text: from __future__ import absolute_import
  
  from django.db import connection
  from django.db.models import Q
  from django.contrib.gis.geos import HAS_GEOS
  from django.contrib.gis.measure import D # alias for Distance
  from django.contrib.gis.tests.utils import (
      HAS_SPATIAL_DB, mysql, oracle, postgis, spatialite, no_oracle, no_spatialite
  )
  from django.test import TestCase
  from django.utils.unittest import skipUnless
  
  if HAS_GEOS and HAS_SPATIAL_DB:
      from django.contrib.gis.geos import GEOSGeometry, LineString
  
      from .models import (AustraliaCity, Interstate, SouthTexasInterstate,
          SouthTexasCity, SouthTexasCityFt, CensusZipcode, SouthTexasZipcode)
  
  
  @skipUnless(HAS_GEOS and HAS_SPATIAL_DB and not mysql,
      "Geos and spatial db (not mysql) are required.")
  class DistanceTest(TestCase):
  
      if HAS_GEOS and HAS_SPATIAL_DB:
          # A point we are testing distances with -- using a WGS84
          # coordinate that'll be implicitly transormed to that to
          # the coordinate system of the field, EPSG:32140 (Texas South Central
          # w/units in meters)
          stx_pnt = GEOSGeometry('POINT (-95.370401017314293 29.704867409475465)', 4326)
          # Another one for Australia
          au_pnt = GEOSGeometry('POINT (150.791 -34.4919)', 4326)
  
      def get_names(self, qs):
          cities = [c.name for c in qs]
          cities.sort()
          return cities
  
      def test01_init(self):
          "Test initialization of distance models."
          self.assertEqual(9, SouthTexasCity.objects.count())
          self.assertEqual(9, SouthTexasCityFt.objects.count())
          self.assertEqual(11, AustraliaCity.objects.count())
          self.assertEqual(4, SouthTexasZipcode.objects.count())
          self.assertEqual(4, CensusZipcode.objects.count())
          self.assertEqual(1, Interstate.objects.count())
          self.assertEqual(1, SouthTexasInterstate.objects.count())
  
      @no_spatialite
      def test02_dwithin(self):
          "Testing the `dwithin` lookup type."
          # Distances -- all should be equal (except for the
          # degree/meter pair in au_cities, that's somewhat
          # approximate).
          tx_dists = [(7000, 22965.83), D(km=7), D(mi=4.349)]
          au_dists = [(0.5, 32000), D(km=32), D(mi=19.884)]
  
          # Expected cities for Australia and Texas.
          tx_cities = ['Downtown Houston', 'Southside Place']
          au_cities = ['Mittagong', 'Shellharbour', 'Thirroul', 'Wollongong']
  
          # Performing distance queries on two projected coordinate systems one
          # with units in meters and the other in units of U.S. survey feet.
          for dist in tx_dists:
              if isinstance(dist, tuple): dist1, dist2 = dist
              else: dist1 = dist2 = dist
              qs1 = SouthTexasCity.objects.filter(point__dwithin=(self.stx_pnt, dist1))
              qs2 = SouthTexasCityFt.objects.filter(point__dwithin=(self.stx_pnt, dist2))
              for qs in qs1, qs2:
                  self.assertEqual(tx_cities, self.get_names(qs))
  
          # Now performing the `dwithin` queries on a geodetic coordinate system.
          for dist in au_dists:
              if isinstance(dist, D) and not oracle: type_error = True
              else: type_error = False
  
              if isinstance(dist, tuple):
                  if oracle: dist = dist[1]
                  else: dist = dist[0]
  
