class WMTLocations():
"""
Service object used to find stops or stations (locations) - given a position, exact match or fuzzy match,
will return the best matching stop. Subclassed and not called directly
"""
def __init__(self, instance_name):
self.database = WMTDatabase('%s.geodata.db' % instance_name)
self.network = None
self.returned_object = Location
def find_closest(self, position, params):
"""
Find the closest location to the (lat, long) position specified, querying the database with dictionary params, of the format
{ Column Name : value }. Returns an object of class returned_object, or None if none found nearby
"""
# GPSes use WGS84 model of Globe, but Easting/Northing based on OSGB36, so convert to an easting/northing
logging.debug("Position in WGS84 determined as lat/long: %s %s", position[0], position[1])
easting, northing = convertWGS84toOSEastingNorthing(*position)
logging.debug("Translated into OS Easting %s, Northing %s", easting, northing)
# Do a funny bit of Pythagoras to work out closest stop. We can't find square root of a number in sqlite
# but then again, we don't need to, the smallest square will do. Sort by this column in ascending order
# and find the first row
(where_statement, where_values) = self.database.make_where_statement('locations', params)
query = """
SELECT (location_easting - %d)*(location_easting - %d) + (location_northing - %d)*(location_northing - %d) AS dist_squared,
*
FROM locations
WHERE %s
ORDER BY dist_squared
LIMIT 1
""" % (easting, easting, northing, northing, where_statement)
row = self.database.get_row(query, where_values)
if row:
obj = self.returned_object(Distance=sqrt(row['dist_squared']), **row)
logging.debug("Have found nearest location %s", obj)
return obj
else:
logging.debug("No location found near %s, sorry", position)
return None
def find_fuzzy_match(self, stop_or_station_name, params):
"""
Find the best fuzzy match to the query_string, querying the database with dictionary params, of the format
{ Column Name : value, }. Returns an object of class returned_object, or None if no fuzzy match found
"""
if not stop_or_station_name or stop_or_station_name == "Unknown":
return None
# Try to get an exact match first against station names in database
exact_params = params.copy()
exact_params.update({'name': stop_or_station_name})
exact_match = self.find_exact_match(exact_params)
if exact_match:
return exact_match
# Users may not give exact details, so we try to match fuzzily
(where_statement, where_values) = self.database.make_where_statement('locations', params)
rows = self.database.get_rows("SELECT * FROM locations WHERE %s" % where_statement, where_values)
possible_matches = [self.returned_object(**row) for row in rows]
best_match = get_best_fuzzy_match(stop_or_station_name, possible_matches)
if best_match:
return best_match
else:
return None
def find_exact_match(self, params):
"""
Find the exact match for an item matching params. Returns an object of class returned_object, or None if no
fuzzy match found
"""
(where_statement, where_values) = self.database.make_where_statement('locations', params)
row = self.database.get_row("SELECT * FROM locations WHERE %s LIMIT 1" % where_statement, where_values)
if row:
return self.returned_object(**row)
else:
return None
