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.testing;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  import static org.hamcrest.MatcherAssert.assertThat;
  import static org.hamcrest.Matchers.greaterThan;
  
  import java.util.ArrayList;
  import java.util.Collection;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
  import org.apache.beam.sdk.transforms.windowing.GlobalWindow;
  import org.apache.beam.sdk.transforms.windowing.IntervalWindow;
  import org.apache.beam.sdk.transforms.windowing.TimestampCombiner;
  import org.apache.beam.sdk.transforms.windowing.WindowFn;
  import org.apache.beam.sdk.values.TimestampedValue;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Iterables;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.collect.Ordering;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.joda.time.Instant;
  import org.joda.time.ReadableInstant;
  
  /** A utility class for testing {@link WindowFn}s. */
  public class WindowFnTestUtils {
  
    /** Creates a Set of elements to be used as expected output in {@link #runWindowFn}. */
    public static Set<String> set(long... timestamps) {
      Set<String> result = new HashSet<>();
      for (long timestamp : timestamps) {
        result.add(timestampValue(timestamp));
      }
      return result;
    }
  
    /**
     * Runs the {@link WindowFn} over the provided input, returning a map of windows to the timestamps
     * in those windows.
     */
    public static <T, W extends BoundedWindow> Map<W, Set<String>> runWindowFn(
        WindowFn<T, W> windowFn, List<Long> timestamps) throws Exception {
      List<TimestampedValue<T>> timestampedValues = new ArrayList<>();
      for (Long timestamp : timestamps) {
        timestampedValues.add(TimestampedValue.of((T) null, new Instant(timestamp)));
      }
      return runWindowFnWithValue(windowFn, timestampedValues);
    }
  
    /**
     * Runs the {@link WindowFn} over the provided input, returning a map of windows to the timestamps
     * in those windows. This version allows to pass a list of {@link TimestampedValue} in case the
     * values are used to assign windows.
     */
    public static <T, W extends BoundedWindow> Map<W, Set<String>> runWindowFnWithValue(
        WindowFn<T, W> windowFn, List<TimestampedValue<T>> timestampedValues) throws Exception {
  
      final TestWindowSet<W, String> windowSet = new TestWindowSet<>();
      for (final TimestampedValue<T> element : timestampedValues) {
        for (W window : assignedWindowsWithValue(windowFn, element)) {
          windowSet.put(window, timestampValue(element.getTimestamp().getMillis()));
        }
        TestMergeContext<T, W> mergeContext = new TestMergeContext<>(windowSet, windowFn);
        windowFn.mergeWindows(mergeContext);
      }
      Map<W, Set<String>> actual = new HashMap<>();
      for (W window : windowSet.windows()) {
        actual.put(window, windowSet.get(window));
      }
      return actual;
    }
  
    /** runs {@link WindowFn#assignWindows(WindowFn.AssignContext)}. */
    public static <T, W extends BoundedWindow> Collection<W> assignedWindows(
        WindowFn<T, W> windowFn, long timestamp) throws Exception {
      return assignedWindowsWithValue(
          windowFn, TimestampedValue.of((T) null, new Instant(timestamp)));
    }
  
    /**
     * runs {@link WindowFn#assignWindows(WindowFn.AssignContext)}. This version allows passing a
     * {@link TimestampedValue} in case the value is needed to assign windows.
     */
    public static <T, W extends BoundedWindow> Collection<W> assignedWindowsWithValue(
        WindowFn<T, W> windowFn, TimestampedValue<T> timestampedValue) throws Exception {
      TestAssignContext<T, W> assignContext = new TestAssignContext<>(timestampedValue, windowFn);
      return windowFn.assignWindows(assignContext);
    }
  
    private static String timestampValue(long timestamp) {
      return "T" + new Instant(timestamp);
    }
  
