/*
* 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 TUNNEL_POOL__
#define TUNNEL_POOL__

#include <inttypes.h>
#include <set>
#include <vector>
#include <utility>
#include <mutex>
#include <memory>
#include "Identity.h"
#include "LeaseSet.h"
#include "RouterInfo.h"
#include "I2NPProtocol.h"
#include "TunnelBase.h"
#include "RouterContext.h"
#include "Garlic.h"

namespace i2p {
    namespace tunnel {
        const int TUNNEL_POOL_MANAGE_INTERVAL = 10; // in seconds
        const int TUNNEL_POOL_MAX_INBOUND_TUNNELS_QUANTITY = 16;
        const int TUNNEL_POOL_MAX_OUTBOUND_TUNNELS_QUANTITY = 16;

        class Tunnel;

        class InboundTunnel;

        class OutboundTunnel;

        typedef std::shared_ptr<const i2p::data::IdentityEx> Peer;

        struct Path {
            std::vector<Peer> peers;
            bool isShort = true;
            i2p::data::RouterInfo::CompatibleTransports farEndTransports = i2p::data::RouterInfo::eAllTransports;

            void Add(std::shared_ptr<const i2p::data::RouterInfo> r);

            void Reverse();
        };

        /** interface for custom tunnel peer selection algorithm */
        struct ITunnelPeerSelector {
            virtual ~ITunnelPeerSelector() {};

            virtual bool SelectPeers(Path &peers, int hops, bool isInbound) = 0;
        };


        typedef std::function<std::shared_ptr<const i2p::data::RouterInfo>(std::shared_ptr<const i2p::data::RouterInfo>,
                                                                           bool)> SelectHopFunc;

        bool StandardSelectPeers(Path &path, int numHops, bool inbound, SelectHopFunc nextHop);

        class TunnelPool : public std::enable_shared_from_this<TunnelPool> // per local destination
        {
        public:

            TunnelPool(int numInboundHops, int numOutboundHops, int numInboundTunnels,
                       int numOutboundTunnels, int inboundVariance, int outboundVariance);

            ~TunnelPool();

            std::shared_ptr<i2p::garlic::GarlicDestination> GetLocalDestination() const { return m_LocalDestination; };

            void SetLocalDestination(
                    std::shared_ptr<i2p::garlic::GarlicDestination> destination) { m_LocalDestination = destination; };

            void SetExplicitPeers(std::shared_ptr<std::vector<i2p::data::IdentHash> > explicitPeers);

            void CreateTunnels();

            void TunnelCreated(std::shared_ptr<InboundTunnel> createdTunnel);

            void TunnelExpired(std::shared_ptr<InboundTunnel> expiredTunnel);

            void TunnelCreated(std::shared_ptr<OutboundTunnel> createdTunnel);

            void TunnelExpired(std::shared_ptr<OutboundTunnel> expiredTunnel);

            void RecreateInboundTunnel(std::shared_ptr<InboundTunnel> tunnel);

            void RecreateOutboundTunnel(std::shared_ptr<OutboundTunnel> tunnel);

            std::vector<std::shared_ptr<InboundTunnel> > GetInboundTunnels(int num) const;

            std::shared_ptr<OutboundTunnel> GetNextOutboundTunnel(std::shared_ptr<OutboundTunnel> excluded = nullptr,
                                                                  i2p::data::RouterInfo::CompatibleTransports compatible = i2p::data::RouterInfo::eAllTransports) const;

            std::shared_ptr<InboundTunnel> GetNextInboundTunnel(std::shared_ptr<InboundTunnel> excluded = nullptr,
                                                                i2p::data::RouterInfo::CompatibleTransports compatible = i2p::data::RouterInfo::eAllTransports) const;

            std::shared_ptr<OutboundTunnel> GetNewOutboundTunnel(std::shared_ptr<OutboundTunnel> old) const;

            void ManageTunnels(uint64_t ts);

            void ProcessGarlicMessage(std::shared_ptr<I2NPMessage> msg);

            void ProcessDeliveryStatus(std::shared_ptr<I2NPMessage> msg);

            bool IsExploratory() const;

            bool IsActive() const { return m_IsActive; };

            void SetActive(bool isActive) { m_IsActive = isActive; };

            void DetachTunnels();

            int GetNumInboundTunnels() const { return m_NumInboundTunnels; };

            int GetNumOutboundTunnels() const { return m_NumOutboundTunnels; };

            int GetNumInboundHops() const { return m_NumInboundHops; };

            int GetNumOutboundHops() const { return m_NumOutboundHops; };

