::move(timer), this](
                auto& self, asio::error_code ec = {}) mutable {
                if (!ec) {
                    if (start) {
                        start = false;
                        if constexpr (std::derived_from<socket_t,
                                                        asio::basic_stream_socket<typename socket_t::protocol_type>>) {
                            return asio::async_write(_socket, buff_seq, std::move(self));
                        } else if constexpr (std::derived_from<socket_t, asio::basic_datagram_socket<
                                                                             typename socket_t::protocol_type>>) {
                            return _socket.async_send(buff_seq, std::move(self));
                        } else if constexpr (std::derived_from<socket_t, asio::basic_seq_packet_socket<
                                                                             typename socket_t::protocol_type>>) {
                            return _socket.async_send(buff_seq, std::move(self));
                        } else {
                            static_assert(false, "UNKNOWN ASIO-LIBRARY SOCKET TYPE!!!");
                        }
                    }
                }

                if (isTimeout(timer, ec)) {
                    ec = std::make_error_code(std::errc::timed_out);
                } else {  // an error occured in async_write/async_send
                    timer->cancel();
                }

                self.complete(ec);
            },
            token, _socket);
    }


    template <typename TokenT, traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_RECEIVE_TIMEOUT)>
    auto asyncReceive(TokenT&& token, const TimeoutT& timeout = DEFAULT_RECEIVE_TIMEOUT)
    {
        constexpr auto is_async_ctx_t = std::same_as<std::remove_cvref_t<TokenT>, async_call_ctx_t>;

        // check completion token signature and deduce message type
        if constexpr (!adc_asio_special_comp_token_c<TokenT> && !is_async_ctx_t) {
            static_assert(traits::adc_func_traits<TokenT>::arity == 2, "INVALID COMPLETION TOKEN SIGNATURE!");
            static_assert(std::is_same_v<std::remove_cvref_t<traits::adc_func_arg1_t<TokenT>>, std::error_code>,
                          "INVALID COMPLETION TOKEN SIGNATURE!");
            static_assert(traits::adc_output_char_range<
                              std::tuple_element_t<1, typename traits::adc_func_traits<TokenT>::args_t>>,
                          "INVALID COMPLETION TOKEN SIGNATURE!");
        }

        using msg_t = std::conditional_t<
            adc_asio_special_comp_token_c<TokenT> || is_async_ctx_t, RMSGT,
            std::remove_cvref_t<std::tuple_element_t<1, typename traits::adc_func_traits<TokenT>::args_t>>>;

        auto out_flags = std::make_shared<asio::socket_base::message_flags>();

        auto timer = getDeadlineTimer(_socket, timeout);

        return asio::async_compose<TokenT, void(asio::error_code, msg_t)>(
            [out_flags, do_read = true, timer = std::move(timer), this](auto& self, asio::error_code ec = {},
                                                                        size_t nbytes = 0) mutable {
                // RMSGT msg;
                msg_t msg;

                if (!ec) {
                    if (do_read) {
                        do_read = false;
                        if (_receiveQueue.size()) {  // return message from queue
                            timer->cancel();
                            auto imsg = _receiveQueue.front();
                            _receiveQueue.pop();
                            if constexpr (std::is_same_v<msg_t, RMSGT>) {
                                self.complete(std::error_code(), std::move(imsg));
                            } else {
                                self.complete(std::error_code(), {imsg.begin(), imsg.end()});
                            }
                            return;
                        }

                        if constexpr (std::derived_from<socket_t,
                                                        asio::basic_stream_socket<typename socket_t::protocol_type>>) {
                            return asio::async_read(_socket, _streamBuffer, asio::transfer_at_least(1),
                                                    std::move(self));
                        } else if constexpr (std::derived_from<socket_t, asio::basic_datagram_socket<
                                                                             typename socket_t::protocol_type>>) {
                            // datagram, so it should be received at once
                            return _socket.receive(_streamBuffer, std::move(self));
                        } else if constexpr (std::derived_from<socket_t, asio::basic_seq_packet_socket<
                                                                             typename socket_t::protocol_type>>) {
                            // datagram, so it should be received at once
                            return _socket.receive(_streamBuffer, *out_flags, std::move(self));
                        } else {
                            static_assert(false, "UNKNOWN ASIO-LIBRARY SOCKET TYPE!!!");
                        }
                    }

                    // if (!nbytes) {
                    //     do_read = true;
                    //     asio::post(std::move(self));  // initiate consequence socket's read operation
                    //     return;
                    // }

                    auto start_ptr = static_cast<const char*>(_streamBuffer.data().data());

                    // auto sr = this->search(std::span(start_ptr, _streamBuffer.size()));
                    auto net_pack = this->search(std::span(start_ptr, _streamBuffer.size()));
                    // if (!std::get<2>(sr)) {
                    if (net_pack.empty()) {
                        do_read = true;
                        asio::post(std::move(self));  // initiate consequence socket's read operation
                        return;
                    }

                    timer->cancel();  // there were no errors in the asynchronous read-operation, so stop timer

                    // here one has at least a single message
                    // size_t N = std::distance(std::get<0>(sr), std::get<1>(sr));
                    // auto net_pack = std::span{start_ptr, N};

                    std::ranges::copy(this->fromProto(net_pack), std::back_inserter(msg));
                    _streamBuffer.consume(net_pack.size());


                    while (_streamBuffer.size()) {  // search for possible additional session protocol packets
                        start_ptr = static_cast<const char*>(_streamBuffer.data().data());

                        // sr = this->search(std::span(start_ptr, _streamBuffer.size()));
                        net_pack = this->search(std::span(start_ptr, _streamBuffer.size()));

