logos-libp2p-module/tutorial/tutorial_2_custom_config.cpp

/// # Tutorial 2: Custom Node Configuration
///
/// In the [previous tutorial](tutorial_1_node_lifecycle.md), we created a
/// node with default settings that binds to a random port. In this tutorial,
/// we'll learn how to configure the node explicitly — setting a fixed port,
/// changing transports, and passing options via both C++ structs and JSON.
///
/// ## Understanding Libp2pModuleOptions
///
/// The `Libp2pModuleImpl` constructor accepts a `Libp2pModuleOptions` struct
/// that lets you control every aspect of the node. Here are the most common
/// configuration fields:
///
/// | Field | Type | Default | Description |
/// |-------|------|---------|-------------|
/// | `addrs` | `vector<string>` | `["/ip4/127.0.0.1/tcp/0"]` | Listen addresses |
/// | `transport` | `TransportType` | `TRANSPORT_TYPE_TCP` | Transport protocol |
/// | `maxConnections` | `int` | `50` | Max total connections |
/// | `maxConnsPerPeer` | `int` | `1` | Max connections per peer |
/// | `mountGossipsub` | `bool` | `true` | Enable GossipSub |
/// | `mountKad` | `bool` | `true` | Enable Kademlia DHT |
/// | `mountServiceDiscovery` | `bool` | `true` | Enable service discovery |
///
/// ## Binding to a fixed port
///
/// By default nodes bind to port 0 (random). To listen on a specific port,
/// provide a custom address in the `addrs` field.
///
/// -----------

#include <cstdio>
#include <string>
#include "plugin.h"

int main()
{
    printf("=== Tutorial 2: Custom Node Configuration ===\n\n");

    setLogLevel("fatal");

/// ## Method 1: Configure via C++ struct
///
/// The most explicit way to configure a node is by constructing
/// `Libp2pModuleOptions` directly and passing it to the constructor.
    Libp2pModuleOptions options;

    // Listen on TCP port 9090 on all interfaces
    options.addrs = {"/ip4/0.0.0.0/tcp/9090"};

    // Limit to 10 total connections
    options.maxConnections = 10;

    // Allow up to 2 connections from the same peer
    options.maxConnsPerPeer = 2;

    // We don't need GossipSub or Kademlia for this basic example
    options.mountGossipsub = false;
    options.mountKad = false;
    options.mountServiceDiscovery = false;

    printf("Creating node with custom configuration...\n");
    printf("  Listen address: %s\n", options.addrs[0].c_str());
    printf("  Max connections: %d\n", options.maxConnections);
    printf("  Max per peer: %d\n", options.maxConnsPerPeer);

    Libp2pModuleImpl node(options);

    StdLogosResult startRes = node.start();
    if (!startRes.success) {
        fprintf(stderr, "Failed to start node: %s\n",
                startRes.error.c_str());
        return 1;
    }

/// Verify that the node is actually listening on the configured port:
    StdLogosResult info = node.peerInfo();
    if (!info.success) {
        fprintf(stderr, "Failed to get node info: %s\n",
                info.error.c_str());
        return 1;
    }

    printf("\nNode is live!\n");
    printf("  Peer ID: %s\n",
           info.value["peerId"].get<std::string>().c_str());
    for (const auto& addr : info.value["addrs"]) {
        printf("  Listening on: %s\n",
               addr.get<std::string>().c_str());
    }

    node.stop();

/// ## Method 2: Configure via JSON
///
/// When integrating with larger systems (e.g. `logoscore`), you'll
/// often receive configuration as JSON. The same options can be
/// supplied via `Libp2pModuleOptions::fromJson()`.
    printf("\n--- Method 2: JSON configuration ---\n");

    std::string jsonConfig = R"({
        "addrs": ["/ip4/127.0.0.1/tcp/9091"],
        "maxConnections": 20,
        "mountGossipsub": false,
        "mountKad": false,
        "mountServiceDiscovery": false
    })";

    bool parseOk;
    std::string parseErr;
    auto jsonOpts = Libp2pModuleOptions::fromJson(jsonConfig, parseOk, &parseErr);

    if (!parseOk) {
        fprintf(stderr, "Failed to parse JSON config: %s\n",
                parseErr.c_str());
        return 1;
    }

    printf("Parsed JSON config:\n");
    printf("  Listen address: %s\n", jsonOpts.addrs[0].c_str());
    printf("  Max connections: %d\n", jsonOpts.maxConnections);

    Libp2pModuleImpl nodeFromJson(jsonOpts);

    StdLogosResult jsonStartRes = nodeFromJson.start();
    if (!jsonStartRes.success) {
        fprintf(stderr, "Failed to start JSON-configured node: %s\n",
                jsonStartRes.error.c_str());
        return 1;
    }

    StdLogosResult info2 = nodeFromJson.peerInfo();
    if (!info2.success) {
        fprintf(stderr, "Failed to get JSON-configured node info: %s\n",
                info2.error.c_str());
        return 1;
    }

    printf("\nJSON-configured node is live!\n");
    printf("  Peer ID: %s\n",
           info2.value["peerId"].get<std::string>().c_str());
    for (const auto& addr : info2.value["addrs"]) {
        printf("  Listening on: %s\n",
               addr.get<std::string>().c_str());
    }

    nodeFromJson.stop();

    return 0;
}

/// ## Summary
///
/// In this tutorial you learned:
///   - How to configure a node with a fixed port
///   - How to control connection limits
///   - How to pass options via C++ struct or JSON
///   - How to verify the node's actual bound addresses

/// ## Run tutorial
///
/// ```bash
/// ./build/tutorial/tutorial_2_custom_config
/// ```

/// ## Exercise: Try different configurations
///
/// Experiment with these variations:
///
/// ```cpp
/// // QUIC transport instead of TCP
/// options.transport = TRANSPORT_TYPE_QUIC;
/// options.addrs = {"/ip4/127.0.0.1/udp/9092/quic-v1"};
///
/// // Listen on multiple addresses
/// options.addrs = {
///     "/ip4/0.0.0.0/tcp/9093",
///     "/ip4/0.0.0.0/tcp/9094"
/// };
/// ```