fix: add sequence numbers and sender timestamps for message ordering (#7)

src-tauri/src/commands/messaging.rs

@@ -22,6 +22,10 @@ struct WireMessage<'a> {
     id: &'a str,
     ct: String,
     n: u32,
+    /// Sender-side sequence number for ordering enforcement
+    seq: u64,
+    /// Sender-side unix timestamp (seconds) for cross-peer consistency
+    ts: u64,
 }
 
 /// Encrypt and send a message to the active peer.
@@ -38,20 +42,25 @@ pub async fn send_message(
     let id = uuid::Uuid::new_v4().to_string();
     let now = now_secs();
 
-    let (ct, counter) = {
+    let (ct, counter, seq) = {
         let mut sess = state.session.lock().await;
         let session = sess.as_mut().ok_or("no active session")?;
-        session
+        let (ct, counter) = session
             .ratchet
             .encrypt(content.as_bytes())
-            .map_err(|e| e.to_string())?
+            .map_err(|e| e.to_string())?;
+        let seq = session.send_seq;
+        session.send_seq += 1;
+        (ct, counter, seq)
     };
 
     let wire = serde_json::to_vec(&WireMessage {
         t: "msg",
         id: &id,
         ct: B64.encode(&ct),
         n: counter,
+        seq,
+        ts: now,
     })
     .map_err(|e| e.to_string())?;
 

src-tauri/src/commands/session.rs

@@ -307,6 +307,8 @@ async fn handle_incoming(
         ratchet,
         stream_writer: writer,
         started_at: now_secs(),
+        send_seq: 0,
+        recv_seq: 0,
     });
 
     // Emit session established event
@@ -418,6 +420,8 @@ pub async fn initiate_session(
         ratchet,
         stream_writer: writer,
         started_at: now_secs(),
+        send_seq: 0,
+        recv_seq: 0,
     });
 
     let _ = app.emit("session_established", serde_json::json!({ "peer_dest": peer_dest }));
@@ -460,6 +464,12 @@ struct WireMessage {
     id: String,
     ct: String,
     n: u32,
+    /// Sender-side sequence number for ordering enforcement
+    #[serde(default)]
+    seq: u64,
+    /// Sender-side unix timestamp (seconds)
+    #[serde(default)]
+    ts: u64,
 }
 
 async fn handle_incoming_message(app: &AppHandle, frame: &[u8]) -> anyhow::Result<()> {
@@ -478,6 +488,21 @@ async fn handle_incoming_message(app: &AppHandle, frame: &[u8]) -> anyhow::Resul
     let plaintext_buf = {
         let mut sess = state.session.lock().await;
         let session = sess.as_mut().ok_or_else(|| anyhow::anyhow!("no session"))?;
+
+        // Enforce message ordering via sender sequence number
+        if wire.seq != session.recv_seq {
+            log::warn!(
+                "out-of-order message: expected seq={}, got seq={}",
+                session.recv_seq,
+                wire.seq
+            );
+            // Still process but warn — I2P may reorder occasionally
+        }
+        // Advance expected sequence to the maximum seen + 1
+        if wire.seq >= session.recv_seq {
+            session.recv_seq = wire.seq + 1;
+        }
+
         session.ratchet.decrypt(&ct, wire.n)?
     };
 
@@ -489,11 +514,14 @@ async fn handle_incoming_message(app: &AppHandle, frame: &[u8]) -> anyhow::Resul
         0
     };
 
+    // Use sender timestamp if provided, fall back to local time
+    let msg_timestamp = if wire.ts > 0 { wire.ts } else { now };
+
     let entry = MessageEntry {
         id: wire.id.clone(),
         content: SecureBuffer::from_slice(content.as_bytes()),
         is_mine: false,
-        timestamp: now,
+        timestamp: msg_timestamp,
         expires_at,
     };
     // Wipe plaintext intermediate — the content now lives only in SecureBuffer

src-tauri/src/state.rs

@@ -53,6 +53,10 @@ pub struct ActiveSession {
     /// Write half of the active I2P tunnel stream.
     pub stream_writer: WriteHalf<TcpStream>,
     pub started_at: u64,
+    /// Monotonic send-side sequence number for message ordering.
+    pub send_seq: u64,
+    /// Expected next receive-side sequence number for ordering enforcement.
+    pub recv_seq: u64,
 }
 
 // ── Settings ──────────────────────────────────────────────────────────────────

src/components/ChatWindow.tsx

@@ -95,9 +95,15 @@ export default function ChatWindow() {
     );
   }
 
+  // Sort messages by timestamp then by id for consistent ordering
+  const sorted = [...state.messages].sort((a, b) => {
+    if (a.timestamp !== b.timestamp) return a.timestamp - b.timestamp;
+    return a.id.localeCompare(b.id);
+  });
+
   return (
     <div className="flex-1 overflow-y-auto px-4 py-3 flex flex-col gap-2">
-      {state.messages.map((msg) => (
+      {sorted.map((msg) => (
         <MessageBubble key={msg.id} msg={msg} />
       ))}
       <div ref={bottomRef} />