#include <llarp/routing/handler.hpp>
#include <llarp/service/protocol.hpp>
#include "buffer.hpp"
#include "mem.hpp"

namespace llarp
{
  namespace service
  {
    ProtocolMessage::ProtocolMessage()
    {
      tag.Zero();
    }

    ProtocolMessage::ProtocolMessage(const ConvoTag& t) : tag(t)
    {
    }

    ProtocolMessage::~ProtocolMessage()
    {
    }

    void
    ProtocolMessage::PutBuffer(llarp_buffer_t buf)
    {
      payload.resize(buf.sz);
      memcpy(payload.data(), buf.base, buf.sz);
      payload.shrink_to_fit();
    }

    void
    ProtocolMessage::ProcessAsync(void* user)
    {
      ProtocolMessage* self = static_cast< ProtocolMessage* >(user);
      self->handler->HandleDataMessage(self);
      delete self;
    }

    bool
    ProtocolMessage::DecodeKey(llarp_buffer_t k, llarp_buffer_t* buf)
    {
      bool read = false;
      if(!BEncodeMaybeReadDictInt("a", proto, read, k, buf))
        return false;
      if(llarp_buffer_eq(k, "d"))
      {
        llarp_buffer_t strbuf;
        if(!bencode_read_string(buf, &strbuf))
          return false;
        PutBuffer(strbuf);
        return true;
      }
      if(!BEncodeMaybeReadDictEntry("i", introReply, read, k, buf))
        return false;
      if(!BEncodeMaybeReadDictEntry("s", sender, read, k, buf))
        return false;
      if(!BEncodeMaybeReadDictEntry("t", tag, read, k, buf))
        return false;
      if(!BEncodeMaybeReadDictInt("v", version, read, k, buf))
        return false;
      return read;
    }

    bool
    ProtocolMessage::BEncode(llarp_buffer_t* buf) const
    {
      if(!bencode_start_dict(buf))
        return false;
      if(!BEncodeWriteDictInt("a", proto, buf))
        return false;
      if(!bencode_write_bytestring(buf, "d", 1))
        return false;
      if(!bencode_write_bytestring(buf, payload.data(), payload.size()))
        return false;
      if(!BEncodeWriteDictEntry("i", introReply, buf))
        return false;
      if(!BEncodeWriteDictEntry("s", sender, buf))
        return false;
      if(!tag.IsZero())
      {
        if(!BEncodeWriteDictEntry("t", tag, buf))
          return false;
      }
      if(!bencode_write_version_entry(buf))
        return false;
      return bencode_end(buf);
    }

    ProtocolFrame::~ProtocolFrame()
    {
    }

    bool
    ProtocolFrame::BEncode(llarp_buffer_t* buf) const
    {
      if(!bencode_start_dict(buf))
        return false;

      if(!BEncodeWriteDictMsgType(buf, "A", "H"))
        return false;
      if(!C.IsZero())
      {
        if(!BEncodeWriteDictEntry("C", C, buf))
          return false;
      }
      if(!BEncodeWriteDictEntry("D", D, buf))
        return false;

      if(!BEncodeWriteDictEntry("N", N, buf))
        return false;
      if(!T.IsZero())
      {
        if(!BEncodeWriteDictEntry("T", T, buf))
          return false;
      }
      if(!BEncodeWriteDictInt("V", version, buf))
        return false;
      if(!BEncodeWriteDictEntry("Z", Z, buf))
        return false;
      return bencode_end(buf);
    }

