brandling-safari/shared/Net.cpp

#include "Net.h"

#include <enet/enet.h>

#include <cstdio>
#include <cstring>

namespace bs::net {

namespace {
bool gInit = false;
constexpr const char* kQuery = "BSAFARI?";
constexpr const char* kReply = "BSAFARI!";

// ENetBuffer's field order differs per platform (it aliases iovec / WSABUF).
ENetBuffer buffer(void* data, size_t size) {
    ENetBuffer b;
    b.data = data;
    b.dataLength = size;
    return b;
}
}  // namespace

bool initialize() {
    if (gInit) return true;
    if (enet_initialize() != 0) return false;
    gInit = true;
    return true;
}

void shutdown() {
    if (gInit) enet_deinitialize();
    gInit = false;
}

Host::~Host() {
    if (host_) {
        for (auto& [id, p] : peers_) enet_peer_disconnect_now(p, 0);
        enet_host_flush(host_);
        enet_host_destroy(host_);
    }
}

bool Host::listen(uint16_t port, size_t maxPeers) {
    ENetAddress addr;
    addr.host = ENET_HOST_ANY;
    addr.port = port;
    host_ = enet_host_create(&addr, maxPeers, kChannelCount, 0, 0);
    return host_ != nullptr;
}

bool Host::connect(const std::string& address, uint16_t port) {
    if (!host_) host_ = enet_host_create(nullptr, 1, kChannelCount, 0, 0);
    if (!host_) return false;
    ENetAddress addr;
    if (enet_address_set_host(&addr, address.c_str()) != 0) return false;
    addr.port = port;
    ENetPeer* p = enet_host_connect(host_, &addr, kChannelCount, 0);
    if (!p) return false;
    uint32_t id = nextId_++;
    p->data = reinterpret_cast<void*>(uintptr_t(id));
    peers_[id] = p;
    enet_peer_timeout(p, 0, 4000, 8000);
    return true;
}

bool Host::poll(Event& ev, uint32_t timeoutMs) {
    ev = Event{};
    if (!host_) return false;
    ENetEvent e;
    int r = enet_host_service(host_, &e, timeoutMs);
    if (r <= 0) return false;
    switch (e.type) {
        case ENET_EVENT_TYPE_CONNECT: {
            uint32_t id = uint32_t(uintptr_t(e.peer->data));
            if (!id) {  // incoming connection
                id = nextId_++;
                e.peer->data = reinterpret_cast<void*>(uintptr_t(id));
                peers_[id] = e.peer;
                enet_peer_timeout(e.peer, 0, 5000, 10000);
            }
            ev.type = Event::Connect;
            ev.peer = id;
            return true;
        }
        case ENET_EVENT_TYPE_DISCONNECT: {
            uint32_t id = uint32_t(uintptr_t(e.peer->data));
            peers_.erase(id);
            e.peer->data = nullptr;
            ev.type = Event::Disconnect;
            ev.peer = id;
            return true;
        }
        case ENET_EVENT_TYPE_RECEIVE: {
            ev.type = Event::Receive;
            ev.peer = uint32_t(uintptr_t(e.peer->data));
            ev.data.assign(e.packet->data, e.packet->data + e.packet->dataLength);
            enet_packet_destroy(e.packet);
            return true;
        }
        default: return false;
    }
}

void Host::send(uint32_t peer, Channel ch, const std::vector<uint8_t>& data) {
    auto it = peers_.find(peer);
    if (it == peers_.end() || data.empty()) return;
    ENetPacket* pk = enet_packet_create(data.data(), data.size(), ch == Reliable ? ENET_PACKET_FLAG_RELIABLE : 0);
    if (enet_peer_send(it->second, ch, pk) != 0) enet_packet_destroy(pk);
}

void Host::disconnect(uint32_t peer) {
    auto it = peers_.find(peer);
    if (it != peers_.end()) enet_peer_disconnect_later(it->second, 0);
}

void Host::flush() {
    if (host_) enet_host_flush(host_);
}

std::string Host::address(uint32_t peer) const {
    auto it = peers_.find(peer);
    if (it == peers_.end()) return "?";
    char buf[64] = {};
    enet_address_get_host_ip(&it->second->address, buf, sizeof buf);
    return buf;
}

uint32_t Host::roundTripMs(uint32_t peer) const {
    auto it = peers_.find(peer);
    return it == peers_.end() ? 0 : it->second->roundTripTime;
}

