+/*
+ * Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.yangtools.yang.data.impl.schema.tree;
+
+import com.google.common.base.Optional;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
+import org.opendaylight.yangtools.yang.data.api.schema.ContainerNode;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNodeContainer;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.DataValidationFailedException;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.ModificationType;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.TreeType;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.spi.TreeNode;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.spi.TreeNodeFactory;
+import org.opendaylight.yangtools.yang.data.api.schema.tree.spi.Version;
+import org.opendaylight.yangtools.yang.data.impl.schema.ImmutableNodes;
+import org.opendaylight.yangtools.yang.model.api.ContainerSchemaNode;
+
+/**
+ * Structural containers are special in that they appear when implied by child
+ * nodes and disappear whenever they are empty. We could implement this as a
+ * subclass of {@link SchemaAwareApplyOperation}, but the automatic semantic
+ * is quite different from all the other strategies. We create a
+ * {@link PresenceContainerModificationStrategy} to tap into that logic, but
+ * wrap it so we only call out into it
+ */
+final class StructuralContainerModificationStrategy extends ModificationApplyOperation {
+ /**
+ * Fake TreeNode version used in {@link #checkApplicable(YangInstanceIdentifier, NodeModification, Optional)}.
+ * It is okay to use a global constant, as the delegate will ignore it anyway. For
+ * {@link #apply(ModifiedNode, Optional, Version)} we will use the appropriate version as provided to us.
+ */
+ private static final Version FAKE_VERSION = Version.initial();
+ private final PresenceContainerModificationStrategy delegate;
+
+ StructuralContainerModificationStrategy(final ContainerSchemaNode schemaNode, final TreeType treeType) {
+ this.delegate = new PresenceContainerModificationStrategy(schemaNode, treeType);
+ }
+
+ private Optional<TreeNode> fakeMeta(final Version version) {
+ final ContainerNode container = ImmutableNodes.containerNode(delegate.getSchema().getQName());
+ return Optional.of(TreeNodeFactory.createTreeNode(container, version));
+ }
+
+ @Override
+ Optional<TreeNode> apply(final ModifiedNode modification, final Optional<TreeNode> storeMeta, final Version version) {
+ final Optional<TreeNode> ret;
+ if (modification.getOperation() == LogicalOperation.TOUCH && !storeMeta.isPresent()) {
+ // Container is not present, let's take care of the 'magically appear' part of our job
+ ret = delegate.apply(modification, fakeMeta(version), version);
+
+ // Fake container got removed: that is a no-op
+ if (!ret.isPresent()) {
+ modification.resolveModificationType(ModificationType.UNMODIFIED);
+ return ret;
+ }
+
+ // If the delegate indicated SUBTREE_MODIFIED, account for the fake and report APPEARED
+ if (modification.getModificationType() == ModificationType.SUBTREE_MODIFIED) {
+ modification.resolveModificationType(ModificationType.APPEARED);
+ }
+ } else {
+ // Container is present, run normal apply operation
+ ret = delegate.apply(modification, storeMeta, version);
+
+ // Container was explicitly deleted, no magic required
+ if (!ret.isPresent()) {
+ return ret;
+ }
+ }
+
+ /*
+ * At this point ret is guaranteed to be present. We need to take care of the 'magically disappear' part of
+ * our job. Check if there are any child nodes left. If there are none, remove this container and turn the
+ * modification into a DISAPPEARED.
+ */
+ if (((NormalizedNodeContainer<?, ?, ?>) ret.get().getData()).getValue().isEmpty()) {
+ modification.resolveModificationType(ModificationType.DISAPPEARED);
+ return Optional.absent();
+ }
+
+ return ret;
+ }
+
+ @Override
+ void checkApplicable(final YangInstanceIdentifier path, final NodeModification modification, final Optional<TreeNode> current) throws DataValidationFailedException {
+ if (modification.getOperation() == LogicalOperation.TOUCH && !current.isPresent()) {
+ // Structural containers are created as needed, so we pretend this container is here
+ delegate.checkApplicable(path, modification, fakeMeta(FAKE_VERSION));
+ } else {
+ delegate.checkApplicable(path, modification, current);
+ }
+ }
+
+ @Override
+ void verifyStructure(final NormalizedNode<?, ?> modification, final boolean verifyChildren) throws IllegalArgumentException {
+ delegate.verifyStructure(modification, verifyChildren);
+ }
+
+ @Override
+ ChildTrackingPolicy getChildPolicy() {
+ return delegate.getChildPolicy();
+ }
+
+ @Override
+ public Optional<ModificationApplyOperation> getChild(final PathArgument child) {
+ return delegate.getChild(child);
+ }
+}