From 09565f4580d9cf647bcf1a4441fcb6a19bde2ef6 Mon Sep 17 00:00:00 2001
From: Chaitanya Munukutla <chaitanya.m61292@gmail.com>
Date: Sun, 11 Aug 2024 13:07:12 +0530
Subject: [PATCH] Handle swarm peer additions and expiration

Signed-off-by: Chaitanya Munukutla <chaitanya.m61292@gmail.com>
---
 server/src/handlers/swarm.rs | 49 +++++++++++++++++++++++++++++++++---
 1 file changed, 45 insertions(+), 4 deletions(-)

diff --git a/server/src/handlers/swarm.rs b/server/src/handlers/swarm.rs
index 4a44d42..6d7a356 100644
--- a/server/src/handlers/swarm.rs
+++ b/server/src/handlers/swarm.rs
@@ -1,14 +1,23 @@
 use crate::p2p::behaviour::{Behaviour, BehaviourEvent};
-use async_std::io;
 use futures::{prelude::*, select};
 use libp2p::kad::store::MemoryStore;
 use libp2p::kad::Mode;
 use libp2p::swarm::SwarmEvent;
-use libp2p::{kad, mdns, noise, tcp, yamux};
+use libp2p::{kad, mdns, noise, tcp, yamux, Multiaddr};
+use std::env;
 use std::error::Error;
 use std::time::Duration;
 
 pub(crate) async fn init_swarm() -> Result<(), Box<dyn Error>> {
+    let default_swarm_port = 7001;
+    let swarm_port: u16 = env::var("SWARM_PORT")
+        .ok()
+        .and_then(|p| p.parse().ok())
+        .unwrap_or(default_swarm_port);
+
+    let default_swarm_host = String::from("0.0.0.0");
+    let swarm_host = env::var("SWARM_HOST").ok().unwrap_or(default_swarm_host);
+
     let mut swarm = libp2p::SwarmBuilder::with_new_identity()
         .with_async_std()
         .with_tcp(
@@ -23,7 +32,11 @@ pub(crate) async fn init_swarm() -> Result<(), Box<dyn Error>> {
                     MemoryStore::new(key.public().to_peer_id()),
                 ),
                 mdns: mdns::async_io::Behaviour::new(
-                    mdns::Config::default(),
+                    mdns::Config {
+                        ttl: Duration::from_secs(20),
+                        query_interval: Duration::from_secs(5),
+                        enable_ipv6: false,
+                    },
                     key.public().to_peer_id(),
                 )?,
             })
@@ -34,7 +47,28 @@ pub(crate) async fn init_swarm() -> Result<(), Box<dyn Error>> {
     swarm.behaviour_mut().kademlia.set_mode(Some(Mode::Server));
 
     // Listen on all interfaces and whatever port the OS assigns.
-    swarm.listen_on("/ip4/0.0.0.0/tcp/0".parse()?)?;
+
+    let swarm_addr: Multiaddr = format!("/ip4/{}/tcp/{}", swarm_host, swarm_port).parse()?;
+    match swarm.listen_on(swarm_addr) {
+        Ok(listener_id) => {
+            println!("Swarm active, listener_id={}", listener_id);
+        }
+        Err(err) => {
+            eprintln!("failed to initialise swarm {:?}", err);
+        }
+    }
+
+    if let Some(swarm_peer_url) = env::var("SWARM_PEER").ok() {
+        let peer_addr: Multiaddr = swarm_peer_url.parse()?;
+        match swarm.dial(peer_addr.clone()) {
+            Ok(_) => {
+                println!("dialed peer={}", peer_addr);
+            }
+            Err(err) => {
+                eprintln!("failed to dial peer={}, err={:?}", peer_addr, err);
+            }
+        }
+    }
 
     tokio::spawn(async move {
         loop {
@@ -45,9 +79,16 @@ pub(crate) async fn init_swarm() -> Result<(), Box<dyn Error>> {
                     },
                     SwarmEvent::Behaviour(BehaviourEvent::Mdns(mdns::Event::Discovered(list))) => {
                         for (peer_id, multiaddr) in list {
+                            println!("Connected to peer: peer_id={}, addr={}", peer_id, multiaddr);
                             swarm.behaviour_mut().kademlia.add_address(&peer_id, multiaddr);
                         }
                     }
+                    SwarmEvent::Behaviour(BehaviourEvent::Mdns(mdns::Event::Expired(list))) => {
+                        for (peer_id, multiaddr) in list {
+                            println!("Disconnected from peer: peer_id={}, addr={}", peer_id, multiaddr);
+                            swarm.behaviour_mut().kademlia.remove_address(&peer_id, &multiaddr);
+                        }
+                    }
                     SwarmEvent::Behaviour(BehaviourEvent::Kademlia(kad::Event::OutboundQueryProgressed { result, ..})) => {
                         match result {
                             kad::QueryResult::GetProviders(Ok(kad::GetProvidersOk::FoundProviders { key, providers, .. })) => {