Load and dump config

PFERD/config.py

@@ -0,0 +1,101 @@
+import configparser
+import os
+from pathlib import Path
+from typing import Optional
+
+from .utils import prompt_yes_no
+
+
+class ConfigLoadException(Exception):
+    pass
+
+
+class ConfigDumpException(Exception):
+    pass
+
+
+class Config:
+    @staticmethod
+    def _default_path() -> Path:
+        if os.name == "posix":
+            return Path("~/.config/PFERD/pferd.cfg").expanduser()
+        elif os.name == "nt":
+            return Path("~/AppData/Roaming/PFERD/pferd.cfg").expanduser()
+        else:
+            return Path("~/.pferd.cfg").expanduser()
+
+    def __init__(self, parser: configparser.ConfigParser):
+        self._parser = parser
+        # TODO Load and validate config into dataclasses
+
+    @staticmethod
+    def _fail_load(path: Path, reason: str) -> None:
+        print(f"Failed to load config file at {path}")
+        print(f"Reason: {reason}")
+        raise ConfigLoadException()
+
+    @staticmethod
+    def load_parser(path: Optional[Path] = None) -> configparser.ConfigParser:
+        """
+        May throw a ConfigLoadException.
+        """
+
+        if not path:
+            path = Config._default_path()
+
+        parser = configparser.ConfigParser()
+
+        # Using config.read_file instead of config.read because config.read
+        # would just ignore a missing file and carry on.
+        try:
+            with open(path) as f:
+                parser.read_file(f, source=str(path))
+        except FileNotFoundError:
+            Config._fail_load(path, "File does not exist")
+        except IsADirectoryError:
+            Config._fail_load(path, "That's a directory, not a file")
+        except PermissionError:
+            Config._fail_load(path, "Insufficient permissions")
+
+        return parser
+
+    @staticmethod
+    def _fail_dump(path: Path, reason: str) -> None:
+        print(f"Failed to dump config file to {path}")
+        print(f"Reason: {reason}")
+        raise ConfigDumpException()
+
+    def dump(self, path: Optional[Path] = None) -> None:
+        """
+        May throw a ConfigDumpException.
+        """
+
+        if not path:
+            path = self._default_path()
+
+        print(f"Dumping config to {path}")
+
+        try:
+            path.parent.mkdir(parents=True, exist_ok=True)
+        except PermissionError:
+            self._fail_dump(path, "Could not create parent directory")
+
+        try:
+            # Ensuring we don't accidentally overwrite any existing files by
+            # always asking before overwriting a file.
+            try:
+                # x = open for exclusive creation, failing if the file already
+                # exists
+                with open(path, "x") as f:
+                    self._parser.write(f)
+            except FileExistsError:
+                print("That file already exists.")
+                if prompt_yes_no("Overwrite it?", default=False):
+                    with open(path, "w") as f:
+                        self._parser.write(f)
+                else:
+                    self._fail_dump(path, "File already exists")
+        except IsADirectoryError:
+            self._fail_dump(path, "That's a directory, not a file")
+        except PermissionError:
+            self._fail_dump(path, "Insufficient permissions")