Refactor, make default notrim

yt_dlp/__init__.py

@@ -1,3 +1,4 @@
+import codecs
 import sys
 
 if sys.version_info < (3, 9):
@@ -429,6 +430,21 @@ def validate_options(opts):
     }
 
     # Other options
+    opts.trim_file_name_mode = 'c'
+    if opts.trim_file_name is not None:
+        mobj = re.match(r'(?:(?P<length>\d+)(?P<mode>b|c)?|notrim)', opts.trim_file_name)
+        validate(mobj, 'trim filenames', opts.trim_file_name)
+        if opts.trim_file_name == 'notrim':
+            opts.trim_file_name = 0
+        else:
+            opts.trim_file_name = int(mobj.group('length'))
+            opts.trim_file_name_mode = mobj.group('mode') or 'c'
+    if opts.filesystem_encoding is not None:
+        try:
+            codecs.lookup(opts.filesystem_encoding)
+        except LookupError:
+            raise ValueError(f'Invalid filesystem encoding: {opts.filesystem_encoding}')
+
     if opts.playlist_items is not None:
         try:
             tuple(PlaylistEntries.parse_playlist_items(opts.playlist_items))
@@ -886,6 +902,7 @@ def parse_options(argv=None):
         'max_downloads': opts.max_downloads,
         'prefer_free_formats': opts.prefer_free_formats,
         'trim_file_name': opts.trim_file_name,
+        'trim_file_name_mode': opts.trim_file_name_mode,
         'filesystem_encoding': opts.filesystem_encoding,
         'verbose': opts.verbose,
         'dump_intermediate_pages': opts.dump_intermediate_pages,