              # Creating the query set.
              qs = AustraliaCity.objects.order_by('name')
              if type_error:
                  # A ValueError should be raised on PostGIS when trying to pass
                  # Distance objects into a DWithin query using a geodetic field.
                  self.assertRaises(ValueError, AustraliaCity.objects.filter(point__dwithin=(self.au_pnt, dist)).count)
              else:
                  self.assertEqual(au_cities, self.get_names(qs.filter(point__dwithin=(self.au_pnt, dist))))
  
      def test03a_distance_method(self):
          "Testing the `distance` GeoQuerySet method on projected coordinate systems."
          # The point for La Grange, TX
          lagrange = GEOSGeometry('POINT(-96.876369 29.905320)', 4326)
          # Reference distances in feet and in meters. Got these values from
          # using the provided raw SQL statements.
          #  SELECT ST_Distance(point, ST_Transform(ST_GeomFromText('POINT(-96.876369 29.905320)', 4326), 32140)) FROM distapp_southtexascity;
          m_distances = [147075.069813, 139630.198056, 140888.552826,
                         138809.684197, 158309.246259, 212183.594374,
                         70870.188967, 165337.758878, 139196.085105]
          #  SELECT ST_Distance(point, ST_Transform(ST_GeomFromText('POINT(-96.876369 29.905320)', 4326), 2278)) FROM distapp_southtexascityft;
          # Oracle 11 thinks this is not a projected coordinate system, so it's s
          # not tested.
          ft_distances = [482528.79154625, 458103.408123001, 462231.860397575,
                          455411.438904354, 519386.252102563, 696139.009211594,
                          232513.278304279, 542445.630586414, 456679.155883207]
  
          # Testing using different variations of parameters and using models
          # with different projected coordinate systems.
          dist1 = SouthTexasCity.objects.distance(lagrange, field_name='point')
          dist2 = SouthTexasCity.objects.distance(lagrange)  # Using GEOSGeometry parameter
          if spatialite or oracle:
              dist_qs = [dist1, dist2]
          else:
              dist3 = SouthTexasCityFt.objects.distance(lagrange.ewkt) # Using EWKT string parameter.
              dist4 = SouthTexasCityFt.objects.distance(lagrange)
              dist_qs = [dist1, dist2, dist3, dist4]
  
          # Original query done on PostGIS, have to adjust AlmostEqual tolerance
          # for Oracle.
          if oracle: tol = 2
          else: tol = 5
  
          # Ensuring expected distances are returned for each distance queryset.
          for qs in dist_qs:
              for i, c in enumerate(qs):
                  self.assertAlmostEqual(m_distances[i], c.distance.m, tol)
                  self.assertAlmostEqual(ft_distances[i], c.distance.survey_ft, tol)
  
      @no_spatialite
      def test03b_distance_method(self):
          "Testing the `distance` GeoQuerySet method on geodetic coordnate systems."
          if oracle: tol = 2
          else: tol = 5
  
          # Testing geodetic distance calculation with a non-point geometry
          # (a LineString of Wollongong and Shellharbour coords).
          ls = LineString( ( (150.902, -34.4245), (150.87, -34.5789) ) )
          if oracle or connection.ops.geography:
              # Reference query:
              #  SELECT ST_distance_sphere(point, ST_GeomFromText('LINESTRING(150.9020 -34.4245,150.8700 -34.5789)', 4326)) FROM distapp_australiacity ORDER BY name;
              distances = [1120954.92533513, 140575.720018241, 640396.662906304,
                           60580.9693849269, 972807.955955075, 568451.8357838,
                           40435.4335201384, 0, 68272.3896586844, 12375.0643697706, 0]
              qs = AustraliaCity.objects.distance(ls).order_by('name')
              for city, distance in zip(qs, distances):
                  # Testing equivalence to within a meter.
                  self.assertAlmostEqual(distance, city.distance.m, 0)
          else:
              # PostGIS 1.4 and below is limited to disance queries only
              # to/from point geometries, check for raising of ValueError.
              self.assertRaises(ValueError, AustraliaCity.objects.distance, ls)
              self.assertRaises(ValueError, AustraliaCity.objects.distance, ls.wkt)
  
