# FieldEntry.java

    /*
    ** Module   : FieldEntry.java
    ** Abstract : abstract base class for passing data lists to I/O helpers
    **
    ** Copyright (c) 2006-2024, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --JPRM-- -----------------------------Description-----------------------------
    ** 001 GES 20060925   @29899 Created initial version as abstract base class for passing data lists
    **                           to I/O helpers.
    ** 002 SIY 20071001   @35315 Made class suitable for network transfers. Ref: #35314
    ** 003 SIY 20071003   @35348 Added resolveData() method. Header cleanup. Ref: #35347.
    ** 004 CA  20170827          Added support for dynamic array expansion.
    ** 005 VVT 20241107          NPE in toArray fixed: the method should support nulls in the input array.
    **                           See #9303.
    */
    /*
    ** 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.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.util;

    import java.io.Externalizable;
    import java.util.*;

    /**
     * This class provides an abstract base for passing data lists to I/O helpers.
     */
    public abstract class FieldEntry
    implements Externalizable
    {
       /**
        * Resolve the entries in the given array.  These can be individual {@link FieldEntry} instances
        * or {@link ExtentExpansion} instances - in the later case, we rely on calling
        * {@link ExtentExpansion#expand()} to get us the array.
        *
        * @param    entries
        *           The entries to resolve.
        *
        * @return   See above.
        */
       @SuppressWarnings("unchecked")
       public static FieldEntry[] toArray(Object... entries)
       {
          List<FieldEntry> res = new LinkedList<>();

          for (Object entry : entries)
          {
             if (entry == null)
             {
                continue;
             }

             if (entry instanceof FieldEntry)
             {
                res.add((FieldEntry) entry);
             }
             else if (entry instanceof ExtentExpansion)
             {
                res.addAll(Arrays.asList(((ExtentExpansion<FieldEntry>) entry).expand()));
             }
             else
             {
                throw new IllegalArgumentException("Could not resolve " + entry.getClass() + "!");
             }
          }

          return res.toArray(new FieldEntry[0]);
       }

       /**
        * Renders the contained field definition to the given stream.
        *
        * @param    out
        *           The stream to which the field should be rendered.
        *
        * @throws   ErrorConditionException
        *           On any error during I/O.
        */
       public abstract void output(Stream out)
       throws ErrorConditionException;

       /**
        * Notify instance that it is about to be transferred so all resolvable
        * data should be resolved and prepared for sending via network.
        */
       public abstract void resolveData();
    }