Introduce the Factory pattern via LocationServiceFactory as a way to …

…create new LocationServices in an extensible way.

app/data/__init__.py

@@ -4,18 +4,8 @@
 from ..services.location.nyt import NYTLocationService
 
 # Mapping of services to data-sources.
-DATA_SOURCES = {
-    "jhu": JhuLocationService(),
-    "csbs": CSBSLocationService(),
-    "nyt": NYTLocationService(),
-}
-
-
-def data_source(source):
-    """
-    Retrieves the provided data-source service.
-
-    :returns: The service.
-    :rtype: LocationService
-    """
-    return DATA_SOURCES.get(source.lower())
+DATA_SOURCES = [
+    "jhu",
+    "csbs",
+    "nyt",
+]

app/main.py

@@ -14,7 +14,7 @@
 from sentry_sdk.integrations.asgi import SentryAsgiMiddleware
 
 from .config import get_settings
-from .data import data_source
+from .services.location import LocationServiceFactory
 from .routers import V1, V2
 from .utils.httputils import setup_client_session, teardown_client_session
 
@@ -74,7 +74,9 @@ async def add_datasource(request: Request, call_next):
     Attach the data source to the request.state.
     """
     # Retrieve the datas ource from query param.
-    source = data_source(request.query_params.get("source", default="jhu"))
+    source_name = request.query_params.get("source", default="jhu")
+    location_service_factory = LocationServiceFactory()
+    source = location_service_factory.create(source_name)
 
     # Abort with 404 if source cannot be found.
     if not source:

app/routers/v2.py

@@ -107,4 +107,4 @@ async def sources():
     """
     Retrieves a list of data-sources that are availble to use.
     """
-    return {"sources": list(DATA_SOURCES.keys())}
+    return {"sources": DATA_SOURCES}

app/services/location/locationservicefactory.py

@@ -0,0 +1,16 @@
+
+
+from ..location.csbs import CSBSLocationService
+from ..location.jhu import JhuLocationService
+from ..location.nyt import NYTLocationService
+
+
+class LocationServiceFactory:
+    def create(location_service_name):
+        lowercase_service_name = location_service_name.lower()
+        if lowercase_service_name == 'csbs':
+            return CSBSLocationService()
+        elif lowercase_service_name == 'jhu':
+            return JhuLocationService()
+        elif lowercase_service_name == 'nyt':
+            return NYTLocationService()