/*
 * 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.io.IOException;

import org.apache.lucene.util.AttributeSource;
import org.apache.lucene.util.BytesRef;

A base TermsEnum that adds default implementations for

  
attributes()
  
termState()
  
seekExact(BytesRef)
  
seekExact(BytesRef, TermState)

In some cases, the default implementation may be slow and consume huge memory, so subclass SHOULD have its own
implementation if possible.
/**
 * A base TermsEnum that adds default implementations for
 * <ul>
 *   <li>{@link #attributes()}</li>
 *   <li>{@link #termState()}</li>
 *   <li>{@link #seekExact(BytesRef)}</li>
 *   <li>{@link #seekExact(BytesRef, TermState)}</li>
 * </ul>
 *
 * In some cases, the default implementation may be slow and consume huge memory, so subclass SHOULD have its own
 * implementation if possible.
 */
public abstract class BaseTermsEnum extends TermsEnum {

  private AttributeSource atts = null;
  
  
Sole constructor. (For invocation by subclass
 constructors, typically implicit.) /** Sole constructor. (For invocation by subclass
   *  constructors, typically implicit.) */
  protected BaseTermsEnum() {
    super();
  }

  @Override
  public TermState termState() throws IOException {
    return new TermState() {
      @Override
      public void copyFrom(TermState other) {
        throw new UnsupportedOperationException();
      }
    };
  }

  @Override
  public boolean seekExact(BytesRef text) throws IOException {
    return seekCeil(text) == SeekStatus.FOUND;
  }

  @Override
  public void seekExact(BytesRef term, TermState state) throws IOException {
    if (!seekExact(term)) {
      throw new IllegalArgumentException("term=" + term + " does not exist");
    }
  }

  public AttributeSource attributes() {
    if (atts == null) {
      atts = new AttributeSource();
    }
    return atts;
  }
}