#!/usr/bin/env python

# -*- coding: utf-8  -*-

################################################################################

#

#  sqlalchemy-pervasive -- SQLAlchemy Dialect for Pervasive PSQL

#  Copyright © 2013 Lance Edgar

#

#  This file is part of sqlalchemy-pervasive.

#

#  sqlalchemy-pervasive is free software: you can redistribute it and/or modify

#  it under the terms of the GNU General Public License as published by the

#  Free Software Foundation, either version 3 of the License, or (at your

#  option) any later version.

#

#  sqlalchemy-pervasive is distributed in the hope that it will be useful, but

#  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

#  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for

#  more details.

#

#  You should have received a copy of the GNU General Public License along with

#  sqlalchemy-pervasive.  If not, see <http://www.gnu.org/licenses/>.

#

################################################################################

"""

Support for the Pervasive PSQL database engine.

"""

from sqlalchemy.sql.compiler import SQLCompiler

from sqlalchemy.engine.default import DefaultDialect

from sqlalchemy.exc import InvalidRequestError

class PervasiveCompiler(SQLCompiler):

    """

    Custom SQL statement compiler for Pervasive PSQL.

    """

    # This logic was basically copied from the ``sqlalchemy-access`` dialect.

    def get_select_precolumns(self, select):

        s = 'DISTINCT ' if select._distinct else ''

        if select._limit:

            s += 'TOP {0} '.format(select._limit)

        if select._offset:

            raise InvalidRequestError(

                "Pervasive PSQL does not support TOP (limit) with an offset")

        return s

    def limit_clause(self, select):

        return ""

class PervasiveDialect(DefaultDialect):

    name = 'pervasive'

    statement_compiler = PervasiveCompiler