dolphin/Source/Core/Common/TraversalClient.h

// This file is public domain, in case it's useful to anyone. -comex

#pragma once

#include <cstddef>
#include <list>
#include <memory>
#include <string>
#include <string_view>

#include <enet/enet.h>

#include "Common/CommonTypes.h"
#include "Common/Thread.h"
#include "Common/TraversalProto.h"

class TraversalClientClient
{
public:
  virtual ~TraversalClientClient() = default;
  virtual void OnTraversalStateChanged() = 0;
  virtual void OnConnectReady(ENetAddress addr) = 0;
  virtual void OnConnectFailed(TraversalConnectFailedReason reason) = 0;
};

class TraversalClient
{
public:
  enum class State
  {
    Connecting,
    Connected,
    Failure,
  };
  enum class FailureReason
  {
    BadHost = 0x300,
    VersionTooOld,
    ServerForgotAboutUs,
    SocketSendError,
    ResendTimeout,
  };
  TraversalClient(ENetHost* netHost, const std::string& server, const u16 port);
  ~TraversalClient();

  TraversalHostId GetHostID() const;
  State GetState() const;
  FailureReason GetFailureReason() const;

  bool HasFailed() const { return m_State == State::Failure; }
  bool IsConnecting() const { return m_State == State::Connecting; }
  bool IsConnected() const { return m_State == State::Connected; }

  void Reset();
  void ConnectToClient(std::string_view host);
  void ReconnectToServer();
  void Update();
  void HandleResends();

  TraversalClientClient* m_Client = nullptr;

private:
  struct OutgoingTraversalPacketInfo
  {
    TraversalPacket packet;
    int tries;
    u32 sendTime;
  };
  void HandleServerPacket(TraversalPacket* packet);
  // called from NetHost
  bool TestPacket(u8* data, size_t size, ENetAddress* from);
  void ResendPacket(OutgoingTraversalPacketInfo* info);
  TraversalRequestId SendTraversalPacket(const TraversalPacket& packet);
  void OnFailure(FailureReason reason);
  void HandlePing();
  static int ENET_CALLBACK InterceptCallback(ENetHost* host, ENetEvent* event);

  ENetHost* m_NetHost;
  TraversalHostId m_HostId{};
  State m_State{};
  FailureReason m_FailureReason{};
  TraversalRequestId m_ConnectRequestId = 0;
  bool m_PendingConnect = false;
  std::list<OutgoingTraversalPacketInfo> m_OutgoingTraversalPackets;
  ENetAddress m_ServerAddress{};
  std::string m_Server;
  u16 m_port;
  u32 m_PingTime = 0;
};
extern std::unique_ptr<TraversalClient> g_TraversalClient;
// the NetHost connected to the TraversalClient.
extern std::unique_ptr<ENetHost> g_MainNetHost;
// Create g_TraversalClient and g_MainNetHost if necessary.
bool EnsureTraversalClient(const std::string& server, u16 server_port, u16 listen_port = 0);
void ReleaseTraversalClient();