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.util;
  
  import org.apache.beam.sdk.annotations.Internal;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.state.StateContext;
  import org.apache.beam.sdk.transforms.CombineWithContext.Context;
  import org.apache.beam.sdk.values.PCollectionView;
  
  /** Factory that produces {@code Combine.Context} based on different inputs. */
  @Internal
  public class CombineContextFactory {
  
    private static final Context NULL_CONTEXT =
        new Context() {
          @Override
          public PipelineOptions getPipelineOptions() {
            throw new IllegalArgumentException("cannot call getPipelineOptions() in a null context");
          }
  
          @Override
          public <T> T sideInput(PCollectionView<T> view) {
            throw new IllegalArgumentException("cannot call sideInput() in a null context");
          }
        };
  
    /** Returns a fake {@code Combine.Context} for tests. */
    public static Context nullContext() {
      return NULL_CONTEXT;
    }
  
    /** Returns a {@code Combine.Context} that wraps a {@link StateContext}. */
    public static Context createFromStateContext(final StateContext<?> c) {
      return new Context() {
        @Override
        public PipelineOptions getPipelineOptions() {
          return c.getPipelineOptions();
        }
  
        @Override
        public <T> T sideInput(PCollectionView<T> view) {
          return c.sideInput(view);
        }
      };
    }
  }
  