/*
 * 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.runners.core;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.ImmutableSet;
import java.util.Collection;
import java.util.Set;
import org.apache.beam.sdk.transforms.windowing.BoundedWindow;
import org.apache.beam.sdk.transforms.windowing.WindowFn;

/**
 * Implementation of {@link ActiveWindowSet} used with {@link WindowFn WindowFns} that don't support
 * merging.
 *
 * @param <W> the types of windows being managed
 */
public class NonMergingActiveWindowSet<W extends BoundedWindow> implements ActiveWindowSet<W> {
  @Override
  public void cleanupTemporaryWindows() {}

  @Override
  public void persist() {}

  @Override
  public Set<W> getActiveAndNewWindows() {
    // Only supported when merging.
    throw new java.lang.UnsupportedOperationException();
  }

  @Override
  public boolean isActive(W window) {
    // Windows should never disappear, since we don't support merging.
    return true;
  }

  @Override
  public boolean isActiveOrNew(W window) {
    return true;
  }

  @Override
  public void ensureWindowExists(W window) {}

  @Override
  public void ensureWindowIsActive(W window) {}

  @Override
  @VisibleForTesting
  public void addActiveForTesting(W window) {}

  @Override
  public void remove(W window) {}

  @Override
  public void merge(MergeCallback<W> mergeCallback) throws Exception {}

  @Override
  public void merged(W window) {}

  @Override
  public Set<W> readStateAddresses(W window) {
    return ImmutableSet.of(window);
  }

  @Override
  public W writeStateAddress(W window) {
    return window;
  }

  @Override
  public W mergedWriteStateAddress(Collection<W> toBeMerged, W mergeResult) {
    return mergeResult;
  }
}
