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.runners.samza.runtime;
  
  import java.io.Serializable;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.samza.config.Config;
  import org.apache.samza.context.Context;
  import org.apache.samza.operators.Scheduler;
  import org.joda.time.Instant;
  
  /**
   * Interface of Samza operator for BEAM. This interface demultiplexes messages from BEAM so that
   * elements and side inputs can be handled separately in Samza. Watermark propagation can be
   * overridden so we can hold watermarks for side inputs. The output values and watermark will be
   * collected via {@link OpEmitter}.
   */
  public interface Op<InT, OutT, K> extends Serializable {
    /**
     * A hook that allows initialization for any non-serializable operator state, such as getting
     * stores.
     *
     * <p>While an emitter is supplied to this function it is not usable except in the methods {@link
     * #processElement(WindowedValue, OpEmitter)}, {@link #processWatermark(Instant, OpEmitter)}, and
     * {@link #processSideInput(String, WindowedValue, OpEmitter)}.
     */
    default void open(
        Config config,
        Context context,
        Scheduler<KeyedTimerData<K>> timerRegistry,
        OpEmitter<OutT> emitter) {}
  
    void processElement(WindowedValue<InT> inputElement, OpEmitter<OutT> emitter);
  
    default void processWatermark(Instant watermark, OpEmitter<OutT> emitter) {
      emitter.emitWatermark(watermark);
    }
  
    default void processSideInput(
        String id, WindowedValue<? extends Iterable<?>> elements, OpEmitter<OutT> emitter) {
      throw new UnsupportedOperationException("Side inputs not supported for: " + this.getClass());
    }
  
    default void processSideInputWatermark(Instant watermark, OpEmitter<OutT> emitter) {}
  
    default void processTimer(KeyedTimerData<K> keyedTimerData, OpEmitter<OutT> emitter) {}
  
    default void close() {}
  }
  