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>

7 files changed, 274 insertions, 577 deletions

diff --git a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/AbstractCompositeWriter.java b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/AbstractCompositeWriter.java
index 0212c086b..5f1391c74 100644
--- a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/AbstractCompositeWriter.java
+++ b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/AbstractCompositeWriter.java
@@ -18,82 +18,33 @@ package io.fd.honeycomb.v3po.translate.impl.write;
 
 import static com.google.common.base.Preconditions.checkArgument;
 
-import com.google.common.base.Optional;
-import com.google.common.collect.Lists;
-import io.fd.honeycomb.v3po.translate.impl.TraversalType;
-import io.fd.honeycomb.v3po.translate.util.RWUtils;
-import io.fd.honeycomb.v3po.translate.write.ChildWriter;
 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.ArrayList;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
-import org.opendaylight.yangtools.yang.binding.Augmentation;
-import org.opendaylight.yangtools.yang.binding.ChildOf;
 import org.opendaylight.yangtools.yang.binding.DataObject;
 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-public abstract class AbstractCompositeWriter<D extends DataObject> implements Writer<D> {
+abstract class AbstractCompositeWriter<D extends DataObject> implements Writer<D> {
 
     private static final Logger LOG = LoggerFactory.getLogger(AbstractCompositeWriter.class);
 
-    private final Map<Class<? extends DataObject>, ChildWriter<? extends ChildOf<D>>> childWriters;
-    private final Map<Class<? extends DataObject>, ChildWriter<? extends Augmentation<D>>> augWriters;
     private final InstanceIdentifier<D> instanceIdentifier;
-    private TraversalType traversalType;
 
-    public AbstractCompositeWriter(final Class<D> type,
-                                   final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                                   final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                                   final TraversalType traversalType) {
-        this.traversalType = traversalType;
-        this.instanceIdentifier = InstanceIdentifier.create(type);
-        this.childWriters = RWUtils.uniqueLinkedIndex(childWriters, RWUtils.MANAGER_CLASS_FUNCTION);
-        this.augWriters = RWUtils.uniqueLinkedIndex(augWriters, RWUtils.MANAGER_CLASS_AUG_FUNCTION);
+    AbstractCompositeWriter(final InstanceIdentifier<D> type) {
+        this.instanceIdentifier = type;
     }
 
     protected void writeCurrent(final InstanceIdentifier<D> id, final D data, final WriteContext ctx)
         throws WriteFailedException {
         LOG.debug("{}: Writing current: {} data: {}", this, id, data);
-
-        switch (traversalType) {
-            case PREORDER: {
-                LOG.trace("{}: Writing current attributes", this);
-                writeCurrentAttributes(id, data, ctx);
-                writeChildren(id, data, ctx);
-                break;
-            }
-            case POSTORDER: {
-                writeChildren(id, data, ctx);
-                LOG.trace("{}: Writing current attributes", this);
-                writeCurrentAttributes(id, data, ctx);
-                break;
-            }
-        }
-
+        writeCurrentAttributes(id, data, ctx);
         LOG.debug("{}: Current node written successfully", this);
     }
 
-    private void writeChildren(final InstanceIdentifier<D> id, final D data, final WriteContext ctx)
-        throws WriteFailedException {
-        for (ChildWriter<? extends ChildOf<D>> child : childWriters.values()) {
-            LOG.debug("{}: Writing child in: {}", this, child);
-            child.writeChild(id, data, ctx);
-        }
-
-        for (ChildWriter<? extends Augmentation<D>> child : augWriters.values()) {
-            LOG.debug("{}: Writing augment in: {}", this, child);
-            child.writeChild(id, data, ctx);
-        }
-    }
-
     protected void updateCurrent(final InstanceIdentifier<D> id, final D dataBefore, final D dataAfter,
                                  final WriteContext ctx) throws WriteFailedException {
         LOG.debug("{}: Updating current: {} dataBefore: {}, datAfter: {}", this, id, dataBefore, dataAfter);
@@ -103,69 +54,14 @@ public abstract class AbstractCompositeWriter<D extends DataObject> implements W
             // No change, ignore
             return;
         }
-
-        switch (traversalType) {
-            case PREORDER: {
-                LOG.trace("{}: Updating current attributes", this);
-                updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
-                updateChildren(id, dataBefore, dataAfter, ctx);
-                break;
-            }
-            case POSTORDER: {
-                updateChildren(id, dataBefore, dataAfter, ctx);
-                LOG.trace("{}: Updating current attributes", this);
-                updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
-                break;
-            }
-        }
-
+        updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
         LOG.debug("{}: Current node updated successfully", this);
     }
 
