HONEYCOMB-94 Reimplement writer registry with better ordering options

Now the registry is flat and allows for full control of writer execution order

Change-Id: I864e1d676588ffe59b596145e0829e81b1a1ed2f
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>

14 files changed, 703 insertions, 454 deletions

diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/RWUtils.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/RWUtils.java
index b712e159c..55ae9ecf0 100644
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/RWUtils.java
+++ b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/RWUtils.java
@@ -23,13 +23,13 @@ import com.google.common.collect.Iterables;
 import com.google.common.collect.Maps;
 import io.fd.honeycomb.v3po.translate.SubtreeManager;
 import io.fd.honeycomb.v3po.translate.read.ChildReader;
-import io.fd.honeycomb.v3po.translate.write.ChildWriter;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import java.util.stream.Collector;
 import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
 import javax.annotation.Nonnull;
 import org.opendaylight.yangtools.yang.binding.Augmentation;
 import org.opendaylight.yangtools.yang.binding.ChildOf;
@@ -79,18 +79,10 @@ public final class RWUtils {
         return Collections.emptyList();
     }
 
-    public static <T> List<ChildWriter<? extends ChildOf<T>>> emptyChildWriterList() {
-        return Collections.emptyList();
-    }
-
     public static <T> List<ChildReader<? extends Augmentation<T>>> emptyAugReaderList() {
         return Collections.emptyList();
     }
 
-    public static <T> List<ChildWriter<? extends Augmentation<T>>> emptyAugWriterList() {
-        return Collections.emptyList();
-    }
-
     public static <T> List<ChildReader<? extends Augmentation<T>>> singletonAugReaderList(
         ChildReader<? extends Augmentation<T>> item) {
         return Collections.<ChildReader<? extends Augmentation<T>>>singletonList(item);
@@ -101,16 +93,6 @@ public final class RWUtils {
         return Collections.<ChildReader<? extends ChildOf<T>>>singletonList(item);
     }
 
