Fix BLE identity state races

bitchatTests/Services/BLEAnnounceThrottleTests.swift

@@ -5,7 +5,7 @@ import Testing
 struct BLEAnnounceThrottleTests {
     @Test
     func firstAnnounceIsAllowed() {
-        var throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
+        let throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
 
         let shouldSend = throttle.shouldSend(force: false, now: Date(timeIntervalSince1970: 100))
 
@@ -15,7 +15,7 @@ struct BLEAnnounceThrottleTests {
     @Test
     func regularAnnounceUsesNormalMinimumInterval() {
         let now = Date(timeIntervalSince1970: 100)
-        var throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
+        let throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
 
         let first = throttle.shouldSend(force: false, now: now)
         let suppressed = throttle.shouldSend(force: false, now: now.addingTimeInterval(9.9))
@@ -29,7 +29,7 @@ struct BLEAnnounceThrottleTests {
     @Test
     func forcedAnnounceUsesShorterMinimumInterval() {
         let now = Date(timeIntervalSince1970: 100)
-        var throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
+        let throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
 
         let first = throttle.shouldSend(force: false, now: now)
         let suppressed = throttle.shouldSend(force: true, now: now.addingTimeInterval(1.9))
@@ -43,10 +43,40 @@ struct BLEAnnounceThrottleTests {
     @Test
     func elapsedReportsTimeSinceAcceptedSend() {
         let now = Date(timeIntervalSince1970: 100)
-        var throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
+        let throttle = BLEAnnounceThrottle(normalMinimumInterval: 10, forcedMinimumInterval: 2)
 
         _ = throttle.shouldSend(force: false, now: now)
 
         #expect(throttle.elapsed(since: now.addingTimeInterval(3)) == 3)
     }
+
+    @Test
+    func concurrentRequestsAdmitOnlyOneAnnounce() {
+        let now = Date(timeIntervalSince1970: 100)
+        let throttle = BLEAnnounceThrottle(
+            normalMinimumInterval: 10,
+            forcedMinimumInterval: 2
+        )
+        let accepted = LockedCounter()
+
+        DispatchQueue.concurrentPerform(iterations: 1_000) { _ in
+            if throttle.shouldSend(force: false, now: now) {
+                accepted.increment()
+            }
+        }
+
+        #expect(accepted.value == 1)
+        #expect(throttle.elapsed(since: now.addingTimeInterval(3)) == 3)
+    }
+}
+
+private final class LockedCounter: @unchecked Sendable {
+    private let lock = NSLock()
+    private var count = 0
+
+    var value: Int { lock.withLock { count } }
+
+    func increment() {
+        lock.withLock { count += 1 }
+    }
 }