Load and dump config

.gitignore

@@ -1,4 +1,4 @@
-/.mypy_cache/
+.mypy_cache/
 /.venv/
 /PFERD.egg-info/
 __pycache__/

PFERD/__init__.py

@@ -1,2 +1,40 @@
+import argparse
+from pathlib import Path
+
+from .config import Config, ConfigDumpException, ConfigLoadException
+
+
 def main() -> None:
-    print("Hello world")
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--config", "-c",
+        type=Path,
+        metavar="PATH",
+        help="specify custom config file path",
+    )
+    parser.add_argument(
+        "--dump-config",
+        nargs="?",
+        const=True,
+        type=Path,
+        metavar="PATH",
+        help="dump current configuration to a file and exit."
+        " Uses default config file path if no path is specified",
+    )
+    args = parser.parse_args()
+
+    try:
+        config_parser = Config.load_parser(args.config)
+        config = Config(config_parser)
+    except ConfigLoadException:
+        exit(1)
+
+    if args.dump_config:
+        path = None if args.dump_config is True else args.dump_config
+        try:
+            config.dump(path)
+        except ConfigDumpException:
+            exit(1)
+        exit()
+
+    print(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")

PFERD/utils.py

@@ -1,98 +1,25 @@
+from typing import Optional
+
+
+def prompt_yes_no(query: str, default: Optional[bool]) -> bool:
     """
-A few utility bobs and bits.
-"""
-
-import re
-from pathlib import Path, PurePath
-from typing import Optional, Tuple, Union
-
-import bs4
-import requests
-
-from .progress import ProgressSettings, progress_for, size_from_headers
-
-PathLike = Union[PurePath, str, Tuple[str, ...]]
-
-
-def to_path(pathlike: PathLike) -> Path:
-    """
-    Convert a given PathLike into a Path.
-    """
-    if isinstance(pathlike, tuple):
-        return Path(*pathlike)
-    return Path(pathlike)
-
-
-Regex = Union[str, re.Pattern]
-
-
-def to_pattern(regex: Regex) -> re.Pattern:
-    """
-    Convert a regex to a re.Pattern.
-    """
-    if isinstance(regex, re.Pattern):
-        return regex
-    return re.compile(regex)
-
-
-def soupify(response: requests.Response) -> bs4.BeautifulSoup:
-    """
-    Wrap a requests response in a bs4 object.
-    """
-
-    return bs4.BeautifulSoup(response.text, "html.parser")
-
-
-def stream_to_path(
-        response: requests.Response,
-        target: Path,
-        progress_name: Optional[str] = None,
-        chunk_size: int = 1024 ** 2
-) -> None:
-    """
-    Download a requests response content to a file by streaming it. This
-    function avoids excessive memory usage when downloading large files. The
-    chunk_size is in bytes.
-
-    If progress_name is None, no progress bar will be shown. Otherwise a progress
-    bar will appear, if the download is bigger than an internal threshold.
-    """
-
-    with response:
-        length = size_from_headers(response)
-        if progress_name and length and int(length) > 1024 * 1024 * 10:  # 10 MiB
-            settings: Optional[ProgressSettings] = ProgressSettings(progress_name, length)
-        else:
-            settings = None
-
-        with open(target, 'wb') as file_descriptor:
-            with progress_for(settings) as progress:
-                for chunk in response.iter_content(chunk_size=chunk_size):
-                    file_descriptor.write(chunk)
-                    progress.advance(len(chunk))
-
-
-def prompt_yes_no(question: str, default: Optional[bool] = None) -> bool:
-    """
-    Prompts the user a yes/no question and returns their choice.
+    Asks the user a yes/no question and returns their choice.
     """
 
     if default is True:
-        prompt = "[Y/n]"
+        query += " [Y/n] "
     elif default is False:
-        prompt = "[y/N]"
+        query += " [y/N] "
     else:
-        prompt = "[y/n]"
-
-    text = f"{question} {prompt} "
-    wrong_reply = "Please reply with 'yes'/'y' or 'no'/'n'."
+        query += " [y/n] "
 
     while True:
-        response = input(text).strip().lower()
-        if response in {"yes", "ye", "y"}:
+        response = input(query).strip().lower()
+        if response == "y":
             return True
-        if response in {"no", "n"}:
+        elif response == "n":
             return False
-        if response == "" and default is not None:
+        elif response == "" and default is not None:
             return default
-        print(wrong_reply)
+
+        print("Please answer with 'y' or 'n'.")