fix(lib): advertise real slot, speed and queue figures in search replies

Every reply to a peer's search claimed a free upload slot, no speed and
an empty queue, whatever the sharer was doing, and searchers rank
sources on exactly those fields. A reply now says whether a slot is
free, the bytes per second of the last completed upload, and how many
uploads are waiting.

soulseek-rs-lib/examples/stress.rs

@@ -415,7 +415,7 @@ impl SeederState {
             })
             .collect();
         let response =
-            build_file_search_response(&self.name, token, &entries, 1, 0);
+            build_file_search_response(&self.name, token, &entries, 1, 0, 0);
 
         let Ok(mut guard) = self.conn.lock() else {
             return;

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

@@ -150,6 +150,9 @@ fn build_search_response(
     own_username: &str,
     token: u32,
     query: &str,
+    free_slot: bool,
+    speed: u32,
+    queue_length: u32,
 ) -> Option<crate::message::Message> {
     let matches = shares.search(query);
     if matches.is_empty() {
@@ -168,8 +171,9 @@ fn build_search_response(
         own_username,
         token,
         &entries,
-        1,
-        0,
+        u8::from(free_slot),
+        speed,
+        queue_length,
     ))
 }
 
@@ -376,6 +380,9 @@ pub struct ClientContext {
     upload_seq: u64,
     /// How many uploads may be in flight at once.
     upload_slots: usize,
+    /// Bytes per second of the last completed upload, advertised in search
+    /// replies; zero until one has finished.
+    last_upload_speed: u32,
     /// Queued-upload states that came and went between two polls of
     /// [`Client::uploads`]. A caller sampling that snapshot would otherwise
     /// never see a peer that queued and was served inside one poll interval,
@@ -458,6 +465,7 @@ impl ClientContext {
             upload_queue: Vec::new(),
             upload_seq: 0,
             upload_slots: DEFAULT_UPLOAD_SLOTS,
+            last_upload_speed: 0,
             upload_events: Vec::new(),
             downloads: DownloadStore::new(),
             actor_system,

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

@@ -593,6 +593,9 @@ impl Client {
                                 &own_username,
                                 token,
                                 &query,
+                                ctx.has_free_upload_slot(),
+                                ctx.last_upload_speed,
+                                ctx.upload_queue.len() as u32,
                             ),
                             Err(e) => {
                                 error!("[client] IncomingSearch read: {}", e);

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

@@ -160,8 +160,9 @@ fn build_search_response_matches_shares_and_echoes_token() {
     std::fs::write(dir.join("probe_xyzzy.bin"), b"data").unwrap();
     let shares = Shares::scan(&dir).unwrap();
 
-    let response = build_search_response(&shares, "me", 99, "xyzzy")
-        .expect("a matching share yields a response");
+    let response =
+        build_search_response(&shares, "me", 99, "xyzzy", true, 0, 0)
+            .expect("a matching share yields a response");
     let mut decoded =
         crate::message::Message::new_with_data(response.get_buffer());
     decoded.set_pointer(8);
@@ -170,7 +171,10 @@ fn build_search_response_matches_shares_and_echoes_token() {
     assert_eq!(result.token, 99);
     assert!(result.files.iter().any(|f| f.name.contains("probe_xyzzy")));
 
-    assert!(build_search_response(&shares, "me", 1, "nomatch").is_none());
+    assert!(
+        build_search_response(&shares, "me", 1, "nomatch", true, 0, 0)
+            .is_none()
+    );
     let _ = std::fs::remove_dir_all(dir);
 }
 

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

@@ -123,7 +123,7 @@ impl ClientContext {
         mut next_token: impl FnMut() -> u32,
     ) -> (Option<PeerRegistry>, Vec<UploadOffer>) {
         let mut offers = Vec::new();
-        while self.uploads_in_flight() < self.upload_slots {
+        while self.has_free_upload_slot() {
             let Some(index) = next_to_serve(&self.upload_queue) else {
                 break;
             };
@@ -190,6 +190,10 @@ impl ClientContext {
                 .count()
     }
 
