content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  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.
   */
  
  package org.apache.ambari.server.collections;
  
  import java.lang.reflect.InvocationTargetException;
  import java.lang.reflect.Method;
  import java.lang.reflect.Type;
  import java.util.Collections;
  import java.util.Map;
  import java.util.Objects;
  
  import org.apache.ambari.server.collections.functors.PredicateClassFactory;
  import org.apache.commons.lang.StringUtils;
  
  import com.google.common.reflect.TypeToken;
  import com.google.gson.Gson;
  
  /**
   * PredicateUtils is a utility class providing methods to help perform tasks on {@link Predicate}s.
   */
  public class PredicateUtils {
    private static final Type PARSED_TYPE = new TypeToken<Map<String, Object>>() {
    }.getType();
  
    /**
     * Safely serializes the specified {@link Predicate} to a {@link Map}
     *
     * @param predicate the {@link Predicate} to process
     * @return a {@link Map} or null of the supplied predicate is null
     */
    public static Map<String, Object> toMap(Predicate predicate) {
      return (predicate == null) ? null : predicate.toMap();
    }
  
    /**
     * Builds a {@link Predicate} from a {@link Map}
     *
     * @param map a map containing the details of the predicate to create.
     * @return a {@link Predicate}
     */
    public static Predicate fromMap(Map<?, ?> map) {
      Predicate predicate = null;
  
      if ((map != null) && !map.isEmpty()) {
        if (map.size() == 1) {
          Map.Entry<?, ?> entry = map.entrySet().iterator().next();
          String name = Objects.toString(entry.getKey());
  
          Class<? extends Predicate> predicateClass = PredicateClassFactory.getPredicateClass(name);
  
          if (predicateClass == null) {
            throw new IllegalArgumentException(String.format("Unexpected predicate name - %s", name));
          } else {
            try {
              // Dynamically locate and invoke the static toMap method for the named Predicate
              // implementation using reflection
              Method method = predicateClass.getMethod("fromMap", Map.class);
              if (method == null) {
                throw new UnsupportedOperationException(String.format("Cannot translate data to a %s - %s", predicateClass.getName(), "Failed to find toMap method"));
              } else {
                predicate = (Predicate) method.invoke(null, Collections.singletonMap(name, entry.getValue()));
              }
            } catch (NoSuchMethodException | InvocationTargetException | IllegalAccessException e) {
              throw new UnsupportedOperationException(String.format("Cannot translate data to a %s - %s", predicateClass.getName(), e.getLocalizedMessage()), e);
            }
          }
        } else {
          throw new IllegalArgumentException(String.format("Too many map entries have been encountered - %d", map.size()));
        }
      }
  
      return predicate;
    }
  
  
    /**
     * Safely serializes the specified {@link Predicate} to a JSON-formatted {@link String}
     *
     * @param predicate the {@link Predicate} to process
     * @return a {@link String} or null of the supplied predicate is null
     */
    public static String toJSON(Predicate predicate) {
      return (predicate == null) ? null : predicate.toJSON();
    }
  
    /**
     * Builds a {@link Predicate} from a JSON-formatted {@link String}
     *
     * @param json a string containing the details of the predicate to create.
     * @return a {@link Predicate}
     * @see #fromMap(Map)
     */
    public static Predicate fromJSON(String json) {
      Map<String, Object> map = new Gson().fromJson(json, PARSED_TYPE);
      return (StringUtils.isEmpty(json) ? null : fromMap(map));
    }
  }
  