          # Got the reference distances using the raw SQL statements:
          #  SELECT ST_distance_spheroid(point, ST_GeomFromText('POINT(151.231341 -33.952685)', 4326), 'SPHEROID["WGS 84",6378137.0,298.257223563]') FROM distapp_australiacity WHERE (NOT (id = 11));
          #  SELECT ST_distance_sphere(point, ST_GeomFromText('POINT(151.231341 -33.952685)', 4326)) FROM distapp_australiacity WHERE (NOT (id = 11));  st_distance_sphere
          if connection.ops.postgis and connection.ops.proj_version_tuple() >= (4, 7, 0):
              # PROJ.4 versions 4.7+ have updated datums, and thus different
              # distance values.
              spheroid_distances = [60504.0628957201, 77023.9489850262, 49154.8867574404,
                                    90847.4358768573, 217402.811919332, 709599.234564757,
                                    640011.483550888, 7772.00667991925, 1047861.78619339,
                                    1165126.55236034]
              sphere_distances = [60580.9693849267, 77144.0435286473, 49199.4415344719,
                                  90804.7533823494, 217713.384600405, 709134.127242793,
                                  639828.157159169, 7786.82949717788, 1049204.06569028,
                                  1162623.7238134]
  
          else:
              spheroid_distances = [60504.0628825298, 77023.948962654, 49154.8867507115,
                                    90847.435881812, 217402.811862568, 709599.234619957,
                                    640011.483583758, 7772.00667666425, 1047861.7859506,
                                    1165126.55237647]
              sphere_distances = [60580.7612632291, 77143.7785056615, 49199.2725132184,
                                  90804.4414289463, 217712.63666124, 709131.691061906,
                                  639825.959074112, 7786.80274606706, 1049200.46122281,
                                  1162619.7297006]
  
          # Testing with spheroid distances first.
          hillsdale = AustraliaCity.objects.get(name='Hillsdale')
          qs = AustraliaCity.objects.exclude(id=hillsdale.id).distance(hillsdale.point, spheroid=True)
          for i, c in enumerate(qs):
              self.assertAlmostEqual(spheroid_distances[i], c.distance.m, tol)
          if postgis:
              # PostGIS uses sphere-only distances by default, testing these as well.
              qs =  AustraliaCity.objects.exclude(id=hillsdale.id).distance(hillsdale.point)
              for i, c in enumerate(qs):
                  self.assertAlmostEqual(sphere_distances[i], c.distance.m, tol)
  
      @no_oracle # Oracle already handles geographic distance calculation.
      def test03c_distance_method(self):
          "Testing the `distance` GeoQuerySet method used with `transform` on a geographic field."
          # Normally you can't compute distances from a geometry field
          # that is not a PointField (on PostGIS 1.4 and below).
          if not connection.ops.geography:
              self.assertRaises(ValueError, CensusZipcode.objects.distance, self.stx_pnt)
  
          # We'll be using a Polygon (created by buffering the centroid
          # of 77005 to 100m) -- which aren't allowed in geographic distance
          # queries normally, however our field has been transformed to
          # a non-geographic system.
          z = SouthTexasZipcode.objects.get(name='77005')
  
          # Reference query:
          # SELECT ST_Distance(ST_Transform("distapp_censuszipcode"."poly", 32140), ST_GeomFromText('<buffer_wkt>', 32140)) FROM "distapp_censuszipcode";
          dists_m = [3553.30384972258, 1243.18391525602, 2186.15439472242]
  
          # Having our buffer in the SRID of the transformation and of the field
          # -- should get the same results. The first buffer has no need for
          # transformation SQL because it is the same SRID as what was given
          # to `transform()`.  The second buffer will need to be transformed,
          # however.
          buf1 = z.poly.centroid.buffer(100)
          buf2 = buf1.transform(4269, clone=True)
          ref_zips = ['77002', '77025', '77401']
  
          for buf in [buf1, buf2]:
              qs = CensusZipcode.objects.exclude(name='77005').transform(32140).distance(buf)
              self.assertEqual(ref_zips, self.get_names(qs))
              for i, z in enumerate(qs):
                  self.assertAlmostEqual(z.distance.m, dists_m[i], 5)
  
      def test04_distance_lookups(self):
          "Testing the `distance_lt`, `distance_gt`, `distance_lte`, and `distance_gte` lookup types."
          # Retrieving the cities within a 20km 'donut' w/a 7km radius 'hole'
          # (thus, Houston and Southside place will be excluded as tested in
          # the `test02_dwithin` above).
          qs1 = SouthTexasCity.objects.filter(point__distance_gte=(self.stx_pnt, D(km=7))).filter(point__distance_lte=(self.stx_pnt, D(km=20)))
  
