HONEYCOMB-9: Split impl module into smaller parts

Change-Id: I9232e0adfe611cb97951080839b28a7b62ba5484
Signed-off-by: Maros Marsalek <mmarsale@cisco.com>

11 files changed, 927 insertions, 0 deletions

diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/DelegatingReaderRegistry.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/DelegatingReaderRegistry.java
new file mode 100644
index 000000000..5217024e8
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/DelegatingReaderRegistry.java
@@ -0,0 +1,113 @@
+/*
+ * 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.vpp.facade.impl.read.util;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.base.Optional;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.LinkedListMultimap;
+import com.google.common.collect.Multimap;
+import io.fd.honeycomb.v3po.vpp.facade.impl.util.VppRWUtils;
+import io.fd.honeycomb.v3po.vpp.facade.read.ListVppReader;
+import io.fd.honeycomb.v3po.vpp.facade.read.ReadContext;
+import io.fd.honeycomb.v3po.vpp.facade.read.ReadFailedException;
+import io.fd.honeycomb.v3po.vpp.facade.read.ReaderRegistry;
+import io.fd.honeycomb.v3po.vpp.facade.read.VppReader;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import javax.annotation.Nonnull;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Simple reader registry able to perform and aggregated read (ROOT read) on top of all provided readers. Also able to
+ * delegate a specific read to one of the delegate readers.
+ *
+ * This could serve as a utility to hold & hide all available readers in upper layers.
+ */
+public final class DelegatingReaderRegistry implements ReaderRegistry {
+
+    private static final Logger LOG = LoggerFactory.getLogger(DelegatingReaderRegistry.class);
+
+    private final Map<Class<? extends DataObject>, VppReader<? extends DataObject>> rootReaders;
+
+    /**
+     * Create new {@link DelegatingReaderRegistry}
+     *
+     * @param rootReaders List of delegate readers
+     */
+    public DelegatingReaderRegistry(@Nonnull final List<VppReader<? extends DataObject>> rootReaders) {
+        this.rootReaders = VppRWUtils.uniqueLinkedIndex(checkNotNull(rootReaders), VppRWUtils.MANAGER_CLASS_FUNCTION);
+    }
+
+    @Override
+    @Nonnull
+    public Multimap<InstanceIdentifier<? extends DataObject>, ? extends DataObject> readAll(
+        @Nonnull final ReadContext ctx) throws ReadFailedException {
+
+        LOG.debug("Reading from all delegates: {}", this);
+        LOG.trace("Reading from all delegates: {}", rootReaders.values());
+
+        final Multimap<InstanceIdentifier<? extends DataObject>, DataObject> objects = LinkedListMultimap.create();
+        for (VppReader<? extends DataObject> rootReader : rootReaders.values()) {
+            LOG.debug("Reading from delegate: {}", rootReader);
+
+            if (rootReader instanceof ListVppReader) {
+                final List<? extends DataObject> listEntries =
+                        ((ListVppReader) rootReader).readList(rootReader.getManagedDataObjectType(), ctx);
+                if (!listEntries.isEmpty()) {
+                    objects.putAll(rootReader.getManagedDataObjectType(), listEntries);
+                }
+            } else {
+                final Optional<? extends DataObject> read = rootReader.read(rootReader.getManagedDataObjectType(), ctx);
+                if (read.isPresent()) {
+                    objects.putAll(rootReader.getManagedDataObjectType(), Collections.singletonList(read.get()));
+                }
+            }
+        }
+
+        return objects;
+    }
+
+    @Nonnull
+    @Override
+    public Optional<? extends DataObject> read(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                               @Nonnull final ReadContext ctx)
+            throws ReadFailedException {
+        final InstanceIdentifier.PathArgument first = checkNotNull(
+                Iterables.getFirst(id.getPathArguments(), null), "Empty id");
