create config object (#8)

src/banks/config.py

@@ -1,14 +1,38 @@
+import json
 import os
 from pathlib import Path
+from typing import Any
 
 from platformdirs import user_data_path
 
 from .utils import strtobool
 
 
-class BanksConfig:
-    ASYNC_ENABLED: bool = strtobool(os.environ.get("BANKS_ASYNC_ENABLED", "false"))
-    USER_DATA_PATH: Path = Path(os.environ.get("BANKS_USER_DATA_PATH", "")) or user_data_path("banks")
+class _BanksConfig:
+    ASYNC_ENABLED: bool = False
+    USER_DATA_PATH: Path = user_data_path("banks")
 
+    def __init__(self, env_var_prefix: str = "BANKS_"):
+        self._env_var_prefix = env_var_prefix
 
-config = BanksConfig()
+    def __getattribute__(self, name: str) -> Any:
+        # Raise an attribute error if the name of the config is unknown
+        original_value = super().__getattribute__(name)
+
+        # Env var takes precedence
+        prefix = super().__getattribute__("_env_var_prefix")
+        value = os.environ.get(f"{prefix}{name}")
+        if value is None:
+            return original_value
+
+        # Convert string from env var to the actual type
+        t = super().__getattribute__("__annotations__")[name]
+        if t == bool:
+            value = strtobool(value)
+        else:
+            value = t(value)
+
+        return value
+
+
+config = _BanksConfig()

tests/test_config.py

@@ -0,0 +1,37 @@
+from pathlib import Path
+
+from platformdirs import user_data_path
+
+from banks.config import _BanksConfig
+
+
+def test_config_defaults():
+    c = _BanksConfig()
+    assert c.ASYNC_ENABLED == False
+    assert c.USER_DATA_PATH == user_data_path("banks")
+
+
+def test_config_env_override(monkeypatch):
+    c = _BanksConfig()
+    monkeypatch.setenv("BANKS_ASYNC_ENABLED", "true")
+    assert c.ASYNC_ENABLED == True
+    monkeypatch.setenv("BANKS_ASYNC_ENABLED", "false")
+    assert c.ASYNC_ENABLED == False
+    monkeypatch.setenv("BANKS_USER_DATA_PATH", "/")
+    assert c.USER_DATA_PATH == Path("/")
+
+    class TestConfig(_BanksConfig):
+        FOO: int = 0
+
+    c = TestConfig()
+    assert c.FOO == 0
+    monkeypatch.setenv("BANKS_FOO", "42")
+    assert c.FOO == 42
+
+
+def test_config_env_prefix(monkeypatch):
+    c = _BanksConfig("BANKS_TEST_")
+    monkeypatch.setenv("BANKS_ASYNC_ENABLED", "true")
+    assert c.ASYNC_ENABLED == False
+    monkeypatch.setenv("BANKS_TEST_ASYNC_ENABLED", "true")
+    assert c.ASYNC_ENABLED == True