C_server.hpp

/*
 * Copyright 2026 Guillaume Guillet
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#ifndef _FGE_C_SERVER_HPP_INCLUDED
#define _FGE_C_SERVER_HPP_INCLUDED
 
#include "FastEngine/fge_extern.hpp"
#include "C_socket.hpp"
#include "FastEngine/C_flag.hpp"
#include "FastEngine/network/C_clientList.hpp"
#include "FastEngine/network/C_netCommand.hpp"
#include "FastEngine/network/C_packet.hpp"
#include "FastEngine/network/C_protocol.hpp"
#include <condition_variable>
#include <future>
#include <memory>
#include <mutex>
#include <queue>
#include <thread>
 
 
#if defined(FGE_ENABLE_SERVER_NETWORK_RANDOM_LOST) || defined(FGE_ENABLE_CLIENT_NETWORK_RANDOM_LOST)
    #include "FastEngine/C_random.hpp"
#endif
 
#define FGE_SERVER_DEFAULT_MAXPACKET 200
#define FGE_SERVER_MAX_TIME_DIFFERENCE_REALM                                                                           \
    std::chrono::milliseconds                                                                                          \
    {                                                                                                                  \
        2000                                                                                                           \
    }
 
#define FGE_SERVER_PACKET_RECEPTION_TIMEOUT_MS 250
#define FGE_SERVER_CLIENTS_MAP_GC_DELAY_MS 5000
 
namespace fge
{
using ObjectSid = uint32_t;
} // namespace fge
 
namespace fge::net
{
 
class ServerSideNetUdp;
class ClientSideNetUdp;
 
enum class FluxProcessResults
{
    USER_RETRIEVABLE,
 
    INTERNALLY_HANDLED,
    INTERNALLY_DISCARDED,
 
    NONE_AVAILABLE
};
 
enum class ReturnEvents
{
    REVT_SIMPLE,
    REVT_OBJECT,
    REVT_ASK_FULL_UPDATE,
    REVT_COMPLEX
};
 
class FGE_API ReturnPacketHandler
{
public:
    ReturnPacketHandler() = default;
    virtual ~ReturnPacketHandler() = default;
 
    [[nodiscard]] std::optional<Error>
    handleReturnPacket(ClientSharedPtr const& refClient, ClientContext& clientContext, ReceivedPacketPtr& packet) const;
 
    mutable UniqueCallbackHandler<ClientSharedPtr const&, Identity const&, ReceivedPacketPtr const&>
            _onClientReturnPacket;
    mutable UniqueCallbackHandler<ClientSharedPtr const&, Identity const&, uint16_t, ReceivedPacketPtr const&>
            _onClientReturnEvent;
    mutable UniqueCallbackHandler<ClientSharedPtr const&, Identity const&, uint16_t> _onClientSimpleReturnEvent;
    mutable UniqueCallbackHandler<ClientSharedPtr const&,
                                  Identity const&,
                                  uint16_t,
                                  ObjectSid,
                                  ObjectSid,
                                  ReceivedPacketPtr const&>
            _onClientObjectReturnEvent;
    mutable UniqueCallbackHandler<ClientSharedPtr const&, Identity const&> _onClientAskFullUpdate;
};

class FGE_API NetFluxUdp
{
public:
    NetFluxUdp(bool defaultFlux);
    NetFluxUdp(NetFluxUdp const& r) = delete;
    NetFluxUdp(NetFluxUdp&& r) noexcept = delete;
    virtual ~NetFluxUdp();
 
    NetFluxUdp& operator=(NetFluxUdp const& r) = delete;
    NetFluxUdp& operator=(NetFluxUdp&& r) noexcept = delete;
 
    void clearPackets();
    [[nodiscard]] ReceivedPacketPtr popNextPacket();
 
    [[nodiscard]] std::size_t getPacketsSize() const;
    [[nodiscard]] bool isEmpty() const;
 
    void setMaxPackets(std::size_t n);
    [[nodiscard]] std::size_t getMaxPackets() const;
 
