package liquibase.sql.visitor;

 import java.util.HashMap;

 import java.util.Map;

 public class SqlVisitorFactory {

     @SuppressWarnings("unchecked")

     private final Map<String, Class> tagToClassMap;

     private static final SqlVisitorFactory instance = new SqlVisitorFactory();

     @SuppressWarnings("unchecked")

     private SqlVisitorFactory() {

         tagToClassMap = new HashMap<String, Class>();

         Class[] visitors = new Class[] { PrependSqlVisitor.class, AppendSqlVisitor.class,

                 RegExpReplaceSqlVisitor.class, ReplaceSqlVisitor.class, };

         try {

             for (Class<SqlVisitor> visitorClass : visitors) {

                 SqlVisitor visitor = visitorClass.newInstance();

                 tagToClassMap.put(visitor.getName(), visitorClass);

             }

         } catch (Exception e) {

             throw new RuntimeException(e);

         }

     }

     public static SqlVisitorFactory getInstance() {

         return instance;

     }

     /**

      * Create a new Change subclass based on the given tag name.

      */

     public SqlVisitor create(String tagName) {

         Class<?> aClass = tagToClassMap.get(tagName);

         if (aClass == null) {

             throw new RuntimeException("Unknown tag: " + tagName);

         }

         try {

             return (SqlVisitor) aClass.newInstance();

         } catch (Exception e) {

             throw new RuntimeException(e);

         }

     }

 }