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.windowing;
  
  import java.util.Objects;
  import org.apache.beam.sdk.coders.Coder;
  import org.apache.beam.sdk.transforms.display.DisplayData;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  
  /**
   * A {@link WindowFn} that windows values into fixed-size timestamp-based windows.
   *
   * <p>For example, in order to partition the data into 10 minute windows:
   *
   * <pre>{@code
   * PCollection<Integer> items = ...;
   * PCollection<Integer> windowedItems = items.apply(
   *   Window.<Integer>into(FixedWindows.of(Duration.standardMinutes(10))));
   * }</pre>
   */
  public class FixedWindows extends PartitioningWindowFn<Object, IntervalWindow> {
  
    /** Size of this window. */
    private final Duration size;
  
    /** Offset of this window. Windows start at time N * size + offset, where 0 is the epoch. */
    private final Duration offset;
  
    /**
     * Partitions the timestamp space into half-open intervals of the form [N * size, (N + 1) * size),
     * where 0 is the epoch.
     */
    public static FixedWindows of(Duration size) {
      return new FixedWindows(size, Duration.ZERO);
    }
  
    /**
     * Partitions the timestamp space into half-open intervals of the form [N * size + offset, (N + 1)
     * * size + offset), where 0 is the epoch.
     *
     * @throws IllegalArgumentException if offset is not in [0, size)
     */
    public FixedWindows withOffset(Duration offset) {
      return new FixedWindows(size, offset);
    }
  
    private FixedWindows(Duration size, Duration offset) {
      if (offset.isShorterThan(Duration.ZERO) || !offset.isShorterThan(size)) {
        throw new IllegalArgumentException(
            "FixedWindows WindowingStrategies must have 0 <= offset < size");
      }
      this.size = size;
      this.offset = offset;
    }
  
    @Override
    public IntervalWindow assignWindow(Instant timestamp) {
      Instant start =
          new Instant(
              timestamp.getMillis()
                  - timestamp.plus(size).minus(offset).getMillis() % size.getMillis());
  
      // The global window is inclusive of max timestamp, while interval window excludes its
      // upper bound
      Instant endOfGlobalWindow = GlobalWindow.INSTANCE.maxTimestamp().plus(Duration.millis(1));
  
      // The end of the window is either start + size if that is within the allowable range, otherwise
      // the end of the global window. Truncating the window drives many other
      // areas of this system in the appropriate way automatically.
      //
      // Though it is curious that the very last representable fixed window is shorter than the rest,
      // when we are processing data in the year 294247, we'll probably have technology that can
      // account for this.
      Instant end =
          start.isAfter(endOfGlobalWindow.minus(size)) ? endOfGlobalWindow : start.plus(size);
  
      return new IntervalWindow(start, end);
    }
  
    @Override
    public void populateDisplayData(DisplayData.Builder builder) {
      super.populateDisplayData(builder);
      builder
          .add(DisplayData.item("size", size).withLabel("Window Duration"))
          .addIfNotDefault(
              DisplayData.item("offset", offset).withLabel("Window Start Offset"), Duration.ZERO);
    }
  
    @Override
    public Coder<IntervalWindow> windowCoder() {
      return IntervalWindow.getCoder();
    }
  
    @Override
    public boolean isCompatible(WindowFn<?, ?> other) {
      return this.equals(other);
    }
  
    @Override
    public void verifyCompatibility(WindowFn<?, ?> other) throws IncompatibleWindowException {
      if (!this.isCompatible(other)) {
        throw new IncompatibleWindowException(
            other,
            String.format(
                "Only %s objects with the same size and offset are compatible.",
                FixedWindows.class.getSimpleName()));
      }
    }
  
    public Duration getSize() {
      return size;
    }
  
    public Duration getOffset() {
      return offset;
    }
  
    @Override
    public boolean equals(@Nullable Object object) {
      if (!(object instanceof FixedWindows)) {
        return false;
      }
      FixedWindows other = (FixedWindows) object;
      return getOffset().equals(other.getOffset()) && getSize().equals(other.getSize());
    }
  
    @Override
    public int hashCode() {
      return Objects.hash(size, offset);
    }
  }
  