          # Can't determine the units on SpatiaLite from PROJ.4 string, and
          # Oracle 11 incorrectly thinks it is not projected.
          if spatialite or oracle:
              dist_qs = (qs1,)
          else:
              qs2 = SouthTexasCityFt.objects.filter(point__distance_gte=(self.stx_pnt, D(km=7))).filter(point__distance_lte=(self.stx_pnt, D(km=20)))
              dist_qs = (qs1, qs2)
  
          for qs in dist_qs:
              cities = self.get_names(qs)
              self.assertEqual(cities, ['Bellaire', 'Pearland', 'West University Place'])
  
          # Doing a distance query using Polygons instead of a Point.
          z = SouthTexasZipcode.objects.get(name='77005')
          qs = SouthTexasZipcode.objects.exclude(name='77005').filter(poly__distance_lte=(z.poly, D(m=275)))
          self.assertEqual(['77025', '77401'], self.get_names(qs))
          # If we add a little more distance 77002 should be included.
          qs = SouthTexasZipcode.objects.exclude(name='77005').filter(poly__distance_lte=(z.poly, D(m=300)))
          self.assertEqual(['77002', '77025', '77401'], self.get_names(qs))
  
      def test05_geodetic_distance_lookups(self):
          "Testing distance lookups on geodetic coordinate systems."
          # Line is from Canberra to Sydney.  Query is for all other cities within
          # a 100km of that line (which should exclude only Hobart & Adelaide).
          line = GEOSGeometry('LINESTRING(144.9630 -37.8143,151.2607 -33.8870)', 4326)
          dist_qs = AustraliaCity.objects.filter(point__distance_lte=(line, D(km=100)))
  
          if oracle or connection.ops.geography:
              # Oracle and PostGIS 1.5 can do distance lookups on arbitrary geometries.
              self.assertEqual(9, dist_qs.count())
              self.assertEqual(['Batemans Bay', 'Canberra', 'Hillsdale',
                                'Melbourne', 'Mittagong', 'Shellharbour',
                                'Sydney', 'Thirroul', 'Wollongong'],
                               self.get_names(dist_qs))
          else:
              # PostGIS 1.4 and below only allows geodetic distance queries (utilizing
              # ST_Distance_Sphere/ST_Distance_Spheroid) from Points to PointFields
              # on geometry columns.
              self.assertRaises(ValueError, dist_qs.count)
  
              # Ensured that a ValueError was raised, none of the rest of the test is
              # support on this backend, so bail now.
              if spatialite: return
  
          # Too many params (4 in this case) should raise a ValueError.
          self.assertRaises(ValueError, len,
                            AustraliaCity.objects.filter(point__distance_lte=('POINT(5 23)', D(km=100), 'spheroid', '4')))
  
          # Not enough params should raise a ValueError.
          self.assertRaises(ValueError, len,
                            AustraliaCity.objects.filter(point__distance_lte=('POINT(5 23)',)))
  
          # Getting all cities w/in 550 miles of Hobart.
          hobart = AustraliaCity.objects.get(name='Hobart')
          qs = AustraliaCity.objects.exclude(name='Hobart').filter(point__distance_lte=(hobart.point, D(mi=550)))
          cities = self.get_names(qs)
          self.assertEqual(cities, ['Batemans Bay', 'Canberra', 'Melbourne'])
  
          # Cities that are either really close or really far from Wollongong --
          # and using different units of distance.
          wollongong = AustraliaCity.objects.get(name='Wollongong')
          d1, d2 = D(yd=19500), D(nm=400) # Yards (~17km) & Nautical miles.
  