    bool
    ProtocolFrame::DecodeKey(llarp_buffer_t key, llarp_buffer_t* val)
    {
      bool read = false;
      if(llarp_buffer_eq(key, "A"))
      {
        llarp_buffer_t strbuf;
        if(!bencode_read_string(val, &strbuf))
          return false;
        if(strbuf.sz != 1)
          return false;
        return *strbuf.cur == 'H';
      }
      if(!BEncodeMaybeReadDictEntry("D", D, read, key, val))
        return false;
      if(!BEncodeMaybeReadDictEntry("C", C, read, key, val))
        return false;
      if(!BEncodeMaybeReadDictEntry("N", N, read, key, val))
        return false;
      if(!BEncodeMaybeReadDictInt("S", S, read, key, val))
        return false;
      if(!BEncodeMaybeReadDictEntry("T", T, read, key, val))
        return false;
      if(!BEncodeMaybeReadVersion("V", version, LLARP_PROTO_VERSION, read, key,
                                  val))
        return false;
      if(!BEncodeMaybeReadDictEntry("Z", Z, read, key, val))
        return false;
      return read;
    }

    bool
    ProtocolFrame::DecryptPayloadInto(llarp_crypto* crypto,
                                      const byte_t* sharedkey,
                                      ProtocolMessage& msg) const
    {
      msg.PutBuffer(D.Buffer());
      auto buf = llarp::Buffer(msg.payload);
      return crypto->xchacha20(buf, sharedkey, N);
    }

    bool
    ProtocolFrame::EncryptAndSign(llarp_crypto* crypto,
                                  const ProtocolMessage& msg,
                                  const byte_t* sessionKey,
                                  const Identity& localIdent)
    {
      byte_t tmp[MAX_PROTOCOL_MESSAGE_SIZE];
      auto buf = llarp::StackBuffer< decltype(tmp) >(tmp);
      // encode message
      if(!msg.BEncode(&buf))
        return false;
      // rewind
      buf.sz  = buf.cur - buf.base;
      buf.cur = buf.base;
      // encrypt
      crypto->xchacha20(buf, sessionKey, N);
      // put encrypted buffer
      D = buf;
      // zero out signature
      Z.Zero();
      // reset size
      buf.sz = sizeof(tmp);
      // encode frame
      if(!BEncode(&buf))
        return false;
      // rewind
      buf.sz  = buf.cur - buf.base;
      buf.cur = buf.base;
      // sign
      return localIdent.Sign(crypto, Z, buf);
    }

    struct AsyncFrameDecrypt
    {
      llarp_crypto* crypto;
      llarp_logic* logic;
      ProtocolMessage* msg;
      const Identity& m_LocalIdentity;
      IDataHandler* handler;
      const ProtocolFrame* frame;

      AsyncFrameDecrypt(llarp_logic* l, llarp_crypto* c,
                        const Identity& localIdent, IDataHandler* h,
                        ProtocolMessage* m, const ProtocolFrame* f)
          : crypto(c)
          , logic(l)
          , msg(m)
          , m_LocalIdentity(localIdent)
          , handler(h)
          , frame(f)
      {
      }

      static void
      Work(void* user)
      {
        AsyncFrameDecrypt* self = static_cast< AsyncFrameDecrypt* >(user);
        auto crypto             = self->crypto;
        SharedSecret K;
        SharedSecret sharedKey;
        // copy
        ProtocolFrame frame;
        frame = *self->frame;
        if(!crypto->pqe_decrypt(self->frame->C, K,
                                pq_keypair_to_secret(self->m_LocalIdentity.pq)))
        {
          llarp::LogError("pqke failed C=", self->frame->C);
          frame.Dump< MAX_PROTOCOL_MESSAGE_SIZE >();
          delete self->msg;
          delete self;
          return;
        }
        // decrypt
        auto buf = frame.D.Buffer();
        crypto->xchacha20(*buf, K, self->frame->N);
        if(!self->msg->BDecode(buf))
        {
          llarp::LogError("failed to decode inner protocol message");
          llarp::DumpBuffer(*buf);
          delete self->msg;
          delete self;
          return;
        }
        // verify signature of outer message after we parsed the inner message
        if(!self->frame->Verify(crypto, self->msg->sender))
        {
          llarp::LogError("intro frame has invalid signature Z=",
                          self->frame->Z, " from ", self->msg->sender);
          self->frame->Dump< MAX_PROTOCOL_MESSAGE_SIZE >();
          delete self->msg;
          delete self;
          return;
        }
        byte_t tmp[64];
        // K
        memcpy(tmp, K, 32);
        // PKE (A, B, N)
        if(!self->m_LocalIdentity.KeyExchange(
               crypto->dh_server, tmp + 32, self->msg->sender, self->frame->N))
        {
          llarp::LogError("x25519 key exchange failed");
          self->frame->Dump< MAX_PROTOCOL_MESSAGE_SIZE >();
          delete self->msg;
          delete self;
          return;
        }
        // S = HS( K + PKE( A, B, N))
        crypto->shorthash(sharedKey, StackBuffer< decltype(tmp) >(tmp));

