lokinet/llarp/rpc/rpc_server.hpp

#pragma once

#include "rpc_request_definitions.hpp"
#include "json_bt.hpp"
#include <nlohmann/json_fwd.hpp>
#include <stdexcept>
#include <string_view>
#include <llarp/config/config.hpp>
#include <oxenmq/oxenmq.h>
#include <oxenmq/message.h>
#include <oxenmq/address.h>
#include <oxen/log/omq_logger.hpp>

namespace llarp
{
  struct AbstractRouter;
}  // namespace llarp

namespace
{
  static auto logcat = llarp::log::Cat("lokinet.rpc");
}  // namespace

namespace llarp::rpc
{
  using LMQ_ptr = std::shared_ptr<oxenmq::OxenMQ>;
  using DeferredSend = oxenmq::Message::DeferredSend;

  class RPCServer;

  //  Stores RPC request callback
  struct rpc_callback
  {
    using result_type = std::variant<oxenc::bt_value, nlohmann::json, std::string>;
    //  calls with incoming request data; returns response body or throws exception
    void (*invoke)(oxenmq::Message&, RPCServer&);
  };

  //  RPC request registration
  //    Stores references to RPC requests in a unordered map for ease of reference
  //    when adding to server. To add endpoints, define in rpc_request_definitions.hpp
  //    and register in rpc_server.cpp
  extern const std::unordered_map<std::string, rpc_callback> rpc_request_map;

  //  Exception used to signal various types of errors with a request back to the caller.  This
  //  exception indicates that the caller did something wrong: bad data, invalid value, etc., but
  //  don't indicate a local problem (and so we'll log them only at debug).  For more serious,
  //  internal errors a command should throw some other stl error (e.g. std::runtime_error or
  //  perhaps std::logic_error), which will result in a local daemon warning (and a generic internal
  //  error response to the user).
  //
  //  For JSON RPC these become an error response with the code as the error.code value and the
  //  string as the error.message.
  //  For HTTP JSON these become a 500 Internal Server Error response with the message as the body.
  //  For OxenMQ the code becomes the first part of the response and the message becomes the
  //  second part of the response.
  struct rpc_error : std::runtime_error
  {
    /// \param message - a message to send along with the error code (see general description
    /// above).
    rpc_error(std::string message)
        : std::runtime_error{"RPC error: " + message}, message{std::move(message)}
    {}

    std::string message;
  };

  template <typename Result_t>
  void
  SetJSONResponse(Result_t result, json& j)
  {
    j["result"] = result;
  }

  inline void
  SetJSONError(std::string_view msg, json& j)
  {
    j["error"] = msg;
  }

  class RPCServer
  {
   public:
    explicit RPCServer(LMQ_ptr, AbstractRouter&);
    ~RPCServer() = default;

    void
    HandleLogsSubRequest(oxenmq::Message& m);

    void
    AddCategories();

    void
    invoke(Halt& halt);
    void
    invoke(Version& version);
    void
    invoke(Status& status);
    void
    invoke(GetStatus& getstatus);
    void
    invoke(QuicConnect& quicconnect);
    void
    invoke(QuicListener& quiclistener);
    void
    invoke(LookupSnode& lookupsnode);
    void
    invoke(MapExit& mapexit);
    void
    invoke(ListExits& listexits);
    void
    invoke(UnmapExit& unmapexit);
    void
    invoke(SwapExits& swapexits);
    void
    invoke(DNSQuery& dnsquery);
    void
    invoke(Config& config);

    LMQ_ptr m_LMQ;
    AbstractRouter& m_Router;
    oxen::log::PubsubLogger log_subs;
  };

  template <typename RPC>
  class EndpointHandler
  {
   public:
    RPCServer& server;
    RPC rpc{};

    EndpointHandler(RPCServer& _server, DeferredSend _replier) : server{_server}
    {
      rpc.replier.emplace(std::move(_replier));
    }

    void
    operator()()
    {
      try
      {
        server.invoke(rpc);
      }
      catch (const rpc_error& e)
      {
        log::info(logcat, "RPC request 'rpc.{}' failed with: {}", rpc.name, e.what());
        SetJSONError(
            fmt::format("RPC request 'rpc.{}' failed with: {}", rpc.name, e.what()), rpc.response);
      }
      catch (const std::exception& e)
      {
        log::info(logcat, "RPC request 'rpc.{}' raised an exception: {}", rpc.name, e.what());
        SetJSONError(
            fmt::format("RPC request 'rpc.{}' raised an exception: {}", rpc.name, e.what()),
            rpc.response);
      }

      if (rpc.replier.has_value())
      {
        rpc.send_response();
      }
    }
  };

}  // namespace llarp::rpc