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.construction;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  
  import java.util.Collection;
  import java.util.Map;
  import java.util.concurrent.TimeUnit;
  import org.apache.beam.sdk.fn.splittabledofn.RestrictionTrackers;
  import org.apache.beam.sdk.fn.splittabledofn.RestrictionTrackers.ClaimObserver;
  import org.apache.beam.sdk.options.PipelineOptions;
  import org.apache.beam.sdk.runners.AppliedPTransform;
  import org.apache.beam.sdk.runners.PTransformOverrideFactory;
  import org.apache.beam.sdk.state.State;
  import org.apache.beam.sdk.state.TimeDomain;
  import org.apache.beam.sdk.state.Timer;
  import org.apache.beam.sdk.state.TimerMap;
  import org.apache.beam.sdk.transforms.DoFn;
  import org.apache.beam.sdk.transforms.PTransform;
  import org.apache.beam.sdk.transforms.ParDo;
  import org.apache.beam.sdk.transforms.Reshuffle;
  import org.apache.beam.sdk.transforms.Values;
  import org.apache.beam.sdk.transforms.reflect.DoFnInvoker;
  import org.apache.beam.sdk.transforms.reflect.DoFnInvoker.ArgumentProvider;
  import org.apache.beam.sdk.transforms.reflect.DoFnInvoker.BaseArgumentProvider;
  import org.apache.beam.sdk.transforms.reflect.DoFnInvokers;
  import org.apache.beam.sdk.transforms.reflect.DoFnSignatures;
  import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
  import org.apache.beam.sdk.transforms.splittabledofn.SplitResult;
  import org.apache.beam.sdk.transforms.splittabledofn.WatermarkEstimator;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.PaneInfo;
  import org.apache.beam.sdk.util.OutputBuilderSupplier;
  import org.apache.beam.sdk.values.KV;
  import org.apache.beam.sdk.values.OutputBuilder;
  import org.apache.beam.sdk.values.PCollection;
  import org.apache.beam.sdk.values.PCollection.IsBounded;
  import org.apache.beam.sdk.values.PCollectionTuple;
  import org.apache.beam.sdk.values.PCollectionView;
  import org.apache.beam.sdk.values.Row;
  import org.apache.beam.sdk.values.TupleTag;
  import org.apache.beam.sdk.values.WindowedValues;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.util.concurrent.Uninterruptibles;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Instant;
  
  /**
   * Utility transforms and overrides for running bounded splittable DoFn's naively, by implementing
   * {@link SplittableParDo.ProcessKeyedElements} using a simple {@link Reshuffle} and {@link ParDo}.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public class SplittableParDoNaiveBounded {
    /**
     * Overrides a {@link SplittableParDo.ProcessKeyedElements} into {@link SplittableProcessNaive}.
     */
    public static class OverrideFactory<InputT, OutputT, RestrictionT, WatermarkEstimatorStateT>
        implements PTransformOverrideFactory<
            PCollection<KV<byte[], KV<InputT, RestrictionT>>>,
            PCollectionTuple,
            SplittableParDo.ProcessKeyedElements<
                InputT, OutputT, RestrictionT, WatermarkEstimatorStateT>> {
      @Override
      public PTransformReplacement<
              PCollection<KV<byte[], KV<InputT, RestrictionT>>>, PCollectionTuple>
          getReplacementTransform(
              AppliedPTransform<
                      PCollection<KV<byte[], KV<InputT, RestrictionT>>>,
                      PCollectionTuple,
                      SplittableParDo.ProcessKeyedElements<
                          InputT, OutputT, RestrictionT, WatermarkEstimatorStateT>>
                  transform) {
        checkArgument(
            DoFnSignatures.signatureForDoFn(transform.getTransform().getFn()).isBoundedPerElement()
                == IsBounded.BOUNDED,
            "Expecting a bounded-per-element splittable DoFn");
        return PTransformReplacement.of(
            PTransformReplacements.getSingletonMainInput(transform),
            new SplittableProcessNaive<>(transform.getTransform()));
      }
  
