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.datatype.DataTypeFactory;
  import liquibase.datatype.LiquibaseDataType;
  import liquibase.exception.ValidationErrors;
  import liquibase.ext.spatial.datatype.GeometryType;
  import liquibase.sql.Sql;
  import liquibase.sql.UnparsedSql;
  import liquibase.sqlgenerator.SqlGenerator;
  import liquibase.sqlgenerator.SqlGeneratorChain;
  import liquibase.sqlgenerator.core.AbstractSqlGenerator;
  import liquibase.statement.core.AddColumnStatement;
  import liquibase.util.StringUtils;
  
  /**
   * <code>AddGeometryColumnGeneratorGeoDB</code> is a SQL generator that
   * specializes in GeoDB. Regardless of the column type, the next SQL generator
   * in the chain is invoked to handle the normal column addition. If the column
   * to be added has a geometry type, the <code>AddGeometryColumn</code> stored
   * procedure is invoked to ensure that the necessary metadata is created in the
   * database.
   */
  public class AddGeometryColumnGeneratorGeoDB extends
        AbstractSqlGenerator<AddColumnStatement> {
     /**
      * @see liquibase.sqlgenerator.core.AbstractSqlGenerator#supports(liquibase.statement.SqlStatement,
      *      liquibase.database.Database)
      */
     @Override
     public boolean supports(final AddColumnStatement statement,
           final Database database) {
        return database instanceof DerbyDatabase
              || database instanceof H2Database;
     }
  
     /**
      * @see liquibase.sqlgenerator.core.AbstractSqlGenerator#getPriority()
      */
     @Override
     public int getPriority() {
        return SqlGenerator.PRIORITY_DATABASE + 1;
     }
  
     @Override
     public ValidationErrors validate(final AddColumnStatement statement,
           final Database database, final SqlGeneratorChain sqlGeneratorChain) {
        final ValidationErrors errors = new ValidationErrors();
        final LiquibaseDataType dataType = DataTypeFactory.getInstance()
              .fromDescription(statement.getColumnType(), database);
  
        // Ensure that the SRID parameter is provided.
        if (dataType instanceof GeometryType) {
           final GeometryType geometryType = (GeometryType) dataType;
           if (geometryType.getSRID() == null) {
              errors.addError("The SRID parameter is required on the geometry type");
           }
        }
        final ValidationErrors chainErrors = sqlGeneratorChain.validate(
              statement, database);
        if (chainErrors != null) {
           errors.addAll(chainErrors);
        }
        return errors;
     }
  
     @Override
     public Sql[] generateSql(final AddColumnStatement statement,
           final Database database, final SqlGeneratorChain sqlGeneratorChain) {
  
        GeometryType geometryType = null;
        final LiquibaseDataType dataType = DataTypeFactory.getInstance()
              .fromDescription(statement.getColumnType(), database);
        if (dataType instanceof GeometryType) {
           geometryType = (GeometryType) dataType;
        }
  
        final boolean isGeometryColumn = geometryType != null;
  
        // The AddGeometryColumn procedure handles the column already being
        // present, so let a
        // downstream SQL generator handle the typical column addition logic (e.g.
        // placement in the
        // table) then invoke the procedure.
        final List<Sql> list = new ArrayList<Sql>();
        list.addAll(Arrays.asList(sqlGeneratorChain.generateSql(statement,
              database)));
        if (isGeometryColumn) {
           String schemaName = statement.getSchemaName();
           if (schemaName == null) {
              schemaName = database.getDefaultSchemaName();
           }
           final String tableName = statement.getTableName();
          final String columnName = statement.getColumnName();
 
          final int srid = geometryType.getSRID();
          final String geomType = StringUtils.trimToNull(geometryType
                .getGeometryType()) == null ? "'Geometry'" : "'"
                + database.escapeStringForDatabase(geometryType
                      .getGeometryType()) + "'";
          final String sql = "CALL AddGeometryColumn('" + schemaName + "', '"
                + tableName + "', '" + columnName + "', " + srid + ", "
                + geomType + ", 2)";
          final Sql addGeometryColumn = new UnparsedSql(sql);
          list.add(addGeometryColumn);
       }
       return list.toArray(new Sql[list.size()]);
    }
 }