package liquibase.snapshot;

 import java.util.ArrayList;

 import java.util.Comparator;

 import java.util.List;

 import java.util.Set;

 import java.util.SortedSet;

 import java.util.TreeSet;

 import liquibase.database.Database;

 import liquibase.diff.DiffStatusListener;

 import liquibase.exception.DatabaseException;

 import liquibase.servicelocator.ServiceLocator;

 public class DatabaseSnapshotGeneratorFactory {

     private static DatabaseSnapshotGeneratorFactory instance;

     private List<DatabaseSnapshotGenerator> registry = new ArrayList<DatabaseSnapshotGenerator>();

     private DatabaseSnapshotGeneratorFactory() {

         try {

             Class[] classes = ServiceLocator.getInstance().findClasses(DatabaseSnapshotGenerator.class);

             for (Class<? extends DatabaseSnapshotGenerator> clazz : classes) {

                 register(clazz.getConstructor().newInstance());

             }

         } catch (Exception e) {

             throw new RuntimeException(e);

         }

     }

     public static DatabaseSnapshotGeneratorFactory getInstance() {

         if (instance == null) {

             instance = new DatabaseSnapshotGeneratorFactory();

         }

         return instance;

     }

     public DatabaseSnapshotGenerator getGenerator(Database database) {

         return getGenerators(database).iterator().next();

     }

     /**

      * Get generators supporting database, sorted from highest priority to lowest.

      * 

      * @param database

      * @return

      */

     public SortedSet<DatabaseSnapshotGenerator> getGenerators(final Database database) {

         SortedSet<DatabaseSnapshotGenerator> generators = new TreeSet<DatabaseSnapshotGenerator>(

                 new Comparator<DatabaseSnapshotGenerator>() {

                     @Override

                     public int compare(DatabaseSnapshotGenerator o1, DatabaseSnapshotGenerator o2) {

                         return -1 * Integer.valueOf(o1.getPriority(database)).compareTo(o2.getPriority(database));

                     }

                 });

         for (DatabaseSnapshotGenerator generator : registry) {

             if (generator.supports(database)) {

                 generators.add(generator);

             }

         }

         return generators;

     }

     /**

      * Get generator for database with highest priority.

      */

     public DatabaseSnapshot createSnapshot(Database database, String schema, Set<DiffStatusListener> listeners)

             throws DatabaseException {

         return getGenerator(database).createSnapshot(database, schema, listeners);

     }

     /**

      * Returns instances of all implemented database types.

      */

     public List<DatabaseSnapshotGenerator> getRegistry() {

         return registry;

     }

     public void register(DatabaseSnapshotGenerator snapshotGenerator) {

         registry.add(0, snapshotGenerator);

     }

     public static void resetAll() {

         instance = null;

     }

 }