from ctypes import c_void_p

from types import NoneType

from django.contrib.gis.geos.error import GEOSException, GEOSIndexError

# Trying to import GDAL libraries, if available.  Have to place in

# try/except since this package may be used outside GeoDjango.

try:

    from django.contrib.gis import gdal

except ImportError:

    # A 'dummy' gdal module.

    class GDALInfo(object):

        HAS_GDAL = False

        GEOJSON = False

    gdal = GDALInfo()

# NumPy supported?

try:

    import numpy

except ImportError:

    numpy = False

class GEOSBase(object):

    """

    Base object for GEOS objects that has a pointer access property

    that controls access to the underlying C pointer.

    """

    # Initially the pointer is NULL.

    _ptr = None

    # Default allowed pointer type.

    ptr_type = c_void_p

    # Pointer access property.

    def _get_ptr(self):

        # Raise an exception if the pointer isn't valid don't

        # want to be passing NULL pointers to routines --

        # that's very bad.

        if self._ptr: return self._ptr

        else: raise GEOSException('NULL GEOS %s pointer encountered.' % self.__class__.__name__)

    def _set_ptr(self, ptr):

        # Only allow the pointer to be set with pointers of the

        # compatible type or None (NULL).

        if isinstance(ptr, (self.ptr_type, NoneType)):

            self._ptr = ptr

        else:

            raise TypeError('Incompatible pointer type')

    # Property for controlling access to the GEOS object pointers.  Using

    # this raises an exception when the pointer is NULL, thus preventing

    # the C library from attempting to access an invalid memory location.

    ptr = property(_get_ptr, _set_ptr)