-    private void updateChildren(final InstanceIdentifier<D> id, final D dataBefore, final D dataAfter,
-                                final WriteContext ctx) throws WriteFailedException {
-        for (ChildWriter<? extends ChildOf<D>> child : childWriters.values()) {
-            LOG.debug("{}: Updating child in: {}", this, child);
-            child.updateChild(id, dataBefore, dataAfter, ctx);
-        }
-
-        for (ChildWriter<? extends Augmentation<D>> child : augWriters.values()) {
-            LOG.debug("{}: Updating augment in: {}", this, child);
-            child.updateChild(id, dataBefore, dataAfter, ctx);
-        }
-    }
-
     protected void deleteCurrent(final InstanceIdentifier<D> id, final D dataBefore, final WriteContext ctx)
         throws WriteFailedException {
         LOG.debug("{}: Deleting current: {} dataBefore: {}", this, id, dataBefore);
-
-        switch (traversalType) {
-            case PREORDER: {
-                deleteChildren(id, dataBefore, ctx);
-                LOG.trace("{}: Deleting current attributes", this);
-                deleteCurrentAttributes(id, dataBefore, ctx);
-                break;
-            }
-            case POSTORDER: {
-                LOG.trace("{}: Deleting current attributes", this);
-                deleteCurrentAttributes(id, dataBefore, ctx);
-                deleteChildren(id, dataBefore, ctx);
-                break;
-            }
-        }
-    }
-
-    private void deleteChildren(final InstanceIdentifier<D> id, final D dataBefore, final WriteContext ctx)
-        throws WriteFailedException {
-        for (ChildWriter<? extends Augmentation<D>> child : reverseCollection(augWriters.values())) {
-            LOG.debug("{}: Deleting augment in: {}", this, child);
-            child.deleteChild(id, dataBefore, ctx);
-        }
-
-        for (ChildWriter<? extends ChildOf<D>> child : reverseCollection(childWriters.values())) {
-            LOG.debug("{}: Deleting child in: {}", this, child);
-            child.deleteChild(id, dataBefore, ctx);
-        }
+        deleteCurrentAttributes(id, dataBefore, ctx);
     }
 
     @SuppressWarnings("unchecked")
@@ -177,28 +73,20 @@ public abstract class AbstractCompositeWriter<D extends DataObject> implements W
         LOG.debug("{}: Updating : {}", this, id);
         LOG.trace("{}: Updating : {}, from: {} to: {}", this, id, dataBefore, dataAfter);
 
-        if (idPointsToCurrent(id)) {
-            if(isWrite(dataBefore, dataAfter)) {
-                writeCurrent((InstanceIdentifier<D>) id, castToManaged(dataAfter), ctx);
-            } else if(isDelete(dataBefore, dataAfter)) {
-                deleteCurrent((InstanceIdentifier<D>) id, castToManaged(dataBefore), ctx);
-            } else {
-                checkArgument(dataBefore != null && dataAfter != null, "No data to process");
-                updateCurrent((InstanceIdentifier<D>) id, castToManaged(dataBefore), castToManaged(dataAfter), ctx);
-            }
+        checkArgument(idPointsToCurrent(id), "Cannot handle data: %s. Only: %s can be handled by writer: %s",
+                id, getManagedDataObjectType(), this);
+
+        if (isWrite(dataBefore, dataAfter)) {
+            writeCurrent((InstanceIdentifier<D>) id, castToManaged(dataAfter), ctx);
+        } else if (isDelete(dataBefore, dataAfter)) {
+            deleteCurrent((InstanceIdentifier<D>) id, castToManaged(dataBefore), ctx);
         } else {
-            if (isWrite(dataBefore, dataAfter)) {
-                writeSubtree(id, dataAfter, ctx);
-            } else if (isDelete(dataBefore, dataAfter)) {
-                deleteSubtree(id, dataBefore, ctx);
-            } else {
-                checkArgument(dataBefore != null && dataAfter != null, "No data to process");
-                updateSubtree(id, dataBefore, dataAfter, ctx);
-            }
+            checkArgument(dataBefore != null && dataAfter != null, "No data to process");
+            updateCurrent((InstanceIdentifier<D>) id, castToManaged(dataBefore), castToManaged(dataAfter), ctx);
         }
     }
 
-    private void checkDataType(final @Nullable DataObject dataAfter) {
+    private void checkDataType(@Nonnull final DataObject dataAfter) {
         checkArgument(getManagedDataObjectType().getTargetType().isAssignableFrom(dataAfter.getClass()));
     }
 
@@ -217,100 +105,10 @@ public abstract class AbstractCompositeWriter<D extends DataObject> implements W
         return dataAfter == null && dataBefore != null;
     }
 