-    public static <T> List<ChildWriter<? extends ChildOf<T>>> singletonChildWriterList(
-        ChildWriter<? extends ChildOf<T>> item) {
-        return Collections.<ChildWriter<? extends ChildOf<T>>>singletonList(item);
-    }
-
-    public static <T> List<ChildWriter<? extends Augmentation<T>>> singletonAugWriterList(
-        ChildWriter<? extends Augmentation<T>> item) {
-        return Collections.<ChildWriter<? extends Augmentation<T>>>singletonList(item);
-    }
-
     /**
      * Replace last item in ID with a provided IdentifiableItem of the same type
      */
@@ -197,4 +179,21 @@ public final class RWUtils {
         return (InstanceIdentifier<D>) InstanceIdentifier.create(Iterables.concat(
             parentId.getPathArguments(), Collections.singleton(t)));
     }
+
+    /**
+     * Transform a keyed instance identifier into a wildcarded one.
+     */
+    public static InstanceIdentifier<?> makeIidWildcarded(final InstanceIdentifier<?> id) {
+        final List<InstanceIdentifier.PathArgument> transformedPathArguments =
+                StreamSupport.stream(id.getPathArguments().spliterator(), false)
+                        .map(RWUtils::cleanPathArgumentFromKeys)
+                        .collect(Collectors.toList());
+        return InstanceIdentifier.create(transformedPathArguments);
+    }
+
+    private static InstanceIdentifier.PathArgument cleanPathArgumentFromKeys(final InstanceIdentifier.PathArgument pathArgument) {
+        return pathArgument instanceof InstanceIdentifier.IdentifiableItem<?, ?>
+                ? new InstanceIdentifier.Item<>(pathArgument.getType())
+                : pathArgument;
+    }
 }
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/CloseableWriterRegistry.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/CloseableWriterRegistry.java
deleted file mode 100644
index cd53a4f8b..000000000
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/CloseableWriterRegistry.java
+++ /dev/null
@@ -1,65 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.v3po.translate.util.write;
-
-import io.fd.honeycomb.v3po.translate.TranslationException;
-import io.fd.honeycomb.v3po.translate.write.WriteContext;
-import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
-import io.fd.honeycomb.v3po.translate.write.WriterRegistry;
-import java.util.Map;
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-/**
- * WriterRegistry wrapper providing AutoCloseable interface.
- */
-public final class CloseableWriterRegistry implements WriterRegistry, AutoCloseable {
-    private final WriterRegistry writerRegistry;
-
-    public CloseableWriterRegistry( final WriterRegistry writerRegistry) {
-        this.writerRegistry = writerRegistry;
-    }
-
-    @Override
-    public void update(
-            @Nonnull final Map<InstanceIdentifier<?>, DataObject> nodesBefore,
-            @Nonnull final Map<InstanceIdentifier<?>, DataObject> nodesAfter,
-            @Nonnull final WriteContext ctx) throws TranslationException {
-        writerRegistry.update(nodesBefore, nodesAfter, ctx);
-    }
-
-    @Override
-    public void update(
-            @Nonnull final InstanceIdentifier<? extends DataObject> id,
-            @Nullable final DataObject dataBefore, @Nullable final DataObject dataAfter,
-            @Nonnull final WriteContext ctx) throws WriteFailedException {
-        writerRegistry.update(id, dataBefore, dataAfter, ctx);
-    }
-
-    @Nonnull
-    @Override
-    public InstanceIdentifier<DataObject> getManagedDataObjectType() {
-        return writerRegistry.getManagedDataObjectType();
-    }
-
-    @Override
-    public void close() throws Exception {
-        // NOOP
-    }
-}
\ No newline at end of file
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/DelegatingWriterRegistry.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/DelegatingWriterRegistry.java
deleted file mode 100644
index 061d3fa4a..000000000
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/DelegatingWriterRegistry.java
+++ /dev/null
@@ -1,182 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.v3po.translate.util.write;
-
-import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Preconditions.checkNotNull;
-
-import com.google.common.collect.HashMultimap;
-import com.google.common.collect.Iterables;
-import com.google.common.collect.Lists;
-import com.google.common.collect.Multimap;
-import io.fd.honeycomb.v3po.translate.util.RWUtils;
-import io.fd.honeycomb.v3po.translate.write.WriteContext;
-import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
-import io.fd.honeycomb.v3po.translate.write.Writer;
-import io.fd.honeycomb.v3po.translate.write.WriterRegistry;
-import java.util.LinkedList;
-import java.util.List;
-import java.util.Map;
-import javax.annotation.Nonnull;
-import javax.annotation.Nullable;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-import org.slf4j.Logger;
-import org.slf4j.LoggerFactory;
-
-/**
- * Simple writer registry able to perform and aggregated write (ROOT write) on top of all provided writers. Also able to
- * delegate a specific write to one of the delegate writers.
- *
- * This could serve as a utility to hold & hide all available writers in upper layers.
- */
-public final class DelegatingWriterRegistry implements WriterRegistry {
-
-    private static final Logger LOG = LoggerFactory.getLogger(DelegatingWriterRegistry.class);
-
-    private final Map<Class<? extends DataObject>, Writer<? extends DataObject>> rootWriters;
-
-    /**
-     * Create new {@link DelegatingWriterRegistry}
-     *
-     * @param rootWriters List of delegate writers
-     */
-    public DelegatingWriterRegistry(@Nonnull final List<Writer<? extends DataObject>> rootWriters) {
-        this.rootWriters = RWUtils.uniqueLinkedIndex(checkNotNull(rootWriters), RWUtils.MANAGER_CLASS_FUNCTION);
-    }
-
-    /**
-     * @throws UnsupportedOperationException This getter is not supported for writer registry since it does not manage a
-     *                                       specific node type
-     */
-    @Nonnull
-    @Override
-    public InstanceIdentifier<DataObject> getManagedDataObjectType() {
-        throw new UnsupportedOperationException("Root registry has no type");
-    }
-
-    @Override
-    public void update(@Nonnull final InstanceIdentifier<? extends DataObject> id,
-                       @Nullable final DataObject dataBefore,
-                       @Nullable final DataObject dataAfter,
-                       @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier.PathArgument first = checkNotNull(
-                Iterables.getFirst(id.getPathArguments(), null), "Empty id");
-        final Writer<? extends DataObject> writer = rootWriters.get(first.getType());
-        checkNotNull(writer,
-                "Unable to write %s. Missing writer. Current writers for: %s", id, rootWriters.keySet());
-        writer.update(id, dataBefore, dataAfter, ctx);
-    }
-
-    @Override
-    public void update(@Nonnull final Map<InstanceIdentifier<?>, DataObject> nodesBefore,
-                       @Nonnull final Map<InstanceIdentifier<?>, DataObject> nodesAfter,
-                       @Nonnull final WriteContext ctx) throws WriteFailedException {
-
-        Multimap<InstanceIdentifier<?>, InstanceIdentifier<?>> rootIdToNestedIds = HashMultimap.create();
-        try {
-            checkAllWritersPresent(nodesBefore, rootIdToNestedIds);
-            checkAllWritersPresent(nodesAfter, rootIdToNestedIds);
-        } catch (IllegalArgumentException e) {
-            LOG.warn("Unable to process update", e);
-            throw e;
-        }
-
-        final List<InstanceIdentifier<?>> processedNodes = Lists.newArrayList();
-
-        for (Map.Entry<Class<? extends DataObject>, Writer<? extends DataObject>> rootWriterEntry : rootWriters
-                .entrySet()) {
-
-            final InstanceIdentifier<? extends DataObject> id = rootWriterEntry.getValue().getManagedDataObjectType();
-            // FIXME !! this is not ideal, we are not handling nested updates in expected order
-            // Root writers are invoked in order they were registered, but nested updates are not, since they are
-            // iterated here.
-            //
-            for (InstanceIdentifier<?> specificInstanceIdentifier : rootIdToNestedIds.get(id)) {
-                final DataObject dataBefore = nodesBefore.get(specificInstanceIdentifier);
-                final DataObject dataAfter = nodesAfter.get(specificInstanceIdentifier);
-
-                // No change to current writer
-                if (dataBefore == null && dataAfter == null) {
-                    continue;
-                }
-
-                try {
-                    LOG.debug("ChangesProcessor.applyChanges() processing dataBefore={}, dataAfter={}", dataBefore, dataAfter);
-                    update(specificInstanceIdentifier, dataBefore, dataAfter, ctx);
-                    processedNodes.add(id);
-                } catch (Exception e) {
-                    LOG.error("Error while processing data change of: {} (before={}, after={})", id, dataBefore, dataAfter, e);
-                    throw new BulkUpdateException(id, new ReverterImpl(this, processedNodes, nodesBefore, nodesAfter, ctx), e);
-                }
-            }
-        }
-    }
-
-    private void checkAllWritersPresent(final @Nonnull Map<InstanceIdentifier<?>, DataObject> nodesBefore,
-                                        final @Nonnull Multimap<InstanceIdentifier<?>, InstanceIdentifier<?>> rootIdToNestedIds) {
-        for (final InstanceIdentifier<?> changeId : nodesBefore.keySet()) {
-            final InstanceIdentifier.PathArgument first = Iterables.getFirst(changeId.getPathArguments(), null);
-            checkNotNull(first, "Empty identifier detected");
-            final InstanceIdentifier<? extends DataObject> rootId = InstanceIdentifier.create(first.getType());
-            checkArgument(rootWriters.keySet().contains(first.getType()),
-                    "Unable to handle change. Missing dedicated writer for: %s", first.getType());
-            rootIdToNestedIds.put(rootId, changeId);
-        }
-    }
-
-    private static final class ReverterImpl implements Reverter {
-        private final WriterRegistry delegatingWriterRegistry;
-        private final List<InstanceIdentifier<?>> processedNodes;
-        private final Map<InstanceIdentifier<?>, DataObject> nodesBefore;
-        private final Map<InstanceIdentifier<?>, DataObject> nodesAfter;
-        private final WriteContext ctx;
-
-        ReverterImpl(final WriterRegistry delegatingWriterRegistry,
-                            final List<InstanceIdentifier<?>> processedNodes,
-                            final Map<InstanceIdentifier<?>, DataObject> nodesBefore,
-                            final Map<InstanceIdentifier<?>, DataObject> nodesAfter, final WriteContext ctx) {
-            this.delegatingWriterRegistry = delegatingWriterRegistry;
-            this.processedNodes = processedNodes;
-            this.nodesBefore = nodesBefore;
-            this.nodesAfter = nodesAfter;
-            this.ctx = ctx;
-        }
-
-        @Override
-        public void revert() throws RevertFailedException {
-            final LinkedList<InstanceIdentifier<?>> notReverted = new LinkedList<>(processedNodes);
-
-            while (notReverted.size() > 0) {
-                final InstanceIdentifier<?> node = notReverted.peekLast();
-                LOG.debug("ChangesProcessor.revertChanges() processing node={}", node);
-
-                final DataObject dataBefore = nodesBefore.get(node);
-                final DataObject dataAfter = nodesAfter.get(node);
-
-                // revert a change by invoking writer with reordered arguments
-                try {
-                    delegatingWriterRegistry.update(node, dataAfter, dataBefore, ctx);
-                    notReverted.removeLast(); // change was successfully reverted
-                } catch (Exception e) {
-                    throw new RevertFailedException(notReverted, e);
-                }
-
-            }
-        }
-    }
-}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterCustomizer.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterCustomizer.java
deleted file mode 100644
index 9f9c9f53e..000000000
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterCustomizer.java
+++ /dev/null
@@ -1,49 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.v3po.translate.util.write;
-
-import io.fd.honeycomb.v3po.translate.spi.write.RootWriterCustomizer;
-import io.fd.honeycomb.v3po.translate.write.WriteContext;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-/**
- * Customizer not performing any changes on current level. Suitable for nodes that don't have any leaves and all of
- * its child nodes are managed by dedicated writers
- */
-public class NoopWriterCustomizer<D extends DataObject> implements RootWriterCustomizer<D> {
-
-    @Override
-    public void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataAfter,
-                                       @Nonnull final WriteContext ctx) {
-
-    }
-
-    @Override
-    public void updateCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                        @Nonnull final D dataAfter,
-                                        @Nonnull final WriteContext ctx) {
-
-    }
-
-    @Override
-    public void deleteCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                        @Nonnull final WriteContext ctx) {
-
-    }
-}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterRegistry.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterRegistry.java
index 866854212..236ad8917 100644
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterRegistry.java
+++ b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/NoopWriterRegistry.java
@@ -20,7 +20,6 @@ import io.fd.honeycomb.v3po.translate.TranslationException;
 import io.fd.honeycomb.v3po.translate.write.WriteContext;
 import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
 import io.fd.honeycomb.v3po.translate.write.WriterRegistry;
-import java.util.Map;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
 import org.opendaylight.yangtools.yang.binding.DataObject;
@@ -32,19 +31,11 @@ import org.slf4j.LoggerFactory;
  * Empty registry that does not perform any changes. Can be used in data layer, if we want to disable passing data to
  * translation layer.
  */
-public class NoopWriterRegistry implements WriterRegistry {
+public class NoopWriterRegistry implements WriterRegistry, AutoCloseable {
 
