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.beam.sdk.transforms;
  
  import java.io.Serializable;
  import java.util.Arrays;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Set;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Sets;
  
  /** Describes the run-time requirements of a {@link Contextful}, such as access to side inputs. */
  @SuppressWarnings({
    "rawtypes" // TODO(https://github.com/apache/beam/issues/20447)
  })
  public final class Requirements implements Serializable {
    private final Collection<PCollectionView<?>> sideInputs;
  
    private Requirements(Collection<PCollectionView<?>> sideInputs) {
      this.sideInputs = sideInputs;
    }
  
    /** The side inputs that this {@link Contextful} needs access to. */
    public Collection<PCollectionView<?>> getSideInputs() {
      return sideInputs;
    }
  
    /** Describes the need for access to the given side inputs. */
    public static Requirements requiresSideInputs(Collection<PCollectionView<?>> sideInputs) {
      return new Requirements(sideInputs);
    }
  
    /** Like {@link #requiresSideInputs(Collection)}. */
    public static Requirements requiresSideInputs(PCollectionView<?>... sideInputs) {
      return requiresSideInputs(Arrays.asList(sideInputs));
    }
  
    /** Describes an empty set of requirements. */
    public static Requirements empty() {
      return new Requirements(Collections.emptyList());
    }
  
    /** Whether this is an empty set of requirements. */
    public boolean isEmpty() {
      return sideInputs.isEmpty();
    }
  
    public static Requirements union(Contextful... contextfuls) {
      Set<PCollectionView<?>> sideInputs = Sets.newHashSet();
      for (Contextful c : contextfuls) {
        sideInputs.addAll(c.getRequirements().getSideInputs());
      }
      return requiresSideInputs(sideInputs);
    }
  }
  