/*
 * 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.lucene.index;

import java.util.List;

Information about upcoming impacts, ie. (freq, norm) pairs.
/**
 * Information about upcoming impacts, ie. (freq, norm) pairs.
 */
public abstract class Impacts {

  
Sole constructor. Typically invoked by sub classes. /** Sole constructor. Typically invoked by sub classes. */
  protected Impacts() {}

  
Return the number of levels on which we have impacts.
The returned value is always greater than 0 and may not always be the
same, even on a single postings list, depending on the current doc ID.
/**
   * Return the number of levels on which we have impacts.
   * The returned value is always greater than 0 and may not always be the
   * same, even on a single postings list, depending on the current doc ID.
   */
  public abstract int numLevels();

  
Return the maximum inclusive doc ID until which the list of impacts returned by getImpacts(int) is valid. This is a non-decreasing function of level. /**
   * Return the maximum inclusive doc ID until which the list of impacts
   * returned by {@link #getImpacts(int)} is valid. This is a non-decreasing
   * function of {@code level}.
   */
  public abstract int getDocIdUpTo(int level);

  
Return impacts on the given level. These impacts are sorted by increasing frequency and increasing unsigned norm, and only valid until the doc ID returned by getDocIdUpTo(int) for the same level, included. The returned list is never empty. NOTE: There is no guarantee that these impacts actually appear in postings, only that they trigger scores that are greater than or equal to the impacts that actually appear in postings. /**
   * Return impacts on the given level. These impacts are sorted by increasing
   * frequency and increasing unsigned norm, and only valid until the doc ID
   * returned by {@link #getDocIdUpTo(int)} for the same level, included.
   * The returned list is never empty.
   * NOTE: There is no guarantee that these impacts actually appear in postings,
   * only that they trigger scores that are greater than or equal to the impacts
   * that actually appear in postings.
   */
  public abstract List<Impact> getImpacts(int level);

}