content: /*
   *  Copyright 2023 The original 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
   *
   *      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 dev.morling.onebrc;
  
  import static java.util.stream.Collectors.*;
  
  import java.io.IOException;
  import java.nio.file.Files;
  import java.nio.file.Paths;
  import java.util.Map;
  import java.util.TreeMap;
  import java.util.stream.Collector;
  
  public class CalculateAverage {
  
      private static final String FILE = "./measurements.txt";
  
      private static record Measurement(String station, double value) {
          private Measurement(String[] parts) {
              this(parts[0], Double.parseDouble(parts[1]));
          }
      }
  
      private static record ResultRow(double min, double mean, double max) {
          public String toString() {
              return round(min) + "/" + round(mean) + "/" + round(max);
          }
  
          private double round(double value) {
              return Math.round(value * 10.0) / 10.0;
          }
      };
  
      private static class MeasurementAggregator {
          private double min = Double.POSITIVE_INFINITY;
          private double max = Double.NEGATIVE_INFINITY;
          private double sum;
          private long count;
      }
  
      public static void main(String[] args) throws IOException {
          // Map<String, Double> measurements1 = Files.lines(Paths.get(FILE))
          // .map(l -> l.split(";"))
          // .collect(groupingBy(m -> m[0], averagingDouble(m -> Double.parseDouble(m[1]))));
          //
          // measurements1 = new TreeMap<>(measurements1.entrySet()
          // .stream()
          // .collect(toMap(e -> e.getKey(), e -> Math.round(e.getValue() * 10.0) / 10.0)));
          // System.out.println(measurements1);
  
          Collector<Measurement, MeasurementAggregator, ResultRow> collector = Collector.of(
                  MeasurementAggregator::new,
                  (a, m) -> {
                      a.min = Math.min(a.min, m.value);
                      a.max = Math.max(a.max, m.value);
                      a.sum += m.value;
                      a.count++;
                  },
                  (agg1, agg2) -> {
                      var res = new MeasurementAggregator();
                      res.min = Math.min(agg1.min, agg2.min);
                      res.max = Math.max(agg1.max, agg2.max);
                      res.sum = agg1.sum + agg2.sum;
                      res.count = agg1.count + agg2.count;
  
                      return res;
                  },
                  agg -> {
                      return new ResultRow(agg.min, agg.sum / agg.count, agg.max);
                  });
  
          Map<String, ResultRow> measurements = new TreeMap<>(Files.lines(Paths.get(FILE))
                  .map(l -> new Measurement(l.split(";")))
                  .collect(groupingBy(m -> m.station(), collector)));
  
          System.out.println(measurements);
      }
  }
  