# pysybase.py
# Copyright (C) 2010 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php

"""
Support for Sybase via the python-sybase driver.

http://python-sybase.sourceforge.net/

Connect strings are of the form::

    sybase+pysybase://<username>:<password>@<dsn>/[database name]

Unicode Support
---------------

The python-sybase driver does not appear to support non-ASCII strings of any
kind at this time.

"""

from sqlalchemy import types as sqltypes, processors
from sqlalchemy.dialects.sybase.base import SybaseDialect, \
                                        SybaseExecutionContext, SybaseSQLCompiler


class _SybNumeric(sqltypes.Numeric):
    def result_processor(self, dialect, type_):
        if not self.asdecimal:
            return processors.to_float
        else:
            return sqltypes.Numeric.result_processor(self, dialect, type_)

class SybaseExecutionContext_pysybase(SybaseExecutionContext):

    def set_ddl_autocommit(self, dbapi_connection, value):
        if value:
            # call commit() on the Sybase connection directly,
            # to avoid any side effects of calling a Connection 
            # transactional method inside of pre_exec()
            dbapi_connection.commit()

    def pre_exec(self):
        SybaseExecutionContext.pre_exec(self)

        for param in self.parameters:
            for key in list(param):
                param["@" + key] = param[key]
                del param[key]


class SybaseSQLCompiler_pysybase(SybaseSQLCompiler):
    def bindparam_string(self, name):
        return "@" + name
   
class SybaseDialect_pysybase(SybaseDialect):
    driver = 'pysybase'
    execution_ctx_cls = SybaseExecutionContext_pysybase
    statement_compiler = SybaseSQLCompiler_pysybase

    colspecs={
       sqltypes.Numeric:_SybNumeric,
       sqltypes.Float:sqltypes.Float
    }

    @classmethod
    def dbapi(cls):
        import Sybase
        return Sybase

    def create_connect_args(self, url):
        opts = url.translate_connect_args(username='user', password='passwd')

        return ([opts.pop('host')], opts)

    def do_executemany(self, cursor, statement, parameters, context=None):
        # calling python-sybase executemany yields:
        # TypeError: string too long for buffer
        for param in parameters:
            cursor.execute(statement, param)

    def _get_server_version_info(self, connection):
       vers = connection.scalar("select @@version_number")
       # i.e. 15500, 15000, 12500 == (15, 5, 0, 0), (15, 0, 0, 0), (12, 5, 0, 0)
       return (vers / 1000, vers % 1000 / 100, vers % 100 / 10, vers % 10)

    def is_disconnect(self, e):
        if isinstance(e, (self.dbapi.OperationalError, self.dbapi.ProgrammingError)):
            msg = str(e)
            return ('Unable to complete network request to host' in msg or
                    'Invalid connection state' in msg or
                    'Invalid cursor state' in msg)
        else:
            return False

dialect = SybaseDialect_pysybase
