Add ConfigFile

great_ai/src/great_ai/utilities/config_file/config_file.py

@@ -0,0 +1,52 @@
+from pathlib import Path
+import os
+from typing import Dict, Union
+
+from ..logger import get_logger
+from .parse_error import ParseError
+from .pattern import pattern
+
+ENVIRONMENT_VARIABLE_KEY_PREFIX = 'ENV'
+
+logger = get_logger('ConfigFile')
+
+class ConfigFile:
+    def __init__(self, path: Union[Path, str], ignore_missing_environment_variables:bool=False) -> None:
+        if not isinstance(path, Path):
+            path = Path(path)
+        self._path = path
+        self._ignore_missing_environment_variables = ignore_missing_environment_variables
+        self._key_values: Dict[str, str] = {}
+
+        self._parse()
+
+    def _parse(self):
+        with open(self._path, encoding='utf-8') as f:
+            lines: str = f.read()
+
+        matches = pattern.findall(lines)
+        for key, *values in matches:
+            if key in self._key_values:
+                raise KeyError(f'Key `{key}` has been already defined and its value is `{value}`')
+
+            try:
+                value = next(v for v in values if v)
+            except StopIteration:
+                raise ParseError(f'Cannot parse config file ({self._path.absolute()}), error at key `{key}`')
+
+            if value.startswith(f'{ENVIRONMENT_VARIABLE_KEY_PREFIX}:'):
+                _, value = value.split(':')
+                if value not in os.environ:
+                    issue = f'The value of `{key}` contains the "{ENVIRONMENT_VARIABLE_KEY_PREFIX}` prefix but `{value}` is not defined as an environment variable'
+                    if self._ignore_missing_environment_variables:
+                        logger.warning(f'{issue}, defaulting to `None`')
+                    else:
+                        raise KeyError(issue)
+                value = os.environ[value]
+            
+            self._key_values[key] = value
+
+    def __getattr__(self, key: str) -> str:
+        if key in self._key_values:
+            return self._key_values[key]
+        raise KeyError(f'Key `{key}` is not found in configuration file ({self._path.absolute()})')