/*
 * Copyright 2018 Confluent Inc.
 *
 * Licensed under the Confluent Community License (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.confluent.io/confluent-community-license
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OF ANY KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations under the License.
 */

package io.confluent.ksql.function.udaf;

/**
 * {@code TableUdaf} is an {@link Udaf} that can be used to
 * aggregate KSQL tables.
 * @param <V> value type
 * @param <A> aggregate type
 */
public interface TableUdaf<V, A> extends Udaf<V, A> {
  /**
   * Called to update a value when a record with the same key
   * has been updated. When called this function should
   * reverse the operation that was performed during {@link Udaf#aggregate(Object, Object)}
   * @param valueToUndo   value that has been changed
   * @param aggregateValue the current aggregate
   * @return new aggregate
   */
  A undo(V valueToUndo, A aggregateValue);
}
