org.apache.usergrid.persistence.collection.mvcc.changelog.ChangeLogGeneratorImpl.java Source code

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Here is the source code for org.apache.usergrid.persistence.collection.mvcc.changelog.ChangeLogGeneratorImpl.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  The ASF licenses this file to You
 * 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.  For additional information regarding
 * copyright in this work, please see the NOTICE file in the top level
 * directory of this distribution.
 */
package org.apache.usergrid.persistence.collection.mvcc.changelog;

import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import org.apache.usergrid.persistence.collection.MvccEntity;
import org.apache.usergrid.persistence.model.entity.Entity;
import org.apache.usergrid.persistence.model.field.Field;

import com.google.common.base.Optional;
import com.google.common.base.Preconditions;
import com.google.common.collect.Sets;

/**
 * A default implementation of {@link ChangeLogGenerator}.
 */
public class ChangeLogGeneratorImpl implements ChangeLogGenerator {

    /**
     * See parent comment {@link ChangeLogGenerator#getChangeLog(java.util.Collection)}
     */
    @Override
    public ChangeLog getChangeLog(Collection<MvccEntity> mvccEntities) {

        Preconditions.checkArgument(mvccEntities.size() > 0,
                "You must specify at least 1 entities for a change log");

        //TODO, this is a SWAG on the entity size, this may be too little or too much.
        final ChangeLogImpl changeLog = new ChangeLogImpl(50);

        Iterator<MvccEntity> iterator = mvccEntities.iterator();

        Set<String> previousFieldNames = getFieldNames(iterator.next().getEntity());

        Set<String> currentFieldNames = null;

        while (iterator.hasNext()) {

            final MvccEntity mvccEntity = iterator.next();

            currentFieldNames = getFieldNames(mvccEntity.getEntity());

            if (mvccEntity.getStatus() == MvccEntity.Status.DELETED) {
                changeLog.clear();
                continue;
            }

            final Entity currentEntity = mvccEntity.getEntity().orNull();

            //get all fields in the current field that aren't in the previous fields
            final Set<String> deletedFields = Sets.difference(previousFieldNames, currentFieldNames);

            changeLog.addDeletes(deletedFields);

            for (String addedField : currentFieldNames) {
                changeLog.addWrite(currentEntity.getField(addedField));
            }

            previousFieldNames = currentFieldNames;
        }

        //subtract off the the last set of fields from the entity
        if (currentFieldNames != null) {
            changeLog.clear(currentFieldNames);
        }

        return changeLog;
    }

    /**
     * Get all the fieldNames on this entity
     */
    private Set<String> getFieldNames(final Optional<Entity> entity) {
        if (!entity.isPresent()) {
            return Collections.emptySet();
        }

        Collection<Field> fields = entity.get().getFields();

        Set<String> fieldNames = new HashSet<>(fields.size());

        for (final Field field : entity.get().getFields()) {
            fieldNames.add(field.getName());
        }

        return fieldNames;
    }
}