Adds rate limiting actor

src/main/java/eu/lucaventuri/fibry/Stereotypes.java

@@ -891,6 +891,43 @@ public Actor<HttpUrlDownload<byte[]>, Void, Void> binaryDownloader() {
             return binaryDownloader(new Scheduler(), 30, true);
         }
 
+        public <T> BaseActor<T, Void, Void> rateLimited(Consumer<T> actorLogic, int msBetweenCalls) {
+            NamedStateActorCreator<Void> config = anonymous().initialState(null);
+
+            Consumer<T> rateLimitedLogic = value -> {
+                long start = System.currentTimeMillis();
+
+                actorLogic.accept(value);
+
+                long end = System.currentTimeMillis() - start;
+
+                if (msBetweenCalls > (end - start))
+                    SystemUtils.sleep(msBetweenCalls - (end - start));
+            };
+
+            return config.newActor(rateLimitedLogic);
+        }
+
+        public <T, R> BaseActor<T, R, Void> rateLimitedReturn(Function<T, R> actorLogic, int msBetweenCalls) {
+            NamedStateActorCreator<Void> config = anonymous().initialState(null);
+
+            Function<T, R> rateLimitedLogic = value -> {
+                long start = System.currentTimeMillis();
+
+                R result = actorLogic.apply(value);
+
+                long end = System.currentTimeMillis();
+
+                if (msBetweenCalls > (end - start)) {
+                    SystemUtils.sleep(msBetweenCalls - (end - start));
+                }
+
+                return result;
+            };
+
+            return config.newActorWithReturn(rateLimitedLogic);
+        }
+
         /**
          * Process messages in batches, after grouping by the key and counting how many messages are received.
          * e.g. ['a', 'a', 'b', 'c', 'a'] would generate ['a':3, 'b':1, 'c':1]

src/test/java/eu/lucaventuri/fibry/TestStereotypes.java

@@ -816,4 +816,18 @@ public void testBytesDownloader() throws IOException, InterruptedException {
             server.stop(0);
         }
     }
+
+    @Test
+    public void testRateLimit() throws ExecutionException, InterruptedException {
+        long start = System.currentTimeMillis();
+
+        try (var actor = Stereotypes.auto().rateLimitedReturn(item -> 0, 20)) {
+            actor.sendMessageReturn("A");
+            actor.sendMessageReturn("B");
+            actor.sendMessageReturn("C").get();
+        }
+
+        var time = System.currentTimeMillis() - start;
+        assertTrue(time >= 60 );
+    }
 }