improve: discriminator improvements

operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/IndexDiscriminator.java

@@ -0,0 +1,45 @@
+package io.javaoperatorsdk.operator.api.reconciler;
+
+import java.util.Optional;
+import java.util.function.Function;
+
+import io.fabric8.kubernetes.api.model.HasMetadata;
+import io.javaoperatorsdk.operator.processing.event.source.informer.InformerEventSource;
+
+public class IndexDiscriminator<R extends HasMetadata, P extends HasMetadata>
+    implements ResourceDiscriminator<R, P> {
+
+  private final String indexName;
+  private final String eventSourceName;
+  private final Function<P, String> keyMapper;
+
+  public IndexDiscriminator(String indexName, Function<P, String> keyMapper) {
+    this(indexName, null, keyMapper);
+  }
+
+  public IndexDiscriminator(String indexName, String eventSourceName,
+      Function<P, String> keyMapper) {
+    this.indexName = indexName;
+    this.eventSourceName = eventSourceName;
+    this.keyMapper = keyMapper;
+  }
+
+  @Override
+  public Optional<R> distinguish(Class<R> resource,
+      P primary,
+      Context<P> context) {
+
+    InformerEventSource<R, P> eventSource =
+        (InformerEventSource<R, P>) context
+            .eventSourceRetriever()
+            .getResourceEventSourceFor(resource, eventSourceName);
+    var resources = eventSource.byIndex(indexName, keyMapper.apply(primary));
+    if (resources.isEmpty()) {
+      return Optional.empty();
+    } else if (resources.size() > 1) {
+      throw new IllegalStateException("More than one resource found");
+    } else {
+      return Optional.of(resources.get(0));
+    }
+  }
+}

operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/indexdiscriminator/IndexDiscriminatorTestReconciler.java

@@ -81,10 +81,10 @@ public Map<String, EventSource> prepareEventSources(
 
     firstDependentResourceConfigMap
         .setResourceDiscriminator(
-            new IndexDiscriminator(CONFIG_MAP_INDEX_1, FIRST_CONFIG_MAP_SUFFIX_1));
+            new TestIndexDiscriminator(CONFIG_MAP_INDEX_1, FIRST_CONFIG_MAP_SUFFIX_1));
     secondDependentResourceConfigMap
         .setResourceDiscriminator(
-            new IndexDiscriminator(CONFIG_MAP_INDEX_2, FIRST_CONFIG_MAP_SUFFIX_2));
+            new TestIndexDiscriminator(CONFIG_MAP_INDEX_2, FIRST_CONFIG_MAP_SUFFIX_2));
     return EventSourceInitializer.nameEventSources(eventSource);
   }
 

operator-framework/src/test/java/io/javaoperatorsdk/operator/sample/indexdiscriminator/TestIndexDiscriminator.java

@@ -0,0 +1,14 @@
+package io.javaoperatorsdk.operator.sample.indexdiscriminator;
+
+import io.fabric8.kubernetes.api.model.ConfigMap;
+import io.javaoperatorsdk.operator.api.reconciler.IndexDiscriminator;
+
+import static io.javaoperatorsdk.operator.sample.indexdiscriminator.IndexDiscriminatorTestReconciler.configMapKeyFromPrimary;
+
+public class TestIndexDiscriminator
+    extends IndexDiscriminator<ConfigMap, IndexDiscriminatorTestCustomResource> {
+
+  public TestIndexDiscriminator(String indexName, String nameSuffix) {
+    super(indexName, p -> configMapKeyFromPrimary(p, nameSuffix));
+  }
+}