#include <algorithm>
#include "util/I2PEndian.h"
#include "crypto/CryptoConst.h"
#include "Tunnel.h"
#include "NetworkDatabase.h"
#include "util/Timestamp.h"
#include "Garlic.h"
#include "transport/Transports.h"
#include "TunnelPool.h"

namespace i2p
{
namespace tunnel
{
    TunnelPool::TunnelPool (i2p::garlic::GarlicDestination * localDestination, int numInboundHops, int numOutboundHops, int numInboundTunnels, int numOutboundTunnels):
        m_LocalDestination (localDestination), m_NumInboundHops (numInboundHops), m_NumOutboundHops (numOutboundHops),
        m_NumInboundTunnels (numInboundTunnels), m_NumOutboundTunnels (numOutboundTunnels), m_IsActive (true)
    {
    }

    TunnelPool::~TunnelPool ()
    {
        DetachTunnels ();
    }

    void TunnelPool::SetExplicitPeers (std::shared_ptr<std::vector<i2p::data::IdentHash> > explicitPeers)
    {
        m_ExplicitPeers = explicitPeers;
        if (m_ExplicitPeers)
        {
            int size = m_ExplicitPeers->size ();
            if (m_NumInboundHops > size) 
            {
                m_NumInboundHops = size;
                LogPrint (eLogInfo, "Inbound tunnel length has been adjusted to ", size, " for explicit peers");
            } 
            if (m_NumOutboundHops > size) 
            {
                m_NumOutboundHops = size;
                LogPrint (eLogInfo, "Outbound tunnel length has been adjusted to ", size, " for explicit peers");
            } 
            m_NumInboundTunnels = 1;
            m_NumOutboundTunnels = 1;
        }   
    }

    void TunnelPool::DetachTunnels ()
    {
        {
            std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);  
            for (auto it: m_InboundTunnels)
                it->SetTunnelPool (nullptr);
            m_InboundTunnels.clear ();
        }
        {
            std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex);
            for (auto it: m_OutboundTunnels)
                it->SetTunnelPool (nullptr);
            m_OutboundTunnels.clear ();
        }
        m_Tests.clear ();
    }   
        
    void TunnelPool::TunnelCreated (std::shared_ptr<InboundTunnel> createdTunnel)
    {
        if (!m_IsActive) return;
        {
            std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);
            m_InboundTunnels.insert (createdTunnel);
        }
        if (m_LocalDestination)
            m_LocalDestination->SetLeaseSetUpdated ();
    }

    void TunnelPool::TunnelExpired (std::shared_ptr<InboundTunnel> expiredTunnel)
    {
        if (expiredTunnel)
        {   
            expiredTunnel->SetTunnelPool (nullptr);
            for (auto it: m_Tests)
                if (it.second.second == expiredTunnel) it.second.second = nullptr;

            std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);
            m_InboundTunnels.erase (expiredTunnel);
        }   
    }   

    void TunnelPool::TunnelCreated (std::shared_ptr<OutboundTunnel> createdTunnel)
    {
        if (!m_IsActive) return;
        {
            std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex);
            m_OutboundTunnels.insert (createdTunnel);
        }
        //CreatePairedInboundTunnel (createdTunnel);
    }

    void TunnelPool::TunnelExpired (std::shared_ptr<OutboundTunnel> expiredTunnel)
    {
        if (expiredTunnel)
        {
            expiredTunnel->SetTunnelPool (nullptr);
            for (auto it: m_Tests)
                if (it.second.first == expiredTunnel) it.second.first = nullptr;

            std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex);
            m_OutboundTunnels.erase (expiredTunnel);
        }
    }
        
    std::vector<std::shared_ptr<InboundTunnel> > TunnelPool::GetInboundTunnels (int num) const
    {
        std::vector<std::shared_ptr<InboundTunnel> > v;
        int i = 0;
        std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);
        for (auto it : m_InboundTunnels)
        {
            if (i >= num) break;
            if (it->IsEstablished ())
            {
                v.push_back (it);
                i++;
            }   
        }   
        return v;
    }