    /** Test implementation of AssignContext. */
    private static class TestAssignContext<T, W extends BoundedWindow>
        extends WindowFn<T, W>.AssignContext {
      private TimestampedValue<T> timestampedValue;
  
      public TestAssignContext(TimestampedValue<T> timestampedValue, WindowFn<T, W> windowFn) {
        windowFn.super();
        this.timestampedValue = timestampedValue;
      }
  
      @Override
      public T element() {
        return timestampedValue.getValue();
      }
  
      @Override
      public Instant timestamp() {
        return timestampedValue.getTimestamp();
      }
  
      @Override
      public BoundedWindow window() {
        return GlobalWindow.INSTANCE;
      }
    }
  
    /** Test implementation of MergeContext. */
    private static class TestMergeContext<T, W extends BoundedWindow>
        extends WindowFn<T, W>.MergeContext {
      private TestWindowSet<W, ?> windowSet;
  
      public TestMergeContext(TestWindowSet<W, ?> windowSet, WindowFn<T, W> windowFn) {
        windowFn.super();
        this.windowSet = windowSet;
      }
  
      @Override
      public Collection<W> windows() {
        return windowSet.windows();
      }
  
      @Override
      public void merge(Collection<W> toBeMerged, W mergeResult) {
        windowSet.merge(toBeMerged, mergeResult);
      }
    }
  
    /**
     * A WindowSet useful for testing WindowFns that simply collects the placed elements into
     * multisets.
     */
    private static class TestWindowSet<W extends BoundedWindow, V> {
  
      private Map<W, Set<V>> elements = new HashMap<>();
  
      public void put(W window, V value) {
        Set<V> all = elements.computeIfAbsent(window, k -> new HashSet<>());
        all.add(value);
      }
  
      public void merge(Collection<W> otherWindows, W window) {
        if (otherWindows.isEmpty()) {
          return;
        }
        Set<V> merged = new HashSet<>();
        if (elements.containsKey(window) && !otherWindows.contains(window)) {
          merged.addAll(elements.get(window));
        }
        for (W w : otherWindows) {
          if (!elements.containsKey(w)) {
            throw new IllegalArgumentException("Tried to merge a non-existent window:" + w);
          }
          merged.addAll(elements.get(w));
          elements.remove(w);
        }
        elements.put(window, merged);
      }
  
      public Collection<W> windows() {
        return elements.keySet();
      }
  
      // For testing.
  
      public Set<V> get(W window) {
        return elements.get(window);
      }
    }
  
    /**
     * Verifies that later-ending merged windows from any of the timestamps hold up output of
     * earlier-ending windows, using the provided {@link WindowFn} and {@link TimestampCombiner}.
     *
     * <p>Given a list of lists of timestamps, where each list is expected to merge into a single
     * window with end times in ascending order, assigns and merges windows for each list (as though
     * each were a separate key/user session). Then combines each timestamp in the list according to
     * the provided {@link TimestampCombiner}.
     *
     * <p>Verifies that a overlapping windows do not hold each other up via the watermark.
     */
    public static <T, W extends IntervalWindow> void validateGetOutputTimestamps(
        WindowFn<T, W> windowFn,
        TimestampCombiner timestampCombiner,
        List<List<Long>> timestampsPerWindow)
        throws Exception {
  
      List<List<TimestampedValue<T>>> timestampValuesPerWindow = new ArrayList<>();
      for (List<Long> timestamps : timestampsPerWindow) {
        List<TimestampedValue<T>> timestampedValues = new ArrayList<>();
        for (Long timestamp : timestamps) {
          TimestampedValue<T> tv = TimestampedValue.of(null, new Instant(timestamp));
          timestampedValues.add(tv);
        }
        timestampValuesPerWindow.add(timestampedValues);
      }
      validateGetOutputTimestampsWithValue(windowFn, timestampCombiner, timestampValuesPerWindow);
    }
  
