/*
 * 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.phoenix.expression.aggregator;

import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import org.apache.phoenix.schema.SortOrder;
import org.apache.phoenix.schema.tuple.Tuple;
import org.apache.phoenix.schema.types.PDataType;
import org.apache.phoenix.schema.types.PLong;
import org.apache.phoenix.util.SizedUtil;

/**
 * Aggregator for COUNT aggregations
 * @since 0.1
 */
public class CountAggregator extends BaseAggregator {

  private long count = 0;
  private byte[] buffer = null;

  public CountAggregator() {
    super(SortOrder.getDefault());
  }

  public CountAggregator(LongSumAggregator clientAgg) {
    this();
    count = clientAgg.getSum();
  }

  @Override
  public void aggregate(Tuple tuple, ImmutableBytesWritable ptr) {
    count++;
  }

  @Override
  public boolean isNullable() {
    return false;
  }

  @Override
  public boolean evaluate(Tuple tuple, ImmutableBytesWritable ptr) {
    if (buffer == null) {
      buffer = new byte[getDataType().getByteSize()];
    }
    getDataType().getCodec().encodeLong(count, buffer, 0);
    ptr.set(buffer);
    return true;
  }

  @Override
  public final PDataType getDataType() {
    return PLong.INSTANCE;
  }

  @Override
  public void reset() {
    count = 0;
    buffer = null;
    super.reset();
  }

  @Override
  public String toString() {
    return "COUNT [count=" + count + "]";
  }

  @Override
  public int getSize() {
    return super.getSize() + SizedUtil.LONG_SIZE + SizedUtil.ARRAY_SIZE
      + getDataType().getByteSize();
  }

}
