tinyzero4 · October 5, 2023 14:57 · Oct 5, 2023
diff --git a/Tracker.java b/Tracker.java
@@ -0,0 +1,49 @@
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentSkipListSet;
+import java.util.concurrent.atomic.AtomicInteger;
+
+import static java.lang.Integer.parseInt;
+import static java.util.Objects.requireNonNull;
+
+public class Tracker {
+
+    private final ConcurrentHashMap<String, AtomicInteger> byTypeCounters = new ConcurrentHashMap<>();
+    private final ConcurrentHashMap<String, ConcurrentSkipListSet<Integer>> byTypeDeAllocations = new ConcurrentHashMap<>();
+
+    public String allocate(String hostType) {
+        requireNonNull(hostType);
+        if (hostType.isBlank()) throw new IllegalArgumentException("hostType should not be blank");
+
+        Integer nextVersion = null;
+
+        var deallocations = byTypeDeAllocations.get(hostType);
+        if (deallocations != null) {
+            nextVersion = deallocations.pollFirst();
+        }
+
+        if (nextVersion == null) {
+            var byTypeCounter = byTypeCounters.getOrDefault(hostType, new AtomicInteger(0));
+            nextVersion = byTypeCounter.incrementAndGet();
+            byTypeCounters.put(hostType, byTypeCounter);
+        }
+
+        return hostType + ":" + nextVersion;
+    }
+
+    public void deallocate(String hostname) {
+        requireNonNull(hostname);
+        if (hostname.isBlank()) throw new IllegalArgumentException("hostname should not be blank");
+
+        var parts = hostname.split(":");
+        if (parts.length != 2) throw new IllegalArgumentException("invalid hostname definition");
+
+        var hostType = parts[0];
+        var version = parseInt(parts[1]);
+
+        var deallocations = byTypeDeAllocations.getOrDefault(hostType, new ConcurrentSkipListSet<>());
+        deallocations.add(version);
+        byTypeDeAllocations.put(hostType, deallocations);
+
+    }
+
+}