    std::shared_ptr<OutboundTunnel> TunnelPool::GetNextOutboundTunnel (std::shared_ptr<OutboundTunnel> excluded) const
    {
        std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex); 
        return GetNextTunnel (m_OutboundTunnels, excluded);
    }   

    std::shared_ptr<InboundTunnel> TunnelPool::GetNextInboundTunnel (std::shared_ptr<InboundTunnel> excluded) const
    {
        std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);  
        return GetNextTunnel (m_InboundTunnels, excluded);
    }

    template<class TTunnels>
    typename TTunnels::value_type TunnelPool::GetNextTunnel (TTunnels& tunnels, typename TTunnels::value_type excluded) const
    {
        if (tunnels.empty ()) return nullptr;       
        CryptoPP::RandomNumberGenerator& rnd = i2p::context.GetRandomNumberGenerator ();
        uint32_t ind = rnd.GenerateWord32 (0, tunnels.size ()/2), i = 0;
        typename TTunnels::value_type tunnel = nullptr;
        for (auto it: tunnels)
        {   
            if (it->IsEstablished () && it != excluded)
            {
                tunnel = it;
                i++;
            }
            if (i > ind && tunnel) break;
        }
        if (!tunnel && excluded && excluded->IsEstablished ()) tunnel = excluded;
        return tunnel;
    }

    std::shared_ptr<OutboundTunnel> TunnelPool::GetNewOutboundTunnel (std::shared_ptr<OutboundTunnel> old) const
    {
        if (old && old->IsEstablished ()) return old;
        std::shared_ptr<OutboundTunnel> tunnel; 
        if (old)
        {
            std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex); 
            for (auto it: m_OutboundTunnels)
                if (it->IsEstablished () && old->GetEndpointRouter ()->GetIdentHash () == it->GetEndpointRouter ()->GetIdentHash ())
                {
                    tunnel = it;
                    break;
                }
        }
    
        if (!tunnel)
            tunnel = GetNextOutboundTunnel ();      
        return tunnel;
    }

    void TunnelPool::CreateTunnels ()
    {
        int num = 0;
        {
            std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);
            for (auto it : m_InboundTunnels)
                if (it->IsEstablished ()) num++;
        }
        for (int i = num; i < m_NumInboundTunnels; i++)
            CreateInboundTunnel (); 
        
        num = 0;
        {
            std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex); 
            for (auto it : m_OutboundTunnels)
                if (it->IsEstablished ()) num++;
        }
        for (int i = num; i < m_NumOutboundTunnels; i++)
            CreateOutboundTunnel ();    
    }

    void TunnelPool::TestTunnels ()
    {
        auto& rnd = i2p::context.GetRandomNumberGenerator ();
        for (auto it: m_Tests)
        {
            LogPrint ("Tunnel test ", (int)it.first, " failed"); 
            // if test failed again with another tunnel we consider it failed
            if (it.second.first)
            {   
                if (it.second.first->GetState () == eTunnelStateTestFailed)
                {   
                    it.second.first->SetState (eTunnelStateFailed);
                    std::unique_lock<std::mutex> l(m_OutboundTunnelsMutex);
                    m_OutboundTunnels.erase (it.second.first);
                }
                else
                    it.second.first->SetState (eTunnelStateTestFailed);
            }   
            if (it.second.second)
            {
                if (it.second.second->GetState () == eTunnelStateTestFailed)
                {   
                    it.second.second->SetState (eTunnelStateFailed);
                    {
                        std::unique_lock<std::mutex> l(m_InboundTunnelsMutex);
                        m_InboundTunnels.erase (it.second.second);
                    }
                    if (m_LocalDestination)
                        m_LocalDestination->SetLeaseSetUpdated ();
                }   
                else
                    it.second.second->SetState (eTunnelStateTestFailed);
            }   
        }
        m_Tests.clear ();
        // new tests    
        auto it1 = m_OutboundTunnels.begin ();
        auto it2 = m_InboundTunnels.begin ();
        while (it1 != m_OutboundTunnels.end () && it2 != m_InboundTunnels.end ())
        {
            bool failed = false;
            if ((*it1)->IsFailed ())
            {   
                failed = true;
                it1++;
            }
            if ((*it2)->IsFailed ())
            {   
                failed = true;
                it2++;
            }
            if (!failed)
            {
                uint32_t msgID = rnd.GenerateWord32 ();
                m_Tests[msgID] = std::make_pair (*it1, *it2);
                (*it1)->SendTunnelDataMsg ((*it2)->GetNextIdentHash (), (*it2)->GetNextTunnelID (),
                    CreateDeliveryStatusMsg (msgID));
                it1++; it2++;
            }   
        }
    }

