/*
 * Copyright 2010 The Apache Software Foundation
 *
 * 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.hadoop.hbase.filter;

import org.apache.hadoop.hbase.KeyValue;

import java.util.List;

/**
 * Abstract base class to help you implement new Filters.  Common "ignore" or NOOP type
 * methods can go here, helping to reduce boiler plate in an ever-expanding filter
 * library.
 *
 * If you could instantiate FilterBase, it would end up being a "null" filter -
 * that is one that never filters anything.
 */
public abstract class FilterBase implements Filter {

  /**
   * Filters that are purely stateless and do nothing in their reset() methods can inherit
   * this null/empty implementation.
   *
   * @inheritDoc
   */
  @Override
  public void reset() {
  }

  /**
   * Filters that do not filter by row key can inherit this implementation that
   * never filters anything. (ie: returns false).
   *
   * @inheritDoc
   */
  @Override
  public boolean filterRowKey(byte [] buffer, int offset, int length) {
    return false;
  }

  /**
   * Filters that never filter all remaining can inherit this implementation that
   * never stops the filter early.
   *
   * @inheritDoc
   */
  @Override
  public boolean filterAllRemaining() {
    return false;
  }

  /**
   * Filters that dont filter by key value can inherit this implementation that
   * includes all KeyValues.
   *
   * @inheritDoc
   */
  @Override
  public ReturnCode filterKeyValue(KeyValue ignored) {
    return ReturnCode.INCLUDE;
  }

  /**
   * Filters that never filter by modifying the returned List of KeyValues can
   * inherit this implementation that does nothing.
   *
   * @inheritDoc
   */
  @Override
  public void filterRow(List<KeyValue> ignored) {
  }

  /**
   * Fitlers that never filter by modifying the returned List of KeyValues can
   * inherit this implementation that does nothing.
   *
   * @inheritDoc
   */
  @Override
  public boolean hasFilterRow() {
    return false;
  }

  /**
   * Filters that never filter by rows based on previously gathered state from
   * {@link #filterKeyValue(KeyValue)} can inherit this implementation that
   * never filters a row.
   *
   * @inheritDoc
   */
  @Override
  public boolean filterRow() {
    return false;
  }

  /**
   * Filters that are not sure which key must be next seeked to, can inherit
   * this implementation that, by default, returns a null KeyValue.
   *
   * @inheritDoc
   */
  public KeyValue getNextKeyHint(KeyValue currentKV) {
    return null;
  }

}