creation pattern

app/services/location/csbs.py

@@ -22,7 +22,7 @@ class CSBSLocationService(LocationService):
 
     async def get_all(self):
         # Get the locations.
-        locations = await get_locations()
+        locations = await CSBSGateway.get_instance().get_locations()
         return locations
 
     async def get(self, loc_id):  # pylint: disable=arguments-differ
@@ -31,72 +31,84 @@ async def get(self, loc_id):  # pylint: disable=arguments-differ
         return locations[loc_id]
 
 
-# Base URL for fetching data
-BASE_URL = "https://facts.csbs.org/covid-19/covid19_county.csv"
-
-
-@cached(cache=TTLCache(maxsize=1, ttl=1800))
-async def get_locations():
-    """
-    Retrieves county locations; locations are cached for 1 hour
-
-    :returns: The locations.
-    :rtype: dict
-    """
-    data_id = "csbs.locations"
-    LOGGER.info(f"{data_id} Requesting data...")
-    # check shared cache
-    cache_results = await check_cache(data_id)
-    if cache_results:
-        LOGGER.info(f"{data_id} using shared cache results")
-        locations = cache_results
-    else:
-        LOGGER.info(f"{data_id} shared cache empty")
-        async with httputils.CLIENT_SESSION.get(BASE_URL) as response:
-            text = await response.text()
-
-        LOGGER.debug(f"{data_id} Data received")
-
-        data = list(csv.DictReader(text.splitlines()))
-        LOGGER.debug(f"{data_id} CSV parsed")
-
-        locations = []
-
-        for i, item in enumerate(data):
-            # General info.
-            state = item["State Name"]
-            county = item["County Name"]
-
-            # Ensure country is specified.
-            if county in {"Unassigned", "Unknown"}:
-                continue
-
-            # Date string without "EDT" at end.
-            last_update = " ".join(item["Last Update"].split(" ")[0:2])
-
-            # Append to locations.
-            locations.append(
-                CSBSLocation(
-                    # General info.
-                    i,
-                    state,
-                    county,
-                    # Coordinates.
-                    Coordinates(item["Latitude"], item["Longitude"]),
-                    # Last update (parse as ISO).
-                    datetime.strptime(last_update, "%Y-%m-%d %H:%M").isoformat() + "Z",
-                    # Statistics.
-                    int(item["Confirmed"] or 0),
-                    int(item["Death"] or 0),
+class CSBSGateway(LocationGateway):
+    __instance = None
+
+    @staticmethod
+    def get_instance():
+        if CSBSGateway.__instance is None:
+            CSBSGateway.__instance = CSBSGateway()
+
+        return CSBSGateway.__instance
+
+    def __init__(self):
+        self.BASE_URL = "https://facts.csbs.org/covid-19/covid19_county.csv"
+
+        if CSBSGateway.__instance is not None:
+            raise Exception("The system already has one instance")
+
+    @cached(cache=TTLCache(maxsize=1, ttl=1800))
+    async def get_locations(self):
+        """
+        Retrieves county locations; locations are cached for 1 hour
+
+        :returns: The locations.
+        :rtype: dict
+        """
+        data_id = "csbs.locations"
+        LOGGER.info(f"{data_id} Requesting data...")
+        # check shared cache
+        cache_results = await check_cache(data_id)
+        if cache_results:
+            LOGGER.info(f"{data_id} using shared cache results")
+            locations = cache_results
+        else:
+            LOGGER.info(f"{data_id} shared cache empty")
+            async with httputils.CLIENT_SESSION.get(self.BASE_URL) as response:
+                text = await response.text()
+
+            LOGGER.debug(f"{data_id} Data received")
+
+            data = list(csv.DictReader(text.splitlines()))
+            LOGGER.debug(f"{data_id} CSV parsed")
+
+            locations = []
+
+            for i, item in enumerate(data):
+                # General info.
+                state = item["State Name"]
+                county = item["County Name"]
+
+                # Ensure country is specified.
+                if county in {"Unassigned", "Unknown"}:
+                    continue
+
+                # Date string without "EDT" at end.
+                last_update = " ".join(item["Last Update"].split(" ")[0:2])
+
+                # Append to locations.
+                locations.append(
+                    CSBSLocation(
+                        # General info.
+                        i,
+                        state,
+                        county,
+                        # Coordinates.
+                        Coordinates(item["Latitude"], item["Longitude"]),
+                        # Last update (parse as ISO).
+                        datetime.strptime(last_update, "%Y-%m-%d %H:%M").isoformat() + "Z",
+                        # Statistics.
+                        int(item["Confirmed"] or 0),
+                        int(item["Death"] or 0),
+                    )
                 )
-            )
-        LOGGER.info(f"{data_id} Data normalized")
-        # save the results to distributed cache
-        # TODO: fix json serialization
-        try:
-            await load_cache(data_id, locations)
-        except TypeError as type_err:
-            LOGGER.error(type_err)
-
-    # Return the locations.
-    return locations
+            LOGGER.info(f"{data_id} Data normalized")
+            # save the results to distributed cache
+            # TODO: fix json serialization
+            try:
+                await load_cache(data_id, locations)
+            except TypeError as type_err:
+                LOGGER.error(type_err)
+
+        # Return the locations.
+        return locations