-    private void writeSubtree(final InstanceIdentifier<? extends DataObject> id,
-                              final DataObject dataAfter, final WriteContext ctx) throws WriteFailedException {
-        LOG.debug("{}: Writing subtree: {}", this, id);
-
-        final Writer<? extends ChildOf<D>> writer = getNextChildWriter(id);
-        final Writer<? extends Augmentation<D>> augWriter = getNextAgumentationWriter(id);
-
-        if (writer != null) {
-            LOG.debug("{}: Writing subtree: {} in: {}", this, id, writer);
-            writer.update(id, null, dataAfter, ctx);
-        } else if (augWriter != null) {
-            LOG.debug("{}: Updating augmented subtree: {} in: {}", this, id, augWriter);
-            augWriter.update(id, null, dataAfter, ctx);
-        } else {
-            // If there's no dedicated writer, use write current
-            // But we need current data after to do so
-            final InstanceIdentifier<D> currentId = RWUtils.cutId(id, getManagedDataObjectType());
-            Optional<D> currentDataAfter = ctx.readAfter(currentId);
-            LOG.debug("{}: Dedicated subtree writer missing for: {}. Writing current.", this,
-                RWUtils.getNextId(id, getManagedDataObjectType()).getType(), currentDataAfter);
-            writeCurrent(currentId, castToManaged(currentDataAfter.get()), ctx);
-        }
-    }
-
     private boolean idPointsToCurrent(final @Nonnull InstanceIdentifier<? extends DataObject> id) {
         return id.getTargetType().equals(getManagedDataObjectType().getTargetType());
     }
 