+        final VppReader<? extends DataObject> vppReader = rootReaders.get(first.getType());
+        checkNotNull(vppReader,
+                "Unable to read %s. Missing reader. Current readers for: %s", id, rootReaders.keySet());
+        LOG.debug("Reading from delegate: {}", vppReader);
+        return vppReader.read(id, ctx);
+    }
+
+    /**
+     * @throws UnsupportedOperationException This getter is not supported for reader registry since it does not manage a
+     *                                       specific node type
+     */
+    @Nonnull
+    @Override
+    public InstanceIdentifier<DataObject> getManagedDataObjectType() {
+        throw new UnsupportedOperationException("Root registry has no type");
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/NoopReaderCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/NoopReaderCustomizer.java
new file mode 100644
index 000000000..5b78cdbba
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/NoopReaderCustomizer.java
@@ -0,0 +1,32 @@
+/*
+ * 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.vpp.facade.impl.read.util;
+
+import io.fd.honeycomb.v3po.vpp.facade.Context;
+import io.fd.honeycomb.v3po.vpp.facade.spi.read.RootVppReaderCustomizer;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+public abstract class NoopReaderCustomizer<C extends DataObject, B extends Builder<C>> implements
+    RootVppReaderCustomizer<C, B> {
+
+    @Override
+    public void readCurrentAttributes(InstanceIdentifier<C> id, final B builder, final Context context) {
+        // Noop
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveChildReaderCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveChildReaderCustomizer.java
new file mode 100644
index 000000000..a83269658
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveChildReaderCustomizer.java
@@ -0,0 +1,57 @@
+/*
+ * 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.vpp.facade.impl.read.util;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
+import io.fd.honeycomb.v3po.vpp.facade.impl.util.ReflectionUtils;
+import io.fd.honeycomb.v3po.vpp.facade.spi.read.ChildVppReaderCustomizer;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.util.Collections;
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+
+/**
+ * Might be slow !
+ */
+public class ReflexiveChildReaderCustomizer<C extends DataObject, B extends Builder<C>>
+    extends ReflexiveRootReaderCustomizer<C, B>
+    implements ChildVppReaderCustomizer<C,B> {
+
+    public ReflexiveChildReaderCustomizer(final Class<B> builderClass) {
+        super(builderClass);
+    }
+
+    // TODO Could be just a default implementation in interface (making this a mixin)
+
+    @Override
+    public void merge(final Builder<? extends DataObject> parentBuilder, final C readValue) {
+        final Optional<Method> method =
+            ReflectionUtils.findMethodReflex(parentBuilder.getClass(), "set",
+                Collections.<Class<?>>singletonList(readValue.getClass()), parentBuilder.getClass());
+
+        Preconditions.checkArgument(method.isPresent(), "Unable to set %s to %s", readValue, parentBuilder);
+
+        try {
+            method.get().invoke(parentBuilder, readValue);
+        } catch (IllegalAccessException | InvocationTargetException e) {
+            throw new IllegalArgumentException("Unable to set " + readValue + " to " + parentBuilder, e);
+        }
+    }
+
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveRootReaderCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveRootReaderCustomizer.java
new file mode 100644
index 000000000..b78bcdc06
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/read/util/ReflexiveRootReaderCustomizer.java
@@ -0,0 +1,42 @@
+/*
+ * 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.vpp.facade.impl.read.util;
+
+import org.opendaylight.yangtools.concepts.Builder;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+
+/**
+ * Might be slow !
