feat: re-add contextual map to context (#985)

Author: metacosm

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

@@ -2,22 +2,97 @@
 
 import java.util.Collections;
 import java.util.List;
+import java.util.Optional;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.stream.Collectors;
 
 import io.javaoperatorsdk.operator.OperatorException;
 
+/**
+ * Contextual information related to {@link DependentResource} either to retrieve the actual
+ * implementations to interact with them or to pass information between them and/or the reconciler
+ */
+@SuppressWarnings("rawtypes")
 public class ManagedDependentResourceContext {
 
-  private List<DependentResource> dependentResources;
+  private final List<DependentResource> dependentResources;
+  private final ConcurrentHashMap attributes = new ConcurrentHashMap();
+
+  /**
+   * Retrieve a contextual object, if it exists and is of the specified expected type, associated
+   * with the specified key. Contextual objects can be used to pass data between the reconciler and
+   * dependent resources and are scoped to the current reconciliation.
+   * 
+   * @param key the key identifying which contextual object to retrieve
+   * @param expectedType the class representing the expected type of the contextual object
+   * @param <T> the type of the expected contextual object
+   * @return an Optional containing the contextual object or {@link Optional#empty()} if no such
+   *         object exists or doesn't match the expected type
+   */
+  public <T> Optional<T> get(Object key, Class<T> expectedType) {
+    return Optional.ofNullable(attributes.get(key))
+        .filter(expectedType::isInstance)
+        .map(expectedType::cast);
+  }
+
+  /**
+   * Associates the specified contextual value to the specified key. If the value is {@code null},
+   * the semantics of this operation is defined as removing the mapping associated with the
+   * specified key.
+   * 
+   * @param key the key identifying which contextual object to add or remove from the context
+   * @param value the value to add to the context or {@code null} to remove an existing entry
+   *        associated with the specified key
+   * @return an Optional containing the previous value associated with the key or
+   *         {@link Optional#empty()} if none existed
+   */
+  @SuppressWarnings("unchecked")
+  public Optional put(Object key, Object value) {
+    if (value == null) {
+      return Optional.ofNullable(attributes.remove(key));
+    }
+    return Optional.ofNullable(attributes.put(key, value));
+  }
+
+  /**
+   * Retrieves the value associated with the key or fail with an exception if none exists.
+   *
+   * @param key the key identifying which contextual object to retrieve
+   * @param expectedType the expected type of the value to retrieve
+   * @param <T> the type of the expected contextual object
+   * @return the contextual object value associated with the specified key
+   * @see #get(Object, Class)
+   */
+  public <T> T getMandatory(Object key, Class<T> expectedType) {
+    return get(key, expectedType).orElseThrow(() -> new IllegalStateException(
+        "Mandatory attribute (key: " + key + ", type: " + expectedType.getName()
+            + ") is missing or not of the expected type"));
+  }
 
   public ManagedDependentResourceContext(List<DependentResource> dependentResources) {
-    this.dependentResources = dependentResources;
+    this.dependentResources = Collections.unmodifiableList(dependentResources);
   }
 
+  /**
+   * Retrieve all the known {@link DependentResource} implementations
+   * 
+   * @return a list of known {@link DependentResource} implementations
+   */
   public List<DependentResource> getDependentResources() {
-    return Collections.unmodifiableList(dependentResources);
+    return dependentResources;
   }
 
+  /**
+   * Retrieve the dependent resource implementation associated with the specified resource type.
+   * 
+   * @param resourceClass the dependent resource class for which we want to retrieve the associated
+   *        dependent resource implementation
+   * @param <T> the type of the resources for which we want to retrieve the associated dependent
+   *        resource implementation
+   * @return the associated dependent resource implementation if it exists or an exception if it
+   *         doesn't or several implementations are associated with the specified resource type
+   */
+  @SuppressWarnings("unchecked")
   public <T extends DependentResource> T getDependentResource(Class<T> resourceClass) {
     var resourceList =
         dependentResources.stream()