+    pub(super) fn has_free_upload_slot(&self) -> bool {
+        self.uploads_in_flight() < self.upload_slots
+    }
+
     /// The peers still waiting, in the order they will be served, each carrying
     /// its own 1-based place.
     pub(super) fn queued_uploads(&self) -> Vec<UploadInfo> {

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

@@ -145,8 +145,9 @@ impl Client {
                 &bytes_sent,
                 &cancel,
             );
+            let streamed = result.as_ref().ok().copied();
             let status = match &result {
-                Ok(()) => UploadStatus::Completed,
+                Ok(_) => UploadStatus::Completed,
                 Err(e) if e.kind() == std::io::ErrorKind::Interrupted => {
                     UploadStatus::Cancelled
                 }
@@ -158,7 +159,13 @@ impl Client {
             if let Ok(mut ctx) = context.write_safe()
                 && let Some(upload) = ctx.active_uploads.get_mut(&token)
             {
+                let secs = upload.started.elapsed().as_secs_f64();
                 upload.status = status;
+                if let Some(bytes) = streamed
+                    && secs > 0.0
+                {
+                    ctx.last_upload_speed = (bytes as f64 / secs) as u32;
+                }
             }
             // The slot this transfer held is free now, so whoever is next in
             // line gets it without waiting for another request to arrive.

soulseek-rs-lib/src/message/peer/file_search_response.rs

@@ -22,6 +22,7 @@ pub fn build_file_search_response(
     files: &[FileEntry],
     slots: u8,
     speed: u32,
+    queue_length: u32,
 ) -> Message {
     let mut payload = Message::new();
     payload
@@ -39,7 +40,10 @@ pub fn build_file_search_response(
             payload.write_int32(code).write_int32(value);
         }
     }
-    payload.write_int8(slots).write_int32(speed).write_int32(0); // free upload slots / queue length (well-formed trailer)
+    payload
+        .write_int8(slots)
+        .write_int32(speed)
+        .write_int32(queue_length);
 
     let compressed = compress_stored(&payload.get_data());
     Message::new()
@@ -112,7 +116,7 @@ fn build_file_search_response_roundtrips_through_the_decoder() {
             attribs: &[],
         },
     ];
-    let message = build_file_search_response("e2e_sharer", 42, &files, 1, 0);
+    let message = build_file_search_response("e2e_sharer", 42, &files, 1, 0, 0);
 
     // Decode via the exact production decoder used for real peer responses:
     // the dispatcher positions the pointer at 8 (past length + code).
@@ -132,3 +136,18 @@ fn build_file_search_response_roundtrips_through_the_decoder() {
     assert!(result.files[1].attribs.is_empty());
     assert_eq!(result.slots, 1);
 }
+
+#[test]
+fn the_trailer_carries_slots_speed_and_queue_length() {
+    let message = build_file_search_response("me", 1, &[], 0, 900, 7);
+    let mut body = Message::new_with_data(
+        crate::utils::zlib::deflate(&message.get_data()[4..]).unwrap(),
+    );
+    body.read_string();
+    body.read_int32();
+    assert_eq!(body.read_int32(), 0, "no files");
+    assert_eq!(
+        (body.read_int8(), body.read_int32(), body.read_int32()),
+        (0, 900, 7)
+    );
+}

soulseek-rs-lib/src/peer/upload_peer.rs

@@ -19,7 +19,8 @@ use crate::trace;
 /// START_DOWNLOAD offset before we stream the file.
 ///
 /// `bytes_sent` is updated as the transfer progresses, and setting `cancel`
-/// aborts the stream with an [`io::ErrorKind::Interrupted`] error.
+/// aborts the stream with an [`io::ErrorKind::Interrupted`] error. Returns the
+/// bytes streamed by this call, which a resumed transfer's prefix is not.
 ///
 /// # Errors
 /// Returns any I/O error opening the file or talking to the peer.
@@ -31,7 +32,7 @@ pub fn serve_file(
     path: &Path,
     bytes_sent: &AtomicU64,
     cancel: &AtomicBool,
-) -> io::Result<()> {
+) -> io::Result<u64> {
     let mut file = File::open(path)?;
 
