From da5ae3e46a3daa6489a98fd2c7d198e83eee86b4 Mon Sep 17 00:00:00 2001
From: Milos Stankovic <82043364+morph-dev@users.noreply.github.com>
Date: Mon, 3 Feb 2025 20:10:51 +0200
Subject: [PATCH] refactor: rename "merge" to "consolidate" and update
 documentation

---
 src/peer.rs      | 37 ++++++++++++++++++++++++++-----------
 src/socket.rs    |  4 ++--
 src/testutils.rs |  5 +++--
 3 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/src/peer.rs b/src/peer.rs
index 0b0ac16..f668276 100644
--- a/src/peer.rs
+++ b/src/peer.rs
@@ -9,10 +9,25 @@ pub trait ConnectionPeer: Debug + Clone + Send + Sync {
     /// Returns peer's id
     fn id(&self) -> Self::Id;
 
-    /// Merge the given object into `Self` whilst consuming it.
+    /// Consolidates two peers into one.
+    ///
+    /// It's possible that we have two instances that represent the same peer (equal `peer_id`),
+    /// and we need to consolidate them into one. This can happen when [Peer]-s passed with
+    /// [UtpSocket::accept_with_cid](crate::socket::UtpSocket::accept_with_cid) or
+    /// [UtpSocket::connect_with_cid](crate::socket::UtpSocket::connect_with_cid), and returned by
+    /// [AsyncUdpSocket::recv_from](crate::udp::AsyncUdpSocket::recv_from) contain peers (not just
+    /// `peer_id`).
+    ///
+    /// The structure implementing this trait can decide on the exact behavior. Some examples:
+    /// - If structure is simple (i.e. two peers are the same iff all fields are the same), return
+    ///   either (see implementation for `SocketAddr`)
+    /// - If we can determine which peer is newer (e.g. using timestamp or version field), return
+    ///   newer peer
+    /// - If structure behaves more like a key-value map whose values don't change over time,
+    ///   merge key-value pairs from both instances into one
     ///
     /// Should panic if ids are not matching.
-    fn merge(&mut self, other: Self);
+    fn consolidate(a: Self, b: Self) -> Self;
 }
 
 impl ConnectionPeer for SocketAddr {
@@ -22,8 +37,9 @@ impl ConnectionPeer for SocketAddr {
         *self
     }
 
-    fn merge(&mut self, other: Self) {
-        assert!(self == &other)
+    fn consolidate(a: Self, b: Self) -> Self {
+        assert!(a == b, "Consolidating non-equal peers");
+        a
     }
 }
 
@@ -61,20 +77,19 @@ impl<P: ConnectionPeer> Peer<P> {
         self.peer.as_ref()
     }
 
-    /// Merge the given peer into `Self` whilst consuming it.
+    /// Consolidates given peer into `Self` whilst consuming it.
+    ///
+    /// See [ConnectionPeer::consolidate] for details.
     ///
     /// Panics if ids are not matching.
-    pub fn merge(&mut self, other: Self) {
-        assert!(self.id == other.id);
+    pub fn consolidate(&mut self, other: Self) {
+        assert!(self.id == other.id, "Consolidating with non-equal peer");
         let Some(other_peer) = other.peer else {
             return;
         };
 
         self.peer = match self.peer.take() {
-            Some(mut peer) => {
-                peer.merge(other_peer);
-                Some(peer)
-            }
+            Some(peer) => Some(P::consolidate(peer, other_peer)),
             None => Some(other_peer),
         };
     }
diff --git a/src/socket.rs b/src/socket.rs
index d219604..ca5dd1b 100644
--- a/src/socket.rs
+++ b/src/socket.rs
@@ -121,7 +121,7 @@ where
                                     // create a new stream for that connection. Otherwise, add the
                                     // connection to the incoming connections.
                                     if let Some(accept_with_cid) = awaiting.remove(&cid) {
-                                        peer.merge(accept_with_cid.peer);
+                                        peer.consolidate(accept_with_cid.peer);
 
                                         let (connected_tx, connected_rx) = oneshot::channel();
                                         let (events_tx, events_rx) = mpsc::unbounded_channel();
@@ -177,7 +177,7 @@ where
                             awaiting.insert(accept_with_cid.cid.clone(), accept_with_cid);
                             continue;
                         };
-                        peer.merge(accept_with_cid.peer);
+                        peer.consolidate(accept_with_cid.peer);
                         Self::select_accept_helper(accept_with_cid.cid, peer, syn, conns.clone(), accept_with_cid.accept, socket_event_tx.clone());
                     }
                     Some(accept) = accepts_rx.recv(), if !incoming_conns.is_empty() => {
diff --git a/src/testutils.rs b/src/testutils.rs
index 84cb3fd..2ea0f00 100644
--- a/src/testutils.rs
+++ b/src/testutils.rs
@@ -81,8 +81,9 @@ impl ConnectionPeer for char {
         *self
     }
 
-    fn merge(&mut self, other: Self) {
-        assert!(*self == other)
+    fn consolidate(a: Self, b: Self) -> Self {
+        assert!(a == b, "Consolidating non-equal peers");
+        a
     }
 }