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Google Cloud Dataflow Java SDK provides a simple, Java-based interface for processing virtually any size data using Google cloud resources. This artifact includes entire Dataflow Java SDK.

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/*
 * Copyright (C) 2015 Google Inc.
 *
 * 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 com.google.cloud.dataflow.sdk.util;

import com.google.cloud.dataflow.sdk.options.PipelineOptions;
import com.google.cloud.dataflow.sdk.transforms.CombineWithContext.Context;
import com.google.cloud.dataflow.sdk.transforms.DoFn;
import com.google.cloud.dataflow.sdk.transforms.windowing.BoundedWindow;
import com.google.cloud.dataflow.sdk.util.state.StateContext;
import com.google.cloud.dataflow.sdk.values.PCollectionView;

/**
 * Factory that produces {@code Combine.Context} based on different inputs.
 */
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 sideInput(PCollectionView 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 {@code DoFn.ProcessContext}.
   */
  public static Context createFromProcessContext(final DoFn.ProcessContext c) {
    return new Context() {
      @Override
      public PipelineOptions getPipelineOptions() {
        return c.getPipelineOptions();
      }

      @Override
      public  T sideInput(PCollectionView view) {
        return c.sideInput(view);
      }
    };
  }

  /**
   * 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 sideInput(PCollectionView view) {
        return c.sideInput(view);
      }
    };
  }

  /**
   * Returns a {@code Combine.Context} from {@code PipelineOptions}, {@code SideInputReader},
   * and the main input window.
   */
  public static Context createFromComponents(final PipelineOptions options,
      final SideInputReader sideInputReader, final BoundedWindow mainInputWindow) {
    return new Context() {
      @Override
      public PipelineOptions getPipelineOptions() {
        return options;
      }

      @Override
      public  T sideInput(PCollectionView view) {
        if (!sideInputReader.contains(view)) {
          throw new IllegalArgumentException("calling sideInput() with unknown view");
        }

        BoundedWindow sideInputWindow =
            view.getWindowingStrategyInternal().getWindowFn().getSideInputWindow(mainInputWindow);
        return sideInputReader.get(view, sideInputWindow);
      }
    };
  }
}