     private static final Logger LOG = LoggerFactory.getLogger(NoopWriterRegistry.class);
 
     @Override
-    public void update(@Nonnull final Map<InstanceIdentifier<?>, DataObject> dataBefore,
-                       @Nonnull final Map<InstanceIdentifier<?>, DataObject> dataAfter, @Nonnull final WriteContext ctx)
-            throws TranslationException {
-        LOG.trace("NoopWriterRegistry.update dataBefore{}, dataAfter={], ctx={}", dataBefore, dataAfter, ctx);
-        // NOOP
-    }
-
-    @Override
     public void update(@Nonnull final InstanceIdentifier<? extends DataObject> id,
                        @Nullable final DataObject dataBefore, @Nullable final DataObject dataAfter,
                        @Nonnull final WriteContext ctx) throws WriteFailedException {
@@ -53,9 +44,20 @@ public class NoopWriterRegistry implements WriterRegistry {
         // NOOP
     }
 
+    @Override
+    public void update(@Nonnull final DataObjectUpdates updates,
+                       @Nonnull final WriteContext ctx) throws TranslationException {
+        // NOOP
+    }
+
     @Nonnull
     @Override
     public InstanceIdentifier<DataObject> getManagedDataObjectType() {
-        throw new UnsupportedOperationException("Root registry has no type");
+        throw new UnsupportedOperationException("Noop registry has no type");
+    }
+
+    @Override
+    public void close() throws Exception {
+        // NOOP
     }
 }
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveAugmentWriterCustomizer.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveAugmentWriterCustomizer.java
deleted file mode 100644
index 6d29214b3..000000000
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveAugmentWriterCustomizer.java
+++ /dev/null
@@ -1,50 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.v3po.translate.util.write;
-
-import static com.google.common.base.Preconditions.checkArgument;
-import static com.google.common.base.Preconditions.checkState;
-
-import com.google.common.base.Optional;
-import io.fd.honeycomb.v3po.translate.spi.write.ChildWriterCustomizer;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.Augmentable;
-import org.opendaylight.yangtools.yang.binding.Augmentation;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-/**
- * Might be slow !
- */
-public class ReflexiveAugmentWriterCustomizer<C extends DataObject> extends NoopWriterCustomizer<C> implements
-    ChildWriterCustomizer<C> {
-
-    @Nonnull
-    @Override
-    @SuppressWarnings("unchecked")
-    public Optional<C> extract(@Nonnull final InstanceIdentifier<C> currentId, @Nonnull final DataObject parentData) {
-        checkArgument(parentData instanceof Augmentable<?>, "Not augmnatable parent object: %s", parentData);
-        final Class<C> currentType = currentId.getTargetType();
-        final Augmentation<?> augmentation = ((Augmentable) parentData).getAugmentation(currentType);
-        if(augmentation == null) {
-            return Optional.absent();
-        } else {
-            checkState(currentType.isAssignableFrom(augmentation.getClass()));
-            return Optional.of(currentType.cast(augmentation));
-        }
-    }
-}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveChildWriterCustomizer.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveChildWriterCustomizer.java
deleted file mode 100644
index 79cdf62c3..000000000
--- a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/ReflexiveChildWriterCustomizer.java
+++ /dev/null
@@ -1,59 +0,0 @@
-/*
- * Copyright (c) 2016 Cisco and/or its affiliates.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at:
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-package io.fd.honeycomb.v3po.translate.util.write;
-
-import com.google.common.base.Optional;
-import com.google.common.base.Preconditions;
-import com.google.common.collect.Iterables;
-import io.fd.honeycomb.v3po.translate.util.ReflectionUtils;
-import io.fd.honeycomb.v3po.translate.spi.write.ChildWriterCustomizer;
-import java.lang.reflect.InvocationTargetException;
-import java.lang.reflect.Method;
-import java.util.Collections;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-/**
- * Might be slow !
- */
-public class ReflexiveChildWriterCustomizer<C extends DataObject> extends NoopWriterCustomizer<C> implements
-    ChildWriterCustomizer<C> {
-
-    @Nonnull
-    @Override
-    @SuppressWarnings("unchecked")
-    public Optional<C> extract(@Nonnull final InstanceIdentifier<C> currentId, @Nonnull final DataObject parentData) {
-        final Class<C> currentType = currentId.getTargetType();
-        final Optional<Method> method = ReflectionUtils.findMethodReflex(getParentType(currentId),
-            "get" + currentType.getSimpleName(), Collections.<Class<?>>emptyList(), currentType);
-
-        Preconditions.checkArgument(method.isPresent(), "Unable to get %s from %s", currentType, parentData);
-
-        try {
-            return method.isPresent()
-                ? Optional.fromNullable((C) method.get().invoke(parentData))
-                : Optional.absent();
-        } catch (IllegalAccessException | InvocationTargetException e) {
-            throw new IllegalArgumentException("Unable to get " + currentType + " from " + parentData, e);
-        }
-    }
-
-    private Class<? extends DataObject> getParentType(final @Nonnull InstanceIdentifier<C> currentId) {
-        return Iterables.get(currentId.getPathArguments(), Iterables.size(currentId.getPathArguments()) - 2).getType();
-    }
-}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistry.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistry.java
new file mode 100644
index 000000000..79d8eb88d
--- /dev/null
+++ b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistry.java
@@ -0,0 +1,334 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.v3po.translate.util.write.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.base.Optional;
+import com.google.common.collect.HashMultimap;
+import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableMultimap;
+import com.google.common.collect.ImmutableSet;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Multimap;
+import com.google.common.collect.Sets;
+import io.fd.honeycomb.v3po.translate.TranslationException;
+import io.fd.honeycomb.v3po.translate.util.RWUtils;
+import io.fd.honeycomb.v3po.translate.write.DataObjectUpdate;
+import io.fd.honeycomb.v3po.translate.write.WriteContext;
+import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
+import io.fd.honeycomb.v3po.translate.write.Writer;
+import io.fd.honeycomb.v3po.translate.write.WriterRegistry;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import javax.annotation.concurrent.ThreadSafe;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Flat writer registry, delegating updates to writers in the order writers were submitted.
+ */
+@ThreadSafe
+final class FlatWriterRegistry implements WriterRegistry {
+
+    private static final Logger LOG = LoggerFactory.getLogger(FlatWriterRegistry.class);
+
+    // All types handled by writers directly or as children
+    private final ImmutableSet<InstanceIdentifier<?>> handledTypes;
+
+    private final Set<InstanceIdentifier<?>> writersOrderReversed;
+    private final Set<InstanceIdentifier<?>> writersOrder;
+    private final Map<InstanceIdentifier<?>, Writer<?>> writers;
+
+    /**
+     * Create flat registry instance.
+     *
+     * @param writers immutable, ordered map of writers to use to process updates. Order of the writers has to be
+     *                one in which create and update operations should be handled. Deletes will be handled in reversed
+     *                order. All deletes are handled before handling all the updates.
+     */
+    FlatWriterRegistry(@Nonnull final ImmutableMap<InstanceIdentifier<?>, Writer<?>> writers) {
+        this.writers = writers;
+        this.writersOrderReversed = Sets.newLinkedHashSet(Lists.reverse(Lists.newArrayList(writers.keySet())));
+        this.writersOrder = writers.keySet();
+        this.handledTypes = getAllHandledTypes(writers);
+    }
+
+    private static ImmutableSet<InstanceIdentifier<?>> getAllHandledTypes(
+            @Nonnull final ImmutableMap<InstanceIdentifier<?>, Writer<?>> writers) {
+        final ImmutableSet.Builder<InstanceIdentifier<?>> handledTypesBuilder = ImmutableSet.builder();
+        for (Map.Entry<InstanceIdentifier<?>, Writer<?>> writerEntry : writers.entrySet()) {
+            final InstanceIdentifier<?> writerType = writerEntry.getKey();
+            final Writer<?> writer = writerEntry.getValue();
+            handledTypesBuilder.add(writerType);
+            if (writer instanceof SubtreeWriter) {
+                handledTypesBuilder.addAll(((SubtreeWriter<?>) writer).getHandledChildTypes());
