Fixed #22603 -- Reorganized classes in django.db.backends.

django/contrib/gis/db/backends/base/models.py

@@ -0,0 +1,218 @@
+import re
+
+from django.contrib.gis import gdal
+from django.utils import six
+from django.utils.encoding import python_2_unicode_compatible
+
+
+@python_2_unicode_compatible
+class SpatialRefSysMixin(object):
+    """
+    The SpatialRefSysMixin is a class used by the database-dependent
+    SpatialRefSys objects to reduce redundant code.
+    """
+    # For pulling out the spheroid from the spatial reference string. This
+    # regular expression is used only if the user does not have GDAL installed.
+    # TODO: Flattening not used in all ellipsoids, could also be a minor axis,
+    # or 'b' parameter.
+    spheroid_regex = re.compile(r'.+SPHEROID\[\"(?P<name>.+)\",(?P<major>\d+(\.\d+)?),(?P<flattening>\d{3}\.\d+),')
+
+    # For pulling out the units on platforms w/o GDAL installed.
+    # TODO: Figure out how to pull out angular units of projected coordinate system and
+    # fix for LOCAL_CS types.  GDAL should be highly recommended for performing
+    # distance queries.
+    units_regex = re.compile(
+        r'.+UNIT ?\["(?P<unit_name>[\w \'\(\)]+)", ?(?P<unit>[\d\.]+)'
+        r'(,AUTHORITY\["(?P<unit_auth_name>[\w \'\(\)]+)",'
+        r'"(?P<unit_auth_val>\d+)"\])?\]([\w ]+)?(,'
+        r'AUTHORITY\["(?P<auth_name>[\w \'\(\)]+)","(?P<auth_val>\d+)"\])?\]$'
+    )
+
+    @property
+    def srs(self):
+        """
+        Returns a GDAL SpatialReference object, if GDAL is installed.
+        """
+        if gdal.HAS_GDAL:
+            # TODO: Is caching really necessary here?  Is complexity worth it?
+            if hasattr(self, '_srs'):
+                # Returning a clone of the cached SpatialReference object.
+                return self._srs.clone()
+            else:
+                # Attempting to cache a SpatialReference object.
+
+                # Trying to get from WKT first.
+                try:
+                    self._srs = gdal.SpatialReference(self.wkt)
+                    return self.srs
+                except Exception as msg:
+                    pass
+
+                try:
+                    self._srs = gdal.SpatialReference(self.proj4text)
+                    return self.srs
+                except Exception as msg:
+                    pass
+
+                raise Exception('Could not get OSR SpatialReference from WKT: %s\nError:\n%s' % (self.wkt, msg))
+        else:
+            raise Exception('GDAL is not installed.')
+
+    @property
+    def ellipsoid(self):
+        """
+        Returns a tuple of the ellipsoid parameters:
+        (semimajor axis, semiminor axis, and inverse flattening).
+        """
+        if gdal.HAS_GDAL:
+            return self.srs.ellipsoid
+        else:
+            m = self.spheroid_regex.match(self.wkt)
+            if m:
+                return (float(m.group('major')), float(m.group('flattening')))
+            else:
+                return None
+
+    @property
+    def name(self):
+        "Returns the projection name."
+        return self.srs.name
+
+    @property
+    def spheroid(self):
+        "Returns the spheroid name for this spatial reference."
+        return self.srs['spheroid']
+
+    @property
+    def datum(self):
+        "Returns the datum for this spatial reference."
+        return self.srs['datum']
+
+    @property
+    def projected(self):
+        "Is this Spatial Reference projected?"
+        if gdal.HAS_GDAL:
+            return self.srs.projected
+        else:
+            return self.wkt.startswith('PROJCS')
+
+    @property
+    def local(self):
+        "Is this Spatial Reference local?"
+        if gdal.HAS_GDAL:
+            return self.srs.local
+        else:
+            return self.wkt.startswith('LOCAL_CS')
+
+    @property
+    def geographic(self):
+        "Is this Spatial Reference geographic?"
+        if gdal.HAS_GDAL:
+            return self.srs.geographic
+        else:
+            return self.wkt.startswith('GEOGCS')
+
+    @property
+    def linear_name(self):
+        "Returns the linear units name."
+        if gdal.HAS_GDAL:
+            return self.srs.linear_name
+        elif self.geographic:
+            return None
+        else:
+            m = self.units_regex.match(self.wkt)
+            return m.group('unit_name')
+
+    @property
+    def linear_units(self):
+        "Returns the linear units."
+        if gdal.HAS_GDAL:
+            return self.srs.linear_units
+        elif self.geographic:
+            return None
+        else:
+            m = self.units_regex.match(self.wkt)
+            return m.group('unit')
+
+    @property
+    def angular_name(self):
+        "Returns the name of the angular units."
+        if gdal.HAS_GDAL:
+            return self.srs.angular_name
+        elif self.projected:
+            return None
+        else:
+            m = self.units_regex.match(self.wkt)
+            return m.group('unit_name')
+
+    @property
+    def angular_units(self):
+        "Returns the angular units."
+        if gdal.HAS_GDAL:
+            return self.srs.angular_units
+        elif self.projected:
+            return None
+        else:
+            m = self.units_regex.match(self.wkt)
+            return m.group('unit')
+
+    @property
+    def units(self):
+        "Returns a tuple of the units and the name."
+        if self.projected or self.local:
+            return (self.linear_units, self.linear_name)
+        elif self.geographic:
+            return (self.angular_units, self.angular_name)
+        else:
+            return (None, None)
+
+    @classmethod
+    def get_units(cls, wkt):
+        """
+        Class method used by GeometryField on initialization to
+        retrieve the units on the given WKT, without having to use
+        any of the database fields.
+        """
+        if gdal.HAS_GDAL:
+            return gdal.SpatialReference(wkt).units
+        else:
+            m = cls.units_regex.match(wkt)
+            return m.group('unit'), m.group('unit_name')
+
+    @classmethod
+    def get_spheroid(cls, wkt, string=True):
+        """
+        Class method used by GeometryField on initialization to
+        retrieve the `SPHEROID[..]` parameters from the given WKT.
+        """
+        if gdal.HAS_GDAL:
+            srs = gdal.SpatialReference(wkt)
+            sphere_params = srs.ellipsoid
+            sphere_name = srs['spheroid']
+        else:
+            m = cls.spheroid_regex.match(wkt)
+            if m:
+                sphere_params = (float(m.group('major')), float(m.group('flattening')))
+                sphere_name = m.group('name')
+            else:
+                return None
+
+        if not string:
+            return sphere_name, sphere_params
+        else:
+            # `string` parameter used to place in format acceptable by PostGIS
+            if len(sphere_params) == 3:
+                radius, flattening = sphere_params[0], sphere_params[2]
+            else:
+                radius, flattening = sphere_params
+            return 'SPHEROID["%s",%s,%s]' % (sphere_name, radius, flattening)
+
+    def __str__(self):
+        """
+        Returns the string representation.  If GDAL is installed,
+        it will be 'pretty' OGC WKT.
+        """
+        try:
+            return six.text_type(self.srs)
+        except Exception:
+            return six.text_type(self.wkt)