feat: add metadata enrichers & refactor

lrcfetch/enrichers/base.py

@@ -0,0 +1,31 @@
+"""
+Author: Uyanide pywang0608@foxmail.com
+Date: 2026-03-31 06:08:16
+Description: Base class for metadata enrichers
+"""
+
+from abc import ABC, abstractmethod
+from typing import Optional
+
+from ..models import TrackMeta
+
+
+class BaseEnricher(ABC):
+    """Attempts to fill missing fields on a TrackMeta.
+
+    Each enricher inspects the track, and returns a dict of field names
+    to values for any fields it can provide.  Only fields that are
+    currently ``None`` on the track will actually be applied.
+    """
+
+    @property
+    @abstractmethod
+    def name(self) -> str: ...
+
+    @abstractmethod
+    def enrich(self, track: TrackMeta) -> Optional[dict]:
+        """Return a dict of {field_name: value} for fields this enricher can fill.
+
+        Return None or an empty dict if nothing can be contributed.
+        """
+        ...