+ */
+public class ReflexiveRootReaderCustomizer<C extends DataObject, B extends Builder<C>>  extends NoopReaderCustomizer<C, B> {
+
+    private final Class<B> builderClass;
+
+    public ReflexiveRootReaderCustomizer(final Class<B> builderClass) {
+        this.builderClass = builderClass;
+    }
+
+    @Override
+    public B getBuilder(InstanceIdentifier<C> id) {
+        try {
+            return builderClass.newInstance();
+        } catch (InstantiationException | IllegalAccessException e) {
+            throw new IllegalStateException("Unable to instantiate " + builderClass, e);
+        }
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/ReflectionUtils.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/ReflectionUtils.java
new file mode 100644
index 000000000..db560622c
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/ReflectionUtils.java
@@ -0,0 +1,79 @@
+/*
+ * 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.vpp.facade.impl.util;
+
+import com.google.common.base.Optional;
+import java.lang.reflect.Method;
+import java.util.List;
+import javax.annotation.Nonnull;
+
+/**
+ * Reflection based utilities
+ */
+public final class ReflectionUtils {
+
+    private ReflectionUtils() {}
+
+    /**
+     * Find a specific method using reflection
+     *
+     * @param managedType Class object to find method in
+     * @param prefix Method name prefix used when finding the method. Case does not matter.
+     * @param paramTypes List of input argument types
+     * @param retType Return type
+     *
+     * @return Found method or Optional.absent() if there's no such method
+     */
+    @Nonnull
+    public static Optional<Method> findMethodReflex(@Nonnull final Class<?> managedType,
+                                                    @Nonnull final String prefix,
+                                                    @Nonnull final List<Class<?>> paramTypes,
+                                                    @Nonnull final Class<?> retType) {
+        for (Method method : managedType.getMethods()) {
+            if(isMethodMatch(prefix, paramTypes, retType, method)) {
+                return Optional.of(method);
+            }
+        }
+
+        return Optional.absent();
+    }
+
+    private static boolean isMethodMatch(final @Nonnull String prefix,
+                                         final @Nonnull List<Class<?>> paramTypes,
+                                         final @Nonnull Class<?> retType, final Method method) {
+        if (!method.getName().toLowerCase().startsWith(prefix.toLowerCase())) {
+            return false;
+        }
+
+        final Class<?>[] parameterTypes = method.getParameterTypes();
+        if (parameterTypes.length != paramTypes.size()) {
+            return false;
+        }
+
+        for (int i = 0; i < parameterTypes.length; i++) {
+            if (!parameterTypes[i].isAssignableFrom(paramTypes.get(i))) {
+                return false;
+            }
+        }
+
+        if (!method.getReturnType().equals(retType)) {
+            return false;
+        }
+
+        return true;
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppApiCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppApiCustomizer.java
new file mode 100644
index 000000000..41090f493
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppApiCustomizer.java
@@ -0,0 +1,41 @@
+/*
+ * 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.vpp.facade.impl.util;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * Abstract utility to hold the vppApi reference.
+ */
+@Beta
+public abstract class VppApiCustomizer {
+
+    private final org.openvpp.vppjapi.vppApi vppApi;
+
+    protected VppApiCustomizer(final org.openvpp.vppjapi.vppApi vppApi) {
+        this.vppApi = vppApi;
+    }
+
+    /**
+     * Get vppApi reference
+     *
+     * @return vppApi reference
+     */
+    public org.openvpp.vppjapi.vppApi getVppApi() {
+        return vppApi;
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppRWUtils.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppRWUtils.java
new file mode 100644
index 000000000..64667b85f
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/util/VppRWUtils.java
@@ -0,0 +1,178 @@
+/*
+ * 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.vpp.facade.impl.util;