                        if (!net_pack.empty()) {
                            // if (std::get<2>(sr)) {
                            // N = std::distance(std::get<0>(sr), std::get<1>(sr));
                            // net_pack = std::span{start_ptr, N};

                            _receiveQueue.emplace();
                            std::ranges::copy(this->fromProto(net_pack), std::back_inserter(_receiveQueue.back()));
                            _streamBuffer.consume(net_pack.size());
                        } else {
                            break;  // exit and hold remaining bytes in stream buffer
                        }
                    }
                }

                if (isTimeout(timer, ec)) {
                    ec = std::make_error_code(std::errc::timed_out);
                } else {  // an error occured in async_*
                    timer->cancel();
                }

                if constexpr (std::is_same_v<msg_t, RMSGT>) {
                    self.complete(ec, std::move(msg));
                } else {
                    // msg_t user_msg{msg.begin(), msg.end()};
                    self.complete(ec, {msg.begin(), msg.end()});
                }
            },
            token, _socket);
    }

    /*    blocking methods    */

    template <traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_ACCEPT_TIMEOUT)>
    auto accept(const endpoint_t& endpoint, const TimeoutT& timeout = DEFAULT_ACCEPT_TIMEOUT)
    {
        std::future<void> ftr = asyncAccept(endpoint, asio::use_future, timeout);
        ftr.get();
    }

    template <traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_CONNECT_TIMEOUT)>
    auto connect(const endpoint_t& endpoint, const TimeoutT& timeout = DEFAULT_CONNECT_TIMEOUT)
    {
        std::future<void> ftr = asyncConnect(endpoint, asio::use_future, timeout);
        ftr.get();
    }

    template <traits::adc_input_char_range R, traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_SEND_TIMEOUT)>
    auto send(const R& msg, const TimeoutT& timeout = DEFAULT_SEND_TIMEOUT)
    {
        std::future<void> ftr = asyncSend(msg, timeout, asio::use_future);
        ftr.get();
    }

    template <traits::adc_time_duration_c TimeoutT = decltype(DEFAULT_RECEIVE_TIMEOUT)>
    auto receive(const TimeoutT& timeout = DEFAULT_RECEIVE_TIMEOUT)
    {
        std::future<RMSGT> ftr = asyncReceive(timeout, asio::use_future);
        return ftr.get();
    }

    std::error_code close()
    {
        std::error_code ec;

        _socket.shutdown(_shutdownType, ec);
        if (!ec) {
            _socket.close(ec);
        }

        return ec;
    }

    /*   additional ASIO-related methods  */

    void clear()
    {
        // clear receiving messages queue
        // NOTE: there is no racing condition here since using asio::strand!
        asio::post(_receiveStrand, [this]() { _receiveQueue = {}; });
    }

    void setShutdownType(asio::socket_base::shutdown_type shutdown_type)
    {
        _shutdownType = shutdown_type;
    }

    asio::socket_base::shutdown_type getShutdownType() const
    {
        return _shutdownType;
    }

protected:
    static constexpr netservice_ident_t _ident =
        std::derived_from<socket_t, asio::basic_stream_socket<typename socket_t::protocol_type>>
            ? "STREAM-SOCKET NETWORK SERVICE"
        : std::derived_from<socket_t, asio::basic_datagram_socket<typename socket_t::protocol_type>>
            ? "DATAGRAM-SOCKET NETWORK SERVICE"
        : std::derived_from<socket_t, asio::basic_seq_packet_socket<typename socket_t::protocol_type>>
            ? "SEQPACKET-SOCKET NETWORK SERVICE"
            : "UNKNOWN";

    asio::io_context& _ioContext;
    asio::io_context::strand _receiveStrand;

    socket_t _socket;

    acceptor_t _acceptor;

    asio::streambuf _streamBuffer;

    std::queue<std::vector<char>> _receiveQueue;

    asio::socket_base::shutdown_type _shutdownType = asio::socket_base::shutdown_both;


    template <typename CancelableT, traits::adc_time_duration_c TimeoutT>
    static std::unique_ptr<asio::steady_timer> getDeadlineTimer(CancelableT& obj,
                                                                const TimeoutT& timeout,
                                                                bool arm = true)
    {
        auto timer = std::make_unique<asio::steady_timer>(obj.get_executor());

        // if (timeout == std::chrono::duration<typename TimeoutT::rep, typename TimeoutT::period>::max()) {
        //     return timer;  // do not arm the timer if MAX duration are given
        // }

        if (arm) {
            std::chrono::seconds max_d = std::chrono::duration_cast<std::chrono::seconds>(
                std::chrono::steady_clock::time_point::max() - std::chrono::steady_clock::now() -
                std::chrono::seconds(1));

            timer->expires_after(timeout < max_d ? timeout : max_d);  // to avoid overflow!
            // timer->expires_after(timeout);

            timer->async_wait([&obj](const std::error_code& ec) mutable {
                if (!ec) {
                    obj.cancel();
                }
            });
        }

        return timer;
    }

    template <typename TimerT>
    static bool isTimeout(const std::unique_ptr<TimerT>& timer, const std::error_code& ec)
    {
        auto exp_time = timer->expiry();
        return (exp_time < std::chrono::steady_clock::now()) && (ec == asio::error::operation_aborted);
    }
};


// static_assert(adc::interfaces::adc_netservice_c<AdcNetServiceASIOBase<asio::ip::tcp, adc::AdcStopSeqSessionProto<>>>,
//               "");

static_assert(adc::interfaces::adc_netsession_proto_c<adc::AdcStopSeqSessionProto<>>, "");

}  // namespace adc::impl