package org.bitrepository.integrityservice.cache.database;
   
   import static org.bitrepository.integrityservice.cache.database.DatabaseConstants.COLLECTIONS_TABLE;
   import static org.bitrepository.integrityservice.cache.database.DatabaseConstants.COLLECTION_ID;
   import static org.bitrepository.integrityservice.cache.database.DatabaseConstants.COLLECTION_KEY;
   
   import java.util.HashMap;
   import java.util.List;
   import java.util.Map;
  
  import org.bitrepository.common.ArgumentValidator;
  import org.bitrepository.service.database.DBConnector;
  import org.bitrepository.service.database.DatabaseUtils;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class IntegrityDAOUtils {
      /** The log.*/
      private Logger log = LoggerFactory.getLogger(getClass());
      
      /** The connector to the database.*/
      protected final DBConnector dbConnector;
      /** Caching of CollectionKeys (mapping from ID to Key) */
      private final Map<String, Long> collectionKeyCache;
      
      
      public IntegrityDAOUtils(DBConnector dbConnector) {
          ArgumentValidator.checkNotNull(dbConnector, "DBConnector dbConnector");
          this.dbConnector = dbConnector;
          collectionKeyCache = new HashMap<String, Long>();
      }
      
      /**
       *  @return The list of collections defined in the database.
       */
      public List<String> retrieveCollectionsInDatabase() {
          String selectSql = "SELECT " + COLLECTION_ID + " FROM " + COLLECTIONS_TABLE;
          return DatabaseUtils.selectStringList(dbConnector, selectSql, new Object[0]);
      }
      
      /**
       * Method to retrieve the database key for the given collectionId
       * @param collectionId The ID of the collection 
       */
      protected Long retrieveCollectionKey(String collectionId) {
          Long key = collectionKeyCache.get(collectionId);
          if(key == null) {
              log.trace("Retrieving key for collection '{}'.", collectionId);
              String sql = "SELECT " + COLLECTION_KEY + " FROM " + COLLECTIONS_TABLE 
                      + " WHERE " + COLLECTION_ID + "= ?";
              key = DatabaseUtils.selectLongValue(dbConnector, sql, collectionId);
              collectionKeyCache.put(collectionId, key);
          }
          return key;
      }
  }