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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;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.SortedSet;
import java.util.TreeMap;
import java.util.TreeSet;

/**
 * Provides a concrete implementation of a database of unit prefixes.
 * 
 * Instances of this class are modifiable.
 * 
 * @author Steven R. Emmerson
 */
public class PrefixDBImpl implements PrefixDB, Serializable {
  private static final long serialVersionUID = 1L;

  /**
   * The set of prefix names.
   * 
   * @serial
   */
  private final SortedSet nameSet;

  /**
   * The set of prefix symbols.
   * 
   * @serial
   */
  private final SortedSet symbolSet;

  /**
   * The mapping between prefix values and prefixes.
   * 
   * @serial
   */
  private final Map valueMap;

  /**
   * Constructs from nothing.
   */
  public PrefixDBImpl() {
    nameSet = new TreeSet<>();
    symbolSet = new TreeSet<>();
    valueMap = new TreeMap<>();
  }

  /**
   * Adds a prefix to the database by name.
   * 
   * @param name
   *        The name of the prefix to be added.
   * @param value
   *        The value of the prefix.
   * @throws PrefixExistsException
   *         Another prefix with the same name or value already exists in
   *         the database.
   */
  public void addName(final String name, final double value) throws PrefixExistsException {
    final Prefix prefix = new PrefixName(name, value);
    nameSet.add(prefix);
  }

  /**
   * Adds a prefix symbol to the database.
   * 
   * @param symbol
   *        The symbol of the prefix to be added.
   * @param value
   *        The value of the prefix.
   * @throws PrefixExistsException
   *         Another prefix with the same symbol or value already exists
   *         in the database.
   */
  public void addSymbol(final String symbol, final double value) throws PrefixExistsException {
    final Prefix prefix = new PrefixSymbol(symbol, value);
    symbolSet.add(prefix);
    valueMap.put(value, prefix);
  }

  /**
   * Gets a prefix by name.
   * 
   * @param string
   *        The name to be matched.
   * @return The prefix whose name matches or null.
   */
  public Prefix getPrefixByName(final String string) {
    return getPrefix(string, nameSet);
  }

  /**
   * Gets a prefix by symbol.
   * 
   * @param string
   *        The symbol to be matched.
   * @return The prefix whose symbol matches or null.
   */
  public Prefix getPrefixBySymbol(final String string) {
    return getPrefix(string, symbolSet);
  }

  /**
   * Gets a prefix by value.
   * 
   * @param value
   *        The value to be matched.
   * @return The prefix whose value matches or null.
   */
  public Prefix getPrefixByValue(final double value) {
    return valueMap.get(value);
  }

  /**
   * Returns the prefix from the given set with the given identifier.
   * 
   * @param string
   *        The prefix identifier.
   * @param set
   *        The set to search.
   */
  private static Prefix getPrefix(final String string, final Set set) {
    for (final Prefix prefix : set) {
      final int comp = prefix.compareTo(string);
      if (comp == 0) {
        return prefix;
      }
      if (comp > 0) {
        break;
      }
    }
    return null;
  }

  /**
   * Returns a string representation of this database.
   * 
   * @return A string representation of this database.
   */
  @Override
  public String toString() {
    return "nameSet=" + nameSet + "symbolSet=" + symbolSet + "valueMap=" + valueMap;
  }

  /**
   * Gets an iterator over the prefixes in the database.
   * 
   * @return An iterator over the entries in the database. The objects
   *         returned by the iterator will be of type Prefix.
   */
  public Iterator iterator() {
    return nameSet.iterator();
  }

}