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.flink.translation.wrappers.streaming.io.source;
  
  import java.io.IOException;
  import java.io.Serializable;
  import java.util.Collections;
  import java.util.List;
  import java.util.NoSuchElementException;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.coders.SerializableCoder;
  import org.apache.beam.sdk.io.UnboundedSource;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Instant;
  
  public class EmptyUnboundedSource<T>
      extends UnboundedSource<T, EmptyUnboundedSource.DummyCheckpointMark> {
  
    Instant watermark = BoundedWindow.TIMESTAMP_MIN_VALUE;
  
    public static class DummyCheckpointMark implements UnboundedSource.CheckpointMark, Serializable {
      @Override
      public void finalizeCheckpoint() {}
    }
  
    @Override
    public List<? extends EmptyUnboundedSource<T>> split(
        int desiredNumSplits, PipelineOptions options) throws Exception {
      return Collections.singletonList(this);
    }
  
    @Override
    public UnboundedReader<T> createReader(
        PipelineOptions options, @Nullable DummyCheckpointMark checkpointMark) {
      return new UnboundedReader<T>() {
        @Override
        public boolean start() throws IOException {
          return advance();
        }
  
        @Override
        public boolean advance() {
          return false;
        }
  
        @Override
        public Instant getWatermark() {
          return watermark;
        }
  
        @Override
        public CheckpointMark getCheckpointMark() {
          return new DummyCheckpointMark();
        }
  
        @Override
        public UnboundedSource<T, ?> getCurrentSource() {
          return EmptyUnboundedSource.this;
        }
  
        @Override
        public T getCurrent() throws NoSuchElementException {
          throw new NoSuchElementException();
        }
  
        @Override
        public Instant getCurrentTimestamp() throws NoSuchElementException {
          throw new NoSuchElementException();
        }
  
        @Override
        public void close() {}
      };
    }
  
    @Override
    public Coder<DummyCheckpointMark> getCheckpointMarkCoder() {
      return SerializableCoder.of(DummyCheckpointMark.class);
    }
  
    public void setWatermark(Instant watermark) {
      this.watermark = watermark;
    }
  }
  