      @Override
      public Map<PCollection<?>, ReplacementOutput> mapOutputs(
          Map<TupleTag<?>, PCollection<?>> outputs, PCollectionTuple newOutput) {
        return ReplacementOutputs.tagged(outputs, newOutput);
      }
    }
  
    static class SplittableProcessNaive<
            InputT, OutputT, RestrictionT, PositionT, WatermarkEstimatorStateT>
        extends PTransform<PCollection<KV<byte[], KV<InputT, RestrictionT>>>, PCollectionTuple> {
      private final SplittableParDo.ProcessKeyedElements<
              InputT, OutputT, RestrictionT, WatermarkEstimatorStateT>
          original;
  
      SplittableProcessNaive(
          SplittableParDo.ProcessKeyedElements<
                  InputT, OutputT, RestrictionT, WatermarkEstimatorStateT>
              original) {
        this.original = original;
      }
  
      @Override
      public PCollectionTuple expand(PCollection<KV<byte[], KV<InputT, RestrictionT>>> input) {
        return input
            .apply("Reshuffle", Reshuffle.of())
            .apply("Drop key", Values.create())
            .apply(
                "NaiveProcess",
                ParDo.of(
                        new NaiveProcessFn<
                            InputT, OutputT, RestrictionT, PositionT, WatermarkEstimatorStateT>(
                            original.getFn(), original.getSideInputMapping()))
                    .withSideInputs(original.getSideInputs())
                    .withOutputTags(original.getMainOutputTag(), original.getAdditionalOutputTags()));
      }
    }
  
    public static class NaiveProcessFn<
            InputT, OutputT, RestrictionT, PositionT, WatermarkEstimatorStateT>
        extends DoFn<KV<InputT, RestrictionT>, OutputT> {
      private final DoFn<InputT, OutputT> fn;
      private final Map<String, PCollectionView<?>> sideInputMapping;
  
      private transient @Nullable DoFnInvoker<InputT, OutputT> invoker;
  
      NaiveProcessFn(DoFn<InputT, OutputT> fn, Map<String, PCollectionView<?>> sideInputMapping) {
        this.fn = fn;
        this.sideInputMapping = sideInputMapping;
      }
  
      @Setup
      public void setup(PipelineOptions options) {
        this.invoker = DoFnInvokers.invokerFor(fn);
        invoker.invokeSetup(
            new BaseArgumentProvider<InputT, OutputT>() {
              @Override
              public PipelineOptions pipelineOptions() {
                return options;
              }
  
              @Override
              public String getErrorContext() {
                return "SplittableParDoNaiveBounded/Setup";
              }
            });
      }
  
      @StartBundle
      public void startBundle(StartBundleContext c) {
        invoker.invokeStartBundle(
            new BaseArgumentProvider<InputT, OutputT>() {
              @Override
              public DoFn<InputT, OutputT>.StartBundleContext startBundleContext(
                  DoFn<InputT, OutputT> doFn) {
                return new DoFn<InputT, OutputT>.StartBundleContext() {
                  @Override
                  public PipelineOptions getPipelineOptions() {
                    return c.getPipelineOptions();
                  }
                };
              }
  
              @Override
              public PipelineOptions pipelineOptions() {
                return c.getPipelineOptions();
              }
  
              @Override
              public String getErrorContext() {
                return "SplittableParDoNaiveBounded/StartBundle";
              }
            });
      }
  
      @ProcessElement
      public void process(ProcessContext c, BoundedWindow w, OutputReceiver<OutputT> outputReceiver) {
        WatermarkEstimatorStateT initialWatermarkEstimatorState =
            (WatermarkEstimatorStateT)
                invoker.invokeGetInitialWatermarkEstimatorState(
                    new BaseArgumentProvider<InputT, OutputT>() {
                      @Override
                      public InputT element(DoFn<InputT, OutputT> doFn) {
                        return c.element().getKey();
                      }
  
                      @Override
                      public Object restriction() {
                        return c.element().getValue();
                      }
  
