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.nexmark.queries;
  
  import static org.hamcrest.MatcherAssert.assertThat;
  
  import java.io.Serializable;
  import java.util.Collection;
  import java.util.HashSet;
  import java.util.Iterator;
  import java.util.Set;
  import org.apache.beam.sdk.nexmark.NexmarkConfiguration;
  import org.apache.beam.sdk.nexmark.model.KnownSize;
  import org.apache.beam.sdk.transforms.SerializableFunction;
  import org.apache.beam.sdk.values.TimestampedValue;
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.hamcrest.core.IsEqual;
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  import org.junit.Assert;
  
  /**
   * Base class for models of the eight NEXMark queries. Provides an assertion function which can be
   * applied against the actual query results to check their consistency with the model.
   */
  @SuppressWarnings({
    "nullness" // TODO(https://github.com/apache/beam/issues/20497)
  })
  public abstract class NexmarkQueryModel<T extends KnownSize> implements Serializable {
    public final NexmarkConfiguration configuration;
  
    NexmarkQueryModel(NexmarkConfiguration configuration) {
      this.configuration = configuration;
    }
  
    /**
     * Return the start of the most recent window of {@code size} and {@code period} which ends
     * strictly before {@code timestamp}.
     */
    static Instant windowStart(Duration size, Duration period, Instant timestamp) {
      long ts = timestamp.getMillis();
      long p = period.getMillis();
      long lim = ts - ts % p;
      long s = size.getMillis();
      return new Instant(lim - s);
    }
  
    /** Convert {@code itr} to strings capturing values and timestamps. */
    static <T> Set<String> toValueTimestamp(Iterator<TimestampedValue<T>> itr) {
      Set<String> strings = new HashSet<>();
      while (itr.hasNext()) {
        strings.add(itr.next().toString());
      }
      return strings;
    }
  
    /** Convert {@code itr} to strings capturing values only. */
    static <T> Set<String> toValue(Iterator<TimestampedValue<T>> itr) {
      Set<String> strings = new HashSet<>();
      while (itr.hasNext()) {
        strings.add(itr.next().getValue().toString());
      }
      return strings;
    }
  
    /** Return simulator for query. */
    public abstract AbstractSimulator<?, T> simulator();
  
    /** Return sub-sequence of results which are significant for model. */
    Iterable<TimestampedValue<T>> relevantResults(Iterable<TimestampedValue<T>> results) {
      return results;
    }
  
    /**
     * Convert iterator of elements to collection of strings to use when testing coherence of model
     * against actual query results.
     */
    protected abstract Collection<String> toCollection(Iterator<TimestampedValue<T>> itr);
  
    /** Return assertion to use on results of pipeline for this query. */
    public SerializableFunction<Iterable<TimestampedValue<T>>, Void> assertionFor() {
      final Collection<String> expectedStrings = toCollection(simulator().results());
      Assert.assertFalse(expectedStrings.isEmpty());
  
      return new SerializableFunction<Iterable<TimestampedValue<T>>, Void>() {
        @Override
        public @Nullable Void apply(Iterable<TimestampedValue<T>> actual) {
          Collection<String> actualStrings = toCollection(relevantResults(actual).iterator());
          assertThat("wrong pipeline output", actualStrings, IsEqual.equalTo(expectedStrings));
          return null;
        }
      };
    }
  }
  