v0.0.8: Server-side message deduplication

Server:
- DedupTracker in AppState: bounded HashSet (10,000 IDs, FIFO eviction)
- send_message: extracts message ID from bincode, drops duplicates
- WS handler: dedup on both binary and JSON message frames
- extract_message_id() parses all WireMessage variants

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/crates/warzone-server/src/state.rs

@@ -1,19 +1,57 @@
-use std::collections::HashMap;
+use std::collections::{HashMap, HashSet, VecDeque};
 use std::sync::Arc;
 use tokio::sync::{Mutex, mpsc};
 
 use crate::db::Database;
 
+/// Maximum number of message IDs to track for deduplication.
+const DEDUP_CAPACITY: usize = 10_000;
+
 /// Per-connection sender: messages are pushed here for instant delivery.
 pub type WsSender = mpsc::UnboundedSender<Vec<u8>>;
 
 /// Connected clients: fingerprint → list of WS senders (multiple devices).
 pub type Connections = Arc<Mutex<HashMap<String, Vec<WsSender>>>>;
 
+/// Bounded dedup tracker: FIFO eviction when capacity is exceeded.
+#[derive(Clone)]
+pub struct DedupTracker {
+    seen: Arc<std::sync::Mutex<HashSet<String>>>,
+    order: Arc<std::sync::Mutex<VecDeque<String>>>,
+}
+
+impl DedupTracker {
+    pub fn new() -> Self {
+        DedupTracker {
+            seen: Arc::new(std::sync::Mutex::new(HashSet::with_capacity(DEDUP_CAPACITY))),
+            order: Arc::new(std::sync::Mutex::new(VecDeque::with_capacity(DEDUP_CAPACITY))),
+        }
+    }
+
+    /// Returns `true` if this ID was already seen (i.e. it is a duplicate).
+    /// If new, inserts it and evicts the oldest if over capacity.
+    pub fn check_and_insert(&self, id: &str) -> bool {
+        let mut seen = self.seen.lock().unwrap();
+        if seen.contains(id) {
+            return true; // duplicate
+        }
+        let mut order = self.order.lock().unwrap();
+        if seen.len() >= DEDUP_CAPACITY {
+            if let Some(oldest) = order.pop_front() {
+                seen.remove(&oldest);
+            }
+        }
+        seen.insert(id.to_string());
+        order.push_back(id.to_string());
+        false // not a duplicate
+    }
+}
+
 #[derive(Clone)]
 pub struct AppState {
     pub db: Arc<Database>,
     pub connections: Connections,
+    pub dedup: DedupTracker,
 }
 
 impl AppState {
@@ -22,6 +60,7 @@ impl AppState {
         Ok(AppState {
             db: Arc::new(db),
             connections: Arc::new(Mutex::new(HashMap::new())),
+            dedup: DedupTracker::new(),
         })
     }