+            }
+        }
+        return handledTypesBuilder.build();
+    }
+
+    @Override
+    public void update(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                       @Nullable final DataObject dataBefore,
+                       @Nullable final DataObject dataAfter,
+                       @Nonnull final WriteContext ctx) throws WriteFailedException {
+        singleUpdate(ImmutableMultimap.of(
+                RWUtils.makeIidWildcarded(id), DataObjectUpdate.create(id, dataBefore, dataAfter)), ctx);
+    }
+
+    @Override
+    public void update(@Nonnull final DataObjectUpdates updates,
+                       @Nonnull final WriteContext ctx) throws TranslationException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        // Optimization
+        if (updates.containsOnlySingleType()) {
+            // First process delete
+            singleUpdate(updates.getDeletes(), ctx);
+            // Next is update
+            singleUpdate(updates.getUpdates(), ctx);
+        } else {
+            // First process deletes
+            bulkUpdate(updates.getDeletes(), ctx, true, writersOrderReversed);
+            // Next are updates
+            bulkUpdate(updates.getUpdates(), ctx, true, writersOrder);
+        }
+
+        LOG.debug("Update successful for types: {}", updates.getTypeIntersection());
+        LOG.trace("Update successful for: {}", updates);
+    }
+
+    private void singleUpdate(@Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                              @Nonnull final WriteContext ctx) throws WriteFailedException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        final InstanceIdentifier<?> singleType = updates.keySet().iterator().next();
+        LOG.debug("Performing single type update for: {}", singleType);
+        Collection<? extends DataObjectUpdate> singleTypeUpdates = updates.get(singleType);
+        Writer<?> writer = getWriter(singleType);
+
+        if (writer == null) {
+            // This node must be handled by a subtree writer, find it and call it or else fail
+            checkArgument(handledTypes.contains(singleType), "Unable to process update. Missing writers for: %s",
+                    singleType);
+            writer = getSubtreeWriterResponsible(singleType);
+            singleTypeUpdates = getParentDataObjectUpdate(ctx, updates, writer);
+        }
+
+        LOG.trace("Performing single type update with writer: {}", writer);
+        for (DataObjectUpdate singleUpdate : singleTypeUpdates) {
+            writer.update(singleUpdate.getId(), singleUpdate.getDataBefore(), singleUpdate.getDataAfter(), ctx);
+        }
+    }
+
+    private Writer<?> getSubtreeWriterResponsible(final InstanceIdentifier<?> singleType) {
+        final Writer<?> writer;// This is slow ( minor TODO-perf )
+        writer = writers.values().stream()
+                .filter(w -> w instanceof SubtreeWriter)
+                .filter(w -> ((SubtreeWriter<?>) w).getHandledChildTypes().contains(singleType))
+                .findFirst()
+                .get();
+        return writer;
+    }
+
+    private Collection<DataObjectUpdate> getParentDataObjectUpdate(final WriteContext ctx,
+                                                                   final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                                                                   final Writer<?> writer) {
+        // Now read data for subtree reader root, but first keyed ID is needed and that ID can be cut from updates
+        InstanceIdentifier<?> firstAffectedChildId = ((SubtreeWriter<?>) writer).getHandledChildTypes().stream()
+                .filter(updates::containsKey)
+                .map(unkeyedId -> updates.get(unkeyedId))
+                .flatMap(doUpdates -> doUpdates.stream())
+                .map(DataObjectUpdate::getId)
+                .findFirst()
+                .get();
+
+        final InstanceIdentifier<?> parentKeyedId =
+                RWUtils.cutId(firstAffectedChildId, writer.getManagedDataObjectType());
+
+        final Optional<? extends DataObject> parentBefore = ctx.readBefore(parentKeyedId);
+        final Optional<? extends DataObject> parentAfter = ctx.readAfter(parentKeyedId);
+        return Collections.singleton(
+                DataObjectUpdate.create(parentKeyedId, parentBefore.orNull(), parentAfter.orNull()));
+    }
+
+    private void bulkUpdate(@Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                            @Nonnull final WriteContext ctx,
+                            final boolean attemptRevert,
+                            @Nonnull final Set<InstanceIdentifier<?>> writersOrder) throws BulkUpdateException {
+        if (updates.isEmpty()) {
+            return;
+        }
+
+        LOG.debug("Performing bulk update with revert attempt: {} for: {}", attemptRevert, updates.keySet());
+
+        // Check that all updates can be handled
+        checkAllTypesCanBeHandled(updates);
+
+        // Capture all changes successfully processed in case revert is needed
+        final Set<InstanceIdentifier<?>> processedNodes = new HashSet<>();
+
+        // Iterate over all writers and call update if there are any related updates
+        for (InstanceIdentifier<?> writerType : writersOrder) {
+            Collection<? extends DataObjectUpdate> writersData = updates.get(writerType);
+            final Writer<?> writer = getWriter(writerType);
+
+            if (writersData.isEmpty()) {
+                // If there are no data for current writer, but it is a SubtreeWriter and there are updates to
+                // its children, still invoke it with its root data
+                if (writer instanceof SubtreeWriter<?> && isAffected(((SubtreeWriter<?>) writer), updates)) {
+                    // Provide parent data for SubtreeWriter for further processing
+                    writersData = getParentDataObjectUpdate(ctx, updates, writer);
+                } else {
+                    // Skipping unaffected writer
+                    // Alternative to this would be modification sort according to the order of writers
+                    continue;
+                }
+            }
+
+            LOG.debug("Performing update for: {}",  writerType);
+            LOG.trace("Performing update with writer: {}", writer);
+
+            for (DataObjectUpdate singleUpdate : writersData) {
+                try {
+                    writer.update(singleUpdate.getId(), singleUpdate.getDataBefore(), singleUpdate.getDataAfter(), ctx);
+                    processedNodes.add(singleUpdate.getId());
+                    LOG.trace("Update successful for type: {}", writerType);
+                    LOG.debug("Update successful for: {}", singleUpdate);
+                } catch (Exception e) {
+                    LOG.error("Error while processing data change of: {} (updates={})", writerType, writersData, e);
+
+                    final Reverter reverter = attemptRevert
+                            ? new ReverterImpl(processedNodes, updates, writersOrder, ctx)
+                            : () -> {}; // NOOP reverter
+
+                    // Find out which changes left unprocessed
+                    final Set<InstanceIdentifier<?>> unprocessedChanges = updates.values().stream()
+                            .map(DataObjectUpdate::getId)
+                            .filter(id -> !processedNodes.contains(id))
+                            .collect(Collectors.toSet());
+                    throw new BulkUpdateException(unprocessedChanges, reverter, e);
+                }
+            }
+        }
+    }
+
+    private void checkAllTypesCanBeHandled(
+            @Nonnull final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates) {
+        if (!handledTypes.containsAll(updates.keySet())) {
+            final Sets.SetView<InstanceIdentifier<?>> missingWriters = Sets.difference(updates.keySet(), handledTypes);
+            LOG.warn("Unable to process update. Missing writers for: {}", missingWriters);
+            throw new IllegalArgumentException("Unable to process update. Missing writers for: " + missingWriters);
+        }
+    }
+
+    /**
+     * Check whether {@link SubtreeWriter} is affected by the updates.
+     *
+     * @return true if there are any updates to SubtreeWriter's child nodes (those marked by SubtreeWriter
+     *         as being taken care of)
+     * */
+    private static boolean isAffected(final SubtreeWriter<?> writer,
+                               final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates) {
+        return !Sets.intersection(writer.getHandledChildTypes(), updates.keySet()).isEmpty();
+    }
+
+    private Writer<?> getWriter(@Nonnull final InstanceIdentifier<?> singleType) {
