package org.djunits.unit.system;
   
   import java.util.Objects;
   
   import org.djutils.exceptions.Throw;
   
   /**
    * Systems of Units such as SI, including SI-derived; cgs (centimeter-gram-second).
    * <p>
   * Copyright (c) 2015-2026 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
   */
  public class UnitSystem
  {
      /** CGS: centimeter-gram-second system. */
      public static final UnitSystem CGS = new UnitSystem("CGS", "centimeter-gram-second system");
  
      /** CGS ESU: centimeter-gram-second system, electrostatic units. */
      public static final UnitSystem CGS_ESU = new UnitSystem("CGS-ESU", "centimeter-gram-second system, electrostatic units");
  
      /** CGS_EMU: centimeter-gram-second system, electromagnetic units. */
      public static final UnitSystem CGS_EMU = new UnitSystem("CGS-EMU", "centimeter-gram-second system, electromagnetic units");
  
      /** Imperial system. */
      public static final UnitSystem IMPERIAL = new UnitSystem("Imperial", "Imperial system");
  
      /** MTS: meter-tonne-second system. */
      public static final UnitSystem MTS = new UnitSystem("MTS", "meter-tonne-second system");
  
      /** Other (or no) system. */
      public static final UnitSystem OTHER = new UnitSystem("Other", "other system");
  
      /** SI units, accepted for use in addition to SI. */
      public static final UnitSystem SI_ACCEPTED = new UnitSystem("SI-accepted", "International System of Units (Accepted Unit)");
  
      /** SI base units: temperature, time, length, mass, luminous intensity, amount of substance and electric current. */
      public static final UnitSystem SI_BASE = new UnitSystem("SI", "International System of Units (Base Unit)");
  
      /** SI derived units, by combining SI-base elements (and quantifiers such as milli or kilo). */
      public static final UnitSystem SI_DERIVED = new UnitSystem("SI-derived", "International System of Units (Derived Unit)");
  
      /** US additions to the Imperial system. */
      public static final UnitSystem US_CUSTOMARY = new UnitSystem("US-customary", "US customary system");
  
      /** AU: Atomic Unit system. */
      public static final UnitSystem AU = new UnitSystem("AU", "Atomic Unit system");
  
      /** The abbreviation of the unit system, such as cgs. */
      private final String id;
  
      /** The name of the unit system, such as centimeter-gram-second. */
      private final String name;
  
      /**
       * Construct a new UnitSystem.
       * @param id the abbreviation of the unit system, such as cgs
       * @param name the name of the unit system, such as centimeter-gram-second
       */
      public UnitSystem(final String id, final String name)
      {
          Throw.whenNull(id, "id");
          Throw.whenNull(name, "name");
          Throw.when(id.strip().length() == 0, IllegalArgumentException.class, "id cannot be empty");
          Throw.when(name.strip().length() == 0, IllegalArgumentException.class, "name cannot be empty");
          this.id = id.strip();
          this.name = name.strip();
      }
  
      /**
       * Retrieve the name of this UnitSystem.
       * @return the name of this UnitSystem, e.g. centimeter-gram-second
       */
      public final String getName()
      {
          return this.name;
      }
  
      /**
       * Retrieve the abbreviation of this UnitSystem.
       * @return the abbreviation of this UnitSystem, e.g., CGS.cgs
       */
      public final String getId()
      {
          return this.id;
      }
  
      @Override
      public int hashCode()
      {
          return Objects.hash(this.id, this.name);
      }
  
      @Override
      @SuppressWarnings("checkstyle:needbraces")
      public boolean equals(final Object obj)
      {
          if (this == obj)
              return true;
         if (obj == null)
             return false;
         if (getClass() != obj.getClass())
             return false;
         UnitSystem other = (UnitSystem) obj;
         return Objects.equals(this.id, other.id) && Objects.equals(this.name, other.name);
     }
 
     @Override
     public String toString()
     {
         return "UnitSystem [id=" + this.id + ", name=" + this.name + "]";
     }
 
 }