/*
* Copyright (c) 2013-2022, The PurpleI2P Project
*
* This file is part of Purple i2pd project and licensed under BSD3
*
* See full license text in LICENSE file at top of project tree
*/

#ifndef SSU_H__
#define SSU_H__

#include <inttypes.h>
#include <string.h>
#include <map>
#include <list>
#include <set>
#include <thread>
#include <mutex>
#include <boost/asio.hpp>
#include "Crypto.h"
#include "util.h"
#include "I2PEndian.h"
#include "Identity.h"
#include "RouterInfo.h"
#include "I2NPProtocol.h"
#include "SSUSession.h"

namespace i2p {
    namespace transport {
        const int SSU_KEEP_ALIVE_INTERVAL = 30; // 30 seconds
        const int SSU_PEER_TEST_TIMEOUT = 60; // 60 seconds
        const int SSU_TO_INTRODUCER_SESSION_DURATION = 3600; // 1 hour
        const int SSU_TO_INTRODUCER_SESSION_EXPIRATION = 4800; // 80 minutes
        const int SSU_TERMINATION_CHECK_TIMEOUT = 30; // 30 seconds
        const size_t SSU_MAX_NUM_INTRODUCERS = 3;
        const size_t SSU_SOCKET_RECEIVE_BUFFER_SIZE = 0x1FFFF; // 128K
        const size_t SSU_SOCKET_SEND_BUFFER_SIZE = 0x1FFFF; // 128K

        struct SSUPacket {
            i2p::crypto::AESAlignedBuffer<SSU_MTU_V6 + 18> buf; // max MTU + iv + size
            boost::asio::ip::udp::endpoint from;
            size_t len;
        };

        class SSUServer {
        public:

            SSUServer(int port);

            ~SSUServer();

            void Start();

            void Stop();

            bool CreateSession(std::shared_ptr<const i2p::data::RouterInfo> router, bool peerTest = false,
                               bool v4only = false);

            bool CreateSession(std::shared_ptr<const i2p::data::RouterInfo> router,
                               std::shared_ptr<const i2p::data::RouterInfo::Address> address, bool peerTest = false);

            void CreateDirectSession(std::shared_ptr<const i2p::data::RouterInfo> router,
                                     boost::asio::ip::udp::endpoint remoteEndpoint, bool peerTest);

            std::shared_ptr<SSUSession> FindSession(const boost::asio::ip::udp::endpoint &e) const;

            std::shared_ptr<SSUSession> GetRandomEstablishedV4Session(std::shared_ptr<const SSUSession> excluded);

            std::shared_ptr<SSUSession> GetRandomEstablishedV6Session(std::shared_ptr<const SSUSession> excluded);

            void DeleteSession(std::shared_ptr<SSUSession> session);

            void DeleteAllSessions();

            boost::asio::io_service &GetService() { return m_Service; };

            i2p::util::MemoryPool<Fragment> &GetFragmentsPool() { return m_FragmentsPool; };

            i2p::util::MemoryPool<IncompleteMessage> &GetIncompleteMessagesPool() { return m_IncompleteMessagesPool; };

            i2p::util::MemoryPool<SentMessage> &GetSentMessagesPool() { return m_SentMessagesPool; };

            uint16_t GetPort() const { return m_Endpoint.port(); };

            bool IsSyncClockFromPeers() const { return m_IsSyncClockFromPeers; };

            void SetLocalAddress(const boost::asio::ip::address &localAddress);

            void Send(const uint8_t *buf, size_t len, const boost::asio::ip::udp::endpoint &to);

            void AddRelay(uint32_t tag, std::shared_ptr<SSUSession> relay);

            void RemoveRelay(uint32_t tag);

            std::shared_ptr<SSUSession> FindRelaySession(uint32_t tag);

            void RescheduleIntroducersUpdateTimer();

            void RescheduleIntroducersUpdateTimerV6();

            void NewPeerTest(uint32_t nonce, PeerTestParticipant role, std::shared_ptr<SSUSession> session = nullptr);

