From 7de1dec3d283f1236b87d0c6f41e67dd67ee7544 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tom=C3=A1=C5=A1=20Bou=C5=A1ka?= <tomas@buvis.net>
Date: Thu, 22 Aug 2024 15:54:51 +0200
Subject: [PATCH] Allow running scripts without configuration file

---
 src/buvis/buvis/adapters/config/config.py | 64 +++++++++++++++--------
 1 file changed, 43 insertions(+), 21 deletions(-)

diff --git a/src/buvis/buvis/adapters/config/config.py b/src/buvis/buvis/adapters/config/config.py
index c6c6b05..4390395 100644
--- a/src/buvis/buvis/adapters/config/config.py
+++ b/src/buvis/buvis/adapters/config/config.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import os
 from pathlib import Path
 
 import yaml
@@ -9,8 +10,11 @@
 
 class ConfigAdapter:
     """
-    Manages configuration settings stored in a YAML file.
-    Provides functionality to load, access, and modify configuration settings.
+    Manages global runtime configuration for BUVIS scripts.
+    Provides functionality to load from YAML file, access, and modify configuration settings.
+
+    If no configuration file path is provided, then it tries to find the path from the `BUVIS_CONFIG_FILE`
+    environment variable. If the environment variable is not set, it defaults to `~/.config/buvis/config.yaml`.
     """
 
     def __init__(self: ConfigAdapter, file_path: Path | None = None) -> None:
@@ -22,38 +26,56 @@ def __init__(self: ConfigAdapter, file_path: Path | None = None) -> None:
         :raises FileNotFoundError: If the configuration file does not exist.
         """
         self._config_dict = {}
-        self.path_config_file = self._determine_config_path(file_path)
 
-        self._load_configuration()
+        existing_file_path = self._determine_config_path(file_path)
+
+        if existing_file_path is not None:
+            self.path_config_file = existing_file_path
+            self._load_configuration()
 
-    def _determine_config_path(self: ConfigAdapter, file_path: Path | None) -> Path:
+    def _determine_config_path(
+        self: ConfigAdapter,
+        file_path: Path | None,
+    ) -> Path | None:
         """
         Determines the absolute path to the configuration file.
-        When no path is provided, the defaults to '~/.config/buvis/config.yaml'.
+
+        This method attempts to resolve the configuration file path based on the provided `file_path`.
+        If `file_path` is provided and exists, it returns the absolute path. If the file does not exist,
+        it raises a FileNotFoundError.
+
+        If no `file_path` is provided, the method tries to find the path from the 'BUVIS_CONFIG_FILE'
+        environment variable. If the environment variable is not set, it defaults to '~/.config/buvis/config.yaml'.
+        If the resolved path from the environment or default exists, it returns the absolute path.
+        If it does not exist, it returns None.
 
         :param file_path: Optional path provided by the user.
         :type file_path: Path | None
-        :return: The absolute path to the configuration file.
-        :rtype: Path
+        :return: The absolute path to the configuration file or None if the default path does not exist.
+        :rtype: Path | None
+        :raises FileNotFoundError: If the provided `file_path` does not exist.
         """
-        if file_path is None:
-            file_path = Path.home() / ".config/buvis/config.yaml"
-        return Path(file_path).absolute()
+        if file_path is not None:
+            if file_path.exists():
+                return file_path.absolute()
+            message = f"The configuration file at {file_path} was not found."
+            raise FileNotFoundError(message)
+
+        # Try getting the path from environment or default to home directory
+        alternative_file_path = Path(
+            os.getenv("BUVIS_CONFIG_FILE", Path.home() / ".config/buvis/config.yaml"),
+        )
+        if alternative_file_path.exists():
+            return alternative_file_path.absolute()
+
+        return None
 
     def _load_configuration(self: ConfigAdapter) -> None:
         """
         Loads the configuration from the YAML file.
-
-        :raises FileNotFoundError: If the configuration file does not exist.
         """
-        if self.path_config_file.exists():
-            with self.path_config_file.open("r") as file:
-                self._config_dict = yaml.safe_load(file) or {}
-        else:
-            message = (
-                f"The configuration file at {self.path_config_file} was not found."
-            )
-            raise FileNotFoundError(message)
+        with self.path_config_file.open("r") as file:
+            self._config_dict = yaml.safe_load(file) or {}
 
     def set_configuration_item(self: ConfigAdapter, key: str, value: object) -> None:
         """