    [[nodiscard]] bool isDefaultFlux() const;
 
protected:
    bool pushPacket(ReceivedPacketPtr&& fluxPck);
    void forcePushPacket(ReceivedPacketPtr fluxPck);
    void forcePushPacketFront(ReceivedPacketPtr fluxPck);
 
    mutable std::mutex _g_mutexFlux;
    std::deque<ReceivedPacketPtr> _g_packets;
    std::size_t _g_remainingPackets{0};
 
private:
    std::size_t g_maxPackets = FGE_SERVER_DEFAULT_MAXPACKET;
    bool g_isDefaultFlux{false};
 
    friend class ServerSideNetUdp;
    friend class PacketReorderer;
};
 
class FGE_API ServerNetFluxUdp : public NetFluxUdp, public ReturnPacketHandler
{
public:
    ServerNetFluxUdp(ServerSideNetUdp& server, bool defaultFlux);
    ~ServerNetFluxUdp() override = default;
 
    void processClients();
    [[nodiscard]] FluxProcessResults process(ClientSharedPtr& refClient, ReceivedPacketPtr& packet);
 
    void disconnectAllClients(std::chrono::milliseconds delay = std::chrono::milliseconds(0)) const;
 
    ClientList _clients;
 
    CallbackHandler<ClientSharedPtr const&> _onClientBadRealm;
    CallbackHandler<ClientSharedPtr, Identity const&> _onClientTimeout;
 
    CallbackHandler<ClientSharedPtr const&, Identity const&> _onClientAcknowledged;
    CallbackHandler<ClientSharedPtr const&, Identity const&> _onClientConnected;
    CallbackHandler<ClientSharedPtr, Identity const&> _onClientDisconnected;
    CallbackHandler<ClientSharedPtr, Identity const&> _onClientDropped;
 
private:
    [[nodiscard]] bool verifyRealm(ClientSharedPtr const& refClient, ReceivedPacketPtr const& packet);
 
    [[nodiscard]] FluxProcessResults processUnknownClient(ClientSharedPtr& refClient, ReceivedPacketPtr& packet);
 
    ServerSideNetUdp* const g_server{nullptr};
    std::chrono::milliseconds g_commandsUpdateTick{0};
    std::chrono::steady_clock::time_point g_lastCommandUpdateTimePoint{std::chrono::steady_clock::now()};
};

class FGE_API ServerSideNetUdp
{
public:
    explicit ServerSideNetUdp(IpAddress::Types addressType = IpAddress::Types::Ipv4);
    ServerSideNetUdp(ServerSideNetUdp const& r) = delete;
    ServerSideNetUdp(ServerSideNetUdp&& r) noexcept = delete;
    ~ServerSideNetUdp();
 
    ServerSideNetUdp& operator=(ServerSideNetUdp const& r) = delete;
    ServerSideNetUdp& operator=(ServerSideNetUdp&& r) noexcept = delete;
 
    void setVersioningString(std::string_view versioningString);
    [[nodiscard]] std::string const& getVersioningString() const;
 
    [[nodiscard]] bool
    start(Port bindPort, IpAddress const& bindIp, IpAddress::Types addressType = IpAddress::Types::None);
    [[nodiscard]] bool start(IpAddress::Types addressType = IpAddress::Types::None);
    void stop();

    [[nodiscard]] ServerNetFluxUdp* newFlux();
 
    [[nodiscard]] ServerNetFluxUdp* getFlux(std::size_t index);
    [[nodiscard]] ServerNetFluxUdp* getDefaultFlux();
 
    [[nodiscard]] std::size_t getFluxSize() const;
 
    [[nodiscard]] IpAddress::Types getAddressType() const;
 
    void closeFlux(NetFluxUdp* flux);
    void closeAllFlux();
 
    void repushPacket(ReceivedPacketPtr&& packet);

    void notifyTransmission();
    [[nodiscard]] bool isRunning() const;
 
    [[nodiscard]] bool announceNewClient(Identity const& identity, ClientSharedPtr const& client);
 
    void sendTo(TransmitPacketPtr& pck, Client const& client, Identity const& id);
    void sendTo(TransmitPacketPtr& pck, Identity const& id);
 
    [[nodiscard]] void* getCryptContext() const;
 
private:
    void threadReception();
    void threadTransmission();
 
    std::unique_ptr<std::thread> g_threadReception;
    std::unique_ptr<std::thread> g_threadTransmission;
 
    std::condition_variable g_transmissionNotifier;
 
    mutable std::mutex g_mutexServer;
 
    std::vector<std::unique_ptr<ServerNetFluxUdp>> g_fluxes;
    ServerNetFluxUdp g_defaultFlux;
    std::queue<std::pair<TransmitPacketPtr, Identity>> g_transmissionQueue;
 
    std::unordered_map<Identity, std::weak_ptr<Client>, IdentityHash> g_clientsMap;
 
