# LoggedCollection.java

    /*
    ** Module   : LoggedCollection.java
    ** Abstract : Helper class which logs changes to a collection, for each AST location.
    **
    ** Copyright (c) 2020, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 CA  20200412 Created initial version, for incremental conversion support.
    ** 002 CA  20200416 Reduce the memory footprint for incremental conversion.
    */
    /*
    ** 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
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    **     the covered work, without written authorization.
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    **
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    **     versions of the covered work must be marked in a reasonable way to make it
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    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.convert.db;

    import java.sql.*;
    import java.util.*;
    import java.util.function.*;

    /**
     * Log all changes to a specified collection, by keeping track of the source AST which made this
     * change.
     * <p>
     * On incremental conversion, this allows restoration of the collection's state, without the
     * currently parsed and converted ASTs.
     * <p>
     * All changes are stored in a work table, which has the same name as the main collection's table,
     * followed by a <code>__work</code> suffix.
     */
    public class LoggedCollection
    {
       /**
        * The changes made to this collection.  The value may be null in case the collection is not
        * a map.
        */
       private final Map<AstKey, Object> changes = new LinkedHashMap<>();

       /**
        * Force certain values to be logged for a source AST.  This allows to identify cases where
        * the map already has a key and a value, but the source AST must keep a different value for
        * this key, even if the values are (almost) identical.
        */
       private final Map<AstKey, Object> forced = new LinkedHashMap<>();

       /**
        * Log this change being made to the collection.
        *
        * @param    fileId
        *           The AST file ID.
        * @param    astId
        *           The source AST ID.
        * @param    key
        *           The collection key.
        * @param    value
        *           The value, which is non-null only for maps.
        */
       public void log(long fileId, long astId, Object key, Object value)
       {
          AstKey changeKey = new AstKey(fileId, astId, key);
          /*
          if (changes.containsKey(changeKey))
          {
             throw new IllegalStateException("Key already exists!");
          }
          */

          changes.put(changeKey, value);
       }

       /**
        * Log this change being made to the collection.
        *
        * @param    fileId
        *           The AST file ID.
        * @param    astId
        *           The source AST ID.
        * @param    key
        *           The collection key.
        */
       public void log(long fileId, long astId, Object key)
       {
          log(fileId, astId, key, null);
       }

       /**
        * Force a change to be logged for the specified source AST.
        *
        * @param    fileId
        *           The AST file ID.
        * @param    astId
        *           The source AST ID.
        * @param    key
        *           The collection key.
        * @param    value
        *           The value, which is non-null only for maps.
        */
       public void force(long fileId, long astId, Object key, Object value)
       {
          AstKey changeKey = new AstKey(fileId, astId, key);

          forced.put(changeKey, value);
       }

       /**
        * Remove all changes having this key.
        *
        * @param    key
        *           The key to be removed.
        */
       public void remove(Object key)
       {
          if (key == null)
          {
             throw new NullPointerException("Invalid key!");
          }

          // delete all logged changes for this key (as we want to remove it);
          Iterator<AstKey> iter = changes.keySet().iterator();
          while (iter.hasNext())
          {
             AstKey changeKey = iter.next();
             if (changeKey.key.equals(key))
             {
                iter.remove();
             }
          }
          iter = forced.keySet().iterator();
          while (iter.hasNext())
          {
             AstKey changeKey = iter.next();
             if (changeKey.key.equals(key))
             {
                iter.remove();
             }
          }
       }

       /**
        * Given a set of keys, retain from the changes only those for which the key exists in this set.
        * <p>
        * This allows the changes to be 'in sync' with the main collection, as certain remove
        * operations on the main collection may not have been logged to the collection.
        *
        * @param    keys
        *           The keys which need to be retained.
        */
       public void retainAll(Set<?> keys)
       {
          Iterator<AstKey> iter = this.changes.keySet().iterator();
          while (iter.hasNext())
          {
             AstKey key = iter.next();
             if (!keys.contains(key.key))
             {
                iter.remove();
             }
          }
       }

       /**
        * Clear all changes.
        */
       public void clear()
       {
          changes.clear();
          forced.clear();
       }

       /**
        * Persist all changes to the database.
        *
        * @param    insertSql
        *           The SQL used to insert into the table.
        * @param    helper
        *           The helper to perform SQL operations.
        * @param    c
        *           A consumer to resolve the arguments for the insert statement.
        */
       public void persist(String insertSql, DBHelper helper, BiFunction<AstKey, Object, Object[]> c)
       {
          changes.putAll(forced);

          helper.persistCollection(changes.keySet(), insertSql, (PreparedStatement ps, Object key) ->
          {
             try
             {
                AstKey astKey = (AstKey) key;
                Object val = changes.get(astKey);

                Object[] args = c.apply(astKey, val);
                for (int i = 0; i < args.length; i++)
                {
                   ps.setObject(i + 1, args[i]);
                }
                ps.addBatch();
             }
             catch (SQLException e)
             {
                throw new RuntimeException(e);
             }
          });
       }

       /**
        * Persist all changes to the database, using the specified statement.
        *
        * @param    ps
        *           The prepared insert statement.
        * @param    c
        *           A consumer to resolve the arguments for the insert statement.
        *
        * @throws   SQLException
        *           For SQL-related errors when setting the statement arguments.
        */
       public void persist(PreparedStatement ps, BiFunction<AstKey, Object, Object[]> c)
       throws SQLException
       {
          for (AstKey astKey : changes.keySet())
          {
             Object val = changes.get(astKey);

             Object[] args = c.apply(astKey, val);
             for (int i = 0; i < args.length; i++)
             {
                ps.setObject(i + 1, args[i]);
             }
             ps.addBatch();
          }
       }

       /**
        * Compact the elements of this collection, to reduce the memory footprint.
        *
        * @param    fileId
        *           The AST file ID which has finished processing.
        * @param    c
        *           A consumer to process the values.
        */
       public void compact(long fileId, Consumer<CustomExternalizable> c)
       {
          for (AstKey key : changes.keySet())
          {
             if (key.fileId != fileId)
             {
                continue;
             }

             Object value = changes.get(key);
             c.accept((CustomExternalizable) value);
          }
       }

       /**
        * A key for a logged change, in a collection.
        */
       static class AstKey
       {
          /** The file AST ID. */
          final long fileId;

          /** The source AST ID. */
          final long astId;

          /** The change key. */
          final Object key;

          /**
           * Create a new instance.
           *
           * @param    fileId
           *           The file AST ID.
           * @param    astId
           *           The source AST ID.
           * @param    key
           *           The change key.
           */
          public AstKey(long fileId, long astId, Object key)
          {
             this.fileId = fileId;
             this.astId = astId;
             this.key = key;
          }

          /**
           * Calculate the hashcode for this key.
           *
           * @return   The hashcode.
           */
          @Override
          public int hashCode()
          {
             int result = 17;

             result = result * 37 + Long.hashCode(fileId);
             result = result * 37 + Long.hashCode(astId);
             result = result * 37 + key.hashCode();

             return result;
          }

          /**
           * Check if this instance is the same as the specified one.
           *
           * @param    obj
           *           The object to compare against.
           *
           * @return   <code>true</code> if the specified object has the same key, file and AST ID
           *           as this one.
           */
          @Override
          public boolean equals(Object obj)
          {
             if (!(obj instanceof AstKey))
             {
                return false;
             }

             AstKey other = (AstKey) obj;

             return this.fileId == other.fileId &&
                    this.astId == other.astId &&
                    this.key.equals(other.key);
          }
       }
    }