-    private void deleteSubtree(final InstanceIdentifier<? extends DataObject> id,
-                               final DataObject dataBefore, final WriteContext ctx) throws WriteFailedException {
-        LOG.debug("{}: Deleting subtree: {}", this, id);
-
-        final Writer<? extends ChildOf<D>> writer = getNextChildWriter(id);
-        final Writer<? extends Augmentation<D>> augWriter = getNextAgumentationWriter(id);
-
-        if (writer != null) {
-            LOG.debug("{}: Deleting subtree: {} in: {}", this, id, writer);
-            writer.update(id, dataBefore, null, ctx);
-        } else if (augWriter != null) {
-            LOG.debug("{}: Updating augmented subtree: {} in: {}", this, id, augWriter);
-            augWriter.update(id, dataBefore, null, ctx);
-        }  else {
-            updateSubtreeFromCurrent(id, ctx);
-        }
-    }
-
-    @SuppressWarnings("unchecked")
-    private void updateSubtreeFromCurrent(final InstanceIdentifier<? extends DataObject> id, final WriteContext ctx)
-        throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.cutId(id, getManagedDataObjectType());
-        Optional<D> currentDataBefore = ctx.readBefore(currentId);
-        Optional<D> currentDataAfter = ctx.readAfter(currentId);
-        LOG.debug("{}: Dedicated subtree writer missing for: {}. Updating current without subtree", this,
-            RWUtils.getNextId(id, getManagedDataObjectType()).getType(), currentDataAfter);
-        updateCurrent((InstanceIdentifier<D>) id, castToManaged(currentDataBefore.orNull()),
-            castToManaged(currentDataAfter.orNull()), ctx);
-    }
-
-    private void updateSubtree(final InstanceIdentifier<? extends DataObject> id,
-                               final DataObject dataBefore,
-                               final DataObject dataAfter,
-                               final WriteContext ctx) throws WriteFailedException {
-        LOG.debug("{}: Updating subtree: {}", this, id);
-        final Writer<? extends ChildOf<D>> writer = getNextChildWriter(id);
-        final Writer<? extends Augmentation<D>> augWriter = getNextAgumentationWriter(id);
-
-        if (writer != null) {
-            LOG.debug("{}: Updating subtree: {} in: {}", this, id, writer);
-            writer.update(id, dataBefore, dataAfter, ctx);
-        } else if (augWriter != null) {
-            LOG.debug("{}: Updating augmented subtree: {} in: {}", this, id, augWriter);
-            augWriter.update(id, dataBefore, dataAfter, ctx);
-        } else {
-            updateSubtreeFromCurrent(id, ctx);
-        }
-    }
-
-    private Writer<? extends ChildOf<D>> getNextChildWriter(final InstanceIdentifier<? extends DataObject> id) {
-        final Class<? extends DataObject> next = RWUtils.getNextId(id, getManagedDataObjectType()).getType();
-        return childWriters.get(next);
-    }
-
-    private Writer<? extends Augmentation<D>> getNextAgumentationWriter(final InstanceIdentifier<? extends DataObject> id) {
-        final Class<? extends DataObject> next = RWUtils.getNextId(id, getManagedDataObjectType()).getType();
-        return augWriters.get(next);
-    }
-
-    private static <T> List<T> reverseCollection(final Collection<T> original) {
-        // TODO find a better reverse mechanism (probably a different collection for child writers is necessary)
-        final ArrayList<T> list = Lists.newArrayList(original);
-        Collections.reverse(list);
-        return list;
-    }
-
     protected abstract void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id,
                                                    @Nonnull final D data,
                                                    @Nonnull final WriteContext ctx) throws WriteFailedException;
diff --git a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeChildWriter.java b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeChildWriter.java
deleted file mode 100644
index 6e0841deb..000000000
--- a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeChildWriter.java
+++ /dev/null
@@ -1,125 +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.impl.write;
-
-import com.google.common.base.Optional;
-import io.fd.honeycomb.v3po.translate.impl.TraversalType;
-import io.fd.honeycomb.v3po.translate.write.ChildWriter;
-import io.fd.honeycomb.v3po.translate.write.WriteContext;
-import io.fd.honeycomb.v3po.translate.util.RWUtils;
-import io.fd.honeycomb.v3po.translate.spi.write.ChildWriterCustomizer;
-import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
-import java.util.List;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.Augmentation;
-import org.opendaylight.yangtools.yang.binding.ChildOf;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-public class CompositeChildWriter<D extends DataObject> extends AbstractCompositeWriter<D>
-    implements ChildWriter<D> {
-
-    private final ChildWriterCustomizer<D> customizer;
-
-    public CompositeChildWriter(@Nonnull final Class<D> type,
-                                @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                                @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                                @Nonnull final ChildWriterCustomizer<D> customizer) {
-        this(type, childWriters, augWriters, customizer, TraversalType.PREORDER);
-    }
-
-
-    public CompositeChildWriter(@Nonnull final Class<D> type,
-                                @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                                @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                                @Nonnull final ChildWriterCustomizer<D> customizer,
-                                @Nonnull final TraversalType traversalType) {
-        super(type, childWriters, augWriters, traversalType);
-        this.customizer = customizer;
-    }
-
-    public CompositeChildWriter(@Nonnull final Class<D> type,
-                                @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                                @Nonnull final ChildWriterCustomizer<D> customizer) {
-        this(type, childWriters, RWUtils.<D>emptyAugWriterList(), customizer);
-    }
-
-    public CompositeChildWriter(@Nonnull final Class<D> type,
-                                @Nonnull final ChildWriterCustomizer<D> customizer) {
-        this(type, RWUtils.<D>emptyChildWriterList(), RWUtils.<D>emptyAugWriterList(), customizer);
-    }
-
-    @Override
-    protected void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D data,
-                                          @Nonnull final WriteContext ctx) throws WriteFailedException {
-        customizer.writeCurrentAttributes(id, data, ctx);
-    }
-
-    @Override
-    protected void deleteCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                           @Nonnull WriteContext ctx) throws WriteFailedException {
-        customizer.deleteCurrentAttributes(id, dataBefore, ctx);
-    }
-
-    @Override
-    protected void updateCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                           @Nonnull final D dataAfter, @Nonnull WriteContext ctx)