    SocketUdp g_socket;
    bool g_running;
 
    void* g_crypt_ctx;
 
    std::string g_versioningString;
};

class FGE_API ClientSideNetUdp : public NetFluxUdp
{
public:
    explicit ClientSideNetUdp(IpAddress::Types addressType = IpAddress::Types::Ipv4);
    ClientSideNetUdp(ClientSideNetUdp const& r) = delete;
    ClientSideNetUdp(ClientSideNetUdp&& r) noexcept = delete;
    ~ClientSideNetUdp() override;
 
    ClientSideNetUdp& operator=(ClientSideNetUdp const& r) = delete;
    ClientSideNetUdp& operator=(ClientSideNetUdp&& r) noexcept = delete;
 
    [[nodiscard]] bool start(Port bindPort,
                             IpAddress const& bindIp,
                             Port connectRemotePort,
                             IpAddress const& connectRemoteAddress,
                             IpAddress::Types addressType = IpAddress::Types::None);
    void stop();
 
    void notifyTransmission();
    [[nodiscard]] bool isRunning() const;
 
    [[nodiscard]] std::future<uint16_t> retrieveMTU();
    [[nodiscard]] std::future<bool> connect(std::string_view versioningString = std::string_view{});
    [[nodiscard]] std::future<void> disconnect();
 
    [[nodiscard]] IpAddress::Types getAddressType() const;
 
    [[nodiscard]] std::size_t waitForPackets(std::chrono::milliseconds time_ms);
 
    [[nodiscard]] Identity const& getClientIdentity() const;
 
    template<class TPacket = Packet>
    void sendTo(TransmitPacketPtr& pck, Identity const& id);
 
    enum ProcessOptions : uint32_t
    {
        OPTION_NONE = 0,
        OPTION_NO_TIMEOUT = 1 << 0,
        OPTION_ONE_SHOT = 1 << 1
    };
    [[nodiscard]] FluxProcessResults process(ReceivedPacketPtr& packet,
                                             EnumFlags<ProcessOptions> options = OPTION_NONE);
 
    void resetReturnPacket();
    [[nodiscard]] TransmitPacketPtr& startComplexReturnEvent(uint16_t id);
    TransmitPacketPtr& startObjectReturnEvent(uint16_t commandIndex, ObjectSid parentSid, ObjectSid targetSid);
    void endReturnEvent();
 
    void simpleReturnEvent(uint16_t id);
    bool askFullUpdateReturnEvent();
 
    void enableReturnPacket(bool enable);
    [[nodiscard]] bool isReturnPacketEnabled() const;
 
    [[nodiscard]] TransmitPacketPtr prepareAndRetrieveReturnPacket();
    [[nodiscard]] std::optional<Error> loopbackReturnPacket(ReturnPacketHandler const& handler);
 
    Client _client; //But it is the server :O
 
    CallbackHandler<ClientSideNetUdp&> _onClientTimeout;
    CallbackHandler<ClientSideNetUdp&> _onClientDisconnected;
 
    CallbackHandler<ClientSideNetUdp&, TransmitPacketPtr&> _onTransmitReturnPacket;
 
private:
    void threadReception();
    void threadTransmission();
 
    TransmitPacketPtr& startReturnEvent(ReturnEvents event);
 
    std::unique_ptr<std::thread> g_threadReception;
    std::unique_ptr<std::thread> g_threadTransmission;
 
    std::condition_variable g_transmissionNotifier;
    std::condition_variable g_receptionNotifier;
 
    SocketUdp g_socket;
    bool g_running{false};
 
    Identity g_clientIdentity;
 
    std::recursive_mutex g_mutexCommands;
 
    bool g_returnPacketEnabled{false};
    TransmitPacketPtr g_returnPacket;
    bool g_returnPacketEventStarted{false};
    std::size_t g_returnPacketStartPosition{0};
    bool g_isAskingFullUpdate{false};
    uint16_t g_returnPacketEventCount{0};
    std::chrono::steady_clock::time_point g_returnPacketTimePoint;
 
    void* g_crypt_ctx{nullptr};
};
 
} // namespace fge::net
 
#include "C_server.inl"
 
#endif // _FGE_C_SERVER_HPP_INCLUDED