            /** i2cp reconfigure */
            bool Reconfigure(int inboundHops, int outboundHops, int inboundQuant, int outboundQuant);

            void SetCustomPeerSelector(ITunnelPeerSelector *selector);

            void UnsetCustomPeerSelector();

            bool HasCustomPeerSelector();

            /** @brief make this tunnel pool yield tunnels that fit latency range [min, max] */
            void RequireLatency(uint64_t min, uint64_t max) {
                m_MinLatency = min;
                m_MaxLatency = max;
            }

            /** @brief return true if this tunnel pool has a latency requirement */
            bool HasLatencyRequirement() const { return m_MinLatency > 0 && m_MaxLatency > 0; }

            /** @brief get the lowest latency tunnel in this tunnel pool regardless of latency requirements */
            std::shared_ptr<InboundTunnel>
            GetLowestLatencyInboundTunnel(std::shared_ptr<InboundTunnel> exclude = nullptr) const;

            std::shared_ptr<OutboundTunnel>
            GetLowestLatencyOutboundTunnel(std::shared_ptr<OutboundTunnel> exclude = nullptr) const;

            // for overriding tunnel peer selection
            std::shared_ptr<const i2p::data::RouterInfo>
            SelectNextHop(std::shared_ptr<const i2p::data::RouterInfo> prevHop, bool reverse) const;

        private:

            void TestTunnels();

            void CreateInboundTunnel();

            void CreateOutboundTunnel();

            void CreatePairedInboundTunnel(std::shared_ptr<OutboundTunnel> outboundTunnel);

            template<class TTunnels>
            typename TTunnels::value_type GetNextTunnel(TTunnels &tunnels,
                                                        typename TTunnels::value_type excluded,
                                                        i2p::data::RouterInfo::CompatibleTransports compatible) const;

            bool SelectPeers(Path &path, bool isInbound);

            bool SelectExplicitPeers(Path &path, bool isInbound);

        private:

            std::shared_ptr<i2p::garlic::GarlicDestination> m_LocalDestination;
            int m_NumInboundHops, m_NumOutboundHops, m_NumInboundTunnels, m_NumOutboundTunnels,
                    m_InboundVariance, m_OutboundVariance;
            std::shared_ptr<std::vector<i2p::data::IdentHash> > m_ExplicitPeers;
            mutable std::mutex m_InboundTunnelsMutex;
            std::set<std::shared_ptr<InboundTunnel>, TunnelCreationTimeCmp> m_InboundTunnels; // recent tunnel appears first
            mutable std::mutex m_OutboundTunnelsMutex;
            std::set<std::shared_ptr<OutboundTunnel>, TunnelCreationTimeCmp> m_OutboundTunnels;
            mutable std::mutex m_TestsMutex;
            std::map<uint32_t, std::pair<std::shared_ptr<OutboundTunnel>, std::shared_ptr<InboundTunnel> > > m_Tests;
            bool m_IsActive;
            uint64_t m_NextManageTime; // in seconds
            std::mutex m_CustomPeerSelectorMutex;
            ITunnelPeerSelector *m_CustomPeerSelector;

            uint64_t m_MinLatency = 0; // if > 0 this tunnel pool will try building tunnels with minimum latency by ms
            uint64_t m_MaxLatency = 0; // if > 0 this tunnel pool will try building tunnels with maximum latency by ms

        public:

            // for HTTP only
            const decltype(m_OutboundTunnels)
            &

            GetOutboundTunnels() const { return m_OutboundTunnels; };
            const decltype(m_InboundTunnels)
            &

            GetInboundTunnels() const { return m_InboundTunnels; };

        };
    }
}

#endif