+
+import com.google.common.base.Function;
+import com.google.common.base.Preconditions;
+import com.google.common.base.Predicate;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Maps;
+import io.fd.honeycomb.v3po.vpp.facade.SubtreeManager;
+import io.fd.honeycomb.v3po.vpp.facade.read.ChildVppReader;
+import io.fd.honeycomb.v3po.vpp.facade.write.ChildVppWriter;
+import java.util.Collection;
+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 final class VppRWUtils {
+
+    private VppRWUtils() {}
+
+    /**
+     * Find next item in ID after provided type
+     */
+    @Nonnull
+    public static InstanceIdentifier.PathArgument getNextId(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                                            @Nonnull final InstanceIdentifier<? extends DataObject> type) {
+        // TODO this is inefficient(maybe, depending on actual Iterable type)
+        final Iterable<InstanceIdentifier.PathArgument> pathArguments = id.getPathArguments();
+        final int i = Iterables.indexOf(pathArguments, new Predicate<InstanceIdentifier.PathArgument>() {
+            @Override
+            public boolean apply(final InstanceIdentifier.PathArgument input) {
+                return input.getType().isAssignableFrom(type.getTargetType());
+            }
+        });
+        Preconditions.checkArgument(i >= 0, "Unable to find %s type in %s", type.getTargetType(), id);
+        return Iterables.get(pathArguments, i + 1);
+    }
+
+    public static <T> List<ChildVppReader<? extends ChildOf<T>>> emptyChildReaderList() {
+        return Collections.emptyList();
+    }
+
+    public static <T> List<ChildVppWriter<? extends ChildOf<T>>> emptyChildWriterList() {
+        return Collections.emptyList();
+    }
+
+    public static <T> List<ChildVppReader<? extends Augmentation<T>>> emptyAugReaderList() {
+        return Collections.emptyList();
+    }
+
+    public static <T> List<ChildVppWriter<? extends Augmentation<T>>> emptyAugWriterList() {
+        return Collections.emptyList();
+    }
+
+    public static <T> List<ChildVppReader<? extends Augmentation<T>>> singletonAugReaderList(
+        ChildVppReader<? extends Augmentation<T>> item) {
+        return Collections.<ChildVppReader<? extends Augmentation<T>>>singletonList(item);
+    }
+
+    public static <T> List<ChildVppReader<? extends ChildOf<T>>> singletonChildReaderList(
+        ChildVppReader<? extends ChildOf<T>> item) {
+        return Collections.<ChildVppReader<? extends ChildOf<T>>>singletonList(item);
+    }
+
+    public static <T> List<ChildVppWriter<? extends ChildOf<T>>> singletonChildWriterList(
+        ChildVppWriter<? extends ChildOf<T>> item) {
+        return Collections.<ChildVppWriter<? extends ChildOf<T>>>singletonList(item);
+    }
+
+    /**
+     * Replace last item in ID with a provided IdentifiableItem of the same type
+     */
+    @SuppressWarnings("unchecked")
+    @Nonnull
+    public static <D extends DataObject & Identifiable<K>, K extends Identifier<D>> InstanceIdentifier<D> replaceLastInId(
+        @Nonnull final InstanceIdentifier<D> id, final InstanceIdentifier.IdentifiableItem<D, K> currentBdItem) {
+
+        final Iterable<InstanceIdentifier.PathArgument> pathArguments = id.getPathArguments();
+        final Iterable<InstanceIdentifier.PathArgument> withoutCurrent =
+            Iterables.limit(pathArguments, Iterables.size(pathArguments) - 1);
+        final Iterable<InstanceIdentifier.PathArgument> concat =
+            Iterables.concat(withoutCurrent, Collections.singleton(currentBdItem));
+        return (InstanceIdentifier<D>) InstanceIdentifier.create(concat);
+    }
+
+    /**
+     * Create IdentifiableItem from target type of provided ID with provided key
+     */
+    @Nonnull
+    public static <D extends DataObject & Identifiable<K>, K extends Identifier<D>> InstanceIdentifier.IdentifiableItem<D, K> getCurrentIdItem(
+        @Nonnull final InstanceIdentifier<D> id, final K key) {
+        return new InstanceIdentifier.IdentifiableItem<>(id.getTargetType(), key);
+    }
+
+    /**
+     * Trim InstanceIdentifier at indexOf(type)
+     */
+    @SuppressWarnings("unchecked")
+    @Nonnull
+    public static <D extends DataObject> InstanceIdentifier<D> cutId(@Nonnull final InstanceIdentifier<? extends DataObject> id,