-        throws WriteFailedException {
-        customizer.updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
-    }
-
-    @Override
-    public void writeChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                           @Nonnull final DataObject parentData, @Nonnull WriteContext ctx)
-        throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Optional<D> currentData = customizer.extract(currentId, parentData);
-        if(currentData.isPresent()) {
-            writeCurrent(currentId, currentData.get(), ctx);
-        }
-    }
-
-    @Override
-    public void deleteChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                            @Nonnull final DataObject parentDataBefore,
-                            @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Optional<D> dataBefore = customizer.extract(currentId, parentDataBefore);
-        if(dataBefore.isPresent()) {
-            deleteCurrent(currentId, dataBefore.get(), ctx);
-        }
-    }
-
-    @Override
-    public void updateChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                            @Nonnull final DataObject parentDataBefore, @Nonnull final DataObject parentDataAfter,
-                            @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Optional<D> before = customizer.extract(currentId, parentDataBefore);
-        final Optional<D> after = customizer.extract(currentId, parentDataAfter);
-
-        if(before.isPresent()) {
-            if(after.isPresent()) {
-                updateCurrent(currentId, before.get(), after.get(), ctx);
-            } else {
-                deleteCurrent(currentId, before.get(), ctx);
-            }
-        } else if (after.isPresent()){
-            writeCurrent(currentId, after.get(), ctx);
-        }
-    }
-}
diff --git a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeListWriter.java b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeListWriter.java
deleted file mode 100644
index fe9e8d5e3..000000000
--- a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeListWriter.java
+++ /dev/null
@@ -1,203 +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.impl.write;
-
-import com.google.common.base.Function;
-import com.google.common.base.Optional;
-import com.google.common.collect.Maps;
-import com.google.common.collect.Sets;
-import io.fd.honeycomb.v3po.translate.impl.TraversalType;
-import io.fd.honeycomb.v3po.translate.spi.write.ListWriterCustomizer;
-import io.fd.honeycomb.v3po.translate.util.RWUtils;
-import io.fd.honeycomb.v3po.translate.write.ChildWriter;
-import io.fd.honeycomb.v3po.translate.write.WriteContext;
-import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
-import java.util.Collections;
-import java.util.List;
-import java.util.Map;
-import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.Augmentation;
-import org.opendaylight.yangtools.yang.binding.ChildOf;
-import org.opendaylight.yangtools.yang.binding.DataObject;
-import org.opendaylight.yangtools.yang.binding.Identifiable;
-import org.opendaylight.yangtools.yang.binding.Identifier;
-import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
-
-public class CompositeListWriter<D extends DataObject & Identifiable<K>, K extends Identifier<D>> extends
-    AbstractCompositeWriter<D>
-    implements ChildWriter<D> {
-
-    private static final Function<DataObject, Object> INDEX_FUNCTION = input -> input instanceof Identifiable<?>
-        ? ((Identifiable<?>) input).getKey()
-        : input;
-
-
-    private final ListWriterCustomizer<D, K> customizer;
-
-    public CompositeListWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                               @Nonnull final ListWriterCustomizer<D, K> customizer) {
-        this(type, childWriters, augWriters, customizer, TraversalType.PREORDER);
-    }
-
-    public CompositeListWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                               @Nonnull final ListWriterCustomizer<D, K> customizer,
-                               @Nonnull final TraversalType traversalType) {
-        super(type, childWriters, augWriters, traversalType);
-        this.customizer = customizer;
-    }
-
-    public CompositeListWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final ListWriterCustomizer<D, K> customizer) {
-        this(type, childWriters, RWUtils.<D>emptyAugWriterList(), customizer);
-    }
-
-    public CompositeListWriter(@Nonnull final Class<D> type,
-                               @Nonnull final ListWriterCustomizer<D, K> customizer) {
-        this(type, RWUtils.<D>emptyChildWriterList(), RWUtils.<D>emptyAugWriterList(), customizer);
-
-    }
-
-    @Override
-    protected void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D data,
-                                          @Nonnull final WriteContext ctx) throws WriteFailedException {
-        customizer.writeCurrentAttributes(id, data, ctx);
-    }
-
-    @Override
-    protected void deleteCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                           @Nonnull final WriteContext ctx) throws WriteFailedException {
-        customizer.deleteCurrentAttributes(id, dataBefore, ctx);
-    }
-
-    @Override
-    protected void updateCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
-                                           @Nonnull final D dataAfter, @Nonnull final WriteContext ctx)
-        throws WriteFailedException {
-        customizer.updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
-    }
-
-    @Override
-    public void writeChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                           @Nonnull final DataObject parentData,
-                           @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Optional<List<D>> currentData = customizer.extract(currentId, parentData);
-        if (currentData.isPresent()) {
-            for (D entry : currentData.get()) {
-                writeCurrent(currentId, entry, ctx);
-            }
-        }
-    }
-
-    @Override
-    public void deleteChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                            @Nonnull final DataObject parentDataBefore,
-                            @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Optional<List<D>> dataBefore = customizer.extract(currentId, parentDataBefore);
-        if (dataBefore.isPresent()) {
-            for (D entry : dataBefore.get()) {
-                deleteCurrent(currentId, entry, ctx);
-            }
-        }
-    }
-
-    private Map<Object, D> listOfIdentifiableToMap(Optional<List<D>> list) {
-        if (list.isPresent()) {
-            return Maps.uniqueIndex(list.get(), INDEX_FUNCTION);
-        } else {
-            return Collections.emptyMap();
-        }
-
-    }
-
-    @Override
-    public void updateChild(@Nonnull final InstanceIdentifier<? extends DataObject> parentId,
-                            @Nonnull final DataObject parentDataBefore, @Nonnull final DataObject parentDataAfter,