          # Normal geodetic distance lookup (uses `distance_sphere` on PostGIS.
          gq1 = Q(point__distance_lte=(wollongong.point, d1))
          gq2 = Q(point__distance_gte=(wollongong.point, d2))
          qs1 = AustraliaCity.objects.exclude(name='Wollongong').filter(gq1 | gq2)
  
          # Geodetic distance lookup but telling GeoDjango to use `distance_spheroid`
          # instead (we should get the same results b/c accuracy variance won't matter
          # in this test case).
          if postgis:
              gq3 = Q(point__distance_lte=(wollongong.point, d1, 'spheroid'))
              gq4 = Q(point__distance_gte=(wollongong.point, d2, 'spheroid'))
              qs2 = AustraliaCity.objects.exclude(name='Wollongong').filter(gq3 | gq4)
              querysets = [qs1, qs2]
          else:
              querysets = [qs1]
  
          for qs in querysets:
              cities = self.get_names(qs)
              self.assertEqual(cities, ['Adelaide', 'Hobart', 'Shellharbour', 'Thirroul'])
  
      def test06_area(self):
          "Testing the `area` GeoQuerySet method."
          # Reference queries:
          # SELECT ST_Area(poly) FROM distapp_southtexaszipcode;
          area_sq_m = [5437908.90234375, 10183031.4389648, 11254471.0073242, 9881708.91772461]
          # Tolerance has to be lower for Oracle and differences
          # with GEOS 3.0.0RC4
          tol = 2
          for i, z in enumerate(SouthTexasZipcode.objects.area()):
              self.assertAlmostEqual(area_sq_m[i], z.area.sq_m, tol)
  
      def test07_length(self):
          "Testing the `length` GeoQuerySet method."
          # Reference query (should use `length_spheroid`).
          # SELECT ST_length_spheroid(ST_GeomFromText('<wkt>', 4326) 'SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]]');
          len_m1 = 473504.769553813
          len_m2 = 4617.668
  
          if spatialite:
              # Does not support geodetic coordinate systems.
              self.assertRaises(ValueError, Interstate.objects.length)
          else:
              qs = Interstate.objects.length()
              if oracle: tol = 2
              else: tol = 3
              self.assertAlmostEqual(len_m1, qs[0].length.m, tol)
  
          # Now doing length on a projected coordinate system.
          i10 = SouthTexasInterstate.objects.length().get(name='I-10')
          self.assertAlmostEqual(len_m2, i10.length.m, 2)
  
      @no_spatialite
      def test08_perimeter(self):
          "Testing the `perimeter` GeoQuerySet method."
          # Reference query:
          # SELECT ST_Perimeter(distapp_southtexaszipcode.poly) FROM distapp_southtexaszipcode;
          perim_m = [18404.3550889361, 15627.2108551001, 20632.5588368978, 17094.5996143697]
          if oracle: tol = 2
          else: tol = 7
          for i, z in enumerate(SouthTexasZipcode.objects.perimeter()):
              self.assertAlmostEqual(perim_m[i], z.perimeter.m, tol)
  
          # Running on points; should return 0.
          for i, c in enumerate(SouthTexasCity.objects.perimeter(model_att='perim')):
              self.assertEqual(0, c.perim.m)
  
      def test09_measurement_null_fields(self):
          "Testing the measurement GeoQuerySet methods on fields with NULL values."
          # Creating SouthTexasZipcode w/NULL value.
          SouthTexasZipcode.objects.create(name='78212')
          # Performing distance/area queries against the NULL PolygonField,
          # and ensuring the result of the operations is None.
          htown = SouthTexasCity.objects.get(name='Downtown Houston')
          z = SouthTexasZipcode.objects.distance(htown.point).area().get(name='78212')
          self.assertEqual(None, z.distance)
          self.assertEqual(None, z.area)
  