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.thrift.TBase;
  
  final class FieldGetters {
    private FieldGetters() {
      // Utility class.
    }
  
    public static <P extends TBase<P, ?>, C extends TBase<C, ?>, G extends TBase<G, ?>>
        FieldGetter<P, G> compose(final FieldGetter<P, C> parent, final FieldGetter<C, G> child) {
  
      return new FieldGetter<P, G>() {
        @Override
        public Class<P> getStructClass() {
          return parent.getStructClass();
        }
  
        @Override
        public Class<G> getValueClass() {
          return child.getValueClass();
        }
  
        @Override
        public Optional<G> apply(P input) {
          Optional<C> parentValue = parent.apply(input);
          if (parentValue.isPresent()) {
            return child.apply(parentValue.get());
          } else {
            return Optional.empty();
          }
        }
      };
    }
  }
  