-                            @Nonnull final WriteContext ctx) throws WriteFailedException {
-        final InstanceIdentifier<D> currentId = RWUtils.appendTypeToId(parentId, getManagedDataObjectType());
-        final Map<Object, D> dataBefore = listOfIdentifiableToMap(customizer.extract(currentId, parentDataBefore));
-        final Map<Object, D> dataAfter = listOfIdentifiableToMap(customizer.extract(currentId, parentDataAfter));
-
-        // The order of delete/write/update operations can have side-effects for devices like VPP
-        // TODO make it configurable
-
-        // First perform delete:
-        for (Object deletedNodeKey : Sets.difference(dataBefore.keySet(), dataAfter.keySet())) {
-            final D deleted = dataBefore.get(deletedNodeKey);
-            deleteCurrent(currentId, deleted, ctx);
-        }
-
-        // Then write/update:
-        for (Map.Entry<Object, D> after : dataAfter.entrySet()) {
-            final D before = dataBefore.get(after.getKey());
-            if(before == null) {
-                writeCurrent(currentId, after.getValue(), ctx);
-            } else {
-                updateCurrent(currentId, before, after.getValue(), ctx);
-            }
-        }
-
-    }
-
-    @Override
-    protected void writeCurrent(final InstanceIdentifier<D> id, final D data, final WriteContext ctx)
-        throws WriteFailedException {
-        // Make sure the key is present
-        if(isWildcarded(id)) {
-            super.writeCurrent(getSpecificId(id, data), data, ctx);
-        } else {
-            super.writeCurrent(id, data, ctx);
-        }
-    }
-
-    @Override
-    protected void updateCurrent(final InstanceIdentifier<D> id, final D dataBefore, final D dataAfter,
-                                 final WriteContext ctx) throws WriteFailedException {
-        // Make sure the key is present
-        if(isWildcarded(id)) {
-            super.updateCurrent(getSpecificId(id, dataBefore), dataBefore, dataAfter, ctx);
-        } else {
-            super.updateCurrent(id, dataBefore, dataAfter, ctx);
-        }
-    }
-
-    @Override
-    protected void deleteCurrent(final InstanceIdentifier<D> id, final D dataBefore, final WriteContext ctx)
-        throws WriteFailedException {
-        // Make sure the key is present
-        if(isWildcarded(id)) {
-            super.deleteCurrent(getSpecificId(id, dataBefore), dataBefore, ctx);
-        } else {
-            super.deleteCurrent(id, dataBefore, ctx);
-        }
-    }
-
-    private boolean isWildcarded(final InstanceIdentifier<D> id) {
-        return id.firstIdentifierOf(getManagedDataObjectType().getTargetType()).isWildcarded();
-    }
-
-    private InstanceIdentifier<D> getSpecificId(final InstanceIdentifier<D> currentId, final D current) {
-        return RWUtils.replaceLastInId(currentId,
-            new InstanceIdentifier.IdentifiableItem<>(currentId.getTargetType(), current.getKey()));
-    }
-}
diff --git a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriter.java b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriter.java
new file mode 100644
index 000000000..b61fb51f7
--- /dev/null
+++ b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriter.java
@@ -0,0 +1,104 @@
+/*
+ * 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.impl.write;
+
+import io.fd.honeycomb.v3po.translate.spi.write.ListWriterCustomizer;
+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 javax.annotation.Nonnull;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * Special writer handling updates for nodes of type list.
+ */
+public final class GenericListWriter<D extends DataObject & Identifiable<K>, K extends Identifier<D>> extends
+    AbstractCompositeWriter<D> implements Writer<D> {
+
+    private final ListWriterCustomizer<D, K> customizer;
+
+    public GenericListWriter(@Nonnull final InstanceIdentifier<D> type,
+                             @Nonnull final ListWriterCustomizer<D, K> customizer) {
+        super(type);
+        this.customizer = customizer;
+    }
+
+    @Override
+    protected void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D data,
+                                          @Nonnull final WriteContext ctx) throws WriteFailedException {
+        customizer.writeCurrentAttributes(id, data, ctx);
+    }
+
+    @Override
+    protected void deleteCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
+                                           @Nonnull final WriteContext ctx) throws WriteFailedException {
+        customizer.deleteCurrentAttributes(id, dataBefore, ctx);
+    }
+
+    @Override
+    protected void updateCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
+                                           @Nonnull final D dataAfter, @Nonnull final WriteContext ctx)
+        throws WriteFailedException {
+        customizer.updateCurrentAttributes(id, dataBefore, dataAfter, ctx);
+    }
+
+    @Override
+    protected void writeCurrent(final InstanceIdentifier<D> id, final D data, final WriteContext ctx)
+        throws WriteFailedException {
+        // Make sure the key is present
+        if (isWildcarded(id)) {
+            super.writeCurrent(getSpecificId(id, data), data, ctx);
+        } else {
+            super.writeCurrent(id, data, ctx);
+        }
+    }
+
+    @Override
+    protected void updateCurrent(final InstanceIdentifier<D> id, final D dataBefore, final D dataAfter,
+                                 final WriteContext ctx) throws WriteFailedException {
+        // Make sure the key is present
+        if (isWildcarded(id)) {
+            super.updateCurrent(getSpecificId(id, dataBefore), dataBefore, dataAfter, ctx);
+        } else {
+            super.updateCurrent(id, dataBefore, dataAfter, ctx);
+        }
+    }
+
+    @Override
+    protected void deleteCurrent(final InstanceIdentifier<D> id, final D dataBefore, final WriteContext ctx)
+        throws WriteFailedException {
+        // Make sure the key is present
+        if (isWildcarded(id)) {
+            super.deleteCurrent(getSpecificId(id, dataBefore), dataBefore, ctx);
+        } else {
+            super.deleteCurrent(id, dataBefore, ctx);
+        }
+    }
+
+    private boolean isWildcarded(final InstanceIdentifier<D> id) {
+        return id.firstIdentifierOf(getManagedDataObjectType().getTargetType()).isWildcarded();
+    }
+
+    private InstanceIdentifier<D> getSpecificId(final InstanceIdentifier<D> currentId, final D current) {
+        return RWUtils.replaceLastInId(currentId,
+            new InstanceIdentifier.IdentifiableItem<>(currentId.getTargetType(), current.getKey()));
+    }
+}
diff --git a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeRootWriter.java b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/GenericWriter.java
index 6f46359ff..6ca80ca37 100644
--- a/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/CompositeRootWriter.java
+++ b/v3po/translate-impl/src/main/java/io/fd/honeycomb/v3po/translate/impl/write/GenericWriter.java
@@ -16,50 +16,26 @@
 
