#include <functional>
#include <optional>

#include <ranczo-io/utils/mqtt_client.hpp>
#include <ranczo-io/utils/json_helpers.hpp>
#include <ranczo-io/utils/memory_resource.hpp>
#include <ranczo-io/utils/logger.hpp>

#include <config.hpp>

#include <boost/asio.hpp>
#include <boost/asio/as_tuple.hpp>
#include <boost/asio/use_awaitable.hpp>
#include <boost/json.hpp>
#include <boost/json/object.hpp>
#include <boost/json/serialize.hpp>
#include <boost/mqtt5.hpp>
#include <boost/mqtt5/types.hpp>
#include <boost/random/uniform_smallint.hpp>
#include <boost/system/detail/error_code.hpp>
#include <boost/system/errc.hpp>
#include <boost/system/result.hpp>
#include <boost/system/system_error.hpp>
#include <boost/uuid/uuid.hpp>
#include <boost/uuid/uuid_generators.hpp>

#include <algorithm>
#include <cstdint>
#include <exception>
#include <memory_resource>
#include <spdlog/spdlog.h>

class perf_counter {
    using clock = std::chrono::steady_clock;
    
    std::string _name;
    clock::time_point _begin;
    
    ranczo::ModuleLogger _log{spdlog::default_logger(), "PerfCounter " + _name};
    
  public:
    explicit perf_counter(std::string_view name)
     : _name(name),
       _begin(clock::now())
    {}
    
    ~perf_counter() {
        const auto end   = clock::now();
        const auto delta = std::chrono::duration_cast<std::chrono::microseconds>(end - _begin).count();
        
        _log.debug("{} took {} us", _name, delta);
    }
};

namespace ranczo {
class Topic {
  public:
    std::string pattern;

    Topic() = default;
    Topic(std::string_view p) : pattern(p) {}

    bool operator==(const std::string_view other) const {
        return match(other);
    }

  private:
    static std::vector< std::string_view > split(std::string_view str) {
        std::vector< std::string_view > tokens;
        size_t start = 0;
        while(start < str.size()) {
            size_t end = str.find('/', start);
            if(end == std::string_view::npos)
                end = str.size();
            tokens.emplace_back(str.substr(start, end - start));
            start = end + 1;
        }
        return tokens;
    }

    bool match(std::string_view topic) const {
        auto pattern_parts = split(pattern);
        auto topic_parts   = split(topic);

        size_t i = 0;
        for(; i < pattern_parts.size(); ++i) {
            if(pattern_parts[i] == "#") {
                return true;
            }

            if(i >= topic_parts.size()) {
                return false;
            }

            if(pattern_parts[i] != "+" && pattern_parts[i] != topic_parts[i]) {
                return false;
            }
        }

        return i == topic_parts.size(); // dokładnie tyle samo segmentów
    }
};

constexpr auto use_nothrow_awaitable = boost::asio::as_tuple(boost::asio::use_awaitable);
using client_type                    = boost::mqtt5::mqtt_client< boost::asio::ip::tcp::socket >;

struct AsyncMqttClient::SubscribtionToken {
    boost::uuids::uuid uuid;
};

struct AsyncMqttClient::AsyncMqttClientImpl {
    const boost::asio::any_io_executor & _executor;
    ModuleLogger _log;
    client_type _mqtt_client;
    std::vector< std::tuple< Topic, callback_t, std::unique_ptr< AsyncMqttClient::SubscribtionToken > > > _callbacks;
    
    AsyncMqttClientImpl(const boost::asio::any_io_executor & executor) : _executor{executor}, _log{spdlog::default_logger(), "MQTT Impl"}, _mqtt_client{_executor} {
        _log.trace("Creating client");
        // Configure the Client.
        // It is mandatory to call brokers() and async_run() to configure the Brokers to connect to and start the Client.
        _mqtt_client
          .brokers("192.168.10.10", 1883)    // Broker that we want to connect to. 1883 is the default TCP port.
          .async_run(boost::asio::detached); // Start the client.

        start();
        _log.trace("Creating client done");
    }

    ~AsyncMqttClientImpl() = default;

    const AsyncMqttClient::SubscribtionToken * add_callback(std::string_view topic, callback_t cb) {
        _log.trace("registering callback for {}", topic);

        auto token       = std::make_unique< AsyncMqttClient::SubscribtionToken >(boost::uuids::random_generator()());
        auto * token_ptr = token.get();

        _callbacks.emplace_back(Topic{topic}, std::move(cb), std::move(token));

        _log.trace("registering callback for {} DONE", topic);
        return token_ptr;
    }

    void remove_callback(const AsyncMqttClient::SubscribtionToken * token) {
        _log.trace("removing callback by token");

        auto it = std::find_if(_callbacks.begin(), _callbacks.end(), [&](const auto & tuple) {
            return std::get< std::unique_ptr< AsyncMqttClient::SubscribtionToken > >(tuple).get() == token;
        });

        if(it != _callbacks.end()) {
            _callbacks.erase(it);
        } else {
            _log.error("token not found");
        }