    void TunnelPool::ProcessGarlicMessage (std::shared_ptr<I2NPMessage> msg)
    {
        if (m_LocalDestination)
            m_LocalDestination->ProcessGarlicMessage (msg);
        else
            LogPrint (eLogWarning, "Local destination doesn't exist. Dropped");
    }   
        
    void TunnelPool::ProcessDeliveryStatus (std::shared_ptr<I2NPMessage> msg)
    {
        const uint8_t * buf = msg->GetPayload ();
        uint32_t msgID = bufbe32toh (buf);
        buf += 4;   
        uint64_t timestamp = bufbe64toh (buf);

        auto it = m_Tests.find (msgID);
        if (it != m_Tests.end ())
        {
            // restore from test failed state if any
            if (it->second.first->GetState () == eTunnelStateTestFailed)
                it->second.first->SetState (eTunnelStateEstablished);
            if (it->second.second->GetState () == eTunnelStateTestFailed)
                it->second.second->SetState (eTunnelStateEstablished);
            LogPrint ("Tunnel test ", it->first, " successive. ", i2p::util::GetMillisecondsSinceEpoch () - timestamp, " milliseconds");
            m_Tests.erase (it);
        }
        else
        {
            if (m_LocalDestination)
                m_LocalDestination->ProcessDeliveryStatusMessage (msg);
            else
                LogPrint (eLogWarning, "Local destination doesn't exist. Dropped");
        }   
    }

    std::shared_ptr<const i2p::data::RouterInfo> TunnelPool::SelectNextHop (std::shared_ptr<const i2p::data::RouterInfo> prevHop) const
    {
        bool isExploratory = (m_LocalDestination == &i2p::context); // TODO: implement it better
        auto hop = isExploratory ? i2p::data::netdb.GetRandomRouter (prevHop): 
            i2p::data::netdb.GetHighBandwidthRandomRouter (prevHop);

        if (!hop || hop->GetProfile ()->IsBad ())
            hop = i2p::data::netdb.GetRandomRouter ();
        return hop; 
    }   

    bool TunnelPool::SelectPeers (std::vector<std::shared_ptr<const i2p::data::RouterInfo> >& hops, bool isInbound)
    {
        if (m_ExplicitPeers) return SelectExplicitPeers (hops, isInbound);
        auto prevHop = i2p::context.GetSharedRouterInfo (); 
        int numHops = isInbound ? m_NumInboundHops : m_NumOutboundHops;
        if (i2p::transport::transports.GetNumPeers () > 25)
        {
            auto r = i2p::transport::transports.GetRandomPeer ();
            if (r && !r->GetProfile ()->IsBad ())
            {
                prevHop = r;
                hops.push_back (r);
                numHops--;
            }
        }
        
        for (int i = 0; i < numHops; i++)
        {
            auto hop = SelectNextHop (prevHop);
            if (!hop)
            {
                LogPrint (eLogError, "Can't select next hop");
                return false;
            }   
            prevHop = hop;
            hops.push_back (hop);
        }       
        return true;
    }   
    
    bool TunnelPool::SelectExplicitPeers (std::vector<std::shared_ptr<const i2p::data::RouterInfo> >& hops, bool isInbound)
    {
        int size = m_ExplicitPeers->size ();
        std::vector<int> peerIndicies;
        for (int i = 0; i < size; i++) peerIndicies.push_back(i);
        std::random_shuffle (peerIndicies.begin(), peerIndicies.end());
    