                      @Override
                      public Instant timestamp(DoFn<InputT, OutputT> doFn) {
                        return c.timestamp();
                      }
  
                      @Override
                      public PipelineOptions pipelineOptions() {
                        return c.getPipelineOptions();
                      }
  
                      @Override
                      public PaneInfo paneInfo(DoFn<InputT, OutputT> doFn) {
                        return c.pane();
                      }
  
                      @Override
                      public BoundedWindow window() {
                        return w;
                      }
  
                      @Override
                      public Object sideInput(String tagId) {
                        PCollectionView<?> view = sideInputMapping.get(tagId);
                        if (view == null) {
                          throw new IllegalArgumentException(
                              "calling getSideInput() with unknown view");
                        }
                        return c.sideInput(view);
                      }
  
                      @Override
                      public String getErrorContext() {
                        return NaiveProcessFn.class.getSimpleName()
                            + ".invokeGetInitialWatermarkEstimatorState";
                      }
                    });
  
        RestrictionT restriction = c.element().getValue();
        WatermarkEstimatorStateT watermarkEstimatorState = initialWatermarkEstimatorState;
        while (true) {
          RestrictionT currentRestriction = restriction;
          WatermarkEstimatorStateT currentWatermarkEstimatorState = watermarkEstimatorState;
  
          RestrictionTracker<RestrictionT, PositionT> tracker =
              RestrictionTrackers.observe(
                  invoker.invokeNewTracker(
                      new BaseArgumentProvider<InputT, OutputT>() {
                        @Override
                        public InputT element(DoFn<InputT, OutputT> doFn) {
                          return c.element().getKey();
                        }
  
                        @Override
                        public RestrictionT restriction() {
                          return currentRestriction;
                        }
  
                        @Override
                        public Instant timestamp(DoFn<InputT, OutputT> doFn) {
                          return c.timestamp();
                        }
  
                        @Override
                        public PipelineOptions pipelineOptions() {
                          return c.getPipelineOptions();
                        }
  
                        @Override
                        public PaneInfo paneInfo(DoFn<InputT, OutputT> doFn) {
                          return c.pane();
                        }
  
                        @Override
                        public BoundedWindow window() {
                          return w;
                        }
  
                        @Override
                        public Object sideInput(String tagId) {
                          PCollectionView<?> view = sideInputMapping.get(tagId);
                          if (view == null) {
                            throw new IllegalArgumentException(
                                "calling getSideInput() with unknown view");
                          }
                          return c.sideInput(view);
                        }
  
                        @Override
                        public String getErrorContext() {
                          return NaiveProcessFn.class.getSimpleName() + ".invokeNewTracker";
                        }
                      }),
                  new ClaimObserver<PositionT>() {
                    @Override
                    public void onClaimed(PositionT position) {}
  
                    @Override
                    public void onClaimFailed(PositionT position) {}
                  });
  
          WatermarkEstimator<WatermarkEstimatorStateT> watermarkEstimator =
              invoker.invokeNewWatermarkEstimator(
                  new BaseArgumentProvider<InputT, OutputT>() {
                    @Override
                    public InputT element(DoFn<InputT, OutputT> doFn) {
                      return c.element().getKey();
                    }
  
                    @Override
                    public RestrictionT restriction() {
                      return currentRestriction;
                    }
  
                    @Override
                    public WatermarkEstimatorStateT watermarkEstimatorState() {
                      return currentWatermarkEstimatorState;
                    }
  
                    @Override
                    public Instant timestamp(DoFn<InputT, OutputT> doFn) {
                      return c.timestamp();
                    }
  
                    @Override
                    public PipelineOptions pipelineOptions() {
                      return c.getPipelineOptions();
                    }
  
                    @Override
                    public PaneInfo paneInfo(DoFn<InputT, OutputT> doFn) {
                      return c.pane();
                    }
  
                    @Override
                    public BoundedWindow window() {
                      return w;
                    }
  
