package liquibase.sqlgenerator.core;

 import java.util.List;

 import liquibase.database.Database;

 import liquibase.database.core.MSSQLDatabase;

 import liquibase.database.core.MySQLDatabase;

 import liquibase.database.core.OracleDatabase;

 import liquibase.database.structure.Index;

 import liquibase.exception.ValidationErrors;

 import liquibase.sql.Sql;

 import liquibase.sql.UnparsedSql;

 import liquibase.sqlgenerator.SqlGeneratorChain;

 import liquibase.statement.core.DropIndexStatement;

 import liquibase.util.StringUtils;

 public class DropIndexGenerator extends AbstractSqlGenerator<DropIndexStatement> {

     @Override

     public ValidationErrors validate(DropIndexStatement statement, Database database,

             SqlGeneratorChain sqlGeneratorChain) {

         ValidationErrors validationErrors = new ValidationErrors();

         validationErrors.checkRequiredField("indexName", statement.getIndexName());

         if (database instanceof MySQLDatabase || database instanceof MSSQLDatabase) {

             validationErrors.checkRequiredField("tableName", statement.getTableName());

         }

         return validationErrors;

     }

     @Override

     public Sql[] generateSql(DropIndexStatement statement, Database database, SqlGeneratorChain sqlGeneratorChain) {

         List<String> associatedWith = StringUtils.splitAndTrim(statement.getAssociatedWith(), ",");

         if (associatedWith != null) {

             if (associatedWith.contains(Index.MARK_PRIMARY_KEY)

                     || associatedWith.contains(Index.MARK_UNIQUE_CONSTRAINT)) {

                 return new Sql[0];

             } else if (associatedWith.contains(Index.MARK_FOREIGN_KEY)) {

                 if (!(database instanceof OracleDatabase || database instanceof MSSQLDatabase)) {

                     return new Sql[0];

                 }

             }

         }

         String schemaName = statement.getTableSchemaName();

         if (database instanceof MySQLDatabase) {

             return new Sql[] { new UnparsedSql("DROP INDEX " + database.escapeIndexName(null, statement.getIndexName())

                     + " ON " + database.escapeTableName(schemaName, statement.getTableName())) };

         } else if (database instanceof MSSQLDatabase) {

             return new Sql[] { new UnparsedSql("DROP INDEX "

                     + database.escapeTableName(schemaName, statement.getTableName()) + "."

                     + database.escapeIndexName(null, statement.getIndexName())) };

         }

         return new Sql[] { new UnparsedSql("DROP INDEX "

                 + database.escapeIndexName(schemaName, statement.getIndexName())) };

     }

 }