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.dataflow.worker;
  
  import static org.apache.beam.sdk.util.Preconditions.checkArgumentNotNull;
  
  import com.google.auto.service.AutoService;
  import java.io.IOException;
  import java.util.Collection;
  import java.util.Map;
  import java.util.NoSuchElementException;
  import org.apache.beam.runners.core.KeyedWorkItem;
  import org.apache.beam.runners.dataflow.util.CloudObject;
  import org.apache.beam.runners.dataflow.worker.util.ValueInEmptyWindows;
  import org.apache.beam.runners.dataflow.worker.util.common.worker.NativeReader;
  import org.apache.beam.runners.dataflow.worker.windmill.Windmill.WorkItem;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.values.WindowedValue;
  import org.apache.beam.sdk.values.WindowedValues.FullWindowedValueCoder;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.ImmutableMap;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.checkerframework.checker.nullness.qual.Nullable;
  
  /**
   * A Reader that receives input data from a Windmill server, and returns a singleton iterable
   * containing the work item.
   */
  @SuppressWarnings({
    "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  class WindowingWindmillReader<K, T> extends NativeReader<WindowedValue<KeyedWorkItem<K, T>>> {
  
    private final Coder<K> keyCoder;
    private final Coder<T> valueCoder;
    private final Coder<? extends BoundedWindow> windowCoder;
    private final Coder<Collection<? extends BoundedWindow>> windowsCoder;
    private StreamingModeExecutionContext context;
  
    WindowingWindmillReader(
        Coder<WindowedValue<KeyedWorkItem<K, T>>> coder, StreamingModeExecutionContext context) {
      FullWindowedValueCoder<KeyedWorkItem<K, T>> inputCoder =
          (FullWindowedValueCoder<KeyedWorkItem<K, T>>) coder;
      this.windowsCoder = inputCoder.getWindowsCoder();
      this.windowCoder = inputCoder.getWindowCoder();
      @SuppressWarnings("unchecked")
      WindmillKeyedWorkItem.FakeKeyedWorkItemCoder<K, T> keyedWorkItemCoder =
          (WindmillKeyedWorkItem.FakeKeyedWorkItemCoder<K, T>) inputCoder.getValueCoder();
      this.keyCoder = keyedWorkItemCoder.getKeyCoder();
      this.valueCoder = keyedWorkItemCoder.getElementCoder();
      this.context = context;
    }
  
    /** A {@link ReaderFactory.Registrar} for grouping windmill sources. */
    @AutoService(ReaderFactory.Registrar.class)
    public static class Registrar implements ReaderFactory.Registrar {
  
      @Override
      public Map<String, ReaderFactory> factories() {
        Factory factory = new Factory();
        return ImmutableMap.of(
            "WindowingWindmillReader",
            factory,
            "org.apache.beam.runners.dataflow.worker.WindowingWindmillReader",
            factory,
            "org.apache.beam.runners.dataflow.worker.BucketingWindmillSource",
            factory);
      }
    }
  
    static class Factory implements ReaderFactory {
      @Override
      public NativeReader<?> create(
          CloudObject spec,
          @Nullable Coder<?> coder,
          @Nullable PipelineOptions options,
          @Nullable DataflowExecutionContext context,
          DataflowOperationContext operationContext)
          throws Exception {
        coder = checkArgumentNotNull(coder);
        @SuppressWarnings({
          "rawtypes", // TODO(https://github.com/apache/beam/issues/20447)
          "unchecked"
        })
        Coder<WindowedValue<KeyedWorkItem<Object, Object>>> typedCoder =
            (Coder<WindowedValue<KeyedWorkItem<Object, Object>>>) coder;
        return WindowingWindmillReader.create(typedCoder, (StreamingModeExecutionContext) context);
      }
    }
  
    /**
     * Creates a {@link WindowingWindmillReader} from the provided {@link Coder} and {@link
     * StreamingModeExecutionContext}.
     */
    public static <K, T> WindowingWindmillReader<K, T> create(
        Coder<WindowedValue<KeyedWorkItem<K, T>>> coder, StreamingModeExecutionContext context) {
      return new WindowingWindmillReader<K, T>(coder, context);
    }
  
    @Override
    public NativeReaderIterator<WindowedValue<KeyedWorkItem<K, T>>> iterator() throws IOException {
      final K key = keyCoder.decode(context.getSerializedKey().newInput(), Coder.Context.OUTER);
      final WorkItem workItem = context.getWorkItem();
      KeyedWorkItem<K, T> keyedWorkItem =
          new WindmillKeyedWorkItem<>(key, workItem, windowCoder, windowsCoder, valueCoder);
      final boolean isEmptyWorkItem =
          (Iterables.isEmpty(keyedWorkItem.timersIterable())
              && Iterables.isEmpty(keyedWorkItem.elementsIterable()));
      final WindowedValue<KeyedWorkItem<K, T>> value = new ValueInEmptyWindows<>(keyedWorkItem);
  
      // Return a noop iterator when current workitem is an empty workitem.
      if (isEmptyWorkItem) {
        return new NativeReaderIterator<WindowedValue<KeyedWorkItem<K, T>>>() {
          @Override
          public boolean start() throws IOException {
            return false;
          }
  
          @Override
          public boolean advance() throws IOException {
            return false;
          }
  
          @Override
          public WindowedValue<KeyedWorkItem<K, T>> getCurrent() {
            throw new NoSuchElementException();
          }
        };
      } else {
        return new NativeReaderIterator<WindowedValue<KeyedWorkItem<K, T>>>() {
          private WindowedValue<KeyedWorkItem<K, T>> current;
  
          @Override
          public boolean start() throws IOException {
            current = value;
            return true;
          }
  
          @Override
          public boolean advance() throws IOException {
            current = null;
            return false;
          }
  
          @Override
          public WindowedValue<KeyedWorkItem<K, T>> getCurrent() {
            if (current == null) {
              throw new NoSuchElementException();
            }
            return value;
          }
        };
      }
    }
  
    @Override
    public boolean supportsRestart() {
      return true;
    }
  }
  