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   1 /**
   2  * Copyright (c) 2010-2022 Contributors to the openHAB project
   3  *
   4  * See the NOTICE file(s) distributed with this work for additional
   5  * information.
   6  *
   7  * This program and the accompanying materials are made available under the
   8  * terms of the Eclipse Public License 2.0 which is available at
   9  * http://www.eclipse.org/legal/epl-2.0
  10  *
  11  * SPDX-License-Identifier: EPL-2.0
  12  */
  13 package org.openhab.binding.ambientweather.internal.util;
  14
  15 import org.eclipse.jdt.annotation.NonNullByDefault;
  16 import org.slf4j.Logger;
  17 import org.slf4j.LoggerFactory;
  18
  19 /**
  20  * The {@link PressureTrend} is responsible for determining the 3 hour
  21  * barometric pressure trend. All calculations are in inches of Mercury.
  22  *
  23  * @author Mark Hilbush - Initial contribution
  24  */
  25 @NonNullByDefault
  26 public class PressureTrend extends SlidingTimeWindow<Double> {
  27     private final Logger logger = LoggerFactory.getLogger(PressureTrend.class);
  28
  29     // Pressure trend is established after 3 hours
  30     private static final long PRESSURE_TREND_PERIOD = 1000 * 60 * 60 * 3;
  31
  32     // Thresholds used to determine pressure trends
  33     private static final double RAPIDLY_THRESHOLD = 0.06;
  34     private static final double STEADY_THRESHOLD = 0.02;
  35
  36     // Pressure trends
  37     private static final String RISING_RAPIDLY = "RISING RAPIDLY";
  38     private static final String RISING = "RISING";
  39     private static final String FALLING_RAPIDLY = "FALLING RAPIDLY";
  40     private static final String FALLING = "FALLING";
  41     private static final String STEADY = "STEADY";
  42     private static final String UNKNOWN = "UNKNOWN";
  43
  44     public PressureTrend() {
  45         super(PRESSURE_TREND_PERIOD);
  46     }
  47
  48     public String getPressureTrend() {
  49         long firstTime;
  50         long lastTime;
  51         double firstValue;
  52         double lastValue;
  53
  54         if (storage.isEmpty()) {
  55             return UNKNOWN;
  56         }
  57
  58         synchronized (storage) {
  59             firstTime = storage.firstKey();
  60             lastTime = storage.lastKey();
  61             firstValue = storage.get(storage.firstKey()).doubleValue();
  62             lastValue = storage.get(storage.lastKey()).doubleValue();
  63         }
  64         if (lastTime - firstTime < period * 0.99) {
  65             // Not within 1% of time period
  66             return UNKNOWN;
  67         }
  68
  69         double pressureDifference = lastValue - firstValue;
  70         String pressureTrend;
  71         if (pressureDifference > RAPIDLY_THRESHOLD) {
  72             pressureTrend = RISING_RAPIDLY;
  73         } else if (pressureDifference > STEADY_THRESHOLD && pressureDifference <= RAPIDLY_THRESHOLD) {
  74             pressureTrend = RISING;
  75         } else if (pressureDifference > -STEADY_THRESHOLD && pressureDifference <= STEADY_THRESHOLD) {
  76             pressureTrend = STEADY;
  77         } else if (pressureDifference > -RAPIDLY_THRESHOLD && pressureDifference <= -STEADY_THRESHOLD) {
  78             pressureTrend = FALLING;
  79         } else {
  80             pressureTrend = FALLING_RAPIDLY;
  81         }
  82         removeOldEntries();
  83         return pressureTrend;
  84     }
  85 }