ArrayOverrideStrategyResolver.java

/*
 * Copyright 2014-2016 CyberVision, Inc.
 *
 * 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 org.kaaproject.kaa.server.common.core.algorithms.override;


import org.apache.avro.Schema;
import org.apache.avro.Schema.Field;
import org.apache.avro.Schema.Type;

import java.io.IOException;
import java.text.MessageFormat;
import java.util.List;
import java.util.Map;


/**
 * The Class ArrayMergeStrategyResolver.
 */
public class ArrayOverrideStrategyResolver {

  public static final String FIELD_OVERRIDE_STRATEGY = "overrideStrategy";

  /**
   * The schema root.
   */
  private final Map<String, Schema> schemaTypes;

  /**
   * Instantiates a new array merge strategy resolver.
   *
   * @param types the configuration schema types
   * @throws IOException Signals that an I/O exception has occurred.
   */
  public ArrayOverrideStrategyResolver(Map<String, Schema> types) throws IOException {
    this.schemaTypes = types;
  }

  /**
   * Resolve.
   *
   * @param name        the parent name
   * @param namespace   the namespace
   * @param childName   the child name
   * @return the array merge strategy
   * @throws OverrideException the merge exception
   */
  public ArrayOverrideStrategy resolve(String name, String namespace, String childName)
          throws OverrideException {
    Schema schemaForParent = schemaTypes.get(namespace + "." + name);
    if (schemaForParent == null) {
      throw new OverrideException(MessageFormat.format(
              "Failed to find Schema with Name ''{0}'' and namespace ''{1}''", name, namespace));
    }
    String mergeStrategyName = findMergeStrategy(schemaForParent, childName);

    ArrayOverrideStrategy mergeStrategy = null;
    if (mergeStrategyName != null) {
      mergeStrategy = ArrayOverrideStrategy.getByName(mergeStrategyName);
    }
    if (mergeStrategy == null) {
      mergeStrategy = ArrayOverrideStrategy.REPLACE;
    }

    return mergeStrategy;
  }

  /**
   * Find merge strategy.
   *
   * @param root           the root
   * @param arrayFieldName the array field name
   * @return the string
   */
  private String findMergeStrategy(Schema root, String arrayFieldName) {
    if (root.getType() != Type.RECORD) {
      return null;
    }
    List<Field> fields = root.getFields();
    for (Field field : fields) {
      if (arrayFieldName.equals(field.name())) {
        return field.getProp(FIELD_OVERRIDE_STRATEGY);
      }
    }
    return null;
  }
}