create a Config abstraction on the Python side

main.py

@@ -24,6 +24,7 @@ import sys
 
 sys.path.append(os.path.join(os.getcwd(), "src"))
 
+from config import Config
 import case
 import pinephone
 import ldtek_battery
@@ -33,8 +34,6 @@ from cadquery.vis import _to_assy
 from vtkmodules.vtkRenderingCore import vtkRenderWindow, vtkWindowToImageFilter
 from vtkmodules.vtkIOImage import vtkPNGWriter
 
-DEFAULT_BATTERY = "ldtek"
-
 
 logger = logging.getLogger(__name__)
 
@@ -77,29 +76,27 @@ def export_png_image(obj: cq.Workplane, file_: str, orientation: str) -> None:
     exporter.Write()
 
 
-def _model(as_assy: bool=False) -> cq.Workplane:
-    logger.info("computing model ...")
-    battery_name = os.environ.get("CASE_BATTERY", DEFAULT_BATTERY)
-    render_phone = os.environ.get("CASE_RENDER_PHONE", "") not in ("", "0")
-    render_phone_only = os.environ.get("CASE_RENDER_PHONE_ONLY", "") not in ("", "0")
+def _model(config: Config, as_assy: bool=False) -> cq.Workplane:
 
     phone = pinephone.PinePhone()
 
-    if render_phone_only:
+    if config.render_phone_only:
         return case.orient_for_printing(phone)
 
     battery = None
-    if battery_name == "ldtek":
+    if config.battery == "ldtek":
         battery = ldtek_battery.LdtekBattery()
-    return case.case(phone, battery=battery, render_phone=render_phone, as_assy=as_assy)
+    elif config.battery:
+        assert False, f"unknown battery: {battery!r}"
+    return case.case(phone, battery=battery, render_phone=config.render_phone, as_assy=as_assy)
 
 _computedModels: dict[(bool,), cq.Workplane] = {}
-def model(as_assy: bool=False) -> cq.Workplane:
+def model(config: Config, as_assy: bool=False) -> cq.Workplane:
     """ memoized wrapper around `_model` """
     global _computedModels
     key = (as_assy, )
     if key not in _computedModels:
-        _computedModels[key] = _model(as_assy=as_assy)
+        _computedModels[key] = _model(config, as_assy=as_assy)
     return _computedModels[key]
 
 def main() -> None:
@@ -117,17 +114,19 @@ def main() -> None:
 
     args = parser.parse_args()
 
+    config = Config.from_env()
+
     if args.render_phone:
-        os.environ["CASE_RENDER_PHONE"] = "1"
+        config.render_phone = args.render_phone
 
     if args.render_phone_only:
-        os.environ["CASE_RENDER_PHONE_ONLY"] = "1"
+        config.render_phone_only = args.render_phone_only
 
     if args.battery:
-        os.environ["CASE_BATTERY"] = args.battery
+        config.battery = args.battery
 
     if args.export_stl:
-        model_ = model()
+        model_ = model(config)
         logger.info("exporting stl to %s", args.export_stl)
         cq.exporters.export(model_, args.export_stl)
 
@@ -139,7 +138,7 @@ def main() -> None:
             orientation = "back"
         if "front" in args.export_png:
             orientation = "front"
-        model_ = model(as_assy=True)
+        model_ = model(config, as_assy=True)
         logger.info("exporting png to %s", args.export_png)
         export_png_image(model_, args.export_png, orientation)
 
@@ -147,7 +146,7 @@ def main() -> None:
         vtk_file = args.export_vtk
         js_var, _ext = os.path.splitext(os.path.basename(vtk_file))
         js_file = f'{vtk_file}.js'
-        model_ = model()
+        model_ = model(config)
         logger.info("exporting VTK (for web rendering) to %s", vtk_file)
         cq.exporters.export(model_, vtk_file, cq.exporters.ExportTypes.VTP)
 
@@ -168,4 +167,4 @@ if __name__ == "__main__":
 else:
     # this `result` var should be picked up by cadquery, in case we were imported by it.
     # note that we don't actually get here until the user presses the `>` render button.
-    result = model()
+    result = model(Config.from_env())

src/config.py

@@ -0,0 +1,35 @@
+import os
+
+from dataclasses import dataclass
+
+DEFAULT_BATTERY = "ldtek"
+
+@dataclass
+class Config:
+    battery: str = DEFAULT_BATTERY
+    render_phone: bool = False
+    render_phone_only: bool = False
+
+    @staticmethod
+    def from_env() -> 'Config':
+        self_ = Config()
+        self_.populate_from_env()
+        return self_
+
+    def populate_from_env(self):
+        """
+        read environment variables, updating `self` with any config discovered
+        """
+        battery = os.environ.get("CASE_BATTERY")
+        if battery is not None:
+            self.battery = battery
+
+        render_phone = os.environ.get("CASE_RENDER_PHONE")
+        if render_phone is not None:
+            self.render_phone = render_phone not in ("", "0")
+
+        render_phone_only = os.environ.get("CASE_RENDER_PHONE_ONLY")
+        if render_phone_only is not None:
+            self.render_phone_only = render_phone_only not in ("", "0")
+
+