/*
    * 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.chukwa.hicc;
  
  import java.util.TreeMap;
  import java.util.Map.Entry;
  
  public class AreaCalculator {
    public static TreeMap<String, Double> getAreas(
        TreeMap<String, TreeMap<String, Double>> dataSet) 
    {
      TreeMap<String, Double> areas = new TreeMap<String, Double>();
      for (Entry<String, TreeMap<String, Double>> entry : dataSet.entrySet()) {
        String key = entry.getKey();
        Double area = getArea(entry.getValue());
        areas.put(key, area);
      }
      return areas;
    }
  
    public static Double getArea(TreeMap<String, Double> data) {
      double area = 0;
      boolean first = true;
      double x0, x1, y0, y1;
      x0 = x1 = y0 = y1 = 0;
      for (Entry<String, Double> entry : data.entrySet()) {
        double x = Double.parseDouble(entry.getKey());
        double y = entry.getValue();
        if (first) {
          x0 = x;
          y0 = y;
          first = false;
        } else {
          x1 = x;
          y1 = y;
          area += getArea(x0, y0, x1, y1);
          x0 = x1;
          y0 = y1;
        }
      }
      return area;
    }
  
    public static Double getArea(double x0, double y0, double x1, double y1) {
      return (x1 - x0) * (y0 + y1) / 2;
    }
  }