#pragma once

#include <algorithm>
#include <functional>
#include <mutex>
#include <string>
#include <tuple>
#include <unordered_map>
#include <vector>

#include <nlohmann/json.hpp>
#include <plog/Init.h>
#include <plog/Log.h>
#include <websocketpp/client.hpp>
#include <websocketpp/config/asio_client.hpp>
#include <uuid_v4.h>

#include "client/web_socket_client.hpp"
#include "data/data.hpp"
#include "signer/signer.hpp"

namespace nostr
{
class NostrService;

class NostrService
{
public:
    NostrService(
        std::shared_ptr<plog::IAppender> appender,
        std::shared_ptr<client::IWebSocketClient> client,
        std::shared_ptr<signer::ISigner> signer);
    NostrService(
        std::shared_ptr<plog::IAppender> appender,
        std::shared_ptr<client::IWebSocketClient> client,
        std::shared_ptr<signer::ISigner> signer,
        std::vector<std::string> relays);
    ~NostrService();

    std::vector<std::string> defaultRelays() const;

    std::vector<std::string> activeRelays() const;

    std::unordered_map<std::string, std::vector<std::string>> subscriptions() const;

    /**
     * @brief Opens connections to the default Nostr relays of the instance, as specified in
     * the constructor.
     * @return A list of the relay URLs to which connections were successfully opened.
     */
    std::vector<std::string> openRelayConnections();

    /**
     * @brief Opens connections to the specified Nostr relays.
     * @returns A list of the relay URLs to which connections were successfully opened.
     */
    std::vector<std::string> openRelayConnections(std::vector<std::string> relays);

    /**
     * @brief Closes all open relay connections.
     */
    void closeRelayConnections();

    /**
     * @brief Closes any open connections to the specified Nostr relays.
     */
    void closeRelayConnections(std::vector<std::string> relays);
    
    /**
     * @brief Publishes a Nostr event to all open relay connections.
     * @returns A tuple of `std::vector<std::string>` objects, of the form `<successes, failures>`, indicating
     * to which relays the event was published successfully, and to which relays the event failed
     * to publish.
     */
    std::tuple<std::vector<std::string>, std::vector<std::string>> publishEvent(std::shared_ptr<data::Event> event);

    /**
     * @brief Queries all open relay connections for events matching the given set of filters, and
     * returns all stored matching events returned by the relays.
     * @param filters The filters to use for the query.
     * @returns A vector of all events matching the filters from all open relay connections.
     * @remark This method runs until the relays send an EOSE message, indicating they have no more
     * stored events matching the given filters.  When the EOSE message is received, the method
     * will close the subscription for each relay and return the received events.
     * @remark Use this method to fetch a batch of events from the relays.  A `limit` value must be
     * set on the filters in the range 1-64, inclusive.  If no valid limit is given, it will be
     * defaulted to 16.
     */
    std::vector<std::shared_ptr<data::Event>> queryRelays(std::shared_ptr<data::Filters> filters);

    /**
     * @brief Queries all open relay connections for events matching the given set of filters.
     * @param filters The filters to use for the query.
     * @param eventHandler A callable object that will be invoked each time the client receives
     * an event matching the filters.
     * @param eoseHandler A callable object that will be invoked when the relay sends an EOSE
     * message.
     * @param closeHandler A callable object that will be invoked when the relay sends a CLOSE
     * message.
     * @returns The ID of the subscription created for the query.
     * @remark By providing a response handler, the caller assumes responsibility for handling all
     * events returned from the relay for the given filters.  The service will not store the
     * events, and they will not be accessible via `getNewEvents`.
     */
    std::string queryRelays(
        std::shared_ptr<data::Filters> filters,
        std::function<void(const std::string&, std::shared_ptr<data::Event>)> eventHandler,
        std::function<void(const std::string&)> eoseHandler,
        std::function<void(const std::string&, const std::string&)> closeHandler);
    
    /**
     * @brief Closes the subscription with the given ID on all open relay connections.
     * @returns A tuple of `std::vector<std::string>` objects, of the form `<successes, failures>`, indicating
     * to which relays the message was sent successfully, and which relays failed to receive the
     * message.
     */
    std::tuple<std::vector<std::string>, std::vector<std::string>> closeSubscription(std::string subscriptionId);

