"""

 The GeometryColumns and SpatialRefSys models for the PostGIS backend.

"""

from django.db import models

from django.contrib.gis.models import SpatialRefSysMixin

# Checking for the presence of GDAL (needed for the SpatialReference object)

from django.contrib.gis.gdal import HAS_GDAL

if HAS_GDAL:

    from django.contrib.gis.gdal import SpatialReference

class GeometryColumns(models.Model):

    """

    The 'geometry_columns' table from the PostGIS. See the PostGIS

    documentation at Ch. 4.2.2.

    """

    f_table_catalog = models.CharField(max_length=256)

    f_table_schema = models.CharField(max_length=256)

    f_table_name = models.CharField(max_length=256)

    f_geometry_column = models.CharField(max_length=256)

    coord_dimension = models.IntegerField()

    srid = models.IntegerField(primary_key=True)

    type = models.CharField(max_length=30)

    class Meta:

        db_table = 'geometry_columns'

    @classmethod

    def table_name_col(cls):

        """

        Returns the name of the metadata column used to store the 

        the feature table name.

        """

        return 'f_table_name'

    @classmethod

    def geom_col_name(cls):

        """

        Returns the name of the metadata column used to store the 

        the feature geometry column.

        """

        return 'f_geometry_column'

    def __unicode__(self):

        return "%s.%s - %dD %s field (SRID: %d)" % \

               (self.f_table_name, self.f_geometry_column,

                self.coord_dimension, self.type, self.srid)

class SpatialRefSys(models.Model, SpatialRefSysMixin):

    """

    The 'spatial_ref_sys' table from PostGIS. See the PostGIS

    documentaiton at Ch. 4.2.1.

    """

    srid = models.IntegerField(primary_key=True)

    auth_name = models.CharField(max_length=256)

    auth_srid = models.IntegerField()

    srtext = models.CharField(max_length=2048)

    proj4text = models.CharField(max_length=2048)

    class Meta:

        db_table = 'spatial_ref_sys'

    @property

    def wkt(self):

        return self.srtext

    @classmethod

    def wkt_col(cls):

        return 'srtext'