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.transforms;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  
  import org.apache.beam.sdk.annotations.Internal;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.FixedWindows;
  import org.apache.beam.sdk.transforms.windowing.Window;
  import org.apache.beam.sdk.values.PBegin;
  import org.apache.beam.sdk.values.PCollection;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  
  /**
   * A {@link PTransform} which produces a sequence of elements at fixed runtime intervals.
   *
   * <p>If applyWindowing() is specified, each element will be assigned to its own fixed window.
   *
   * <p>See {@link PeriodicSequence}.
   */
  public class PeriodicImpulse extends PTransform<PBegin, PCollection<Instant>> {
  
    Instant startTimestamp;
    Instant stopTimestamp;
    @Nullable Duration stopDuration;
    Duration fireInterval;
    boolean applyWindowing = false;
    boolean catchUpToNow = true;
  
    private PeriodicImpulse() {
      this.startTimestamp = Instant.now();
      this.stopTimestamp = BoundedWindow.TIMESTAMP_MAX_VALUE;
      this.fireInterval = Duration.standardMinutes(1);
    }
  
    public static PeriodicImpulse create() {
      return new PeriodicImpulse();
    }
  
    /**
     * Assign a timestamp when the pipeliene starts to produce data.
     *
     * <p>Cannot be used along with {@link #stopAfter}.
     */
    public PeriodicImpulse startAt(Instant startTime) {
      checkArgument(stopDuration == null, "startAt and stopAfter cannot be set at the same time");
      this.startTimestamp = startTime;
      return this;
    }
  
    /**
     * Assign a timestamp when the pipeliene stops producing data.
     *
     * <p>Cannot be used along with {@link #stopAfter}.
     */
    public PeriodicImpulse stopAt(Instant stopTime) {
      checkArgument(stopDuration == null, "stopAt and stopAfter cannot be set at the same time");
      this.stopTimestamp = stopTime;
      return this;
    }
  
    /**
     * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>
     *
     * <p>Assign a time interval at which the pipeliene produces data. This is different from setting
     * {@link #startAt} and {@link #stopAt}, as the first timestamp is determined at run time
     * (pipeline starts processing).
     */
    @Internal
    public PeriodicImpulse stopAfter(Duration duration) {
      this.stopDuration = duration;
      return this;
    }
  
    public PeriodicImpulse withInterval(Duration interval) {
      this.fireInterval = interval;
      return this;
    }
  
    public PeriodicImpulse applyWindowing() {
      this.applyWindowing = true;
      return this;
    }
  
    /**
     * <b><i>For internal use only; no backwards-compatibility guarantees.</i></b>
     *
     * <p>The default behavior is that PeriodicImpulse emits all instants until Instant.now(), then
     * starts firing at the specified interval. If this is set to false, the PeriodicImpulse will
     * perform the interval wait before firing each instant.
     */
    @Internal
    public PeriodicImpulse catchUpToNow(boolean catchUpToNow) {
      this.catchUpToNow = catchUpToNow;
      return this;
    }
  
    @Override
    public PCollection<Instant> expand(PBegin input) {
      PCollection<PeriodicSequence.SequenceDefinition> seqDef;
      if (stopDuration != null) {
        // nonnull guaranteed
        Duration d = stopDuration;
        seqDef =
            input
                .apply(Impulse.create())
                .apply(ParDo.of(new RuntimeSequenceFn(d, fireInterval, catchUpToNow)));
      } else {
        seqDef =
            input.apply(
                Create.of(
                    new PeriodicSequence.SequenceDefinition(
                        startTimestamp, stopTimestamp, fireInterval, catchUpToNow)));
      }
      PCollection<Instant> result = seqDef.apply(PeriodicSequence.create());
  
      if (this.applyWindowing) {
        result =
            result.apply(Window.into(FixedWindows.of(Duration.millis(fireInterval.getMillis()))));
      }
      return result;
    }
  
    /**
     * A DoFn generated a SequenceDefinition at run time. This enables set first element timestamp at
     * pipeline start processing data.
     */
    private static class RuntimeSequenceFn extends DoFn<byte[], PeriodicSequence.SequenceDefinition> {
      Duration stopDuration;
      Duration fireInterval;
      boolean catchUpToNow;
  
      RuntimeSequenceFn(Duration stopDuration, Duration fireInterval, boolean catchUpToNow) {
        this.stopDuration = stopDuration;
        this.fireInterval = fireInterval;
        this.catchUpToNow = catchUpToNow;
      }
  
      @ProcessElement
      public void process(ProcessContext c) {
        Instant now = Instant.now();
        c.output(
            new PeriodicSequence.SequenceDefinition(
                now, now.plus(stopDuration), fireInterval, catchUpToNow));
      }
    }
  }
  