Temperature.java

/**
 * Copyright (c) 2010-2016 by the respective copyright holders.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 */
package org.openhab.binding.ecobee.messages;

import java.math.BigDecimal;
import java.math.MathContext;

import org.codehaus.jackson.annotate.JsonCreator;
import org.codehaus.jackson.annotate.JsonValue;

/**
 * Temperature values are expressed as degrees Fahrenheit, multiplied by 10. For example, a temperature of 72F would be
 * expressed as the value 720. If the user preferences indicate the use of Celsius values, it is the responsibility of
 * the caller to convert values to and from Celsius.
 *
 * <p>
 * Where specified explicitly Degrees F indicates that the temperature will be returned in degrees Fahrenheit accurate
 * to one decimal place (i.e. 18.5F).
 *
 * <p>
 * Methods are included to construct Temperature objects from Celsius, Fahrenheit, or whichever the local temperature
 * scale is.
 *
 * @see <a href="https://www.ecobee.com/home/developer/api/documentation/v1/technical-notes.shtml#representation">Values
 *      and Representation</a>
 * @author John Cocula
 * @since 1.7.0
 */
public class Temperature {

    /**
     * Enum for representing the temperature scale that will be reported.
     */
    public static enum Scale {
        CELSIUS("C"),
        FAHRENHEIT("F");

        private final String scale;

        private Scale(final String scale) {
            this.scale = scale;
        }

        public String value() {
            return scale;
        }

        public static Scale forValue(String v) {
            for (Scale s : Scale.values()) {
                if (s.scale.equals(v)) {
                    return s;
                }
            }
            throw new IllegalArgumentException("Invalid temperature scale: " + v);
        }
    }

    /**
     * The local temperature scale used throughout this JVM. Defaults to Fahrenheit.
     */
    private static Scale localScale = Scale.FAHRENHEIT;

    public static void setLocalScale(final Scale localScale) {
        Temperature.localScale = localScale;
    }

    private BigDecimal temp;

    @JsonValue
    public int value() {
        return temp.intValue();
    }

    /**
     * Construct a Temperature from the Ecobee-style temperature value (Fahrenheit times 10).
     * 
     * @param temp
     *            Ecobee-style temperature value (Fahrenheit times 10)
     */
    @JsonCreator
    public Temperature(int temp) {
        this.temp = new BigDecimal(temp);
    }

    /**
     * Construct a Temperature from the Ecobee-style temperature value (Fahrenheit times 10).
     * 
     * @param temp
     *            Ecobee-style temperature value (Fahrenheit times 10)
     */
    public Temperature(BigDecimal temp) {
        this.temp = temp;
    }

    /**
     * Factory method to construct a Temperature from the local temperature scale.
     * 
     * @param localTemp
     *            the temperature in the local temperature scale.
     * @return a new Temperature object
     */
    public static Temperature fromLocalTemperature(BigDecimal localTemp) {
        if (localScale.equals(Scale.CELSIUS)) {
            return fromCelsius(localTemp);
        } else {
            return fromFahrenheit(localTemp);
        }
    }

    /**
     * Factory method to construct a Temperature from Fahrenheit.
     * 
     * @param fahrenheit
     *            the Fahrenheit temperature
     */
    public static Temperature fromFahrenheit(BigDecimal fahrenheit) {
        return new Temperature(fahrenheit.movePointRight(1));
    }

    private static BigDecimal ONE_POINT_EIGHT = new BigDecimal("1.8");
    private static BigDecimal THIRTY_TWO = new BigDecimal("32");

    /**
     * Factory method to construct a Temperature from Celsius.
     * 
     * @param celsius
     *            the Celsius temperature
     */
    public static Temperature fromCelsius(BigDecimal celsius) {
        return new Temperature(celsius.multiply(ONE_POINT_EIGHT).add(THIRTY_TWO).movePointRight(1));
    }

    /**
     * Convert this temperature to a temperature in the local temperature scale.
     * 
     * @return temperature in the local temperature scale
     */
    public final BigDecimal toLocalTemperature() {
        return localScale == Scale.CELSIUS ? toCelsius() : toFahrenheit();
    }

    /**
     * Convert this Temperature to Fahrenheit.
     * 
     * @return temperature in Fahrenheit
     */
    public final BigDecimal toFahrenheit() {
        return temp.movePointLeft(1);
    }

    /**
     * Convert this Temperature to Celsius.
     * 
     * @return temperature in Celsius
     */
    public final BigDecimal toCelsius() {
        return temp.movePointLeft(1).subtract(THIRTY_TWO).divide(ONE_POINT_EIGHT, MathContext.DECIMAL32);
    }

    @Override
    public String toString() {
        return temp.toString();
    }
}