+                                                                     @Nonnull final InstanceIdentifier<D> type) {
+        final Iterable<InstanceIdentifier.PathArgument> pathArguments = id.getPathArguments();
+        final int i = Iterables.indexOf(pathArguments, new Predicate<InstanceIdentifier.PathArgument>() {
+            @Override
+            public boolean apply(final InstanceIdentifier.PathArgument input) {
+                return input.getType().equals(type.getTargetType());
+            }
+        });
+        Preconditions.checkArgument(i >= 0, "ID %s does not contain %s", id, type);
+        return (InstanceIdentifier<D>) InstanceIdentifier.create(Iterables.limit(pathArguments, i + 1));
+    }
+
+    /**
+     * Create a map from a collection, checking for duplicity in the process
+     */
+    @Nonnull
+    public static <K, V> Map<K, V> uniqueLinkedIndex(@Nonnull final Collection<V> values, @Nonnull final Function<? super V, K> keyFunction) {
+        final Map<K, V> objectObjectLinkedHashMap = Maps.newLinkedHashMap();
+        for (V value : values) {
+            final K key = keyFunction.apply(value);
+            Preconditions.checkArgument(objectObjectLinkedHashMap.put(key, value) == null,
+                "Duplicate key detected : %s", key);
+        }
+        return objectObjectLinkedHashMap;
+    }
+
+    public static final Function<SubtreeManager<? extends DataObject>, Class<? extends DataObject>>
+        MANAGER_CLASS_FUNCTION = new Function<SubtreeManager<? extends DataObject>, Class<? extends DataObject>>() {
+        @Override
+        public Class<? extends DataObject> apply(final SubtreeManager<? extends DataObject> input) {
+            return input.getManagedDataObjectType().getTargetType();
+        }
+    };
+
+    public static final Function<SubtreeManager<? extends Augmentation<?>>, Class<? extends DataObject>>
+        MANAGER_CLASS_AUG_FUNCTION = new Function<SubtreeManager<? extends Augmentation<?>>, Class<? extends DataObject>>() {
+
+        @Override
+        @SuppressWarnings("unchecked")
+        public Class<? extends DataObject> apply(final SubtreeManager<? extends Augmentation<?>> input) {
+            final Class<? extends Augmentation<?>> targetType = input.getManagedDataObjectType().getTargetType();
+            Preconditions.checkArgument(DataObject.class.isAssignableFrom(targetType));
+            return (Class<? extends DataObject>) targetType;
+        }
+    };
+
+    @SuppressWarnings("unchecked")
+    public static <D extends DataObject> InstanceIdentifier<D> appendTypeToId(
+        final InstanceIdentifier<? extends DataObject> parentId, final InstanceIdentifier<D> type) {
+        Preconditions.checkArgument(!parentId.contains(type),
+            "Unexpected InstanceIdentifier %s, already contains %s", parentId, type);
+        final InstanceIdentifier.PathArgument t = Iterables.getOnlyElement(type.getPathArguments());
+        return (InstanceIdentifier<D>) InstanceIdentifier.create(Iterables.concat(
+            parentId.getPathArguments(), Collections.singleton(t)));
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/DelegatingWriterRegistry.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/DelegatingWriterRegistry.java
new file mode 100644
index 000000000..14cec7a55
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/DelegatingWriterRegistry.java
@@ -0,0 +1,176 @@
+/*
+ * 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.vpp.facade.impl.write.util;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+
+import com.google.common.base.Function;
+import com.google.common.collect.Collections2;
+import com.google.common.collect.Iterables;
+import com.google.common.collect.Lists;
+import com.google.common.collect.Sets;
+import io.fd.honeycomb.v3po.vpp.facade.VppException;
+import io.fd.honeycomb.v3po.vpp.facade.impl.util.VppRWUtils;
+import io.fd.honeycomb.v3po.vpp.facade.write.VppWriter;
+import io.fd.honeycomb.v3po.vpp.facade.write.WriteContext;
+import io.fd.honeycomb.v3po.vpp.facade.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 read (ROOT write) on top of all provided writers. Also able to