            PeerTestParticipant GetPeerTestParticipant(uint32_t nonce);

            std::shared_ptr<SSUSession> GetPeerTestSession(uint32_t nonce);

            void UpdatePeerTest(uint32_t nonce, PeerTestParticipant role);

            void RemovePeerTest(uint32_t nonce);

        private:

            void OpenSocket();

            void OpenSocketV6();

            void Run();

            void RunReceivers();

            void RunReceiversV6();

            void Receive();

            void ReceiveV6();

            void HandleReceivedFrom(const boost::system::error_code &ecode, std::size_t bytes_transferred,
                                    SSUPacket *packet);

            void HandleReceivedFromV6(const boost::system::error_code &ecode, std::size_t bytes_transferred,
                                      SSUPacket *packet);

            void HandleReceivedPackets(std::vector<SSUPacket *> packets,
                                       std::map<boost::asio::ip::udp::endpoint, std::shared_ptr<SSUSession> > *sessions);

            void CreateSessionThroughIntroducer(std::shared_ptr<const i2p::data::RouterInfo> router,
                                                std::shared_ptr<const i2p::data::RouterInfo::Address> address,
                                                bool peerTest = false);

            template<typename Filter>
            std::shared_ptr<SSUSession> GetRandomV4Session(Filter filter);

            template<typename Filter>
            std::shared_ptr<SSUSession> GetRandomV6Session(Filter filter);

            std::list<std::shared_ptr<SSUSession> >
            FindIntroducers(int maxNumIntroducers, bool v4, std::set<i2p::data::IdentHash> &excluded);

            void ScheduleIntroducersUpdateTimer();

            void ScheduleIntroducersUpdateTimerV6();

            void HandleIntroducersUpdateTimer(const boost::system::error_code &ecode, bool v4);

            void SchedulePeerTestsCleanupTimer();

            void HandlePeerTestsCleanupTimer(const boost::system::error_code &ecode);

            // timer
            void ScheduleTermination();

            void HandleTerminationTimer(const boost::system::error_code &ecode);

            void ScheduleTerminationV6();

            void HandleTerminationTimerV6(const boost::system::error_code &ecode);

        private:

            struct PeerTest {
                uint64_t creationTime;
                PeerTestParticipant role;
                std::shared_ptr<SSUSession> session; // for Bob to Alice
            };

            volatile bool m_IsRunning;
            std::thread *m_Thread, *m_ReceiversThread, *m_ReceiversThreadV6;
            boost::asio::io_service m_Service, m_ReceiversService, m_ReceiversServiceV6;
            boost::asio::io_service::work m_Work, m_ReceiversWork, m_ReceiversWorkV6;
            boost::asio::ip::udp::endpoint m_Endpoint, m_EndpointV6;
            boost::asio::ip::udp::socket m_Socket, m_SocketV6;
            boost::asio::deadline_timer m_IntroducersUpdateTimer, m_IntroducersUpdateTimerV6,
                    m_PeerTestsCleanupTimer, m_TerminationTimer, m_TerminationTimerV6;
            bool m_IsSyncClockFromPeers;
            std::list<boost::asio::ip::udp::endpoint> m_Introducers, m_IntroducersV6; // introducers we are connected to
            std::map<boost::asio::ip::udp::endpoint, std::shared_ptr<SSUSession> > m_Sessions, m_SessionsV6;
            std::map<uint32_t, std::shared_ptr<SSUSession> > m_Relays; // we are introducer
            std::map<uint32_t, PeerTest> m_PeerTests; // nonce -> creation time in milliseconds

            i2p::util::MemoryPool<Fragment> m_FragmentsPool;
            i2p::util::MemoryPool<IncompleteMessage> m_IncompleteMessagesPool;
            i2p::util::MemoryPool<SentMessage> m_SentMessagesPool;
            i2p::util::MemoryPoolMt<SSUPacket> m_PacketsPool;

        public:
            // for HTTP only
            const decltype(m_Sessions)
            &

            GetSessions() const { return m_Sessions; };
            const decltype(m_SessionsV6)
            &

            GetSessionsV6() const { return m_SessionsV6; };
        };
    }
}

#endif