        _log.trace("removing callback DONE");
    }

    bool has_subscription_for_topic(std::string_view topic) const {
        // sprawdzamy dokładne dopasowanie patternu, nie wildcardowe dopasowanie (==)
        return std::any_of(
          _callbacks.begin(), _callbacks.end(), [&](const auto & tuple) { return std::get< Topic >(tuple).pattern == topic; });
    }

    awaitable_expected< const AsyncMqttClient::SubscribtionToken * > subscribe_with_callback(std::string_view topic, callback_t cb) {
        BOOST_ASSERT(!topic.empty());
        BOOST_ASSERT(cb);

        _log.trace("subscribe_with_callback on topic: {}", topic);

        const bool already = has_subscription_for_topic(topic);

        // zawsze rejestrujemy callback
        const auto * tok = add_callback(topic, std::move(cb));

        if(already) {
            _log.trace("subscription to {} already active, only callback registered", topic);
            co_return tok;
        }

        _log.trace("subscription to {} started", topic);
        auto status = co_await subscribe(topic);
        if(!status) {
            _log.error("failed to subscribe for topic {}", topic);
            remove_callback(tok);
            co_return unexpected{status.error()};
        }

        _log.trace("subscription to {} DONE", topic);
        co_return tok;
    }

    awaitable_expected< void > subscribe(std::string_view topic) {
        _log.trace("subscribe to {}", topic);

        // switch to mqtt strand
        co_await boost::asio::dispatch(_mqtt_client.get_executor(), boost::asio::use_awaitable);

        // Configure the request to subscribe to a Topic.
        boost::mqtt5::subscribe_topic sub_topic = boost::mqtt5::subscribe_topic{topic.data(),
          boost::mqtt5::subscribe_options{
            .max_qos             = boost::mqtt5::qos_e::exactly_once,           // All messages will arrive at QoS 2.
            .no_local            = boost::mqtt5::no_local_e::yes,               // Forward message from Clients with same ID.
            .retain_as_published = boost::mqtt5::retain_as_published_e::retain, // Keep the original RETAIN flag.
            .retain_handling     = boost::mqtt5::retain_handling_e::send // Send retained messages when the subscription is established.
          }};

        // Subscribe to a single Topic.
        _log.trace("calling async_subscribe");
        auto && [ec, sub_codes, sub_props] =
          co_await _mqtt_client.async_subscribe(sub_topic, boost::mqtt5::subscribe_props{}, use_nothrow_awaitable);
        _log.trace("calling async_subscribe DONE");
        // Note: you can subscribe to multiple Topics in one mqtt_client::async_subscribe call.

        // An error can occur as a result of:
        //  a) wrong subscribe parameters
        //  b) mqtt_client::cancel is called while the Client is in the process of subscribing
        if(ec) {
            _log.error("subscribe error: {}", ec.message());
            for(int i{}; i < sub_codes.size(); i++)
                _log.error("subscribe suberror[{}]: {}", i, sub_codes[i].message());
            co_return unexpected{ec};
        }

        if(sub_codes.empty()) {
            _log.error("subscribe result contains no subcodes");
            co_return unexpected{make_error_code(boost::system::errc::protocol_error)};
        }

        _log.info("subscribed to {}", topic);
        for(int i{}; i < sub_codes.size(); i++)
            _log.info("subscribe accepted: {}", sub_codes[i].message());

        co_return _void{}; // Success
    }

    awaitable_expected< void > publish(std::string_view topic, const boost::json::value & value) noexcept {
        _log.trace("publish on: {}", topic);

        // 1) execute in context of mqtt strand
        co_await boost::asio::dispatch(_mqtt_client.get_executor(), boost::asio::use_awaitable);

        // 2) owning copies for topic and payload.
        std::string t{topic};
        std::string payload;
        try {
            payload = boost::json::serialize(value);
        } catch(const std::bad_alloc & e) {
            _log.error("cought bad_alloca exception: {}", e.what());
            co_return unexpected{make_error_code(std::errc::not_enough_memory)};
        }

        // 3) QoS 0: only error code returned
        auto [ec] = co_await _mqtt_client.async_publish< boost::mqtt5::qos_e::at_most_once >(
          std::move(t), std::move(payload), boost::mqtt5::retain_e::no, boost::mqtt5::publish_props{}, boost::asio::as_tuple(boost::asio::use_awaitable));

        if(ec) {
            _log.error("publish returned an exception: {}", ec.message());
            co_return unexpected{ec};
        }

        co_return _void{};
    }

    void
    handle_received_message(const std::string & topic, const std::string & payload, const boost::mqtt5::publish_props & publish_props) {
        perf_counter _ {"handle_received_message"};
        _log.debug("received topic {}, payload {}", topic, payload);

        bool run = false;

        for(const auto & [registeredTopic, cb, token] : _callbacks) {
            if(registeredTopic == topic) {
                run = true;

                // kopiujemy topic/payload do lambda, żeby mieć pewny lifetime
                std::string topic_copy   = topic;
                std::string payload_copy = payload;

                boost::asio::co_spawn(
                  _executor,
                  [this, handler = cb, topic = std::move(topic_copy), payload = std::move(payload_copy), publish_props]() mutable
                  -> boost::asio::awaitable< void > {
                      try {
                          // --- PMR dla requestu ---
                          memory_resource::MonotonicStack_2k_Resource mr;
                          
