feat(distributed): learn our own upload speed by watching ourselves

The child limit is derived from the upload speed the server records for
us, and the server pushes a user's stats to whoever watches that user —
so a client that does not watch itself never learns its own figure and
would carry the default cap forever. Nicotine+ reads the same number off
the stats the server sends about the logged-in user.

We now watch ourselves as each session starts, and the stats that come
back — the initial reply and every later push — set the figure the limit
is derived from. Client::own_average_speed exposes it.

soulseek-rs-lib/src/client/mod.rs

@@ -821,6 +821,12 @@ impl ClientContext {
         self.own_interests.clone()
     }
 
+    /// The upload speed the server records for us, if it has said.
+    #[must_use]
+    pub const fn own_average_speed(&self) -> Option<u32> {
+        self.own_average_speed
+    }
+
     /// Record what the server says our own upload speed is, and re-derive the
     /// child limit from it.
     pub fn set_own_average_speed(&mut self, speed: u32) {

soulseek-rs-lib/src/client/operations.rs

@@ -443,17 +443,35 @@ impl Client {
                         average_speed,
                         shared_files,
                         shared_folders,
-                    } => match client_context.write_safe() {
-                        Ok(mut ctx) => ctx.apply_user_stats(
+                    } => {
+                        // Stats about ourselves carry the speed the server
+                        // records for us — pushed whenever it changes, since
+                        // we watch ourselves — and the distributed child
+                        // limit is derived from it.
+                        let own = username == own_username;
+                        match client_context.write_safe() {
+                            Ok(mut ctx) => {
+                                ctx.apply_user_stats(
                                     username,
                                     average_speed,
                                     shared_files,
                                     shared_folders,
-                        ),
+                                );
+                                if own {
+                                    ctx.set_own_average_speed(average_speed);
+                                }
+                            }
                             Err(e) => {
-                            error!("[client] UserStatsReceived write: {}", e);
+                                error!(
+                                    "[client] UserStatsReceived write: {}",
+                                    e
+                                );
+                            }
+                        }
+                        if own {
+                            Self::announce_child_capacity(&client_context);
+                        }
                     }
-                    },
                     ClientOperation::WatchedUserReceived {
                         username,
                         exists,
@@ -461,19 +479,36 @@ impl Client {
                         average_speed,
                         shared_files,
                         shared_folders,
-                    } => match client_context.write_safe() {
-                        Ok(mut ctx) => ctx.apply_watched_user(
+                    } => {
+                        let own = username == own_username;
+                        match client_context.write_safe() {
+                            Ok(mut ctx) => {
+                                ctx.apply_watched_user(
                                     username,
                                     exists,
                                     status,
                                     average_speed,
                                     shared_files,
                                     shared_folders,
-                        ),
+                                );
+                                // Watching ourselves is how our own recorded
+                                // speed reaches us, and the child limit is
+                                // derived from it.
+                                if own && let Some(speed) = average_speed {
+                                    ctx.set_own_average_speed(speed);
+                                }
+                            }
                             Err(e) => {
-                            error!("[client] WatchedUserReceived write: {}", e);
+                                error!(
+                                    "[client] WatchedUserReceived write: {}",
+                                    e
+                                );
+                            }
+                        }
+                        if own {
+                            Self::announce_child_capacity(&client_context);
+                        }
                     }
-                    },
                     ClientOperation::RoomEvent(event) => {
                         match client_context.write_safe() {
                             Ok(mut ctx) => ctx.apply_room_event(event),
@@ -930,6 +965,15 @@ impl Client {
                             Err(_) => continue,
                         };
                         let Some(sender) = sender else { continue };
+                        // Watch ourselves: the server pushes a user's stats
+                        // to whoever watches them, and our own recorded
+                        // upload speed is what the distributed child limit is
+                        // derived from. Nicotine+ reads the same figure from
+                        // the stats the server sends about the logged-in
+                        // user.
+                        let _ = sender.send(ServerMessage::SendMessage(
+                            MessageFactory::build_watch_user(&own_username),
+                        ));
                         for item in &interests.likes {
                             let _ = sender.send(ServerMessage::SendMessage(
                                 MessageFactory::build_add_thing_i_like(item),

soulseek-rs-lib/src/client/social.rs

@@ -327,6 +327,17 @@ impl Client {
         self.send_server_message(MessageFactory::build_global_recommendations())
     }
 
+    /// The upload speed the server records for us, once it has reported it.
+    /// It is what the distributed child limit is derived from, and it only
+    /// becomes known after an upload has finished and been reported.
+    #[must_use]
+    pub fn own_average_speed(&self) -> Option<u32> {
+        self.context
+            .read_safe()
+            .ok()
+            .and_then(|ctx| ctx.own_average_speed())
+    }
+
     /// What we ourselves like and hate, as set through this client. The
     /// server forgets these when the session ends, so they are re-sent after
     /// each login.

soulseek-rs-lib/tests/e2e.rs

@@ -5113,3 +5113,66 @@ fn our_interests_are_sent_again_after_a_new_login() {
         "a new session should carry the interests too, got {likes:?}"
     );
 }
+
+#[test]
+fn a_finished_upload_teaches_us_our_own_recorded_speed() {
+    // The server records a client's upload speed and pushes it to whoever
+    // watches that user. We watch ourselves at login, which is how our own
+    // figure — the one the distributed child limit is derived from — reaches
+    // us without anyone asking on our behalf.
+    let server = server_or_skip!();
+
+    let share_dir = unique_download_dir();
+    let content: Vec<u8> = (0..8192u32).map(|i| (i % 251) as u8).collect();
+    let filename = "e2e_ownspeed_probe.bin";
+    std::fs::write(share_dir.join(filename), &content).unwrap();
+
+    let (sharer, leecher) = sharer_and_searcher(
+        &server,
+        &share_dir,
+        "e2e_ownspeed_sharer",
+        "e2e_ownspeed_leecher",
+    );
+    assert_eq!(
+        sharer.own_average_speed(),
+        Some(0),
+        "a client that has never uploaded is recorded at zero"
+    );
+
+    let query = "ownspeed";
+    let _ = leecher.search(query, Duration::from_secs(3));
+    let (path, size) = reply_from(&leecher, query, "e2e_ownspeed_sharer")
+        .and_then(|reply| reply.files.into_iter().next())
+        .map(|file| (file.name, file.size))
+        .expect("the leecher should find the file");
+
+    let download_dir = unique_download_dir();
+    let (_download, status_rx) = leecher
+        .download(
+            path,
+            "e2e_ownspeed_sharer".to_string(),
+            size,
+            download_dir.display().to_string(),
+        )
+        .expect("start download");
+    assert!(
+        wait_for_completion(&leecher, &status_rx, Duration::from_secs(25)),
+        "the download should complete"
+    );
+
+    let deadline = Instant::now() + Duration::from_secs(15);
+    while Instant::now() < deadline
+        && sharer.own_average_speed().unwrap_or(0) == 0
+    {
+        std::thread::sleep(Duration::from_millis(250));
+    }
+    assert!(
+        sharer.own_average_speed().unwrap_or(0) > 0,
+        "the speed the server recorded for us should reach us unasked, got          {:?} (info: {:?})",
+        sharer.own_average_speed(),
+        sharer.user_info("e2e_ownspeed_sharer"),
+    );
+
+    let _ = std::fs::remove_dir_all(share_dir);
+    let _ = std::fs::remove_dir_all(download_dir);
+}