#pragma once

#include <chrono>
#include <iostream>
#include <map>
#include <memory>

#include "../external/json.hpp"
#include <boost/asio.hpp>
#include <boost/asio/ssl/stream.hpp>
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/filesystem.hpp>
#include <boost/format.hpp>

#include "swarm.h"

constexpr auto LOKI_SENDER_SNODE_PUBKEY_HEADER = "X-Loki-Snode-PubKey";
constexpr auto LOKI_SNODE_SIGNATURE_HEADER = "X-Loki-Snode-Signature";

template <typename T>
class ChannelEncryption;

class RateLimiter;

namespace http = boost::beast::http; // from <boost/beast/http.hpp>
namespace ssl = boost::asio::ssl;    // from <boost/asio/ssl.hpp>

using request_t = http::request<http::string_body>;
using response_t = http::response<http::string_body>;

namespace loki {
using swarm_callback_t = std::function<void(const block_update_t&)>;

struct message_t;
struct lokid_key_pair_t;

namespace storage {
struct Item;
}

using storage::Item;

enum class SNodeError { NO_ERROR, ERROR_OTHER, NO_REACH, HTTP_ERROR };

struct sn_response_t {
    SNodeError error_code;
    std::shared_ptr<std::string> body;
};

struct blockchain_test_answer_t {
    uint64_t res_height;
};

/// Blockchain test parameters
struct bc_test_params_t {
    uint64_t max_height;
    uint64_t seed;
};

using http_callback_t = std::function<void(sn_response_t)>;

class LokidClient {

    const uint16_t lokid_rpc_port_;
    const char* local_ip_ = "127.0.0.1";
    boost::asio::io_context& ioc_;

  public:
    LokidClient(boost::asio::io_context& ioc, uint16_t port);
    void make_lokid_request(boost::string_view method,
                            const nlohmann::json& params,
                            http_callback_t&& cb) const;
};

constexpr auto SESSION_TIME_LIMIT = std::chrono::seconds(30);

// TODO: the name should indicate that we are actually trying to send data
// unlike in `make_post_request`
void make_http_request(boost::asio::io_context& ioc, const std::string& ip,
                       uint16_t port, const std::shared_ptr<request_t>& req,
                       http_callback_t&& cb);

class HttpClientSession
    : public std::enable_shared_from_this<HttpClientSession> {

    using tcp = boost::asio::ip::tcp;

    boost::asio::io_context& ioc_;
    tcp::socket socket_;
    tcp::endpoint endpoint_;
    http_callback_t callback_;
    boost::asio::steady_timer deadline_timer_;

    boost::beast::flat_buffer buffer_;
    /// NOTE: this needs to be a shared pointer since
    /// it is very common for the same request to be
    /// sent to multiple snodes
    std::shared_ptr<request_t> req_;
    response_t res_;

    bool used_callback_ = false;

    void on_connect();

    void on_write(boost::system::error_code ec, std::size_t bytes_transferred);

    void on_read(boost::system::error_code ec, std::size_t bytes_transferred);

    void trigger_callback(SNodeError error,
                          std::shared_ptr<std::string>&& body);

  public:
    // Resolver and socket require an io_context
    HttpClientSession(boost::asio::io_context& ioc, const tcp::endpoint& ep,
                      const std::shared_ptr<request_t>& req,
                      http_callback_t&& cb);

    // initiate the client connection
    void start();

    ~HttpClientSession();
};

namespace http_server {

class connection_t : public std::enable_shared_from_this<connection_t> {

    using tcp = boost::asio::ip::tcp;

  private:
    boost::asio::io_context& ioc_;
    ssl::context& ssl_ctx_;

    // The socket for the currently connected client.
    tcp::socket socket_;

    // The buffer for performing reads.
    boost::beast::flat_buffer buffer_{8192};
    ssl::stream<tcp::socket&> stream_;

    // The request message.
    request_t request_;

    // The response message.
    response_t response_;

    // whether the response should be sent asyncronously,
    // as opposed to directly after connection_t::process_request
    bool delay_response_ = false;

    ServiceNode& service_node_;

    ChannelEncryption<std::string>& channel_cipher_;

    RateLimiter& rate_limiter_;

    // The timer for repeating an action within one connection
    boost::asio::steady_timer repeat_timer_;
    int repetition_count_ = 0;
    std::chrono::time_point<std::chrono::steady_clock> start_timestamp_;

    // The timer for putting a deadline on connection processing.
    boost::asio::steady_timer deadline_;

    /// TODO: move these if possible
    std::map<std::string, std::string> header_;

    std::stringstream body_stream_;

    // Note that we are only sending a single message through the
    // notification mechanism. If we somehow accumulated multiple
    // messages before notification event happens (unlikely), the
    // following messages will be delivered with the client's
    // consequent (and immediate) retrieve request
    struct notification_context_t {
        // The timer used for internal db polling
        boost::asio::steady_timer timer;
        // the message is stored here momentarily; needed because
        // we can't pass it using current notification mechanism
        boost::optional<message_t> message;
    } notification_ctx_;

  public:
    connection_t(boost::asio::io_context& ioc, ssl::context& ssl_ctx,
                 tcp::socket socket, ServiceNode& sn,
                 ChannelEncryption<std::string>& channel_encryption,
                 RateLimiter& rate_limiter);

    ~connection_t();

    /// Initiate the asynchronous operations associated with the connection.
    void start();

    void notify(const message_t& msg);

    /// "Reset" the connection by sending an empty message list
    void reset();

  private:
    void do_handshake();
    void on_handshake(boost::system::error_code ec);
    /// Asynchronously receive a complete request message.
    void read_request();

    void do_close();
    void on_shutdown(boost::system::error_code ec);

    /// process GET /get_stats/v1
    void on_get_stats();

    /// Check the database for new data, reschedule if empty
    void poll_db(const std::string& pk, const std::string& last_hash);

    /// Determine what needs to be done with the request message
    /// (synchronously).
    void process_request();

    void process_store(const nlohmann::json& params);

    void process_retrieve(const nlohmann::json& params);

    void process_snodes_by_pk(const nlohmann::json& params);

    void process_retrieve_all();

    template <typename T>
    void respond_with_messages(const std::vector<T>& messages);

    /// Asynchronously transmit the response message.
    void write_response();

    /// Syncronously (?) process client store/load requests
    void process_client_req();

    void process_swarm_req(boost::string_view target);

    // Check whether we have spent enough time on this connection.
    void register_deadline();

    /// Process storage test request and repeat if necessary
    void process_storage_test_req(uint64_t height,
                                  const std::string& tester_addr,
                                  const std::string& msg_hash);

    bool parse_header(const char* key);

    template <typename... Args>
    bool parse_header(const char* first, Args... args);

    void handle_wrong_swarm(const std::string& pubKey);

    bool validate_snode_request();
    bool verify_signature(const std::string& signature,
                          const std::string& public_key_b32z);
};

void run(boost::asio::io_context& ioc, std::string& ip, uint16_t port,
         const boost::filesystem::path& base_path, ServiceNode& sn,
         ChannelEncryption<std::string>& channelEncryption,
         RateLimiter& rate_limiter);

} // namespace http_server

} // namespace loki