package org.djunits.unit.scale;
   
   import org.djutils.exceptions.Throw;
   
   /**
    * A Scale for transforming a slope as a grade, where 45 degrees is 1, and 90 degrees is infinite, to radians. The formula is:
    * angle = atan(grade). The factor that is given, is the factor by which the value is multiplied to get a grade. When a scale is
    * constructed for e.g. ratio as a percentage (100% instead of 1), the conversionFactor to apply is 0.01.
    * <p>
   * Copyright (c) 2013-2026 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>.
   * @author Alexander Verbraeck
   * @author Peter Knoppers
   */
  public class GradeScale implements Scale
  {
      /** */
      private static final long serialVersionUID = 20151011L;
  
      /** Multiply by this number to convert to the standard (e.g., SI) unit. */
      private final double conversionFactorToGrade;
  
      /**
       * Construct a Scale for transforming a slope as a grade, where 45 degrees is 1, and 90 degrees is infinite, to radians.
       * @param conversionFactorToGrade the conversion factor by which this number has to be multiplied to convert it to the
       *            standard (e.g., SI) unit.
       */
      public GradeScale(final double conversionFactorToGrade)
      {
          Throw.when(conversionFactorToGrade == 0.0 || !Double.isFinite(conversionFactorToGrade), IllegalArgumentException.class,
                  "conversion factor for grade scale cannnot be 0, NaN or infinity");
          this.conversionFactorToGrade = conversionFactorToGrade;
      }
  
      @Override
      public final double toBaseValue(final double value)
      {
          return Math.atan(value * this.conversionFactorToGrade);
      }
  
      @Override
      public final double fromBaseValue(final double value)
      {
          return Math.tan(value) / this.conversionFactorToGrade;
      }
  
      /**
       * @return conversionFactorToGrade
       */
      public final double getConversionFactorToGrade()
      {
          return this.conversionFactorToGrade;
      }
  
      @Override
      public boolean isBaseScale()
      {
          return false;
      }
  
      @Override
      public int hashCode()
      {
          final int prime = 31;
          int result = 1;
          long temp;
          temp = Double.doubleToLongBits(this.conversionFactorToGrade);
          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 (obj == null)
              return false;
          if (getClass() != obj.getClass())
              return false;
          GradeScale other = (GradeScale) obj;
          if (Double.doubleToLongBits(this.conversionFactorToGrade) != Double.doubleToLongBits(other.conversionFactorToGrade))
              return false;
          return true;
      }
  
      @Override
      public String toString()
      {
          return "GradeScale [conversionFactorToGrade=" + this.conversionFactorToGrade + "]";
      }
  
  }