refactor: make backend selection more flexible

Author: c-wygoda

deploy_cdk/profile.py

@@ -7,4 +7,4 @@ class DeploymentProfile(BaseSettings):
     timeout: PositiveInt = 30
     aws_ecr_repository_arn: str
     image_tag_or_digest: str = "latest"
-    backend_name: str = "landsat"
+    backend_name: str = "stapi_fastapi_landsat:LandsatBackend"

lambda_handler.py

@@ -1,4 +1,5 @@
-import os
+from importlib import import_module
+from os import getenv
 
 from fastapi import FastAPI
 from mangum import Mangum
@@ -7,31 +8,23 @@
 from stapi_fastapi.backend import StapiBackend
 
 
-def get_backend(name: str) -> StapiBackend:
-    match name:
-        case "landsat":
-            from stapi_fastapi_landsat import LandsatBackend
-
-            return LandsatBackend()
-        case "blacksky":
-            from stapi_fastapi_blacksky import BlackskyBackend
-
-            return BlackskyBackend()
-        case "up42":
-            from stapi_fastapi_up42 import StatUp42Backend
-
-            return StatUp42Backend()
-        case "umbra":
-            from stapi_fastapi_umbra import UmbraBackend
-
-            return UmbraBackend()
-        case _:
-            raise TypeError("not a supported backend")
+def get_backend(import_name: str) -> StapiBackend:
+    mod, attr = import_name.split(":", maxsplit=1)
+    mod = import_module(mod)
+    backend_class = getattr(mod, attr)
+    return backend_class()
 
 
 app = FastAPI()
 app.include_router(
-    StapiRouter(backend=get_backend(os.environ.get("BACKEND_NAME", "landsat"))).router
+    StapiRouter(
+        backend=get_backend(
+            getenv(
+                "BACKEND_NAME",
+                "stapi_fastapi_landsat:LandsatBackend",
+            )
+        )
+    ).router
 )
 
 handler = Mangum(app, lifespan="off")

stapi_fastapi/__dev__.py

@@ -1,8 +1,10 @@
 #!/usr/bin/env python3
 
+from importlib import import_module
 from sys import stderr
 
 from fastapi import FastAPI
+from pydantic import field_validator
 
 try:
     from pydantic_settings import BaseSettings
@@ -12,20 +14,31 @@
     exit(1)
 
 from stapi_fastapi.api import StapiRouter
-from stapi_fastapi_tle_backend import StapiMockBackend
 
 
 class DevSettings(BaseSettings):
     port: int = 8000
     host: str = "127.0.0.1"
+    backend_name: str = "stapi_fastapi_landsat:LandsatBackend"
 
+    @field_validator("backend_name", mode="after")
+    def validate_backend(cls, value: str):
+        try:
+            mod, attr = value.split(":", maxsplit=1)
+            mod = import_module(mod)
+            attr = getattr(mod, attr)
+        except ImportError as exc:
+            raise ValueError("not a valid backend") from exc
+        return attr
 
+
+settings = DevSettings()
+backend = settings.backend_name()
 app = FastAPI(debug=True)
-app.include_router(StapiRouter(backend=StapiMockBackend()).router)
+app.include_router(StapiRouter(backend).router)
 
 
 def cli():
-    settings = DevSettings()
     run(
         "stapi_fastapi.__dev__:app", reload=True, host=settings.host, port=settings.port
     )