        self->handler->PutIntroFor(self->msg->tag, self->msg->introReply);
        self->handler->PutSenderFor(self->msg->tag, self->msg->sender);
        self->handler->PutCachedSessionKeyFor(self->msg->tag, sharedKey);

        self->msg->handler = self->handler;
        llarp_logic_queue_job(self->logic,
                              {self->msg, &ProtocolMessage::ProcessAsync});
        delete self;
      }
    };

    ProtocolFrame&
    ProtocolFrame::operator=(const ProtocolFrame& other)
    {
      C = other.C;
      D = other.D;
      N = other.N;
      Z = other.Z;
      T = other.T;
      return *this;
    }

    bool
    ProtocolFrame::AsyncDecryptAndVerify(llarp_logic* logic, llarp_crypto* c,
                                         llarp_threadpool* worker,
                                         const Identity& localIdent,
                                         IDataHandler* handler) const
    {
      if(T.IsZero())
      {
        ProtocolMessage* msg = new ProtocolMessage();
        // we need to dh
        auto dh =
            new AsyncFrameDecrypt(logic, c, localIdent, handler, msg, this);
        llarp_threadpool_queue_job(worker, {dh, &AsyncFrameDecrypt::Work});
        return true;
      }
      const byte_t* shared = nullptr;
      if(!handler->GetCachedSessionKeyFor(T, shared))
      {
        llarp::LogError("No cached session for T=", T);
        return false;
      }
      ServiceInfo si;
      if(!handler->GetSenderFor(T, si))
      {
        llarp::LogError("No sender for T=", T);
        return false;
      }
      if(!Verify(c, si))
      {
        llarp::LogError("Signature failure");
        return false;
      }
      ProtocolMessage* msg = new ProtocolMessage();
      if(!DecryptPayloadInto(c, shared, *msg))
      {
        llarp::LogError("failed to decrypt message");
        delete msg;
        return false;
      }
      msg->handler = handler;
      llarp_logic_queue_job(logic, {msg, &ProtocolMessage::ProcessAsync});
      return true;
    }

    ProtocolFrame::ProtocolFrame()
    {
      T.Zero();
    }

    bool
    ProtocolFrame::Verify(llarp_crypto* crypto, const ServiceInfo& from) const
    {
      ProtocolFrame copy;
      copy = *this;
      // save signature
      // zero out signature for verify
      copy.Z.Zero();
      bool result = false;
      // serialize
      byte_t tmp[MAX_PROTOCOL_MESSAGE_SIZE];
      auto buf = llarp::StackBuffer< decltype(tmp) >(tmp);
      if(copy.BEncode(&buf))
      {
        // rewind buffer
        buf.sz  = buf.cur - buf.base;
        buf.cur = buf.base;
        // verify
        result = from.Verify(crypto, buf, Z);
      }
      // restore signature
      return result;
    }

    bool
    ProtocolFrame::HandleMessage(llarp::routing::IMessageHandler* h,
                                 llarp_router* r) const
    {
      llarp::LogInfo("Got hidden service frame");
      return h->HandleHiddenServiceFrame(this);
    }

  }  // namespace service
}  // namespace llarp