Prune stems whose source song was removed or replaced

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

desktop/stemify/library_core.py

@@ -12,6 +12,7 @@ import os
 import shutil
 import subprocess
 import time
+import unicodedata
 
 import numpy as np
 import soundfile as sf
@@ -105,3 +106,49 @@ def write_track(dest, stems, meta):
         for name in [s["file"] for s in written] + [MARKER]:
             os.replace(os.path.join(part, name), os.path.join(dest, name))
         os.rmdir(part)
+
+
+def _norm(path):
+    return unicodedata.normalize("NFC", os.path.normpath(path)).casefold()
+
+
+def find_stale(src, dst):
+    """Stems folders that no longer match the library.
+
+    Returns (orphans, changed): orphans have no source track any more (removed, renamed or
+    moved); changed still have one, but its size or mtime differs from the marker's, so the
+    stems are of an older version of the song.
+    """
+    expected = {_norm(d): p for p, d in iter_tracks(src, dst)}
+    orphans, changed = [], []
+    for root, dirs, files in os.walk(dst):
+        dirs[:] = [d for d in dirs if not d.startswith(".")]
+        if MARKER not in files:
+            continue
+        dirs[:] = []
+        source = expected.get(_norm(root))
+        if source is None:
+            orphans.append(root)
+            continue
+        try:
+            with open(os.path.join(root, MARKER)) as f:
+                m = json.load(f)
+            if [m["size"], m["mtime_ns"]] != signature(source):
+                changed.append(root)
+        except (OSError, ValueError, KeyError):
+            pass  # unreadable marker or source: leave it alone
+    return sorted(orphans), sorted(changed)
+
+
+def remove_stems(dst, folders):
+    """Delete stems folders, then any parent folders left empty (never dst itself)."""
+    dst = os.path.realpath(dst)
+    for folder in folders:
+        shutil.rmtree(folder)
+        parent = os.path.dirname(os.path.realpath(folder))
+        while parent != dst and parent.startswith(dst + os.sep):
+            try:
+                os.rmdir(parent)
+            except OSError:
+                break
+            parent = os.path.dirname(parent)