+ * delegate a specific read 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 static final Function<InstanceIdentifier<?>, Class<? extends DataObject>> ID_TO_CLASS =
+            new Function<InstanceIdentifier<?>, Class<? extends DataObject>>() {
+                @Override
+                public Class<? extends DataObject> apply(final InstanceIdentifier<?> input) {
+                    return input.getTargetType();
+                }
+            };
+
+    private final Map<Class<? extends DataObject>, VppWriter<? extends DataObject>> rootWriters;
+
+    /**
+     * Create new {@link DelegatingWriterRegistry}
+     *
+     * @param rootWriters List of delegate writers
+     */
+    public DelegatingWriterRegistry(@Nonnull final List<VppWriter<? extends DataObject>> rootWriters) {
+        this.rootWriters = VppRWUtils.uniqueLinkedIndex(checkNotNull(rootWriters), VppRWUtils.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 VppException {
+        final InstanceIdentifier.PathArgument first = checkNotNull(
+                Iterables.getFirst(id.getPathArguments(), null), "Empty id");
+        final VppWriter<? extends DataObject> vppWriter = rootWriters.get(first.getType());
+        checkNotNull(vppWriter,
+                "Unable to write %s. Missing writer. Current writers for: %s", id, rootWriters.keySet());
+        vppWriter.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 VppException {
+        checkAllWritersPresent(nodesBefore);
+        checkAllWritersPresent(nodesAfter);
+
+        final List<InstanceIdentifier<?>> processedNodes = Lists.newArrayList();
+
+        for (Map.Entry<Class<? extends DataObject>, VppWriter<? extends DataObject>> rootWriterEntry : rootWriters
+                .entrySet()) {
+
+            final InstanceIdentifier<? extends DataObject> id = rootWriterEntry.getValue().getManagedDataObjectType();
+
+            final DataObject dataBefore = nodesBefore.get(id);
+            final DataObject dataAfter = nodesAfter.get(id);
+
+            // No change to current writer
+            if (dataBefore == null && dataAfter == null) {
+                continue;
+            }
+
+            LOG.debug("ChangesProcessor.applyChanges() processing dataBefore={}, dataAfter={}", dataBefore, dataAfter);
+
+            try {
+                update(id, 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) {
+        checkArgument(rootWriters.keySet().containsAll(Collections2.transform(nodesBefore.keySet(), ID_TO_CLASS)),
+                "Unable to handle all changes. Missing dedicated writers for: %s",
+                Sets.difference(nodesBefore.keySet(), rootWriters.keySet()));
+    }
+
+    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/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/NoopWriterCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/NoopWriterCustomizer.java
new file mode 100644
index 000000000..96b7d19b4
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/NoopWriterCustomizer.java
@@ -0,0 +1,49 @@
+/*
+ * 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.vpp.facade.impl.write.util;
+
+import io.fd.honeycomb.v3po.vpp.facade.Context;
+import io.fd.honeycomb.v3po.vpp.facade.spi.write.RootVppWriterCustomizer;
+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 RootVppWriterCustomizer<D> {
+
+    @Override
+    public void writeCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataAfter,
+                                       @Nonnull final Context ctx) {
+
+    }
+
+    @Override
+    public void updateCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
+                                        @Nonnull final D dataAfter,
+                                        @Nonnull final Context ctx) {
+
+    }
+
+    @Override
+    public void deleteCurrentAttributes(@Nonnull final InstanceIdentifier<D> id, @Nonnull final D dataBefore,
+                                        @Nonnull final Context ctx) {
+
+    }
+}
diff --git a/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/ReflexiveChildWriterCustomizer.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/ReflexiveChildWriterCustomizer.java
new file mode 100644
index 000000000..820f469d6
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/ReflexiveChildWriterCustomizer.java
@@ -0,0 +1,59 @@
+/*
+ * 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.vpp.facade.impl.write.util;
