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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.analysis.tokenattributes;

import java.nio.CharBuffer;

import org.apache.lucene.util.ArrayUtil;
import org.apache.lucene.util.AttributeImpl;
import org.apache.lucene.util.AttributeReflector;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.BytesRefBuilder;
import org.apache.lucene.util.FutureObjects;

/** Default implementation of {@link CharTermAttribute}. */
public class CharTermAttributeImpl extends AttributeImpl implements CharTermAttribute, TermToBytesRefAttribute, Cloneable {
  private static int MIN_BUFFER_SIZE = 10;
  
  private char[] termBuffer = new char[ArrayUtil.oversize(MIN_BUFFER_SIZE, Character.BYTES)];
  private int termLength = 0;
  
  /** May be used by subclasses to convert to different charsets / encodings for implementing {@link #getBytesRef()}. */
  protected BytesRefBuilder builder = new BytesRefBuilder();
  
  /** Initialize this attribute with empty term text */
  public CharTermAttributeImpl() {}

  @Override
  public final void copyBuffer(char[] buffer, int offset, int length) {
    growTermBuffer(length);
    System.arraycopy(buffer, offset, termBuffer, 0, length);
    termLength = length;
  }

  @Override
  public final char[] buffer() {
    return termBuffer;
  }
  
  @Override
  public final char[] resizeBuffer(int newSize) {
    if(termBuffer.length < newSize){
      // Not big enough; create a new array with slight
      // over allocation and preserve content
      final char[] newCharBuffer = new char[ArrayUtil.oversize(newSize, Character.BYTES)];
      System.arraycopy(termBuffer, 0, newCharBuffer, 0, termBuffer.length);
      termBuffer = newCharBuffer;
    }
    return termBuffer;   
  }
  
  private void growTermBuffer(int newSize) {
    if(termBuffer.length < newSize){
      // Not big enough; create a new array with slight
      // over allocation:
      termBuffer = new char[ArrayUtil.oversize(newSize, Character.BYTES)];
    }
  }

  @Override
  public final CharTermAttribute setLength(int length) {
    FutureObjects.checkFromIndexSize(0, length, termBuffer.length);
    termLength = length;
    return this;
  }
  
  @Override
  public final CharTermAttribute setEmpty() {
    termLength = 0;
    return this;
  }
  
  // *** TermToBytesRefAttribute interface ***

  @Override
  public BytesRef getBytesRef() {
    builder.copyChars(termBuffer, 0, termLength);
    return builder.get();
  }
  
  // *** CharSequence interface ***
  @Override
  public final int length() {
    return termLength;
  }
  
  @Override
  public final char charAt(int index) {
    FutureObjects.checkIndex(index, termLength);
    return termBuffer[index];
  }
  
  @Override
  public final CharSequence subSequence(final int start, final int end) {
    FutureObjects.checkFromToIndex(start, end, termLength);
    return new String(termBuffer, start, end - start);
  }
  
  // *** Appendable interface ***

  @Override
  public final CharTermAttribute append(CharSequence csq) {
    if (csq == null) // needed for Appendable compliance
      return appendNull();
    return append(csq, 0, csq.length());
  }
  
  @Override
  public final CharTermAttribute append(CharSequence csq, int start, int end) {
    if (csq == null) // needed for Appendable compliance
      csq = "null";
    // TODO: the optimized cases (jdk methods) will already do such checks, maybe re-organize this?
    FutureObjects.checkFromToIndex(start, end, csq.length());
    final int len = end - start;
    if (len == 0)
      return this;
    resizeBuffer(termLength + len);
    if (len > 4) { // only use instanceof check series for longer CSQs, else simply iterate
      if (csq instanceof String) {
        ((String) csq).getChars(start, end, termBuffer, termLength);
      } else if (csq instanceof StringBuilder) {
        ((StringBuilder) csq).getChars(start, end, termBuffer, termLength);
      } else if (csq instanceof CharTermAttribute) {
        System.arraycopy(((CharTermAttribute) csq).buffer(), start, termBuffer, termLength, len);
      } else if (csq instanceof CharBuffer && ((CharBuffer) csq).hasArray()) {
        final CharBuffer cb = (CharBuffer) csq;
        System.arraycopy(cb.array(), cb.arrayOffset() + cb.position() + start, termBuffer, termLength, len);
      } else if (csq instanceof StringBuffer) {
        ((StringBuffer) csq).getChars(start, end, termBuffer, termLength);
      } else {
        while (start < end)
          termBuffer[termLength++] = csq.charAt(start++);
        // no fall-through here, as termLength is updated!
        return this;
      }
      termLength += len;
      return this;
    } else {
      while (start < end)
        termBuffer[termLength++] = csq.charAt(start++);
      return this;
    }
  }
  
  @Override
  public final CharTermAttribute append(char c) {
    resizeBuffer(termLength + 1)[termLength++] = c;
    return this;
  }
  
  // *** For performance some convenience methods in addition to CSQ's ***
  
  @Override
  public final CharTermAttribute append(String s) {
    if (s == null) // needed for Appendable compliance
      return appendNull();
    final int len = s.length();
    s.getChars(0, len, resizeBuffer(termLength + len), termLength);
    termLength += len;
    return this;
  }
  
  @Override
  public final CharTermAttribute append(StringBuilder s) {
    if (s == null) // needed for Appendable compliance
      return appendNull();
    final int len = s.length();
    s.getChars(0, len, resizeBuffer(termLength + len), termLength);
    termLength += len;
    return this;
  }
  
  @Override
  public final CharTermAttribute append(CharTermAttribute ta) {
    if (ta == null) // needed for Appendable compliance
      return appendNull();
    final int len = ta.length();
    System.arraycopy(ta.buffer(), 0, resizeBuffer(termLength + len), termLength, len);
    termLength += len;
    return this;
  }

  private CharTermAttribute appendNull() {
    resizeBuffer(termLength + 4);
    termBuffer[termLength++] = 'n';
    termBuffer[termLength++] = 'u';
    termBuffer[termLength++] = 'l';
    termBuffer[termLength++] = 'l';
    return this;
  }
  
  // *** AttributeImpl ***

  @Override
  public int hashCode() {
    int code = termLength;
    code = code * 31 + ArrayUtil.hashCode(termBuffer, 0, termLength);
    return code;
  }

  @Override
  public void clear() {
    termLength = 0;    
  }

  @Override
  public CharTermAttributeImpl clone() {
    CharTermAttributeImpl t = (CharTermAttributeImpl)super.clone();
    // Do a deep clone
    t.termBuffer = new char[this.termLength];
    System.arraycopy(this.termBuffer, 0, t.termBuffer, 0, this.termLength);
    t.builder = new BytesRefBuilder();
    t.builder.copyBytes(builder.get());
    return t;
  }
  
  @Override
  public boolean equals(Object other) {
    if (other == this) {
      return true;
    }
    
    if (other instanceof CharTermAttributeImpl) {
      final CharTermAttributeImpl o = ((CharTermAttributeImpl) other);
      if (termLength != o.termLength)
        return false;
      for(int i=0;i