/*
    * #%L
    * Bitrepository Reference Pillar
    * %%
    * Copyright (C) 2010 - 2013 The State and University Library, The Royal Library and The State Archives, Denmark
    * %%
    * This program is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as 
    * published by the Free Software Foundation, either version 2.1 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 General Lesser Public License for more details.
   * 
   * You should have received a copy of the GNU General Lesser Public 
   * License along with this program.  If not, see
   * <http://www.gnu.org/licenses/lgpl-2.1.html>.
   * #L%
   */
  package org.bitrepository.pillar.cache;
  
  import java.util.Map;
  import org.bitrepository.common.settings.Settings;
  import org.bitrepository.service.database.DBConnector;
  import org.bitrepository.service.database.DatabaseMigrator;
  import org.bitrepository.service.database.DatabaseUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  import static org.bitrepository.pillar.cache.database.DatabaseConstants.CHECKSUM_TABLE;
  import static org.bitrepository.pillar.cache.database.DatabaseConstants.CS_COLLECTION_ID;
  
  /**
   * Migration class for the ChecksumDatabase of the ReferencePillar and ChecksumPillar.
   */
  public class ChecksumDBMigrator extends DatabaseMigrator {
      /** The log.*/
      private static Logger log = LoggerFactory.getLogger(DatabaseUtils.class);
      /** The settings.*/
      private final Settings settings;
      /** The current version of the database. */
      private final Integer currentVersion = 2;
      
      
      /**
       * Constructor.
       * @param connector
       * @param settings
       */
      public ChecksumDBMigrator(DBConnector connector, Settings settings) {
          super(connector);
          this.settings = settings;
      }
      
      @Override
      public void migrate() {
          Map<String, Integer> versions = getTableVersions();
          
          if(!versions.containsKey(CHECKSUM_TABLE)) {
              throw new IllegalStateException("The database does not contain '" + CHECKSUM_TABLE 
                      + "' table as required.");
          }
          if(versions.get(CHECKSUM_TABLE) == 1) {
              migrateChecksumsTableFromVersion1To2();
          }
      }
      
      /**
       * Migrate the ChecksumTable from version 1 to 2.
       * Just adds the column 'collectionid', which is set to the current (or first) collection id.
       */
      private void migrateChecksumsTableFromVersion1To2() {
          log.warn("Migrating the " + CHECKSUM_TABLE + " table from version 1 to 2 in the ChecksumDatabase.");
          
          String alterSql = "ALTER TABLE " + CHECKSUM_TABLE + " ADD COLUMN " + CS_COLLECTION_ID + " VARCHAR(255)";
          updateTable(CHECKSUM_TABLE, 2, alterSql, new Object[0]);
          
          String updateAfterwards = "UPDATE " + CHECKSUM_TABLE + " SET " + CS_COLLECTION_ID + " = ? WHERE " 
                  + CS_COLLECTION_ID + " IS NULL";
          DatabaseUtils.executeStatement(connector, updateAfterwards, settings.getCollections().get(0).getID());
      }
  
      @Override
      public boolean needsMigration() {
          Map<String, Integer> versions = getTableVersions();
          
          if(!versions.containsKey(CHECKSUM_TABLE)) {
              throw new IllegalStateException("The database does not contain '" + CHECKSUM_TABLE 
                      + "' table as required.");
          }
          
          if(versions.get(CHECKSUM_TABLE) < currentVersion) {
              return true;
          } else {
              return false;
          }
      }
 }