        int numHops = isInbound ? m_NumInboundHops : m_NumOutboundHops;     
        for (int i = 0; i < numHops; i++) 
        {
            auto& ident = (*m_ExplicitPeers)[peerIndicies[i]];
            auto r = i2p::data::netdb.FindRouter (ident);
            if (r)
                hops.push_back (r);
            else
            {
                LogPrint (eLogInfo, "Can't find router for ", ident.ToBase64 ());
                i2p::data::netdb.RequestDestination (ident);
                return false;
            }
        }
        return true;
    }
    
    void TunnelPool::CreateInboundTunnel ()
    {
        auto outboundTunnel = GetNextOutboundTunnel ();
        if (!outboundTunnel)
            outboundTunnel = tunnels.GetNextOutboundTunnel ();
        LogPrint ("Creating destination inbound tunnel...");
        std::vector<std::shared_ptr<const i2p::data::RouterInfo> > hops;
        if (SelectPeers (hops, true))
        {
            std::reverse (hops.begin (), hops.end ());  
            auto tunnel = tunnels.CreateTunnel<InboundTunnel> (std::make_shared<TunnelConfig> (hops), outboundTunnel);
            tunnel->SetTunnelPool (shared_from_this ());
        }   
        else
            LogPrint (eLogError, "Can't create inbound tunnel. No peers available");
    }

    void TunnelPool::RecreateInboundTunnel (std::shared_ptr<InboundTunnel> tunnel)
    {
        auto outboundTunnel = GetNextOutboundTunnel ();
        if (!outboundTunnel)
            outboundTunnel = tunnels.GetNextOutboundTunnel ();
        LogPrint ("Re-creating destination inbound tunnel...");
        auto newTunnel = tunnels.CreateTunnel<InboundTunnel> (tunnel->GetTunnelConfig ()->Clone (), outboundTunnel);
        newTunnel->SetTunnelPool (shared_from_this());
    }   
        
    void TunnelPool::CreateOutboundTunnel ()
    {
        auto inboundTunnel = GetNextInboundTunnel ();
        if (!inboundTunnel)
            inboundTunnel = tunnels.GetNextInboundTunnel ();
        if (inboundTunnel)
        {   
            LogPrint ("Creating destination outbound tunnel...");
            std::vector<std::shared_ptr<const i2p::data::RouterInfo> > hops;
            if (SelectPeers (hops, false))
            {   
                auto tunnel = tunnels.CreateTunnel<OutboundTunnel> (
                    std::make_shared<TunnelConfig> (hops, inboundTunnel->GetTunnelConfig ()));
                tunnel->SetTunnelPool (shared_from_this ());
            }   
            else
                LogPrint (eLogError, "Can't create outbound tunnel. No peers available");
        }   
        else
            LogPrint (eLogError, "Can't create outbound tunnel. No inbound tunnels found");
    }   
        
    void TunnelPool::RecreateOutboundTunnel (std::shared_ptr<OutboundTunnel> tunnel)
    {
        auto inboundTunnel = GetNextInboundTunnel ();
        if (!inboundTunnel)
            inboundTunnel = tunnels.GetNextInboundTunnel ();
        if (inboundTunnel)
        {   
            LogPrint ("Re-creating destination outbound tunnel...");
            auto newTunnel = tunnels.CreateTunnel<OutboundTunnel> (
                tunnel->GetTunnelConfig ()->Clone (inboundTunnel->GetTunnelConfig ()));
            newTunnel->SetTunnelPool (shared_from_this ());
        }   
        else
            LogPrint ("Can't re-create outbound tunnel. No inbound tunnels found");
    }       

    void TunnelPool::CreatePairedInboundTunnel (std::shared_ptr<OutboundTunnel> outboundTunnel)
    {
        LogPrint (eLogInfo, "Creating paired inbound tunnel...");
        auto tunnel = tunnels.CreateTunnel<InboundTunnel> (outboundTunnel->GetTunnelConfig ()->Invert (), outboundTunnel);
        tunnel->SetTunnelPool (shared_from_this ());
    }   
}
}