# prerequisites imports 

from ctypes import c_void_p

from django.contrib.gis.gdal.error import OGRException

from django.contrib.gis.gdal.prototypes.ds import \

    get_driver, get_driver_by_name, get_driver_count, get_driver_name, register_all

# For more information, see the OGR C API source code:

#  http://www.gdal.org/ogr/ogr__api_8h.html

#

# The OGR_Dr_* routines are relevant here.

class Driver(object):

    "Wraps an OGR Data Source Driver."

    # Case-insensitive aliases for OGR Drivers.

    _alias = {'esri' : 'ESRI Shapefile',

              'shp' : 'ESRI Shapefile',

              'shape' : 'ESRI Shapefile',

              'tiger' : 'TIGER',

              'tiger/line' : 'TIGER',

              }

    def __init__(self, dr_input):

        "Initializes an OGR driver on either a string or integer input."

        if isinstance(dr_input, basestring):

            # If a string name of the driver was passed in

            self._ptr = None # Initially NULL

            self._register()

            # Checking the alias dictionary (case-insensitive) to see if an alias

            #  exists for the given driver.

            if dr_input.lower() in self._alias:

                name = self._alias[dr_input.lower()]

            else:

                name = dr_input

            # Attempting to get the OGR driver by the string name.

            dr = get_driver_by_name(name)

        elif isinstance(dr_input, int):

            self._register()

            dr = get_driver(dr_input)

        elif isinstance(dr_input, c_void_p):

            dr = dr_input

        else:

            raise OGRException('Unrecognized input type for OGR Driver: %s' % str(type(dr_input)))

        # Making sure we get a valid pointer to the OGR Driver

        if not dr:

            raise OGRException('Could not initialize OGR Driver on input: %s' % str(dr_input))

        self._ptr = dr

    def __str__(self):

        "Returns the string name of the OGR Driver."

        return get_driver_name(self._ptr)

    def _register(self):

        "Attempts to register all the data source drivers."

        # Only register all if the driver count is 0 (or else all drivers

        # will be registered over and over again)

        if not self.driver_count: register_all()

    # Driver properties

    @property

    def driver_count(self):

        "Returns the number of OGR data source drivers registered."

        return get_driver_count()