package org.djunits.unit.scale;
   
   /**
    * Scale with factor and zero point offset.
    * <p>
    * A Scale for linear transformations with an offset that has to be applied first when converting to the standard (SI) unit,
    * before the scaling takes place, e.g. for Temperature. As an example, transform from Degrees Fahrenheit to Kelvin (SI). The
    * conversion is K = (F + 459.67) × 5⁄9, and F = K × 9⁄5 − 459.67.
    * </p>
   * <p>
   * When we have an original scale with offset o1 and scalefactor f1, the calculation to the base unit is
   * 
   * <pre>
   * valueSI = (value1 + o1) * f1
   * </pre>
   * <p>
   * So the offset is expressed in the "unit" of the value. As an example, when we transform degrees Fahrenheit to Kelvin, the
   * factor is 5/9, and the offset is 459.67 (degrees Fahrenheit of 0 degrees Fahrenheit expressed in Kelvin). The formula
   * becomes: K = (F + 459.67) * 5/9. So 0 F is 459.67 * 5/9 = 255.372 K. For Celcius to Kelvin, the scale factor is 1, and the
   * offset 273.15. From Fahrenheit to Celcius, the offset is -32, and the factor is 5/9.
   * </p>
   * <p>
   * When we apply a second offset transformation on a scale, e.g. from Fahrenheit to Celcius to Kelvin, this works as follows: If
   * we combine a second scale factor for a derived unit with offset o2 and scalefactor f2, we need to calculate the ultimate
   * scale to the base (si) unit. The factor then becomes:
   * 
   * <pre>
   * value1  = (value2 + o2) * f2
   * valueSI = (value1 + o1) * f1 = value2 * (f1 * f2) + (f1 * f2 * o2 + f1 * o1)
   * </pre>
   * <p>
   * as an example for F --2--&gt; C --1--&gt; K: o1 = 273.15, f1 = 1, o2 = -32, f2 = 5/9: <br>
   * 110 F = 110*5/9 -32*5/9 + 273.15 = 316.483 K.
   * </p>
   * <p>
   * Copyright (c) 2013-2024 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="https://djunits.org/docs/license.html">DJUNITS License</a>.
   * </p>
   * @author <a href="https://www.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="https://www.tudelft.nl/staff/p.knoppers/">Peter Knoppers</a>
   */
  public class OffsetLinearScale extends LinearScale
  {
      /** */
      private static final long serialVersionUID = 20151011L;
  
      /** The offset that has to be taken into account for conversions, multiplied by the conversionFactorToStandardUnit. */
      private final double offsetToStandardUnit;
  
      /**
       * Construct a Scale for linear transformations with an offset, e.g. for Temperature.
       * @param conversionFactorToStandardUnit double; the conversion factor by which this number has to be multiplied to convert
       *            it to the standard (e.g., SI) unit.
       * @param offsetToStandardUnit the offset that has to be taken into account for conversions; when converting to a standard
       *            unit, the offset is applied first.
       */
      public OffsetLinearScale(final double conversionFactorToStandardUnit, final double offsetToStandardUnit)
      {
          super(conversionFactorToStandardUnit);
          this.offsetToStandardUnit = offsetToStandardUnit;
      }
  
      @Override
      public final double toStandardUnit(final double value)
      {
          return (value + this.offsetToStandardUnit) * getConversionFactorToStandardUnit();
      }
  
      @Override
      public final double fromStandardUnit(final double value)
      {
          return value / getConversionFactorToStandardUnit() - this.offsetToStandardUnit;
      }
  
      /**
       * Retrieve the offset from the standard unit.
       * @return double; the offset from the standard unit
       */
      public final double getOffsetToStandardUnit()
      {
          return this.offsetToStandardUnit;
      }
  
      @Override
      public boolean isBaseSIScale()
      {
          return super.isBaseSIScale() && this.offsetToStandardUnit == 0.0;
      }
  
      @Override
      public int hashCode()
      {
          final int prime = 31;
          int result = super.hashCode();
          long temp;
          temp = Double.doubleToLongBits(this.offsetToStandardUnit);
          result = prime * result + (int) (temp ^ (temp >>> 32));
          return result;
      }
 
     @SuppressWarnings("checkstyle:needbraces")
     @Override
     public boolean equals(final Object obj)
     {
         if (this == obj)
             return true;
         if (!super.equals(obj))
             return false;
         if (getClass() != obj.getClass())
             return false;
         OffsetLinearScale other = (OffsetLinearScale) obj;
         if (Double.doubleToLongBits(this.offsetToStandardUnit) != Double.doubleToLongBits(other.offsetToStandardUnit))
             return false;
         return true;
     }
 
     @Override
     public String toString()
     {
         return "OffsetLinearScale [offsetToStandardUnit=" + this.offsetToStandardUnit + ", conversionFactorToStandardUnit="
                 + this.getConversionFactorToStandardUnit() + "]";
     }
 
 }