+        final Writer<?> writer = writers.get(singleType);
+        checkNotNull(writer,
+                "Unable to write %s. Missing writer. Current writers for: %s", singleType, writers.keySet());
+        return writer;
+    }
+
+    @Nonnull
+    @Override
+    public InstanceIdentifier<DataObject> getManagedDataObjectType() {
+        throw new UnsupportedOperationException("Registry has no managed type");
+    }
+
+    // FIXME unit test
+    private final class ReverterImpl implements Reverter {
+
+        private final Collection<InstanceIdentifier<?>> processedNodes;
+        private final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates;
+        private final Set<InstanceIdentifier<?>> revertDeleteOrder;
+        private final WriteContext ctx;
+
+        ReverterImpl(final Collection<InstanceIdentifier<?>> processedNodes,
+                     final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                     final Set<InstanceIdentifier<?>> writersOrderOriginal,
+                     final WriteContext ctx) {
+            this.processedNodes = processedNodes;
+            this.updates = updates;
+            // Use opposite ordering when executing revert
+            this.revertDeleteOrder =  writersOrderOriginal == FlatWriterRegistry.this.writersOrder
+                    ? FlatWriterRegistry.this.writersOrderReversed
+                    : FlatWriterRegistry.this.writersOrder;
+            this.ctx = ctx;
+        }
+
+        @Override
+        public void revert() throws RevertFailedException {
+            Multimap<InstanceIdentifier<?>, DataObjectUpdate> updatesToRevert =
+                    filterAndRevertProcessed(updates, processedNodes);
+
+            LOG.info("Attempting revert for changes: {}", updatesToRevert);
+            try {
+                // Perform reversed bulk update without revert attempt
+                bulkUpdate(updatesToRevert, ctx, true, revertDeleteOrder);
+                LOG.info("Revert successful");
+            } catch (BulkUpdateException e) {
+                LOG.error("Revert failed", e);
+                throw new RevertFailedException(e.getFailedIds(), e);
+            }
+        }
+
+        /**
+         * Create new updates map, but only keep already processed changes. Switching before and after data for each
+         * update.
+         */
+        private Multimap<InstanceIdentifier<?>, DataObjectUpdate> filterAndRevertProcessed(
+                final Multimap<InstanceIdentifier<?>, ? extends DataObjectUpdate> updates,
+                final Collection<InstanceIdentifier<?>> processedNodes) {
+            final Multimap<InstanceIdentifier<?>, DataObjectUpdate> filtered = HashMultimap.create();
+            for (InstanceIdentifier<?> processedNode : processedNodes) {
+                final InstanceIdentifier<?> wildcardedIid = RWUtils.makeIidWildcarded(processedNode);
+                if (updates.containsKey(wildcardedIid)) {
+                    updates.get(wildcardedIid).stream()
+                            .filter(dataObjectUpdate -> processedNode.contains(dataObjectUpdate.getId()))
+                            .forEach(dataObjectUpdate -> filtered.put(processedNode, dataObjectUpdate.reverse()));
+                }
+            }
+            return filtered;
+        }
+    }
+
+}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistryBuilder.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistryBuilder.java
new file mode 100644
index 000000000..f5d218f55
--- /dev/null
+++ b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/FlatWriterRegistryBuilder.java
@@ -0,0 +1,225 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.v3po.translate.util.write.registry;
+
+import com.google.common.annotations.VisibleForTesting;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.ImmutableMap;
+import io.fd.honeycomb.v3po.translate.util.RWUtils;
+import io.fd.honeycomb.v3po.translate.write.ModifiableWriterRegistry;
+import io.fd.honeycomb.v3po.translate.write.Writer;
+import io.fd.honeycomb.v3po.translate.write.WriterRegistryBuilder;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.NotThreadSafe;
+import org.jgrapht.experimental.dag.DirectedAcyclicGraph;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Builder for {@link FlatWriterRegistry} allowing users to specify inter-writer relationships.
+ */
+@NotThreadSafe
+public final class FlatWriterRegistryBuilder implements ModifiableWriterRegistry, WriterRegistryBuilder, AutoCloseable {
+
+    private static final Logger LOG = LoggerFactory.getLogger(FlatWriterRegistryBuilder.class);
+
+    // Using directed acyclic graph to represent the ordering relationships between writers
+    private final DirectedAcyclicGraph<InstanceIdentifier<?>, WriterRelation>
+            writersRelations = new DirectedAcyclicGraph<>((sourceVertex, targetVertex) -> new WriterRelation());
+    private final Map<InstanceIdentifier<?>, Writer<?>> writersMap = new HashMap<>();
+
+    /**
+     * AddWriter without any special relationship to any other type.
+     */
+    @Override
+    public FlatWriterRegistryBuilder addWriter(@Nonnull final Writer<? extends DataObject> writer) {
+        // Make IID wildcarded just in case
+        // + the way InstanceIdentifier.create + equals work for Identifiable items is unexpected, meaning updates would
+        // not be matched to writers in registry
+        final InstanceIdentifier<?> targetType = RWUtils.makeIidWildcarded(writer.getManagedDataObjectType());
+        checkWriterNotPresentYet(targetType);
+        writersRelations.addVertex(targetType);
+        writersMap.put(targetType, writer);
+        return this;
+    }
+
+    /**
+     * AddWriter without any special relationship to any other type.
+     */
+    @Override
+    public FlatWriterRegistryBuilder addSubtreeWriter(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                      @Nonnull final Writer<? extends DataObject> writer) {
+        addWriter(SubtreeWriter.createForWriter(handledChildren, writer));
+        return this;
+    }
+
+    private void checkWriterNotPresentYet(final InstanceIdentifier<?> targetType) {
+        Preconditions.checkArgument(!writersMap.containsKey(targetType),
+                "Writer for type: %s already present: %s", targetType, writersMap.get(targetType));
+    }
+
+    /**
+     * Add writer with relationship: to be executed before writer handling relatedType.
+     */
+    @Override
+    public FlatWriterRegistryBuilder addWriterBefore(@Nonnull final Writer<? extends DataObject> writer,
+                                                     @Nonnull final InstanceIdentifier<?> relatedType) {
+        final InstanceIdentifier<?> targetType = RWUtils.makeIidWildcarded(writer.getManagedDataObjectType());
+        final InstanceIdentifier<?> wildcardedRelatedType = RWUtils.makeIidWildcarded(relatedType);
+        checkWriterNotPresentYet(targetType);
+        writersRelations.addVertex(targetType);
+        writersRelations.addVertex(wildcardedRelatedType);
+        addEdge(targetType, wildcardedRelatedType);
+        writersMap.put(targetType, writer);
+        return this;
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addSubtreeWriterBefore(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                            @Nonnull final Writer<? extends DataObject> writer,
+                                                            @Nonnull final InstanceIdentifier<?> relatedType) {
+        return addWriterBefore(SubtreeWriter.createForWriter(handledChildren, writer), relatedType);
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addWriterBefore(@Nonnull final Writer<? extends DataObject> writer,
+                                                     @Nonnull final Collection<InstanceIdentifier<?>> relatedTypes) {
+        final InstanceIdentifier<?> targetType = RWUtils.makeIidWildcarded(writer.getManagedDataObjectType());
+        checkWriterNotPresentYet(targetType);
+        writersRelations.addVertex(targetType);
+        relatedTypes.stream()
+                .map(RWUtils::makeIidWildcarded)
+                .forEach(writersRelations::addVertex);
+        relatedTypes.stream()
+                .map(RWUtils::makeIidWildcarded)
+                .forEach(type -> addEdge(targetType, type));
+        writersMap.put(targetType, writer);
+        return this;
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addSubtreeWriterBefore(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                            @Nonnull final Writer<? extends DataObject> writer,
+                                                            @Nonnull final Collection<InstanceIdentifier<?>> relatedTypes) {
