content: /*
   * Copyright 2022 The FeatHub Authors
   *
   * Licensed 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
   *
   *     https://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 com.alibaba.feathub.flink.udf.aggregation;
  
  import org.apache.flink.api.common.typeinfo.TypeInformation;
  import org.apache.flink.api.common.typeinfo.Types;
  import org.apache.flink.api.java.tuple.Tuple2;
  import org.apache.flink.table.api.DataTypes;
  import org.apache.flink.table.types.DataType;
  
  /** Aggregation function that counts the average of values. */
  public class AvgAggFunc<IN_T extends Number>
          implements AggFunc<
                  IN_T,
                  Double,
                  Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>>> {
      private final CountAggFunc countAggFunc;
      private final SumAggFunc<IN_T> sumAggFunc;
  
      public AvgAggFunc(SumAggFunc<IN_T> sumAggFunc) {
          this.countAggFunc = new CountAggFunc();
          this.sumAggFunc = sumAggFunc;
      }
  
      @Override
      public void add(
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> accumulator,
              IN_T value,
              long timestamp) {
          countAggFunc.add(accumulator.f0, value, timestamp);
          sumAggFunc.add(accumulator.f1, value, timestamp);
      }
  
      @Override
      public void merge(
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> target,
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> source) {
          countAggFunc.merge(target.f0, source.f0);
          sumAggFunc.merge(target.f1, source.f1);
      }
  
      @Override
      public void retract(
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> accumulator,
              IN_T value) {
          countAggFunc.retract(accumulator.f0, value);
          sumAggFunc.retract(accumulator.f1, value);
      }
  
      @Override
      public void retractAccumulator(
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> target,
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> source) {
          countAggFunc.retractAccumulator(target.f0, source.f0);
          sumAggFunc.retractAccumulator(target.f1, source.f1);
      }
  
      @Override
      public Double getResult(
              Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>> accumulator) {
          long count = countAggFunc.getResult(accumulator.f0);
          if (count == 0) {
              return null;
          } else {
              return sumAggFunc.getResult(accumulator.f1).doubleValue() / count;
          }
      }
  
      @Override
      public DataType getResultDatatype() {
          return DataTypes.DOUBLE();
      }
  
      @Override
      public TypeInformation<Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>>>
              getAccumulatorTypeInformation() {
          return Types.TUPLE(
                  countAggFunc.getAccumulatorTypeInformation(),
                  sumAggFunc.getAccumulatorTypeInformation());
      }
  
      @Override
      public Tuple2<CountAggFunc.CountAccumulator, SumAggFunc.SumAccumulator<IN_T>>
              createAccumulator() {
          return Tuple2.of(countAggFunc.createAccumulator(), sumAggFunc.createAccumulator());
      }
  }
  