Moved validation inside argparse context

Signed-off-by: Jim Martens <github@2martens.de>

src/twomartens/calendarsync/calendarsync.py

@@ -32,17 +32,10 @@ def main() -> None:
     parser = argparse.ArgumentParser(
         description="Synchronizes jekyll event collection with remote calendar",
     )
-    parser.add_argument('calendar_url', help='URL to the remote calendar ICS location')
-    parser.add_argument('event_collection_path', help='Path to event collection directory')
+    parser.add_argument('calendar_url', type=validate_url, help='URL to the remote calendar ICS location')
+    parser.add_argument('event_collection_path', type=validate_dir, help='Path to event collection directory')
     args = parser.parse_args()
     
-    # handling exceptions
-    parsed_url: ParseResult = urlparse(args.calendar_url)
-    if parsed_url.netloc == '' or parsed_url.scheme == '':
-        raise ValueError('calendar_url: The given calendar url is not a proper URL.')
-    if not isdir(args.event_collection_path):
-        raise ValueError('event_collection_path: The given event collection path is not a directory.')
-    
     sync(args.calendar_url, args.event_collection_path)
 
 
@@ -76,3 +69,31 @@ def sync(calendar_url: str, event_collection_path: str) -> None:
         event_filename = begin.date().isoformat() + '-' + event.name.replace(' ', '_') + '.markdown'
         with open(event_collection_path + event_filename, 'w', encoding='utf-8', newline='\n') as event_file:
             event_file.write(event_content)
+
+
+def validate_url(url: str) -> str:
+    """
+    Validates a URL and returns it on success.
+    
+    :param url: URL to verify
+    :return: verified URL
+    :raises: argparse.ArgumentTypeError if URL is invalid
+    """
+    parsed_url: ParseResult = urlparse(url)
+    if parsed_url.netloc == '' or parsed_url.scheme == '':
+        raise argparse.ArgumentTypeError(f"'{url}' is not a valid URL.")
+    
+    return url
+
+
+def validate_dir(directory: str) -> str:
+    """
+    Validates a directory path and returns it on success.
+    
+    :param directory: path to directory to verify
+    :return: verified directory path
+    :raises: argparse.ArgumentTypeError if directory does not exist
+    """
+    if not isdir(directory):
+        raise argparse.ArgumentTypeError(f"'{directory}' is not an existing directory.")
+    return directory