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/*
 * 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 org.apache.lucene.analysis.TokenStream; // javadocs
import org.apache.lucene.analysis.tokenattributes.OffsetAttribute;
import org.apache.lucene.analysis.tokenattributes.PayloadAttribute;
import org.apache.lucene.analysis.tokenattributes.PositionIncrementAttribute;
import org.apache.lucene.analysis.tokenattributes.TermFrequencyAttribute;
import org.apache.lucene.analysis.tokenattributes.TermToBytesRefAttribute;
import org.apache.lucene.util.AttributeSource;

/**
 * This class tracks the number and position / offset parameters of terms being added to the index.
 * The information collected in this class is also used to calculate the normalization factor for a
 * field.
 *
 * @lucene.experimental
 */
public final class FieldInvertState {
  final int indexCreatedVersionMajor;
  final String name;
  final IndexOptions indexOptions;
  int position;
  int length;
  int numOverlap;
  int offset;
  int maxTermFrequency;
  int uniqueTermCount;
  // we must track these across field instances (multi-valued case)
  int lastStartOffset = 0;
  int lastPosition = 0;
  AttributeSource attributeSource;

  OffsetAttribute offsetAttribute;
  PositionIncrementAttribute posIncrAttribute;
  PayloadAttribute payloadAttribute;
  TermToBytesRefAttribute termAttribute;
  TermFrequencyAttribute termFreqAttribute;

  /** Creates {code FieldInvertState} for the specified field name. */
  public FieldInvertState(int indexCreatedVersionMajor, String name, IndexOptions indexOptions) {
    this.indexCreatedVersionMajor = indexCreatedVersionMajor;
    this.name = name;
    this.indexOptions = indexOptions;
  }

  /** Creates {code FieldInvertState} for the specified field name and values for all fields. */
  public FieldInvertState(
      int indexCreatedVersionMajor,
      String name,
      IndexOptions indexOptions,
      int position,
      int length,
      int numOverlap,
      int offset,
      int maxTermFrequency,
      int uniqueTermCount) {
    this(indexCreatedVersionMajor, name, indexOptions);
    this.position = position;
    this.length = length;
    this.numOverlap = numOverlap;
    this.offset = offset;
    this.maxTermFrequency = maxTermFrequency;
    this.uniqueTermCount = uniqueTermCount;
  }

  /** Re-initialize the state */
  void reset() {
    position = -1;
    length = 0;
    numOverlap = 0;
    offset = 0;
    maxTermFrequency = 0;
    uniqueTermCount = 0;
    lastStartOffset = 0;
    lastPosition = 0;
  }

  // TODO: better name?
  /** Sets attributeSource to a new instance. */
  void setAttributeSource(AttributeSource attributeSource) {
    if (this.attributeSource != attributeSource) {
      this.attributeSource = attributeSource;
      if (attributeSource == null) {
        termAttribute = null;
        termFreqAttribute = null;
        posIncrAttribute = null;
        offsetAttribute = null;
        payloadAttribute = null;
      } else {
        termAttribute = attributeSource.getAttribute(TermToBytesRefAttribute.class);
        termFreqAttribute = attributeSource.addAttribute(TermFrequencyAttribute.class);
        posIncrAttribute = attributeSource.addAttribute(PositionIncrementAttribute.class);
        offsetAttribute = attributeSource.addAttribute(OffsetAttribute.class);
        payloadAttribute = attributeSource.getAttribute(PayloadAttribute.class);
      }
    }
  }

  /**
   * Get the last processed term position.
   *
   * @return the position
   */
  public int getPosition() {
    return position;
  }

  /**
   * Get total number of terms in this field.
   *
   * @return the length
   */
  public int getLength() {
    return length;
  }

  /** Set length value. */
  public void setLength(int length) {
    this.length = length;
  }

  /**
   * Get the number of terms with positionIncrement == 0.
   *
   * @return the numOverlap
   */
  public int getNumOverlap() {
    return numOverlap;
  }

  /** Set number of terms with {@code positionIncrement == 0}. */
  public void setNumOverlap(int numOverlap) {
    this.numOverlap = numOverlap;
  }

  /**
   * Get end offset of the last processed term.
   *
   * @return the offset
   */
  public int getOffset() {
    return offset;
  }

  /**
   * Get the maximum term-frequency encountered for any term in the field. A field containing "the
   * quick brown fox jumps over the lazy dog" would have a value of 2, because "the" appears twice.
   */
  public int getMaxTermFrequency() {
    return maxTermFrequency;
  }

  /** Return the number of unique terms encountered in this field. */
  public int getUniqueTermCount() {
    return uniqueTermCount;
  }

  /**
   * Returns the {@link AttributeSource} from the {@link TokenStream} that provided the indexed
   * tokens for this field.
   */
  public AttributeSource getAttributeSource() {
    return attributeSource;
  }

  /** Return the field's name */
  public String getName() {
    return name;
  }

  /** Return the version that was used to create the index, or 6 if it was created before 7.0. */
  public int getIndexCreatedVersionMajor() {
    return indexCreatedVersionMajor;
  }

  /** Get the index options for this field */
  public IndexOptions getIndexOptions() {
    return indexOptions;
  }
}