# The GDAL C library, OGR exception, and the Field object

from django.contrib.gis.gdal.base import GDALBase

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

from django.contrib.gis.gdal.field import Field

from django.contrib.gis.gdal.geometries import OGRGeometry, OGRGeomType

from django.contrib.gis.gdal.srs import SpatialReference

# ctypes function prototypes

from django.contrib.gis.gdal.prototypes import ds as capi, geom as geom_api

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

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

#

# The OGR_F_* routines are relevant here.

class Feature(GDALBase):

    "A class that wraps an OGR Feature, needs to be instantiated from a Layer object."

    #### Python 'magic' routines ####

    def __init__(self, feat, fdefn):

        "Initializes on the pointers for the feature and the layer definition."

        if not feat or not fdefn:

            raise OGRException('Cannot create OGR Feature, invalid pointer given.')

        self.ptr = feat

        self._fdefn = fdefn

    def __del__(self):

        "Releases a reference to this object."

        if self._ptr: capi.destroy_feature(self._ptr)

    def __getitem__(self, index):

        """

        Gets the Field object at the specified index, which may be either

        an integer or the Field's string label.  Note that the Field object

        is not the field's _value_ -- use the `get` method instead to 

        retrieve the value (e.g. an integer) instead of a Field instance.

        """

        if isinstance(index, basestring):

            i = self.index(index)

        else:

            if index < 0 or index > self.num_fields:

                raise OGRIndexError('index out of range')

            i = index

        return Field(self.ptr, i)

    def __iter__(self):

        "Iterates over each field in the Feature."

        for i in xrange(self.num_fields):

            yield self[i]

    def __len__(self):

        "Returns the count of fields in this feature."

        return self.num_fields

    def __str__(self):

        "The string name of the feature."

        return 'Feature FID %d in Layer<%s>' % (self.fid, self.layer_name)

    def __eq__(self, other):

        "Does equivalence testing on the features."

        return bool(capi.feature_equal(self.ptr, other._ptr))

    #### Feature Properties ####

    @property

    def fid(self):

        "Returns the feature identifier."

        return capi.get_fid(self.ptr)

    @property

    def layer_name(self):

        "Returns the name of the layer for the feature."

        return capi.get_feat_name(self._fdefn)

    @property

    def num_fields(self):

        "Returns the number of fields in the Feature."

        return capi.get_feat_field_count(self.ptr)

    @property

    def fields(self):

        "Returns a list of fields in the Feature."

        return [capi.get_field_name(capi.get_field_defn(self._fdefn, i)) 

                for i in xrange(self.num_fields)]

    @property

    def geom(self):

        "Returns the OGR Geometry for this Feature."

        # Retrieving the geometry pointer for the feature.

        geom_ptr = capi.get_feat_geom_ref(self.ptr)

        return OGRGeometry(geom_api.clone_geom(geom_ptr))

    @property

    def geom_type(self):

        "Returns the OGR Geometry Type for this Feture."

        return OGRGeomType(capi.get_fd_geom_type(self._fdefn))

    #### Feature Methods ####

    def get(self, field):

        """

        Returns the value of the field, instead of an instance of the Field

        object.  May take a string of the field name or a Field object as

        parameters.

        """

        field_name = getattr(field, 'name', field)

        return self[field_name].value

    def index(self, field_name):

        "Returns the index of the given field name."

        i = capi.get_field_index(self.ptr, field_name)

        if i < 0: raise OGRIndexError('invalid OFT field name given: "%s"' % field_name)

        return i