+        return addWriterBefore(SubtreeWriter.createForWriter(handledChildren, writer), relatedTypes);
+    }
+
+    /**
+     * Add writer with relationship: to be executed after writer handling relatedType.
+     */
+    @Override
+    public FlatWriterRegistryBuilder addWriterAfter(@Nonnull final Writer<? extends DataObject> writer,
+                                                    @Nonnull final InstanceIdentifier<?> relatedType) {
+        final InstanceIdentifier<?> targetType = RWUtils.makeIidWildcarded(writer.getManagedDataObjectType());
+        final InstanceIdentifier<?> wildcardedRelatedType = RWUtils.makeIidWildcarded(relatedType);
+        checkWriterNotPresentYet(targetType);
+        writersRelations.addVertex(targetType);
+        writersRelations.addVertex(wildcardedRelatedType);
+        // set edge to indicate before relationship, just reversed
+        addEdge(wildcardedRelatedType, targetType);
+        writersMap.put(targetType, writer);
+        return this;
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addSubtreeWriterAfter(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                           @Nonnull final Writer<? extends DataObject> writer,
+                                                           @Nonnull final InstanceIdentifier<?> relatedType) {
+        return addWriterAfter(SubtreeWriter.createForWriter(handledChildren, writer), relatedType);
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addWriterAfter(@Nonnull final Writer<? extends DataObject> writer,
+                                                    @Nonnull final Collection<InstanceIdentifier<?>> relatedTypes) {
+        final InstanceIdentifier<?> targetType = RWUtils.makeIidWildcarded(writer.getManagedDataObjectType());
+        checkWriterNotPresentYet(targetType);
+        writersRelations.addVertex(targetType);
+        relatedTypes.stream()
+                .map(RWUtils::makeIidWildcarded)
+                .forEach(writersRelations::addVertex);
+        // set edge to indicate before relationship, just reversed
+        relatedTypes.stream()
+                .map(RWUtils::makeIidWildcarded)
+                .forEach(type -> addEdge(type, targetType));
+        writersMap.put(targetType, writer);
+        return this;
+    }
+
+    @Override
+    public FlatWriterRegistryBuilder addSubtreeWriterAfter(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                                           @Nonnull final Writer<? extends DataObject> writer,
+                                                           @Nonnull final Collection<InstanceIdentifier<?>> relatedTypes) {
+        return addWriterAfter(SubtreeWriter.createForWriter(handledChildren, writer), relatedTypes);
+    }
+
+
+    private void addEdge(final InstanceIdentifier<?> targetType,
+                         final InstanceIdentifier<?> relatedType) {
+        try {
+            writersRelations.addDagEdge(targetType, relatedType);
+        } catch (DirectedAcyclicGraph.CycleFoundException e) {
+            throw new IllegalArgumentException(String.format(
+                    "Unable to add writer with relation: %s -> %s. Loop detected", targetType, relatedType), e);
+        }
+    }
+
+    /**
+     * Create FlatWriterRegistry with writers ordered according to submitted relationships.
+     */
+    @Override
+    public FlatWriterRegistry build() {
+        final ImmutableMap<InstanceIdentifier<?>, Writer<?>> mappedWriters = getMappedWriters();
+        LOG.debug("Building writer registry with writers: {}",
+                mappedWriters.keySet().stream()
+                        .map(InstanceIdentifier::getTargetType)
+                        .map(Class::getSimpleName)
+                        .collect(Collectors.joining(", ")));
+        LOG.trace("Building writer registry with writers: {}", mappedWriters);
+        return new FlatWriterRegistry(mappedWriters);
+    }
+
+    @VisibleForTesting
+    ImmutableMap<InstanceIdentifier<?>, Writer<?>> getMappedWriters() {
+        final ImmutableMap.Builder<InstanceIdentifier<?>, Writer<?>> builder = ImmutableMap.builder();
+        // Iterate writer types according to their relationships from graph
+        writersRelations.iterator()
+                .forEachRemaining(writerType -> {
+                    // There might be types stored just for relationship sake, no real writer, ignoring those
+                    if (writersMap.containsKey(writerType)) {
+                        builder.put(writerType, writersMap.get(writerType));
+                    }
+                });
+        return builder.build();
+    }
+
+    @Override
+    public void close() throws Exception {
+        writersMap.clear();
+        writersRelations.removeAllEdges(writersRelations.edgeSet());
+        writersRelations.removeAllVertices(writersRelations.vertexSet());
+    }
+
+    // Represents edges in graph
+    private static final class WriterRelation {}
+}
diff --git a/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/SubtreeWriter.java b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/SubtreeWriter.java
new file mode 100644
index 000000000..e395b29da
--- /dev/null
+++ b/v3po/translate-utils/src/main/java/io/fd/honeycomb/v3po/translate/util/write/registry/SubtreeWriter.java
@@ -0,0 +1,85 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.fd.honeycomb.v3po.translate.util.write.registry;
+
+import static com.google.common.base.Preconditions.checkArgument;
+
+import com.google.common.collect.Iterables;
+import io.fd.honeycomb.v3po.translate.write.WriteContext;
+import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
+import io.fd.honeycomb.v3po.translate.write.Writer;
+import java.util.HashSet;
+import java.util.Set;
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * Simple writer delegate for subtree writers (writers handling also children nodes) providing a list of all the
+ * children nodes being handled.
+ */
+final class SubtreeWriter<D extends DataObject> implements Writer<D> {
+
+    private final Writer<D> delegate;
+    private final Set<InstanceIdentifier<?>> handledChildTypes = new HashSet<>();
+
+    private SubtreeWriter(final Writer<D> delegate, Set<InstanceIdentifier<?>> handledTypes) {
+        this.delegate = delegate;
+        for (InstanceIdentifier<?> handledType : handledTypes) {
+            // Iid has to start with writer's handled root type
+            checkArgument(delegate.getManagedDataObjectType().getTargetType().equals(
+                    handledType.getPathArguments().iterator().next().getType()),
+                    "Handled node from subtree has to be identified by an instance identifier starting from: %s."
+                    + "Instance identifier was: %s", getManagedDataObjectType().getTargetType(), handledType);
+            checkArgument(Iterables.size(handledType.getPathArguments()) > 1,
+                    "Handled node from subtree identifier too short: %s", handledType);
+            handledChildTypes.add(InstanceIdentifier.create(Iterables.concat(
+                    getManagedDataObjectType().getPathArguments(), Iterables.skip(handledType.getPathArguments(), 1))));
+        }
+    }
+
+    /**
+     * Return set of types also handled by this writer. All of the types are children of the type managed by this
+     * writer excluding the type of this writer.
+     */
+    Set<InstanceIdentifier<?>> getHandledChildTypes() {
+        return handledChildTypes;
+    }
+
+    @Override
+    public void update(
+            @Nonnull final InstanceIdentifier<? extends DataObject> id,
+            @Nullable final DataObject dataBefore,
+            @Nullable final DataObject dataAfter, @Nonnull final WriteContext ctx) throws WriteFailedException {
+        delegate.update(id, dataBefore, dataAfter, ctx);
+    }
+
+    @Override
+    @Nonnull
+    public InstanceIdentifier<D> getManagedDataObjectType() {
+        return delegate.getManagedDataObjectType();
+    }
+
+    /**
+     * Wrap a writer as a subtree writer.
+     */
+    static Writer<?> createForWriter(@Nonnull final Set<InstanceIdentifier<?>> handledChildren,
+                                     @Nonnull final Writer<? extends DataObject> writer) {
+        return new SubtreeWriter<>(writer, handledChildren);
+    }
+}
diff --git a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModule.java b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModule.java
index 0eb5062d5..fccd6b1c2 100644
--- a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModule.java
+++ b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModule.java
@@ -42,6 +42,8 @@ public class DelegatingReaderRegistryModule extends org.opendaylight.yang.gen.v1
         return new CloseableReaderRegistry(new DelegatingReaderRegistry(rootReadersDependency));
     }
 
