package liquibase.ext.spatial.sqlgenerator;
   
   import java.util.ArrayList;
   import java.util.Arrays;
   import java.util.List;
   
   import liquibase.database.Database;
   import liquibase.database.core.DerbyDatabase;
   import liquibase.database.core.H2Database;
  import liquibase.exception.ValidationErrors;
  import liquibase.ext.spatial.statement.DropSpatialIndexStatement;
  import liquibase.ext.spatial.utils.GeometryColumnsUtils;
  import liquibase.sql.Sql;
  import liquibase.sql.UnparsedSql;
  import liquibase.sqlgenerator.SqlGeneratorChain;
  import liquibase.sqlgenerator.core.AbstractSqlGenerator;
  import liquibase.statement.SqlStatement;
  import liquibase.statement.core.DropTableStatement;
  
  /**
   * <code>DropSpatialTableGeneratorGeoDB</code> generates the SQL statements for cleaning up any
   * indexes and geometry columns prior to dropping the table.
   */
  public class DropSpatialTableGeneratorGeoDB extends AbstractSqlGenerator<DropTableStatement> {
     /**
      * @see AbstractSqlGenerator#supports(SqlStatement, Database)
      */
     @Override
     public boolean supports(final DropTableStatement statement, final Database database) {
        return database instanceof DerbyDatabase || database instanceof H2Database;
     }
  
     /**
      * @see AbstractSqlGenerator#getPriority()
      */
     @Override
     public int getPriority() {
        return super.getPriority() + 1;
     }
  
     @Override
     public ValidationErrors validate(final DropTableStatement statement, final Database database,
           final SqlGeneratorChain sqlGeneratorChain) {
        return sqlGeneratorChain.validate(statement, database);
     }
  
     @Override
     public Sql[] generateSql(final DropTableStatement statement, final Database database,
           final SqlGeneratorChain sqlGeneratorChain) {
        final List<Sql> list = new ArrayList<Sql>();
        String schemaName = statement.getSchemaName();
        if (schemaName == null) {
           schemaName = database.getDefaultSchemaName();
        }
        final String tableName = statement.getTableName();
  
        // If the table has a geometry column, drop it first.
        if (GeometryColumnsUtils.hasGeometryColumn(database, schemaName, tableName)) {
           dropSpatialIndexIfExists(statement.getCatalogName(), schemaName, tableName, database, list);
           final String sql = "CALL DropGeometryColumns('" + schemaName + "', '" + tableName + "')";
           final Sql addGeometryColumn = new UnparsedSql(sql);
           list.add(addGeometryColumn);
        }
        list.addAll(Arrays.asList(sqlGeneratorChain.generateSql(statement, database)));
        return list.toArray(new Sql[list.size()]);
     }
  
     /**
      * Adds the SQL statement to drop the spatial index if it is present.
      * 
      * @param catalogName
      *           the catalog name.
      * @param schemaName
      *           the schema name.
      * @param tableName
      *           the table name.
      * @param database
      *           the database.
      * @param list
      *           the list of SQL statements to execute.
      */
     protected void dropSpatialIndexIfExists(final String catalogName, final String schemaName,
           final String tableName, final Database database, final List<Sql> list) {
        final DropSpatialIndexGeneratorGeoDB generator = new DropSpatialIndexGeneratorGeoDB();
        final DropSpatialIndexStatement statement = new DropSpatialIndexStatement(null, catalogName,
              schemaName, tableName);
        list.addAll(Arrays.asList(generator.generateSqlIfExists(statement, database)));
     }
  }