feat: add enviroment configuration system

.env.example

@@ -0,0 +1,2 @@
+CLIENT_ID = ''
+CLIENT_SECRET = ''

config.py

@@ -0,0 +1,99 @@
+import logging
+import os
+import typing
+from pathlib import Path
+from typing import Any, Dict, Tuple
+
+import toml
+from pydantic import BaseSettings as PydanticBaseSettings
+from pydantic.env_settings import SettingsSourceCallable
+
+log = logging.getLogger(__name__)
+
+CONFIG_PATHS: list = [
+    f"{os.getcwd()}/config.toml",
+    f"{os.getcwd()}/site/config.toml",
+    "./config.toml",
+]
+
+DEFAULT_CONFIG_PATHS = [os.path.join(os.path.dirname(__file__), "config-default.toml")]
+
+
+def determine_file_path(
+    paths: typing.Union[list, tuple], config_type: str = "default"
+) -> typing.Union[str, None]:
+    """Determine the location of a configuration file, given a list of paths."""
+    path = None
+    for file_path in paths:
+        config_file = Path(file_path)
+        if (config_file).exists():
+            path = config_file
+            log.debug(f"Found {config_type} config at {file_path}")
+            break
+    return path or None
+
+
+DEFAULT_CONFIG_PATH = determine_file_path(DEFAULT_CONFIG_PATHS)
+USER_CONFIG_PATH = determine_file_path(CONFIG_PATHS, config_type="")
+
+
+def toml_default_config_source(settings: PydanticBaseSettings) -> Dict[str, Any]:
+    """
+    A simple settings source that loads variables from a toml file.
+
+    from within the module's source folder.
+    """
+    if DEFAULT_CONFIG_PATH is not None:
+        return dict(**toml.load(DEFAULT_CONFIG_PATH))
+    return dict()
+
+
+def toml_user_config_source(settings: PydanticBaseSettings) -> Dict[str, Any]:
+    """
+    A simple settings source that loads variables from a toml file.
+
+    from within the module's source folder.
+    """
+    if USER_CONFIG_PATH is not None:
+        return dict(**toml.load(USER_CONFIG_PATH))
+    return dict()
+
+
+class BaseSettings(PydanticBaseSettings):
+    """
+    Custom Pydantic base class for settings, with a Config that also loads directly from toml.
+
+    Loading methods are from toml config files, class defaults, passed arguments, and env variables.
+    """
+
+    class Config:
+        """BaseSettings custom default Config."""
+
+        extra = "ignore"
+        env_file_encoding = "utf-8"
+
+        @classmethod
+        def customise_sources(
+            cls,
+            init_settings: SettingsSourceCallable,
+            env_settings: SettingsSourceCallable,
+            file_secret_settings: SettingsSourceCallable,
+        ) -> Tuple[SettingsSourceCallable, ...]:
+            """Modify Pydantic default settings to add toml as a source and priortise env variables."""
+            return (
+                env_settings,
+                init_settings,
+                file_secret_settings,
+                toml_user_config_source,
+                toml_default_config_source,
+            )
+
+
+class SiteConfig(BaseSettings):
+    """Pydantic model for Site Settings."""
+
+    CLIENT_ID: str
+    CLIENT_SECRET: str
+
+
+CONFIG = SiteConfig(_env_file="./.env")

main.py

@@ -3,6 +3,7 @@
 from starlette.staticfiles import StaticFiles
 from starlette.templating import Jinja2Templates
 
+from .config import CONFIG  # noqa: F401  This should be removed once configuration is used.
 
 templates = Jinja2Templates(directory="templates")
 

pyproject.toml

@@ -9,12 +9,13 @@ license = "MIT"
 
 [tool.poetry.dependencies]
 python = "^3.8"
+aiofiles = "^0.7.0"
 coloredlogs = "^15.0"
-pydantic = "^1.8.2"
-starlette = "^0.14.2"
 jinja2 = "^3.0.1"
-aiofiles = "^0.7.0"
+pydantic = "^1.8.2"
 python-dotenv = "^0.17.1"
+starlette = "^0.14.2"
+toml = "^0.10.2"
 uvicorn = {extras = ["standard"], version = "^0.13.4"}
 
 [tool.poetry.extras]