/*
 * 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 com.alipay.sofa.registry.server.shared.comparator;

import com.alipay.sofa.registry.common.model.Triple;
import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

/**
 * @author chen.zhu
 *     <p>Jan 12, 2021
 */
public class AbstractComparator<T> implements Comparator<T> {
  protected Set<T> added = new HashSet<>();
  protected Set<T> removed = new HashSet<>();
  protected Set<T> remainings = new HashSet<>();
  protected volatile int count;

  @Override
  public Set<T> getAdded() {
    return added;
  }

  @Override
  public Set<T> getRemoved() {
    return removed;
  }

  @Override
  public boolean hasAnyChange() {
    return count > 0;
  }

  @Override
  public int totalChange() {
    return count;
  }

  protected <Type> Triple<Set<Type>, Set<Type>, Set<Type>> getDiff(
      Collection<Type> current, Collection<Type> future) {

    Set<Type> added = new HashSet<>(future);
    Set<Type> remaining = new HashSet<>(future);
    Set<Type> deleted = new HashSet<>(current);

    added.removeAll(deleted);
    remaining.retainAll(deleted);
    deleted.removeAll(future);

    return new Triple<Set<Type>, Set<Type>, Set<Type>>(added, remaining, deleted);
  }
}