    /**
     * @brief Closes the subscription with the given ID on the given relay.
     * @returns True if the relay received the CLOSE message, false otherwise.
     * @remark If the subscription does not exist on the given relay, or if the relay is not
     * connected, the method will do nothing and return false.
     */
    bool closeSubscription(std::string subscriptionId, std::string relay);

    /**
     * @brief Closes all open subscriptions on all open relay connections.
     * @returns A list of any subscription IDs that failed to close.
     */
    std::vector<std::string> closeSubscriptions();

    /**
     * @brief Closes all open subscriptions on the given relays.
     * @returns A list of any subscription IDs that failed to close.
     */
    std::vector<std::string> closeSubscriptions(std::vector<std::string> relays);

private:
    ///< The maximum number of events the service will store for each subscription.
    const int MAX_EVENTS_PER_SUBSCRIPTION = 128;

    ///< The WebSocket client used to communicate with relays.
    std::shared_ptr<client::IWebSocketClient> _client;
    ///< The signer used to sign Nostr events.
    std::shared_ptr<signer::ISigner> _signer;

    ///< A mutex to protect the instance properties.
    std::mutex _propertyMutex;
    ///< The default set of Nostr relays to which the service will attempt to connect.
    std::vector<std::string> _defaultRelays;
    ///< The set of Nostr relays to which the service is currently connected.
    std::vector<std::string> _activeRelays; 
    ///< A map from subscription IDs to the relays on which each subscription is open.
    std::unordered_map<std::string, std::vector<std::string>> _subscriptions;

    /**
     * @brief Determines which of the given relays are currently connected.
     * @returns A list of the URIs of currently-open relay connections from the given list.
     */
    std::vector<std::string> getConnectedRelays(std::vector<std::string> relays);

    /**
     * @brief Determines which of the given relays are not currently connected.
     * @returns A list of the URIs of currently-unconnected relays from the given list.
     */
    std::vector<std::string> getUnconnectedRelays(std::vector<std::string> relays);

    /**
     * @brief Determines whether the given relay is currently connected.
     * @returns True if the relay is connected, false otherwise.
     */
    bool isConnected(std::string relay);

    /**
     * @brief Removes the given relay from the instance's list of active relays.
     */
    void eraseActiveRelay(std::string relay);

    /**
     * @brief Opens a connection from the client to the given relay.
     */
    void connect(std::string relay);

    /**
     * @brief Closes the connection from the client to the given relay.
     */
    void disconnect(std::string relay);

    /**
     * @brief Generates a unique subscription ID that may be used to identify event requests.
     * @returns A stringified UUID.
     */
    std::string generateSubscriptionId();

    /**
     * @brief Generates a message requesting a relay to close the subscription with the given ID.
     * @returns A stringified JSON object representing the close request.
     */
    std::string generateCloseRequest(std::string subscriptionId);

    /**
     * @brief Indicates whether the the service has an open subscription with the given ID.
     * @returns True if the service has the subscription, false otherwise.
     */
    bool hasSubscription(std::string subscriptionId);

    /**
     * @brief Indicates whether the service has an open subscription with the given ID on the given
     * relay.
     * @returns True if the subscription exists on the relay, false otherwise.
     */
    bool hasSubscription(std::string subscriptionId, std::string relay);

    /**
     * @brief Parses EVENT messages received from the relay and invokes the given event handler.
     * @param message The raw message received from the relay.
     * @param eventHandler A callable object that will be invoked with the subscription ID and the
     * payload of the event.
     * @param eoseHandler A callable object that will be invoked with the subscription ID when the
     * relay sends an EOSE message, indicating it has reached the end of stored events for the
     * given query.
     * @param closeHandler A callable object that will be invoked with the subscription ID and the
     * message sent by the relay if the subscription is ended by the relay.
     */
    void onSubscriptionMessage(
        std::string message,
        std::function<void(const std::string&, std::shared_ptr<data::Event>)> eventHandler,
        std::function<void(const std::string&)> eoseHandler,
        std::function<void(const std::string&, const std::string&)> closeHandler);
    
    /**
     * @brief Parses OK messages received from the relay and invokes the given acceptance handler.
     * @remark The OK message type is sent to indicate whether the relay has accepted an event sent
     * by the client.  Note that this is distinct from whether the message was successfully sent to
     * the relay over the WebSocket connection.
     */
    void onAcceptance(std::string message, std::function<void(const bool)> acceptanceHandler);
};
} // namespace nostr