 package io.fd.honeycomb.v3po.translate.impl.write;
 
-import io.fd.honeycomb.v3po.translate.impl.TraversalType;
 import io.fd.honeycomb.v3po.translate.spi.write.RootWriterCustomizer;
-import io.fd.honeycomb.v3po.translate.util.RWUtils;
-import io.fd.honeycomb.v3po.translate.write.ChildWriter;
 import io.fd.honeycomb.v3po.translate.write.WriteContext;
 import io.fd.honeycomb.v3po.translate.write.WriteFailedException;
-import java.util.List;
 import javax.annotation.Nonnull;
-import org.opendaylight.yangtools.yang.binding.Augmentation;
-import org.opendaylight.yangtools.yang.binding.ChildOf;
 import org.opendaylight.yangtools.yang.binding.DataObject;
 import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
 
-public class CompositeRootWriter<D extends DataObject> extends AbstractCompositeWriter<D> {
+/**
+ * Special writer handling updates for any complex nodes.
+ */
+public final class GenericWriter<D extends DataObject> extends AbstractCompositeWriter<D> {
 
     private final RootWriterCustomizer<D> customizer;
 
-    public CompositeRootWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                               @Nonnull final RootWriterCustomizer<D> customizer) {
-        this(type, childWriters, augWriters, customizer, TraversalType.PREORDER);
-    }
-
-    public CompositeRootWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final List<ChildWriter<? extends Augmentation<D>>> augWriters,
-                               @Nonnull final RootWriterCustomizer<D> customizer,
-                               @Nonnull final TraversalType traversalType) {
-        super(type, childWriters, augWriters, traversalType);
+    public GenericWriter(@Nonnull final InstanceIdentifier<D> type,
+                         @Nonnull final RootWriterCustomizer<D> customizer) {
+        super(type);
         this.customizer = customizer;
     }
 
