# DataSorter.java

    /*
    ** Module   : DataSorter.java
    ** Abstract : Directional comparator for BaseDataType
    **
    ** Copyright (c) 2004-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- -T- --JPRM-- ----------------Description-----------------
    ** 001 ECF 20080510 ADD  @38477  Created initial version. A Comparator
    **                               implementation for BaseDataType with an
    **                               adjustable direction.
    ** 002 ECF 20080708 CHG  @39079  Abstracted to extend BasicSorter. The base
    **                               class handles Comparables in general. This
    **                               class overrides compare() to handle
    **                               BaseDataTypes specifically.
    ** 003 EVL 20160223              Javadoc fixes to make compatible with Oracle Java 8 for
    **                               Solaris 10.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program is distributed in the hope that it will be useful,
    ** but WITHOUT ANY WARRANTY; without even the implied warranty of
    ** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
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    **     work or Appropriate Legal Notices displayed by works containing the covered
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    **
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    **
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    */

    package com.goldencode.p2j.persist;

    import com.goldencode.p2j.util.*;

    /**
     * An specialization of {@link BasicSorter}, used to sort instances of
     * <code>BaseDataType</code>.  Direction of the sort is specified upon
     * construction.  Unknown value sorts high in an ascending sort.
     * <p>
     * Instances of this class should be retrieved using the static method {@link
     * #getInstance(boolean)}.
     */
    final class DataSorter
    extends BasicSorter<BaseDataType>
    {
       /** Shared instance of an ascending <code>DataSorter</code> */
       private static final DataSorter ASCENDER = new DataSorter(true);

       /** Shared instance of an descending <code>DataSorter</code> */
       private static final DataSorter DESCENDER = new DataSorter(false);

       /**
        * @param ascending
        */
       public DataSorter(boolean ascending)
       {
          super(ascending);
       }

       /**
        * Helper method to retrieve an instance of this class which sorts in the
        * specified direction.
        *
        * @param   ascending
        *          <code>true</code> if sort should be ascending;
        *          <code>false</code> if it should be descending.
        *
        * @return  An instance of this class which sorts in the specified
        *          direction.
        */
       public static DataSorter getInstance(boolean ascending)
       {
          return (ascending ? ASCENDER : DESCENDER);
       }

       /**
        * Compare two <code>BaseDataType</code> instances to determine relative
        * sort order.  The comparison uses the natural order of the objects,
        * except that unknown value always sorts high in an ascending sort.  The
        * result is inverted for descending sorts (meaning unknown value sorts low
        * in a descending sort.
        *
        * @param   d1
        *          First value to compare.  May be unknown, but must not be
        *          <code>null</code>.
        * @param   d2
        *          Second value to compare.  May be unknown, but must not be
        *          <code>null</code>.
        *
        * @return  Positive value if <code>d1</code> &gt; <code>d2</code>;
        *          negative value if <code>d1</code> &lt; <code>d2</code>;
        *          <code>0</code> if <code>d1</code> and <code>d2</code> sort
        *          equivalently.
        */
       public int compare(BaseDataType d1, BaseDataType d2)
       {
          int result = 0;

          if (d1.isUnknown())
          {
             result = (d2.isUnknown() ? 0 : 1);
          }
          else if (d2.isUnknown())
          {
             result = (d1.isUnknown() ? 0 : -1);
          }
          else
          {
             result = d1.compareTo(d2);
          }

          return (result * getDirection());
       }
    }