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/*
 * Copyright (c) 1998-2018 University Corporation for Atmospheric Research/Unidata
 * See LICENSE for license information.
 */
package ucar.units;

import java.io.Serializable;

/**
 * Provides support for abstract base quantities (ex: length, time).
 * 
 * @author Steven R. Emmerson
 */
public abstract class BaseQuantity implements Base, Comparable, Serializable {
  private static final long serialVersionUID = 1L;

  /**
   * The base quantity of amount of substance.
   */
  public static final RegularBaseQuantity AMOUNT_OF_SUBSTANCE;

  /**
   * The base quantity of electric current.
   */
  public static final RegularBaseQuantity ELECTRIC_CURRENT;

  /**
   * The base quantity of length.
   */
  public static final RegularBaseQuantity LENGTH;

  /**
   * The base quantity of luminous intensity.
   */
  public static final RegularBaseQuantity LUMINOUS_INTENSITY;

  /**
   * The base quantity of mass.
   */
  public static final RegularBaseQuantity MASS;

  /**
   * The base quantity of plane angle.
   */
  public static final SupplementaryBaseQuantity PLANE_ANGLE;

  /**
   * The base quantity of solid angle.
   */
  public static final SupplementaryBaseQuantity SOLID_ANGLE;

  /**
   * The base quantity of themodynamic temperature.
   */
  public static final RegularBaseQuantity THERMODYNAMIC_TEMPERATURE;

  /**
   * The base quantity of time.
   */
  public static final RegularBaseQuantity TIME;

  /**
   * The unknown base quantity.
   */
  public static final UnknownBaseQuantity UNKNOWN;

  /**
   * @serial
   */
  private final String name; // never
  // null
  // or
  // empty

  /**
   * @serial
   */
  private final String symbol; // may
  // be
  // null
  // ;
  // never
  // empty

  static {
    AMOUNT_OF_SUBSTANCE = new RegularBaseQuantity("Amount of Substance", "N", true);
    ELECTRIC_CURRENT = new RegularBaseQuantity("Electric Current", "I", true);
    LENGTH = new RegularBaseQuantity("Length", "L", true);
    LUMINOUS_INTENSITY = new RegularBaseQuantity("Luminous Intensity", "J", true);
    MASS = new RegularBaseQuantity("Mass", "M", true);
    PLANE_ANGLE = new SupplementaryBaseQuantity("Plane Angle", null, true);
    SOLID_ANGLE = new SupplementaryBaseQuantity("Solid Angle", null, true);
    THERMODYNAMIC_TEMPERATURE = new RegularBaseQuantity("Thermodynamic Temperature", "T", true);
    TIME = new RegularBaseQuantity("Time", "t", true);
    UNKNOWN = new UnknownBaseQuantity();
  }

  /**
   * Constructs from a name and a symbol.
   * 
   * @param name
   *        Name of the base quantity. Shall be neither null
   *        nor empty.
   * @param symbol
   *        Symbol for the base quantity. May be null but
   *        shall not be empty.
   * @throws NameException
   *         name is null or empty.
   */
  public BaseQuantity(final String name, final String symbol) throws NameException {
    this(name, symbol, true);
    if (name == null || name.length() == 0 || (symbol != null && symbol.length() == 0)) {
      throw new NameException("Invalid name or symbol");
    }
  }

  /**
   * Constructs from a name and a symbol. This is the trusted form of the the
   * constructor for use by subclasses only.
   * 
   * @param name
   *        Name of the base quantity. Shall be neither null
   *        nor empty.
   * @param symbol
   *        Symbol for the base quantity. May be null but
   *        shall not be empty.
   */
  protected BaseQuantity(final String name, final String symbol, final boolean trusted) {
    this.name = name;
    this.symbol = symbol;
  }

  /**
   * Returns the name of the base quantity.
   * 
   * @return The name of the base quantity. Shall not be null or
   *         empty.
   */
  public String getName() {
    return name;
  }

  /**
   * Returns the symbol of the base quantity.
   * 
   * @return The symbol of the base quantity. May be null. If
   *         non-null, then shall not be empty.
   */
  public String getSymbol() {
    return symbol;
  }

  /**
   * Returns the identifier for the base quantity.
   * 
   * @return The base quantity's identifier (i.e. symbol or name).
   */
  public final String getID() {
    final String id = getSymbol();
    return id == null ? getName() : id;
  }

  /**
   * Returns the string representation of the base quantity.
   * 
   * @return The string representation of the base quantity.
   */
  @Override
  public final String toString() {
    return getID();
  }

  /**
   * Indicates if this base quantity is semantically identical to an object.
   * 
   * @param object
   *        The object to examine.
   * @return true if an only if this base quantity is
   *         semantically identical to object.
   */
  @Override
  public boolean equals(final Object object) {
    return this == object
        || object instanceof BaseQuantity && (getName().equalsIgnoreCase(((BaseQuantity) object).getName())
            && (getSymbol() == null || getSymbol().equals(((BaseQuantity) object).getSymbol())));
  }

  /**
   * Returns the hash code of this instance.
   * 
   * @return The hash code of this instance.
   */
  @Override
  public int hashCode() {
    return getName().toLowerCase().hashCode() ^ (getSymbol() == null ? 0 : getSymbol().hashCode());
  }

  /**
   * Compares this base quantity to another base quantity.
   * 
   * @param that
   *        The BaseQuantity to compare against.
   * @return An integer that is negative, zero, or positive depending on
   *         whether this BaseQuantity is less than, equal to, or greater than
   *         that.
   */
  public int compareTo(final BaseQuantity that) {
    int comp;
    if (this == that) {
      comp = 0;
    } else {
      comp = getName().compareToIgnoreCase(that.getName());
      if (comp == 0 && getSymbol() != null) {
        comp = getSymbol().compareTo(that.getSymbol());
      }
    }
    return comp;
  }

  /**
   * Indicates if this base quantity is dimensionless.
   * 
   * @return true if an only if this BaseQuantity is
   *         dimensionless (e.g. BaseQuantity.SOLID_ANGLE).
   */
  public abstract boolean isDimensionless();

}