-    public CompositeRootWriter(@Nonnull final Class<D> type,
-                               @Nonnull final List<ChildWriter<? extends ChildOf<D>>> childWriters,
-                               @Nonnull final RootWriterCustomizer<D> customizer) {
-        this(type, childWriters, RWUtils.<D>emptyAugWriterList(), customizer);
-    }
-
-    public CompositeRootWriter(@Nonnull final Class<D> type,
-                               @Nonnull final RootWriterCustomizer<D> customizer) {
-        this(type, RWUtils.<D>emptyChildWriterList(), RWUtils.<D>emptyAugWriterList(), customizer);
-    }
-
     @Override
     protected void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D data,
                                           @Nonnull final WriteContext ctx) throws WriteFailedException {
diff --git a/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriterTest.java b/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriterTest.java
new file mode 100644
index 000000000..54a7466e1
--- /dev/null
+++ b/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericListWriterTest.java
@@ -0,0 +1,83 @@
+/*
+ * 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.impl.write;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import io.fd.honeycomb.v3po.translate.spi.write.ListWriterCustomizer;
+import io.fd.honeycomb.v3po.translate.write.WriteContext;
+import java.util.Collections;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.Identifiable;
+import org.opendaylight.yangtools.yang.binding.Identifier;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+public class GenericListWriterTest {
+
+    private static final InstanceIdentifier<IdentifiableDataObject>
+            DATA_OBJECT_INSTANCE_IDENTIFIER = InstanceIdentifier.create(IdentifiableDataObject.class);
+    @Mock
+    private ListWriterCustomizer<IdentifiableDataObject, DataObjectIdentifier> customizer;
+    @Mock
+    private WriteContext ctx;
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @Test
+    public void testUpdate() throws Exception {
+        final GenericListWriter<IdentifiableDataObject, DataObjectIdentifier> writer =
+                new GenericListWriter<>(DATA_OBJECT_INSTANCE_IDENTIFIER, customizer);
+
+        final IdentifiableDataObject before = mock(IdentifiableDataObject.class);
+        final DataObjectIdentifier beforeKey = mock(DataObjectIdentifier.class);
+        when(before.getKey()).thenReturn(beforeKey);
+        final IdentifiableDataObject after = mock(IdentifiableDataObject.class);
+        final DataObjectIdentifier keyAfter = mock(DataObjectIdentifier.class);
+        when(after.getKey()).thenReturn(keyAfter);
+
+        assertEquals(DATA_OBJECT_INSTANCE_IDENTIFIER, writer.getManagedDataObjectType());
+
+        final InstanceIdentifier<IdentifiableDataObject> keyedIdBefore =
+                (InstanceIdentifier<IdentifiableDataObject>) InstanceIdentifier.create(Collections
+                        .singleton(new InstanceIdentifier.IdentifiableItem<>(IdentifiableDataObject.class, beforeKey)));
+        final InstanceIdentifier<IdentifiableDataObject> keyedIdAfter =
+                (InstanceIdentifier<IdentifiableDataObject>) InstanceIdentifier.create(Collections
+                        .singleton(new InstanceIdentifier.IdentifiableItem<>(IdentifiableDataObject.class, keyAfter)));
+
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, before, after, ctx);
+        verify(customizer).updateCurrentAttributes(keyedIdBefore, before, after, ctx);
+
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, before, null, ctx);
+        verify(customizer).deleteCurrentAttributes(keyedIdBefore, before, ctx);
+
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, null, after, ctx);
+        verify(customizer).writeCurrentAttributes(keyedIdAfter, after, ctx);
+    }
+
+    private abstract static class IdentifiableDataObject implements DataObject, Identifiable<DataObjectIdentifier> {}
+    private abstract static class DataObjectIdentifier implements Identifier<IdentifiableDataObject> {}
+}
\ No newline at end of file
diff --git a/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericWriterTest.java b/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericWriterTest.java
new file mode 100644
index 000000000..919072bcb
--- /dev/null
+++ b/v3po/translate-impl/src/test/java/io/fd/honeycomb/v3po/translate/impl/write/GenericWriterTest.java
@@ -0,0 +1,64 @@
+/*
+ * 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.impl.write;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+import io.fd.honeycomb.v3po.translate.spi.write.RootWriterCustomizer;
+import io.fd.honeycomb.v3po.translate.write.WriteContext;
+import org.junit.Before;
+import org.junit.Test;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+public class GenericWriterTest {
+
+    private static final InstanceIdentifier<DataObject>
+            DATA_OBJECT_INSTANCE_IDENTIFIER = InstanceIdentifier.create(DataObject.class);
+    @Mock
+    private RootWriterCustomizer<DataObject> customizer;
+    @Mock
+    private WriteContext ctx;
+
+    @Before
+    public void setUp() throws Exception {
+        MockitoAnnotations.initMocks(this);
+    }
+
+    @Test
+    public void testUpdate() throws Exception {
+        final GenericWriter<DataObject> writer =
+                new GenericWriter<>(DATA_OBJECT_INSTANCE_IDENTIFIER, customizer);
+
+        final DataObject before = mock(DataObject.class);
+        final DataObject after = mock(DataObject.class);
+
+        assertEquals(DATA_OBJECT_INSTANCE_IDENTIFIER, writer.getManagedDataObjectType());
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, before, after, ctx);
+        verify(customizer).updateCurrentAttributes(DATA_OBJECT_INSTANCE_IDENTIFIER, before, after, ctx);
+
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, before, null, ctx);
+        verify(customizer).deleteCurrentAttributes(DATA_OBJECT_INSTANCE_IDENTIFIER, before, ctx);
+
+        writer.update(DATA_OBJECT_INSTANCE_IDENTIFIER, null, after, ctx);
+        verify(customizer).writeCurrentAttributes(DATA_OBJECT_INSTANCE_IDENTIFIER, after, ctx);
+    }
+}
\ No newline at end of file