                          json::pmr_memory_resource_adapter adapter_req(&mr);
                          boost::json::storage_ptr sp_req(&adapter_req);

                          // parse payload z PMR
                          auto value = boost::json::parse(payload, sp_req);

                          // --- response_topic z MQTT props ---
                          std::optional< std::string > responseTopic;
                          if(auto rt = publish_props[boost::mqtt5::prop::response_topic]; rt) {
                              responseTopic = *rt; // std::string
                          }

                          CallbackData cbdata{
                            .topic         = topic,
                            .request       = value,
                            .responseTopic = responseTopic // std::optional<std::string>
                          };

                          if(responseTopic) {
                              _log.trace("got response topic, handling it properly");
                              // --- PMR dla response ---
                              ResponseData response;
                              std::array< std::uint8_t, 2048 > responseBuffer{0};

                              std::pmr::monotonic_buffer_resource mr_resp{responseBuffer.data(), responseBuffer.size()};
                              json::pmr_memory_resource_adapter adapter_resp(&mr_resp);
                              boost::json::storage_ptr sp_resp(&adapter_resp);
                              boost::json::value r(sp_resp);
                              response = std::ref(r); // make a reference wrapper object
                              // wywołanie callbacka z możliwością wypełnienia response
                              if(auto result = co_await handler(cbdata, response); !result) {
                                  _log.warn("callback error: {}", result.error().message());
                              }

                              // jeśli mamy ustawiony topic i wypełniony JSON -> odeślij status
                              if(response && cbdata.responseTopic) {
                                  _log.debug("sending response on topic {}", *cbdata.responseTopic);
                                  auto pub_res = co_await publish(*cbdata.responseTopic, *response);
                                  if(!pub_res) {
                                      _log.warn("response publish error: {}", pub_res.error().message());
                                  }
                              }
                          }else{
                              // wywołanie callbacka z pustym response
                              ResponseData response;
                              if(auto result = co_await handler(cbdata, response); !result) {
                                  _log.warn("callback error: {}", result.error().message());
                              }
                          }
                      } catch(const boost::system::system_error & e) {
                          _log.error("received bad json, parsing failed with error: {}/{}", e.code().message(), e.what());
                      } catch(const std::exception & e) {
                          _log.error("callback threw exception: {}", e.what());
                      } catch(...) {
                          _log.error("callback threw unknown exception");
                      }

                      co_return;
                  },
                  boost::asio::detached);
            }
        }

        if(!run) {
            _log.warn("received unsupported topic: {}", topic);
        }
    }

    awaitable_expected< void > listen() {
        _log.trace("client start");
        for(;;) {
            auto && [ec, topic, payload, publish_props] = co_await _mqtt_client.async_receive(use_nothrow_awaitable);
    
            if(ec) {
                _log.warn("receive fail: {}", ec.message());
                continue;
            }

            try {
                handle_received_message(topic, payload, publish_props);
            } catch(const boost::system::system_error & e) {
                _log.error("received bad json, parsing failed with error: {}/{}", e.code().message(), e.what());
                continue;
            } catch(const std::exception & e) {
                _log.error("caught an exception: {}, during callback execution", e.what());
                continue;
            }
        }

        co_return _void{};
    }
    void start() {
        _log.trace("co_spawn mqtt client");
        boost::asio::co_spawn(_mqtt_client.get_executor(), listen(), boost::asio::detached);
    }

    void cancel() {
        _mqtt_client.cancel();
    }
};

AsyncMqttClient::AsyncMqttClient(const boost::asio::any_io_executor & executor)
 : _impl{std::make_unique< AsyncMqttClient::AsyncMqttClientImpl >(executor)} {}

awaitable_expected< const AsyncMqttClient::SubscribtionToken * > AsyncMqttClient::subscribe(std::string_view topic,
  callback_t cb) noexcept {
    BOOST_ASSERT(_impl);
    BOOST_ASSERT(not topic.empty());
    BOOST_ASSERT(cb);

    _log.debug("subscribe");
    co_return ASYNC_TRY(_impl->subscribe_with_callback(topic, std::move(cb)));
}

awaitable_expected< void > AsyncMqttClient::publish(std::string_view topic, const boost::json::value & value) noexcept {
    BOOST_ASSERT(_impl);
    BOOST_ASSERT(not topic.empty());

    _log.debug("publish on {}", topic);
    ASYNC_CHECK(_impl->publish(topic, value));

    co_return _void{};
}

awaitable_expected< void > AsyncMqttClient::listen() const noexcept {
    BOOST_ASSERT(_impl);

    _log.debug("listen");
    ASYNC_CHECK(_impl->listen());

    co_return _void{};
}

void AsyncMqttClient::cancel() {
    BOOST_ASSERT(_impl);

    _log.debug("cancel");
    _impl->cancel();
}

AsyncMqttClient::~AsyncMqttClient() = default;

} // namespace ranczo