#ifndef LLARP_HANDLERS_TUN_HPP
#define LLARP_HANDLERS_TUN_HPP

#include <dns/server.hpp>
#include <ev/ev.h>
#include <ev/vpnio.hpp>
#include <net/ip.hpp>
#include <net/net.hpp>
#include <service/endpoint.hpp>
#include <util/codel.hpp>
#include <util/thread/threading.hpp>

#include <future>

namespace llarp
{
  namespace handlers
  {
    struct TunEndpoint : public service::Endpoint,
                         public dns::IQueryHandler,
                         public std::enable_shared_from_this< TunEndpoint >
    {
      TunEndpoint(const std::string& nickname, AbstractRouter* r,
                  llarp::service::Context* parent, bool lazyVPN = false);
      ~TunEndpoint() override;

      path::PathSet_ptr
      GetSelf() override
      {
        return shared_from_this();
      }

      bool
      SetOption(const std::string& k, const std::string& v) override;

      void
      Tick(llarp_time_t now) override;

      util::StatusObject
      ExtractStatus() const;

      std::unordered_map< std::string, std::string >
      NotifyParams() const override;

      bool
      SupportsV6() const override;

      bool
      ShouldHookDNSMessage(const dns::Message& msg) const override;

      bool
      HandleHookedDNSMessage(
          dns::Message query,
          std::function< void(dns::Message) > sendreply) override;

      void
      TickTun(llarp_time_t now);

      static void
      tunifTick(llarp_tun_io*);

      bool
      MapAddress(const service::Address& remote, huint128_t ip, bool SNode);

      bool
      Start() override;

      bool
      Stop() override;

      bool
      IsSNode() const;

      /// set up tun interface, blocking
      bool
      SetupTun();

      /// overrides Endpoint
      bool
      SetupNetworking() override;

      /// overrides Endpoint
      bool
      HandleInboundPacket(const service::ConvoTag tag,
                          const llarp_buffer_t& pkt,
                          service::ProtocolType t) override
      {
        if(t != service::eProtocolTrafficV4 && t != service::eProtocolTrafficV6)
          return false;
        AlignedBuffer< 32 > addr;
        bool snode = false;
        if(!GetEndpointWithConvoTag(tag, addr, snode))
          return false;
        return HandleWriteIPPacket(
            pkt, [=]() -> huint128_t { return ObtainIPForAddr(addr, snode); });
      }

      /// handle inbound traffic
      bool
      HandleWriteIPPacket(const llarp_buffer_t& buf,
                          std::function< huint128_t(void) > getFromIP);

      /// queue outbound packet to the world
      bool
      QueueOutboundTraffic(llarp::net::IPPacket&& pkt);

      /// get the local interface's address
      huint128_t
      GetIfAddr() const override;

      /// we have an interface addr
      bool
      HasIfAddr() const override
      {
        return true;
      }

      bool
      HasLocalIP(const huint128_t& ip) const;

      std::unique_ptr< llarp_tun_io > tunif;
      llarp_vpn_io* vpnif = nullptr;

      bool
      InjectVPN(llarp_vpn_io* io, llarp_vpn_ifaddr_info info) override
      {
        if(tunif)
          return false;
        m_LazyVPNPromise.set_value(lazy_vpn{info, io});
        return true;
      }

      /// called before writing to tun interface
      static void
      tunifBeforeWrite(llarp_tun_io* t);

      /// handle user to network send buffer flush
      /// called in router logic thread
      static void
      handleNetSend(void*);

      /// called every time we wish to read a packet from the tun interface
      static void
      tunifRecvPkt(llarp_tun_io* t, const llarp_buffer_t& buf);

      /// called in the endpoint logic thread
      static void
      handleTickTun(void* u);

      /// get a key for ip address
      template < typename Addr_t >
      Addr_t
      ObtainAddrForIP(huint128_t ip, bool isSNode)
      {
        Addr_t addr;
        auto itr = m_IPToAddr.find(ip);
        if(itr != m_IPToAddr.end() and m_SNodes[itr->second] == isSNode)
        {
          addr = Addr_t(itr->second);
        }
        // found
        return addr;
      }

      template < typename Addr_t >
      bool
      FindAddrForIP(Addr_t& addr, huint128_t ip);

      bool
      HasAddress(const AlignedBuffer< 32 >& addr) const
      {
        return m_AddrToIP.find(addr) != m_AddrToIP.end();
      }

      /// get ip address for key unconditionally
      huint128_t
      ObtainIPForAddr(const AlignedBuffer< 32 >& addr, bool serviceNode);