     let socket = format!("{host}:{port}")
@@ -78,6 +79,7 @@ pub fn serve_file(
     }
 
     let mut buffer = vec![0u8; 64 * 1024];
+    let mut streamed = 0u64;
     loop {
         if cancel.load(Ordering::Relaxed) {
             return Err(io::Error::new(
@@ -91,6 +93,7 @@ pub fn serve_file(
         }
         stream.write_all(&buffer[..read])?;
         bytes_sent.fetch_add(read as u64, Ordering::Relaxed);
+        streamed += read as u64;
     }
     stream.flush()?;
 
@@ -100,7 +103,7 @@ pub fn serve_file(
     // a slot cap is time no other peer can use.
     stream.shutdown(std::net::Shutdown::Write).ok();
     trace!("[upload] served {} to {}:{}", path.display(), host, port);
-    Ok(())
+    Ok(streamed)
 }
 
 #[cfg(test)]

soulseek-rs-lib/tests/e2e.rs

@@ -1761,6 +1761,15 @@ fn two_real_clients_search_and_download() {
     assert_eq!(upload.username, "e2e_leecher");
     assert_eq!(upload.bytes_sent, size);
 
+    // The next reply advertises what that upload measured.
+    let _ = leecher.search(query, Duration::from_secs(1));
+    let reply = reply_from(&leecher, query, "e2e_sharer")
+        .expect("the sharer answers again");
+    assert!(
+        reply.speed > 0,
+        "a finished upload sets the advertised speed"
+    );
+
     let _ = std::fs::remove_dir_all(share_dir);
     let _ = std::fs::remove_dir_all(download_dir);
 }
@@ -3127,3 +3136,47 @@ fn two_live_searches_never_share_a_token() {
 
     let _ = std::fs::remove_dir_all(share_dir);
 }
+
+// Searchers pick sources by the free-slot flag in a reply, and every reply
+// said "free" whatever the queue looked like.
+#[test]
+fn a_search_reply_reports_no_free_slot_while_the_only_slot_is_taken() {
+    let server = server_or_skip!();
+    let (share, folder) =
+        queue_share("honest", &["blocker.mp3", "probe_honest.bin"]);
+    let (sharer, searcher) = sharer_and_searcher(
+        &server,
+        &share,
+        "e2e_honest_sharer",
+        "e2e_honest_searcher",
+    );
+    sharer.set_upload_slots(1);
+
+    let query = "probe_honest";
+    let _ = searcher.search(query, Duration::from_secs(1));
+    let reply = reply_from(&searcher, query, "e2e_honest_sharer")
+        .expect("the sharer answers");
+    assert_eq!(reply.slots, 1, "nothing is uploading yet");
+
+    let server_addr = format!("{}:{}", server.host, server.port);
+    let listen_addr =
+        format!("127.0.0.1:{}", sharer.listen_port().expect("listening"));
+    let mut blocker = queue_as(
+        &server_addr,
+        &listen_addr,
+        "e2e_honest_blocker",
+        &format!("{folder}\\blocker.mp3"),
+    )
+    .expect("blocker queues");
+    assert!(
+        blocker.takes_a_slot(),
+        "the blocker is offered the only slot"
+    );
+
+    let _ = searcher.search(query, Duration::from_secs(1));
+    let reply = reply_from(&searcher, query, "e2e_honest_sharer")
+        .expect("the sharer answers again");
+    assert_eq!(reply.slots, 0, "the only slot is taken");
+
+    let _ = std::fs::remove_dir_all(share);
+}