Add MountPointNormalizedNodeWriter

With the advent of MountMointNode a NormalizedNode tree can contain
nested mount point data, which is not quite a regular node.

This patch introduces a utility NormalizedNodeWriter, which can
either filter or forward MountPointNodes through a NormalizedNode
stream.

JIRA: YANGTOOLS-1010
Change-Id: Ie8cf6efa0874864461aa761b8a9c6e74a250bbac
Signed-off-by: Robert Varga <robert.varga@pantheon.tech>

diff --git a/yang/rfc8528-data-util/src/main/java/org/opendaylight/yangtools/rcf8528/data/util/MountPointNormalizedNodeWriter.java b/yang/rfc8528-data-util/src/main/java/org/opendaylight/yangtools/rcf8528/data/util/MountPointNormalizedNodeWriter.java
new file mode 100644 (file)
index 0000000..980f8b2
--- /dev/null
+++ b/yang/rfc8528-data-util/src/main/java/org/opendaylight/yangtools/rcf8528/data/util/MountPointNormalizedNodeWriter.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright (c) 2019 PANTHEON.tech, s.r.o. 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.rcf8528.data.util;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static java.util.Objects.requireNonNull;
+
+import com.google.common.annotations.Beta;
+import java.io.IOException;
+import org.eclipse.jdt.annotation.NonNull;
+import org.opendaylight.yangtools.rfc8528.data.api.MountPointNode;
+import org.opendaylight.yangtools.rfc8528.data.api.MountPointStreamWriter;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier.PathArgument;
+import org.opendaylight.yangtools.yang.data.api.schema.DataContainerChild;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeStreamWriter;
+import org.opendaylight.yangtools.yang.data.api.schema.stream.NormalizedNodeWriter;
+
+/**
+ * A {@link MountPointNode}-aware counterpart to {@link NormalizedNodeWriter}. Based on the backing writer's capability
+ * it either forwards or filters MountPointNodes.
+ */
+@Beta
+public abstract class MountPointNormalizedNodeWriter extends NormalizedNodeWriter {
+    private static final class Filtering extends MountPointNormalizedNodeWriter {
+        Filtering(final NormalizedNodeStreamWriter writer) {
+            super(writer);
+        }
+
+        @Override
+        void writeMountPoint(final MountPointNode node) {
+            // No-op
+        }
+    }
+
+    private static final class Forwarding extends MountPointNormalizedNodeWriter {
+        private final MountPointStreamWriter mountWriter;
+
+        Forwarding(final NormalizedNodeStreamWriter writer, final MountPointStreamWriter mountWriter) {
+            super(writer);
+            this.mountWriter = requireNonNull(mountWriter);
+        }
+
+        @Override
+        void writeMountPoint(final MountPointNode node) throws IOException {
+            try (MountPointNormalizedNodeWriter writer = forStreamWriter(mountWriter.startMountPoint(
+                    node.getIdentifier(), node.getMountPointContext()))) {
+                for (DataContainerChild<? extends PathArgument, ?> child : node.getValue()) {
+                    writer.write(child);
+                }
+            }
+        }
+    }
+
+    MountPointNormalizedNodeWriter(final NormalizedNodeStreamWriter writer) {
+        super(writer);
+    }
+
+    public static @NonNull MountPointNormalizedNodeWriter forStreamWriter(final NormalizedNodeStreamWriter writer) {
+        final MountPointStreamWriter mountWriter = writer.getExtensions().getInstance(MountPointStreamWriter.class);
+        return mountWriter == null ? new Filtering(writer) : new Forwarding(writer, mountWriter);
+    }
+
+    public static @NonNull MountPointNormalizedNodeWriter filteringFor(final NormalizedNodeStreamWriter writer) {
+        return new Filtering(writer);
+    }
+
+    public static @NonNull MountPointNormalizedNodeWriter forwardingFor(final NormalizedNodeStreamWriter writer) {
+        final MountPointStreamWriter mountWriter = writer.getExtensions().getInstance(MountPointStreamWriter.class);
+        checkArgument(mountWriter != null, "Writer %s does not support mount points", writer);
+        return new Forwarding(writer, mountWriter);
+    }
+
+    @Override
+    protected final boolean wasProcessedAsCompositeNode(final NormalizedNode<?, ?> node) throws IOException {
+        if (node instanceof MountPointNode) {
+            writeMountPoint((MountPointNode) node);
+            return true;
+        }
+        return super.wasProcessedAsCompositeNode(node);
+    }
+
+    abstract void writeMountPoint(MountPointNode node) throws IOException;
+}