feat: resource cache

Signed-off-by: Attila Mészáros <[email protected]>

Author: csviri

Diff for: operator-framework-core/src/main/java/io/javaoperatorsdk/operator/processing/support/ResourceCache.java

@@ -0,0 +1,55 @@
+package io.javaoperatorsdk.operator.processing.support;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.function.BiPredicate;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.ResourceID;
+
+public class ResourceCache<P extends HasMetadata> {
+
+  private BiPredicate<Pair<P>, P> evictionPredicate;
+  private ConcurrentHashMap<ResourceID, Pair<P>> cache = new ConcurrentHashMap<>();
+
+  public ResourceCache(BiPredicate<Pair<P>, P> evictionPredicate) {
+    this.evictionPredicate = evictionPredicate;
+  }
+
+  public void cacheResource(P beforeUpdate, P afterUpdate) {
+    var resourceId = ResourceID.fromResource(beforeUpdate);
+    cache.put(resourceId, new Pair<>(beforeUpdate, afterUpdate));
+  }
+
+  public P getFreshResource(P newVersion) {
+    var resourceId = ResourceID.fromResource(newVersion);
+    var pair = cache.get(resourceId);
+    if (pair == null) {
+      return newVersion;
+    }
+    if (evictionPredicate.test(pair, newVersion)) {
+      cache.remove(resourceId);
+      return newVersion;
+    } else {
+      return pair.afterUpdate();
+    }
+  }
+
+  public record Pair<T extends HasMetadata>(T beforeUpdate, T afterUpdate) {}
+
+  public static class ResourceVersionComparePredicate<T extends HasMetadata>
+      implements BiPredicate<Pair<T>, T> {
+    @Override
+    public boolean test(Pair<T> updatePair, T newVersion) {
+      return Long.parseLong(updatePair.afterUpdate().getMetadata().getResourceVersion())
+          <= Long.parseLong(newVersion.getMetadata().getResourceVersion());
+    }
+  }
+
+  public static class ResourceVersionEqualityPredicate<T extends HasMetadata>
+      implements BiPredicate<Pair<T>, T> {
+    @Override
+    public boolean test(Pair<T> updatePair, T newVersion) {
+      return !updatePair.beforeUpdate().equals(newVersion.getMetadata().getResourceVersion());
+    }
+  }
+}