+
+import com.google.common.base.Optional;
+import com.google.common.base.Preconditions;
+import com.google.common.collect.Iterables;
+import io.fd.honeycomb.v3po.vpp.facade.impl.util.ReflectionUtils;
+import io.fd.honeycomb.v3po.vpp.facade.spi.write.ChildVppWriterCustomizer;
+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
+    ChildVppWriterCustomizer<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.of((C) method.get().invoke(parentData))
+                : Optional.<C>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/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/TransactionWriteContext.java b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/TransactionWriteContext.java
new file mode 100644
index 000000000..da124b03c
--- /dev/null
+++ b/v3po/vpp-facade-utils/src/main/java/io/fd/honeycomb/v3po/vpp/facade/impl/write/util/TransactionWriteContext.java
@@ -0,0 +1,101 @@
+/*
+ * 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.vpp.facade.impl.write.util;
+
+import com.google.common.base.Optional;
+import com.google.common.util.concurrent.CheckedFuture;
+import io.fd.honeycomb.v3po.vpp.facade.Context;
+import io.fd.honeycomb.v3po.vpp.facade.write.WriteContext;
+import java.util.Map;
+import javax.annotation.Nonnull;
+import org.opendaylight.controller.md.sal.common.api.data.LogicalDatastoreType;
+import org.opendaylight.controller.md.sal.common.api.data.ReadFailedException;
+import org.opendaylight.controller.md.sal.dom.api.DOMDataReadOnlyTransaction;
+import org.opendaylight.mdsal.binding.dom.codec.api.BindingNormalizedNodeSerializer;
+import org.opendaylight.yangtools.yang.binding.DataObject;
+import org.opendaylight.yangtools.yang.binding.InstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.YangInstanceIdentifier;
+import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNode;
+
+/**
+ * Transaction based WriteContext
+ */
+public final class TransactionWriteContext implements WriteContext {
+
+    private final DOMDataReadOnlyTransaction beforeTx;
+    private final DOMDataReadOnlyTransaction afterTx;
+    private final Context ctx;
+    private final BindingNormalizedNodeSerializer serializer;
+
+    public TransactionWriteContext(final BindingNormalizedNodeSerializer serializer,
+                                   final DOMDataReadOnlyTransaction beforeTx,
+                                   final DOMDataReadOnlyTransaction afterTx) {
+        this.serializer = serializer;
+        this.beforeTx = beforeTx;
+        this.afterTx = afterTx;
+        this.ctx = new Context();
+    }
+
+    // TODO make this asynchronous
+
+    @Override
+    public Optional<DataObject> readBefore(@Nonnull final InstanceIdentifier<? extends DataObject> currentId) {
+        return read(currentId, beforeTx);
+    }
+
+    private Optional<DataObject> read(final InstanceIdentifier<? extends DataObject> currentId,
+                                            final DOMDataReadOnlyTransaction tx) {
+        final YangInstanceIdentifier path = serializer.toYangInstanceIdentifier(currentId);
+
+        final CheckedFuture<Optional<NormalizedNode<?, ?>>, ReadFailedException> read =
+                tx.read(LogicalDatastoreType.CONFIGURATION, path);
+
+        try {
+            // TODO once the APIs are asynchronous use just Futures.transform
+            final Optional<NormalizedNode<?, ?>> optional = read.checkedGet();
+
+            if (!optional.isPresent()) {
+                return Optional.absent();
+            }
+
+            final NormalizedNode<?, ?> data = optional.get();
+            final Map.Entry<InstanceIdentifier<?>, DataObject> entry = serializer.fromNormalizedNode(path, data);
+
+            return Optional.of(entry.getValue());
+        } catch (ReadFailedException e) {
+            throw new IllegalStateException("Unable to perform read", e);
+        }
+    }
+
+    @Override
+    public Optional<DataObject> readAfter(@Nonnull final InstanceIdentifier<? extends DataObject> currentId) {
+        return read(currentId, afterTx);
+    }
+
+    @Override
+    public Context getContext() {
+        return ctx;
+    }
+
+    /**
+     * Does not close the transactions
+     */
+    @Override
+    public void close() {
+        ctx.close();
+    }
+}