    /**
     * Verifies that later-ending merged windows from any of the timestampValues hold up output of
     * earlier-ending windows, using the provided {@link WindowFn} and {@link TimestampCombiner}.
     *
     * <p>Given a list of lists of timestampValues, where each list is expected to merge into a single
     * window with end times in ascending order, assigns and merges windows for each list (as though
     * each were a separate key/user session). Then combines each timestamp in the list according to
     * the provided {@link TimestampCombiner}.
     *
     * <p>Verifies that a overlapping windows do not hold each other up via the watermark. This
     * version allows passing {@link TimestampedValue} in case the value is needed to assign windows.
     */
    public static <T, W extends IntervalWindow> void validateGetOutputTimestampsWithValue(
        WindowFn<T, W> windowFn,
        TimestampCombiner timestampCombiner,
        List<List<TimestampedValue<T>>> timestampValuesPerWindow)
        throws Exception {
  
      // Assign windows to each timestamp, then merge them, storing the merged windows in
      // a list in corresponding order to timestampValuesPerWindow
      final List<W> windows = new ArrayList<>();
      for (List<TimestampedValue<T>> timestampValuesForWindow : timestampValuesPerWindow) {
        final Set<W> windowsToMerge = new HashSet<>();
  
        for (TimestampedValue<T> element : timestampValuesForWindow) {
          windowsToMerge.addAll(assignedWindowsWithValue(windowFn, element));
        }
  
        windowFn.mergeWindows(
            windowFn.new MergeContext() {
              @Override
              public Collection<W> windows() {
                return windowsToMerge;
              }
  
              @Override
              public void merge(Collection<W> toBeMerged, W mergeResult) throws Exception {
                windows.add(mergeResult);
              }
            });
      }
  
      // Map every list of input timestampValues timestamps to an output timestamp
      final List<Instant> combinedOutputTimestamps = new ArrayList<>();
      for (int i = 0; i < timestampValuesPerWindow.size(); ++i) {
        List<TimestampedValue<T>> timestampValuesForWindow = timestampValuesPerWindow.get(i);
        W window = windows.get(i);
  
        List<Instant> outputInstants = new ArrayList<>();
        for (TimestampedValue<T> element : timestampValuesForWindow) {
          outputInstants.add(assignOutputTime(timestampCombiner, element.getTimestamp(), window));
        }
  
        combinedOutputTimestamps.add(combineOutputTimes(timestampCombiner, outputInstants));
      }
  
      // Consider windows in increasing order of max timestamp; ensure the output timestamp is after
      // the max timestamp of the previous
      @Nullable W earlierEndingWindow = null;
      for (int i = 0; i < windows.size(); ++i) {
        W window = windows.get(i);
        ReadableInstant outputTimestamp = combinedOutputTimestamps.get(i);
  
        if (earlierEndingWindow != null) {
          assertThat(
              outputTimestamp, greaterThan((ReadableInstant) earlierEndingWindow.maxTimestamp()));
        }
  
        earlierEndingWindow = window;
      }
    }
  
    private static Instant assignOutputTime(
        TimestampCombiner timestampCombiner, Instant inputTimestamp, BoundedWindow window) {
      switch (timestampCombiner) {
        case EARLIEST:
        case LATEST:
          return inputTimestamp;
        case END_OF_WINDOW:
          return window.maxTimestamp();
        default:
          throw new IllegalArgumentException(
              String.format("Unknown %s: %s", TimestampCombiner.class, timestampCombiner));
      }
    }
  
    private static Instant combineOutputTimes(
        TimestampCombiner timestampCombiner, Iterable<Instant> outputInstants) {
      checkArgument(
          !Iterables.isEmpty(outputInstants),
          "Cannot combine zero instants with %s",
          timestampCombiner);
      switch (timestampCombiner) {
        case EARLIEST:
          return Ordering.natural().min(outputInstants);
        case LATEST:
          return Ordering.natural().max(outputInstants);
        case END_OF_WINDOW:
          return outputInstants.iterator().next();
        default:
          throw new IllegalArgumentException(
              String.format("Unknown %s: %s", TimestampCombiner.class, timestampCombiner));
      }
    }
  }
  