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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.storm.metric.api;

import com.twitter.heron.api.metric.MeanReducerState;

public class MeanReducer implements IReducer {
  public MeanReducerState init() {
    return new MeanReducerState();
  }

  public MeanReducerState reduce(MeanReducerState acc, Object input) {
    acc.count++;
    if (input instanceof Double) {
      acc.sum += (Double) input;
    } else if (input instanceof Long) {
      acc.sum += ((Long) input).doubleValue();
    } else if (input instanceof Integer) {
      acc.sum += ((Integer) input).doubleValue();
    } else {
      throw new RuntimeException(
          "MeanReducer::reduce called with unsupported input type `" + input.getClass()
              + "`. Supported types are Double, Long, Integer.");
    }
    return acc;
  }

  public Object extractResult(MeanReducerState acc) {
    if (acc.count > 0) {
      return new Double(acc.sum / (double) acc.count);
    } else {
      return null;
    }
  }
}