      /// flush network traffic
      void
      Flush();

      void
      ResetInternalState() override;

     protected:
      bool
      ShouldFlushNow(llarp_time_t now) const;

      llarp_time_t m_LastFlushAt = 0s;
      using PacketQueue_t        = llarp::util::CoDelQueue<
          net::IPPacket, net::IPPacket::GetTime, net::IPPacket::PutTime,
          net::IPPacket::CompareOrder, net::IPPacket::GetNow >;

      /// queue packet for send on net thread from user
      std::vector< net::IPPacket > m_TunPkts;
      /// queue for sending packets over the network from us
      PacketQueue_t m_UserToNetworkPktQueue;
      /// queue for sending packets to user from network
      PacketQueue_t m_NetworkToUserPktQueue;
      /// return true if we have a remote loki address for this ip address
      bool
      HasRemoteForIP(huint128_t ipv4) const;

      /// mark this address as active
      void
      MarkIPActive(huint128_t ip);

      /// mark this address as active forever
      void
      MarkIPActiveForever(huint128_t ip);

      /// flush ip packets
      virtual void
      FlushSend();

      /// maps ip to key (host byte order)
      std::unordered_map< huint128_t, AlignedBuffer< 32 > > m_IPToAddr;
      /// maps key to ip (host byte order)
      std::unordered_map< AlignedBuffer< 32 >, huint128_t,
                          AlignedBuffer< 32 >::Hash >
          m_AddrToIP;

      /// maps key to true if key is a service node, maps key to false if key is
      /// a hidden service
      std::unordered_map< AlignedBuffer< 32 >, bool, AlignedBuffer< 32 >::Hash >
          m_SNodes;

     private:
      llarp_vpn_io_impl*
      GetVPNImpl()
      {
        if(vpnif && vpnif->impl)
          return static_cast< llarp_vpn_io_impl* >(vpnif->impl);
        return nullptr;
      }

      bool
      QueueInboundPacketForExit(const llarp_buffer_t& buf)
      {
        ManagedBuffer copy{buf};
        return m_NetworkToUserPktQueue.EmplaceIf(
            [&](llarp::net::IPPacket& pkt) -> bool {
              if(!pkt.Load(copy.underlying))
                return false;
              if(SupportsV6())
              {
                if(pkt.IsV4())
                {
                  pkt.UpdateIPv6Address(net::IPPacket::ExpandV4(pkt.srcv4()),
                                        m_OurIP);
                }
                else
                {
                  pkt.UpdateIPv6Address(pkt.srcv6(), m_OurIP);
                }
              }
              else
              {
                if(pkt.IsV4())
                  pkt.UpdateIPv4Address(
                      xhtonl(pkt.srcv4()),
                      xhtonl(net::IPPacket::TruncateV6(m_OurIP)));
                else
                  return false;
              }
              return true;
            });
      }

      template < typename Addr_t, typename Endpoint_t >
      void
      SendDNSReply(Addr_t addr, Endpoint_t ctx,
                   std::shared_ptr< dns::Message > query,
                   std::function< void(dns::Message) > reply, bool snode,
                   bool sendIPv6)
      {
        if(ctx)
        {
          huint128_t ip = ObtainIPForAddr(addr, snode);
          query->answers.clear();
          query->AddINReply(ip, sendIPv6);
        }
        else
          query->AddNXReply();
        reply(*query);
      }
      /// our dns resolver
      std::shared_ptr< dns::Proxy > m_Resolver;

      /// maps ip address to timestamp last active
      std::unordered_map< huint128_t, llarp_time_t > m_IPActivity;
      /// our ip address (host byte order)
      huint128_t m_OurIP;
      /// next ip address to allocate (host byte order)
      huint128_t m_NextIP;
      /// highest ip address to allocate (host byte order)
      huint128_t m_MaxIP;
      /// our ip range we are using
      llarp::IPRange m_OurRange;
      /// upstream dns resolver list
      std::vector< llarp::Addr > m_UpstreamResolvers;
      /// local dns
      llarp::Addr m_LocalResolverAddr;
      /// list of strict connect addresses for hooks
      std::vector< llarp::Addr > m_StrictConnectAddrs;
      /// use v6?
      bool m_UseV6;
      struct lazy_vpn
      {
        llarp_vpn_ifaddr_info info;
        llarp_vpn_io* io;
      };
      std::promise< lazy_vpn > m_LazyVPNPromise;

      /// send packets on endpoint to user using send function
      /// send function returns true to indicate stop iteration and do codel
      /// drop
      void
      FlushToUser(std::function< bool(net::IPPacket&) > sendfunc);
    };

  }  // namespace handlers
}  // namespace llarp

#endif