                    @Override
                    public Object sideInput(String tagId) {
                      PCollectionView<?> view = sideInputMapping.get(tagId);
                      if (view == null) {
                        throw new IllegalArgumentException(
                            "calling getSideInput() with unknown view");
                      }
                      return c.sideInput(view);
                    }
  
                    @Override
                    public String getErrorContext() {
                      return NaiveProcessFn.class.getSimpleName() + ".invokeNewWatermarkEstimator";
                    }
                  });
  
          OutputBuilderSupplier outputBuilderSupplier =
              new OutputBuilderSupplier() {
                @Override
                public <X> WindowedValues.Builder<X> builder(X value) {
                  return WindowedValues.builder(outputReceiver.builder(null)).withValue(value);
                }
              };
  
          ProcessContinuation continuation =
              invoker.invokeProcessElement(
                  new NestedProcessContext<>(
                      fn,
                      c,
                      outputBuilderSupplier,
                      c.element().getKey(),
                      w,
                      tracker,
                      watermarkEstimator,
                      sideInputMapping));
          if (continuation.shouldResume()) {
            // Fetch the watermark before splitting to ensure that the watermark applies to both
            // the primary and the residual.
            watermarkEstimatorState = watermarkEstimator.getState();
            SplitResult<RestrictionT> split = tracker.trySplit(0);
            if (split == null) {
              break;
            }
            restriction = split.getResidual();
            Uninterruptibles.sleepUninterruptibly(
                continuation.resumeDelay().getMillis(), TimeUnit.MILLISECONDS);
          } else {
            break;
          }
        }
      }
  
      @FinishBundle
      public void finishBundle(FinishBundleContext c) {
        invoker.invokeFinishBundle(
            new BaseArgumentProvider<InputT, OutputT>() {
              @Override
              public DoFn<InputT, OutputT>.FinishBundleContext finishBundleContext(
                  DoFn<InputT, OutputT> doFn) {
                return new DoFn<InputT, OutputT>.FinishBundleContext() {
                  @Override
                  public PipelineOptions getPipelineOptions() {
                    return c.getPipelineOptions();
                  }
  
                  @Override
                  public void output(
                      @Nullable OutputT output, Instant timestamp, BoundedWindow window) {
                    throw new UnsupportedOperationException(
                        "Output from FinishBundle for SDF is not supported in naive implementation");
                  }
  
                  @Override
                  public <T> void output(
                      TupleTag<T> tag,
                      T output,
                      Instant timestamp,
                      BoundedWindow window,
                      @Nullable String currentRecordId,
                      @Nullable Long currentRecordOffset) {
                    throw new UnsupportedOperationException(
                        "Output from FinishBundle for SDF is not supported in naive implementation");
                  }
  
                  @Override
                  public void output(
                      @Nullable OutputT output,
                      Instant timestamp,
                      BoundedWindow window,
                      @Nullable String currentRecordId,
                      @Nullable Long currentRecordOffset) {
                    throw new UnsupportedOperationException(
                        "Output from FinishBundle for SDF is not supported in naive implementation");
                  }
  
                  @Override
                  public <T> void output(
                      TupleTag<T> tag, T output, Instant timestamp, BoundedWindow window) {
                    throw new UnsupportedOperationException(
                        "Output from FinishBundle for SDF is not supported in naive implementation");
                  }
                };
              }
  
              @Override
              public PipelineOptions pipelineOptions() {
                return c.getPipelineOptions();
              }
  
              @Override
              public String getErrorContext() {
                return "SplittableParDoNaiveBounded/StartBundle";
              }
            });
      }
  
