feat: staging-dir + clean import_album library helpers

worker/lyra_worker/library.py

@@ -1,4 +1,6 @@
+import os
 import re
+import shutil
 
 from lyra_worker.types import MBTarget
 
@@ -17,3 +19,46 @@ def album_dir(dest_root: str, target: MBTarget) -> str:
     if target.year:
         album = f"{album} ({target.year})"
     return f"{dest_root}/{safe_name(target.artist)}/{album}"
+
+
+_AUDIO_EXT = {".flac", ".mp3", ".m4a", ".opus", ".ogg", ".aac", ".wav"}
+_COVER_STEMS = {"cover", "folder", "front"}
+_COVER_EXT = {".jpg", ".jpeg", ".png"}
+
+
+def staging_dir(dest_root: str, job_id: str) -> str:
+    """A per-job download staging directory, on the same filesystem as the library."""
+    return f"{dest_root}/.staging/{job_id}"
+
+
+def clear_staging_root(dest_root: str) -> None:
+    """Remove every staging dir (called at worker startup to sweep crash orphans)."""
+    shutil.rmtree(f"{dest_root}/.staging", ignore_errors=True)
+
+
+def _find_cover(staging: str) -> str | None:
+    for root, _dirs, files in os.walk(staging):
+        for name in sorted(files):
+            stem, ext = os.path.splitext(name)
+            if ext.lower() in _COVER_EXT and stem.lower() in _COVER_STEMS:
+                return os.path.join(root, name)
+    return None
+
+
+def import_album(staging: str, final: str) -> str:
+    """Move the album's audio files (+ one cover image) from `staging` into a fresh `final`,
+    replacing any existing folder there. Non-audio artifacts and nested subfolders are left
+    behind (the caller removes `staging`). Tolerates a missing `staging`. Returns `final`."""
+    if os.path.isdir(final):
+        shutil.rmtree(final)
+    os.makedirs(final, exist_ok=True)
+    if not os.path.isdir(staging):
+        return final
+    for name in sorted(os.listdir(staging)):
+        src = os.path.join(staging, name)
+        if os.path.isfile(src) and os.path.splitext(name)[1].lower() in _AUDIO_EXT:
+            shutil.move(src, os.path.join(final, name))
+    cover = _find_cover(staging)
+    if cover is not None:
+        shutil.move(cover, os.path.join(final, "cover.jpg"))
+    return final