Add config handler

pyproject.toml

@@ -3,7 +3,12 @@ name = "event_management"
 version = "0.1.0"
 description = "Backed part of the final project assignment for AP7PD"
 authors = [{ name = "Peter Vacho", email = "p_vacho@utb.cz" }]
-dependencies = ["fastapi>=0.115.5", "uvicorn>=0.32.1", "poethepoet>=0.31.1"]
+dependencies = [
+    "fastapi>=0.115.5",
+    "uvicorn>=0.32.1",
+    "poethepoet>=0.31.1",
+    "python-decouple>=3.8",
+]
 readme = "README.md"
 requires-python = ">= 3.12"
 license = { text = "GPL-3.0-or-later" }

requirements-dev.lock

@@ -46,6 +46,8 @@ pydantic==2.10.2
     # via fastapi
 pydantic-core==2.27.1
     # via pydantic
+python-decouple==3.8
+    # via event-management
 pyyaml==6.0.2
     # via poethepoet
     # via pre-commit

requirements.lock

@@ -30,6 +30,8 @@ pydantic==2.10.2
     # via fastapi
 pydantic-core==2.27.1
     # via pydantic
+python-decouple==3.8
+    # via event-management
 pyyaml==6.0.2
     # via poethepoet
 sniffio==1.3.1

src/utils/config.py

@@ -0,0 +1,91 @@
+"""File containing a typed wrapper function around ``decouple.config``."""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from typing import Any, NewType, TypeVar, cast, overload
+
+from decouple import UndefinedValueError, config
+
+__all__ = ["get_config"]
+
+T = TypeVar("T")
+U = TypeVar("U")
+Sentinel = NewType("Sentinel", object)
+_MISSING = cast(Sentinel, object())
+
+
+@overload
+def get_config(
+    search_path: str,
+    *,
+    cast: None = None,
+    default: U | Sentinel = _MISSING,
+) -> str | U: ...
+
+
+@overload
+def get_config(
+    search_path: str,
+    *,
+    cast: Callable[[str], T],
+    default: U | Sentinel = _MISSING,
+) -> T | U: ...
+
+
+def get_config(
+    search_path: str,
+    *,
+    cast: Callable[[str], object] | None = None,
+    default: object = _MISSING,
+) -> object:
+    """Typed wrapper around ``decouple.config`` for static type analysis."""
+    try:
+        val = config(search_path)
+    except UndefinedValueError as exc:
+        if default is not _MISSING:
+            return default
+        raise exc from exc
+
+    # Treat empty strings as unset values
+    if val == "":
+        if default is not _MISSING:
+            return default
+
+        raise UndefinedValueError(
+            f"{search_path} was found, but the content was an empty string. "
+            "Set a non-empty value for the envvar or define a default value."
+        )
+
+    # We run this again, this time with a cast function.
+    # the reason we don't do this immediately is that the empty strings might not
+    # work with the cast function, which could raise various exceptions.
+    if cast is None:
+        cast = lambda x: x
+    return config(search_path, cast=cast)
+
+
+@overload
+def config_cast_list(cast: None = None) -> Callable[[str], list[str]]: ...
+
+
+@overload
+def config_cast_list(cast: Callable[[str], T]) -> Callable[[str], list[T]]: ...
+
+
+def config_cast_list(cast: Callable[[str], object] | None = None) -> Callable[[str], list[Any]]:
+    """Cast function to convert the content of an environmental variable to a list of values.
+
+    This works by splitting the contents of the environmental variable on `,` characters.
+    Currently, there is not support for escaping here, so list variables that require `,`
+    symbol to be present will not work.
+
+    You can use this function in :func:`get_config` for the ``cast`` argument.
+    """
+    if cast is None or cast is str:  # type: ignore[reportUnnecessaryComparison]  # str is infact a subtype of (str) -> object
+        cast = lambda x: x
+
+    def inner(raw_value: str) -> list[Any]:
+        return [cast(x) for x in raw_value.split(",") if x]
+
+    return inner