+
+
     // TODO move to translate-utils
     private static final class CloseableReaderRegistry implements ReaderRegistry, AutoCloseable {
         private final DelegatingReaderRegistry delegatingReaderRegistry;
diff --git a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModuleFactory.java b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModuleFactory.java
index 214ab0f90..24d6c50b8 100644
--- a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModuleFactory.java
+++ b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingReaderRegistryModuleFactory.java
@@ -8,6 +8,13 @@
 * Do not modify this file unless it is present under src/main directory
 */
 package org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406;
+
+import org.opendaylight.controller.config.api.DynamicMBeanWithInstance;
+
 public class DelegatingReaderRegistryModuleFactory extends org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406.AbstractDelegatingReaderRegistryModuleFactory {
 
+    @Override
+    public DelegatingReaderRegistryModule handleChangedClass(final DynamicMBeanWithInstance old) throws Exception {
+        return super.handleChangedClass(old);
+    }
 }
diff --git a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingWriterRegistryModule.java b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingWriterRegistryModule.java
index 0266ca900..7eadde80e 100644
--- a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingWriterRegistryModule.java
+++ b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/DelegatingWriterRegistryModule.java
@@ -1,12 +1,6 @@
 package org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406;
 
-import com.google.common.base.Function;
-import com.google.common.collect.Lists;
-import io.fd.honeycomb.v3po.translate.util.write.CloseableWriterRegistry;
-import io.fd.honeycomb.v3po.translate.util.write.DelegatingWriterRegistry;
-import io.fd.honeycomb.v3po.translate.write.Writer;
-import java.util.List;
-import org.opendaylight.yangtools.yang.binding.DataObject;
+import io.fd.honeycomb.v3po.translate.util.write.registry.FlatWriterRegistryBuilder;
 
