content: /**
   * 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.apache.aurora.scheduler.http.api.security;
  
  import java.util.Optional;
  
  import org.apache.aurora.scheduler.http.api.security.FieldGetter.AbstractFieldGetter;
  import org.apache.thrift.TBase;
  import org.apache.thrift.TFieldIdEnum;
  import org.apache.thrift.meta_data.FieldMetaData;
  import org.apache.thrift.meta_data.FieldValueMetaData;
  import org.apache.thrift.meta_data.StructMetaData;
  
  import static com.google.common.base.Preconditions.checkArgument;
  
  /**
   * Retrieves an optional struct-type field from a struct.
   */
  class ThriftFieldGetter<T extends TBase<T, F>, F extends TFieldIdEnum, V extends TBase<V, ?>>
      extends AbstractFieldGetter<T, V> {
  
    private final F fieldId;
  
    ThriftFieldGetter(Class<T> structClass, F fieldId, Class<V> valueClass) {
      super(structClass, valueClass);
  
      FieldValueMetaData fieldValueMetaData = FieldMetaData
          .getStructMetaDataMap(structClass)
          .get(fieldId)
          .valueMetaData;
  
      checkArgument(fieldValueMetaData instanceof StructMetaData);
      StructMetaData structMetaData = (StructMetaData) fieldValueMetaData;
      checkArgument(
          valueClass.equals(structMetaData.structClass),
          "Value class %s does not match field metadata for %s (expected %s)",
          valueClass.getName(),
          fieldId,
          structMetaData.structClass);
  
      this.fieldId = fieldId;
    }
  
    @Override
    @SuppressWarnings("unchecked")
    public Optional<V> apply(T input) {
      if (input.isSet(fieldId)) {
        return Optional.of((V) input.getFieldValue(fieldId));
      } else {
        return Optional.empty();
      }
    }
  }
  