      @Teardown
      public void teardown() {
        invoker.invokeTeardown();
      }
  
      private static class NestedProcessContext<
              InputT,
              OutputT,
              RestrictionT,
              TrackerT extends RestrictionTracker<RestrictionT, ?>,
              WatermarkEstimatorStateT,
              WatermarkEstimatorT extends WatermarkEstimator<WatermarkEstimatorStateT>>
          extends DoFn<InputT, OutputT>.ProcessContext implements ArgumentProvider<InputT, OutputT> {
  
        private final BoundedWindow window;
        private final DoFn<KV<InputT, RestrictionT>, OutputT>.ProcessContext outerContext;
        private final InputT element;
        private final TrackerT tracker;
        private final WatermarkEstimatorT watermarkEstimator;
        private final Map<String, PCollectionView<?>> sideInputMapping;
        private final OutputBuilderSupplier outputBuilderSupplier;
  
        private NestedProcessContext(
            DoFn<InputT, OutputT> fn,
            DoFn<KV<InputT, RestrictionT>, OutputT>.ProcessContext outerContext,
            OutputBuilderSupplier outputBuilderSupplier,
            InputT element,
            BoundedWindow window,
            TrackerT tracker,
            WatermarkEstimatorT watermarkEstimator,
            Map<String, PCollectionView<?>> sideInputMapping) {
          fn.super();
          this.window = window;
          this.outputBuilderSupplier = outputBuilderSupplier;
          this.outerContext = outerContext;
          this.element = element;
          this.tracker = tracker;
          this.watermarkEstimator = watermarkEstimator;
          this.sideInputMapping = sideInputMapping;
        }
  
        @Override
        public BoundedWindow window() {
          return window;
        }
  
        @Override
        public PaneInfo paneInfo(DoFn<InputT, OutputT> doFn) {
          return outerContext.pane();
        }
  
        @Override
        public PipelineOptions pipelineOptions() {
          return outerContext.getPipelineOptions();
        }
  
        @Override
        public DoFn<InputT, OutputT>.ProcessContext processContext(DoFn<InputT, OutputT> doFn) {
          return this;
        }
  
        @Override
        public DoFn<InputT, OutputT>.OnTimerContext onTimerContext(DoFn<InputT, OutputT> doFn) {
          throw new IllegalStateException();
        }
  
        @Override
        public InputT element(DoFn<InputT, OutputT> doFn) {
          return element;
        }
  
        @Override
        public Object key() {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public Object sideInput(String tagId) {
          PCollectionView<?> view = sideInputMapping.get(tagId);
          if (view == null) {
            throw new IllegalArgumentException("calling getSideInput() with unknown view");
          }
          return sideInput(view);
        }
  
        @Override
        public TimerMap timerFamily(String tagId) {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public Object schemaElement(int index) {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public Instant timestamp(DoFn<InputT, OutputT> doFn) {
          return outerContext.timestamp();
        }
  
        @Override
        public String timerId(DoFn<InputT, OutputT> doFn) {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public OutputReceiver<OutputT> outputReceiver(DoFn<InputT, OutputT> doFn) {
          return new OutputReceiver<OutputT>() {
            @Override
            public OutputBuilder<OutputT> builder(OutputT value) {
              return outputBuilderSupplier
                  .builder(value)
                  .setReceiver(
                      windowedValue ->
                          outerContext.outputWindowedValue(
                              windowedValue.getValue(),
                              windowedValue.getTimestamp(),
                              windowedValue.getWindows(),
                              windowedValue.getPaneInfo()));
            }
          };
        }
  
        @Override
        public MultiOutputReceiver taggedOutputReceiver(DoFn<InputT, OutputT> doFn) {
          return new MultiOutputReceiver() {
            @Override
            public <T> OutputReceiver<T> get(TupleTag<T> tag) {
              return new OutputReceiver<T>() {
                @Override
                public OutputBuilder<T> builder(T value) {
                  return outputBuilderSupplier
                      .builder(value)
                      .setReceiver(
                          windowedValue ->
                              outerContext.outputWindowedValue(
                                  tag,
                                  windowedValue.getValue(),
                                  windowedValue.getTimestamp(),
                                  windowedValue.getWindows(),
                                  windowedValue.getPaneInfo()));
                }
              };
            }
  
            @Override
            public <T> OutputReceiver<Row> getRowReceiver(TupleTag<T> tag) {
              throw new UnsupportedOperationException();
            }
          };
        }
  
        @Override
        public BundleFinalizer bundleFinalizer() {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public Object restriction() {
          return tracker.currentRestriction();
        }
  
