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.cassandra.config;
  
  import java.lang.reflect.Constructor;
  import java.lang.reflect.InvocationTargetException;
  import java.util.Collections;
  import java.util.List;
  import java.util.Map;
  import java.util.function.Predicate;
  import java.util.stream.Collectors;
  
  import com.google.common.base.Objects;
  
  import org.apache.cassandra.exceptions.ConfigurationException;
  import org.apache.cassandra.utils.Shared;
  
  import static org.apache.cassandra.utils.Shared.Scope.SIMULATION;
  
  @Shared(scope = SIMULATION)
  public class ParameterizedClass
  {
      public static final String CLASS_NAME = "class_name";
      public static final String PARAMETERS = "parameters";
  
      public String class_name;
      public Map<String, String> parameters;
  
      public ParameterizedClass()
      {
          // for snakeyaml
      }
  
      public ParameterizedClass(String class_name)
      {
          this(class_name, Collections.emptyMap());
      }
  
      public ParameterizedClass(String class_name, Map<String, String> parameters)
      {
          this.class_name = class_name;
          this.parameters = parameters;
      }
  
      @SuppressWarnings("unchecked")
      public ParameterizedClass(Map<String, ?> p)
      {
          this((String)p.get(CLASS_NAME),
               p.containsKey(PARAMETERS) ? (Map<String, String>)((List<?>)p.get(PARAMETERS)).get(0) : null);
      }
  
      static public <K> K newInstance(ParameterizedClass parameterizedClass, List<String> searchPackages)
      {
          Class<?> providerClass = null;
          if (searchPackages == null || searchPackages.isEmpty())
              searchPackages = Collections.singletonList("");
          for (String searchPackage : searchPackages)
          {
              try
              {
                  if (!searchPackage.isEmpty() && !searchPackage.endsWith("."))
                      searchPackage = searchPackage + '.';
                  String name = searchPackage + parameterizedClass.class_name;
                  providerClass = Class.forName(name);
              }
              catch (ClassNotFoundException e)
              {
                  //no-op
              }
          }
  
          if (providerClass == null)
          {
              String pkgList = '[' + searchPackages.stream().map(p -> '"' + p + '"').collect(Collectors.joining(",")) + ']';
              String error = "Unable to find class " + parameterizedClass.class_name + " in packages " + pkgList;
              throw new ConfigurationException(error);
          }
  
          try
          {
              Constructor<?> mapConstructor = filterConstructor(providerClass, c -> c.getParameterTypes().length == 1 && c.getParameterTypes()[0].equals(Map.class));
              if (mapConstructor != null)
                  return (K) mapConstructor.newInstance(parameterizedClass.parameters == null ? Collections.emptyMap() : parameterizedClass.parameters);
  
              // Falls-back to no-arg constructor
              Constructor<?> noArgsConstructor = filterConstructor(providerClass, c -> c.getParameterTypes().length == 0);
              if (noArgsConstructor != null)
                  return (K) noArgsConstructor.newInstance();
  
              throw new ConfigurationException("No valid constructor found for class " + parameterizedClass.class_name);
          }
          catch (IllegalAccessException | InstantiationException | ExceptionInInitializerError e)
          {
              throw new ConfigurationException("Unable to instantiate parameterized class " + parameterizedClass.class_name, e);
          }
          catch (InvocationTargetException e)
          {
              Throwable cause = e.getCause();
              String error = "Failed to instantiate class " + parameterizedClass.class_name +
                             (cause.getMessage() != null ? ": " + cause.getMessage() : "");
              throw new ConfigurationException(error, cause);
          }
      }
  
      private static Constructor<?> filterConstructor(Class<?> providerClass, Predicate<Constructor<?>> filter)
      {
          for (Constructor<?> constructor : providerClass.getDeclaredConstructors())
          {
              if (filter.test(constructor))
                  return constructor;
          }
  
          return null;
      }
  
      @Override
      public boolean equals(Object that)
      {
          return that instanceof ParameterizedClass && equals((ParameterizedClass) that);
      }
  
      public boolean equals(ParameterizedClass that)
      {
          return Objects.equal(class_name, that.class_name) && Objects.equal(parameters, that.parameters);
      }
  
      @Override
      public int hashCode()
      {
          return Objects.hashCode(class_name, parameters);
      }
  
      @Override
      public String toString()
      {
          return class_name + parameters;
      }
  }
  