// ------------------------------------------------------------------ LAN discovery

Beacon::~Beacon() {
    if (sock_ >= 0) enet_socket_destroy(ENetSocket(sock_));
}

bool Beacon::open(uint16_t discoveryPort) {
    ENetSocket s = enet_socket_create(ENET_SOCKET_TYPE_DATAGRAM);
    if (s == ENET_SOCKET_NULL) return false;
    enet_socket_set_option(s, ENET_SOCKOPT_REUSEADDR, 1);
    enet_socket_set_option(s, ENET_SOCKOPT_NONBLOCK, 1);
    enet_socket_set_option(s, ENET_SOCKOPT_BROADCAST, 1);
    ENetAddress addr;
    addr.host = ENET_HOST_ANY;
    addr.port = discoveryPort;
    if (enet_socket_bind(s, &addr) != 0) {
        enet_socket_destroy(s);
        return false;
    }
    sock_ = intptr_t(s);
    return true;
}

void Beacon::poll(uint16_t gamePort, const std::string& serverName, int players) {
    if (sock_ < 0) return;
    char buf[256];
    for (int i = 0; i < 16; ++i) {
        ENetAddress from;
        ENetBuffer b = buffer(buf, sizeof buf - 1);
        int n = enet_socket_receive(ENetSocket(sock_), &from, &b, 1);
        if (n <= 0) return;
        buf[n] = 0;
        if (std::strncmp(buf, kQuery, std::strlen(kQuery)) != 0) continue;
        char reply[256];
        int len = std::snprintf(reply, sizeof reply, "%s%u|%d|%s", kReply, unsigned(gamePort), players,
                                serverName.substr(0, 120).c_str());
        ENetBuffer out = buffer(reply, size_t(len));
        enet_socket_send(ENetSocket(sock_), &from, &out, 1);
    }
}

Scanner::~Scanner() {
    if (sock_ >= 0) enet_socket_destroy(ENetSocket(sock_));
}

bool Scanner::open() {
    ENetSocket s = enet_socket_create(ENET_SOCKET_TYPE_DATAGRAM);
    if (s == ENET_SOCKET_NULL) return false;
    enet_socket_set_option(s, ENET_SOCKOPT_NONBLOCK, 1);
    enet_socket_set_option(s, ENET_SOCKOPT_BROADCAST, 1);
    ENetAddress addr;
    addr.host = ENET_HOST_ANY;
    addr.port = 0;
    enet_socket_bind(s, &addr);
    sock_ = intptr_t(s);
    return true;
}

void Scanner::ping(uint16_t discoveryPort) {
    if (sock_ < 0) return;
    ENetBuffer b = buffer(const_cast<char*>(kQuery), std::strlen(kQuery));
    ENetAddress to;
    to.host = ENET_HOST_BROADCAST;
    to.port = discoveryPort;
    enet_socket_send(ENetSocket(sock_), &to, &b, 1);
    // also ask localhost directly (broadcast does not always loop back)
    enet_address_set_host(&to, "127.0.0.1");
    enet_socket_send(ENetSocket(sock_), &to, &b, 1);
}

void Scanner::poll(std::vector<ServerInfo>& found) {
    if (sock_ < 0) return;
    char buf[256];
    for (int i = 0; i < 32; ++i) {
        ENetAddress from;
        ENetBuffer b = buffer(buf, sizeof buf - 1);
        int n = enet_socket_receive(ENetSocket(sock_), &from, &b, 1);
        if (n <= 0) return;
        buf[n] = 0;
        size_t rl = std::strlen(kReply);
        if (std::strncmp(buf, kReply, rl) != 0) continue;
        ServerInfo info;
        char ip[64] = {};
        enet_address_get_host_ip(&from, ip, sizeof ip);
        info.address = ip;
        unsigned port = 0;
        int players = 0;
        int consumed = 0;
        if (std::sscanf(buf + rl, "%u|%d|%n", &port, &players, &consumed) < 2) continue;
        info.port = uint16_t(port);
        info.players = players;
        info.name = buf + rl + consumed;
        bool dup = false;
        for (ServerInfo& s : found)
            if (s.port == info.port && (s.address == info.address || s.name == info.name)) {
                s.players = info.players;
                dup = true;
            }
        if (!dup) found.push_back(info);
    }
}

}  // namespace bs::net