        @Override
        public RestrictionTracker<?, ?> restrictionTracker() {
          return tracker;
        }
  
        @Override
        public PipelineOptions getPipelineOptions() {
          return outerContext.getPipelineOptions();
        }
  
        @Override
        public void output(OutputT output) {
          outerContext.output(output);
        }
  
        @Override
        public void outputWithTimestamp(OutputT output, Instant timestamp) {
          outerContext.outputWithTimestamp(output, timestamp);
        }
  
        @Override
        public void outputWindowedValue(
            OutputT output,
            Instant timestamp,
            Collection<? extends BoundedWindow> windows,
            PaneInfo paneInfo) {
          outerContext.outputWindowedValue(output, timestamp, windows, paneInfo);
        }
  
        @Override
        public void outputWindowedValue(
            OutputT output,
            Instant timestamp,
            Collection<? extends BoundedWindow> windows,
            PaneInfo paneInfo,
            @Nullable String currentRecordId,
            @Nullable Long currentRecordOffset) {
          outerContext.outputWindowedValue(
              output, timestamp, windows, paneInfo, currentRecordId, currentRecordOffset);
        }
  
        @Override
        public <T> void output(TupleTag<T> tag, T output) {
          outerContext.output(tag, output);
        }
  
        @Override
        public <T> void outputWithTimestamp(TupleTag<T> tag, T output, Instant timestamp) {
          outerContext.outputWithTimestamp(tag, output, timestamp);
        }
  
        @Override
        public <T> void outputWindowedValue(
            TupleTag<T> tag,
            T output,
            Instant timestamp,
            Collection<? extends BoundedWindow> windows,
            PaneInfo paneInfo) {
          outerContext.outputWindowedValue(tag, output, timestamp, windows, paneInfo);
        }
  
        @Override
        public <T> void outputWindowedValue(
            TupleTag<T> tag,
            T output,
            Instant timestamp,
            Collection<? extends BoundedWindow> windows,
            PaneInfo paneInfo,
            @Nullable String currentRecordId,
            @Nullable Long currentRecordOffset) {
          outerContext.outputWindowedValue(
              tag, output, timestamp, windows, paneInfo, currentRecordId, currentRecordOffset);
        }
  
        @Override
        public InputT element() {
          return element;
        }
  
        @Override
        public <T> T sideInput(PCollectionView<T> view) {
          return outerContext.sideInput(view);
        }
  
        @Override
        public Instant timestamp() {
          return outerContext.timestamp();
        }
  
        @Override
        public PaneInfo pane() {
          return outerContext.pane();
        }
  
        @Override
        public String currentRecordId() {
          return outerContext.currentRecordId();
        }
  
        @Override
        public Long currentRecordOffset() {
          return outerContext.currentRecordOffset();
        }
  
        @Override
        public Object watermarkEstimatorState() {
          throw new UnsupportedOperationException(
              "@WatermarkEstimatorState parameters are not supported.");
        }
  
        @Override
        public WatermarkEstimator<?> watermarkEstimator() {
          return watermarkEstimator;
        }
  
        // ----------- Unsupported methods --------------------
        @Override
        public DoFn<InputT, OutputT>.StartBundleContext startBundleContext(
            DoFn<InputT, OutputT> doFn) {
          throw new IllegalStateException();
        }
  
        @Override
        public DoFn<InputT, OutputT>.FinishBundleContext finishBundleContext(
            DoFn<InputT, OutputT> doFn) {
          throw new IllegalStateException();
        }
  
        @Override
        public OutputReceiver<Row> outputRowReceiver(DoFn<InputT, OutputT> doFn) {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public TimeDomain timeDomain(DoFn<InputT, OutputT> doFn) {
          throw new IllegalStateException();
        }
  
        @Override
        public State state(String stateId, boolean alwaysFetched) {
          throw new UnsupportedOperationException();
        }
  
        @Override
        public Timer timer(String timerId) {
          throw new UnsupportedOperationException();
        }
      }
    }
  }
  