 public class DelegatingWriterRegistryModule extends org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406.AbstractDelegatingWriterRegistryModule {
     public DelegatingWriterRegistryModule(org.opendaylight.controller.config.api.ModuleIdentifier identifier, org.opendaylight.controller.config.api.DependencyResolver dependencyResolver) {
@@ -24,16 +18,9 @@ public class DelegatingWriterRegistryModule extends org.opendaylight.yang.gen.v1
 
     @Override
     public java.lang.AutoCloseable createInstance() {
-        final List<Writer<? extends DataObject>> rootReadersDependency = Lists.transform(getRootWritersDependency(),
-            new Function<Writer, Writer<? extends DataObject>>() {
-
-                @SuppressWarnings("unchecked")
-                @Override
-                public Writer<? extends DataObject> apply(final Writer input) {
-                    return input;
-                }
-            });
-        return new CloseableWriterRegistry(new DelegatingWriterRegistry(rootReadersDependency));
+        final FlatWriterRegistryBuilder flatWriterRegistryBuilder = new FlatWriterRegistryBuilder();
+        getWriterFactoryDependency().forEach(writerFactory -> writerFactory.init(flatWriterRegistryBuilder));
+        return flatWriterRegistryBuilder;
     }
 
 }
diff --git a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/NoopWriterRegistryModule.java b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/NoopWriterRegistryModule.java
index 16c8af359..fedd069f1 100644
--- a/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/NoopWriterRegistryModule.java
+++ b/v3po/translate-utils/src/main/java/org/opendaylight/yang/gen/v1/urn/honeycomb/params/xml/ns/yang/translate/utils/rev160406/NoopWriterRegistryModule.java
@@ -1,7 +1,8 @@
 package org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406;
 
-import io.fd.honeycomb.v3po.translate.util.write.*;
 import io.fd.honeycomb.v3po.translate.util.write.NoopWriterRegistry;
+import io.fd.honeycomb.v3po.translate.write.WriterRegistry;
+import io.fd.honeycomb.v3po.translate.write.WriterRegistryBuilder;
 
 public class NoopWriterRegistryModule extends org.opendaylight.yang.gen.v1.urn.honeycomb.params.xml.ns.yang.translate.utils.rev160406.AbstractNoopWriterRegistryModule {
     public NoopWriterRegistryModule(org.opendaylight.controller.config.api.ModuleIdentifier identifier, org.opendaylight.controller.config.api.DependencyResolver dependencyResolver) {
@@ -19,7 +20,19 @@ public class NoopWriterRegistryModule extends org.opendaylight.yang.gen.v1.urn.h
 
     @Override
     public java.lang.AutoCloseable createInstance() {
-        return new CloseableWriterRegistry(new NoopWriterRegistry());
+        return new NoopWriterRegistryBuilder();
     }
 
+    private static final class NoopWriterRegistryBuilder implements AutoCloseable, WriterRegistryBuilder {
+
+        @Override
+        public WriterRegistry build() {
+            return new NoopWriterRegistry();
+        }
+
+        @Override
+        public void close() throws Exception {
+            // Noop
+        }
+    }
 }