feat(v3): show "N added / M removed" after a library scan (#686)

Completes the Refresh feature: the scanner now reports a delta so the toast can
say what changed instead of a generic confirmation.

Server: delete_missing returns both deltas from its one query -- rows pruned
(removed) and current files not yet in the DB (added) -- and the scan retains
added/removed on the terminal scan-status (previously wiped to 0). Client: the
completion toast shows "N songs added / M removed" (or "up to date"), and a scan
we merely attached to (background / Settings) toasts only when it actually
changed something, so a periodic no-op pass stays silent. library:changed now
carries the delta too.

Verified end to end: empty rescan -> added 0; add a song -> added 1; remove it
-> removed 1.


Claude-Session: https://claude.ai/code/session_01QbexxfTt8q2tAn436MqGWF

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

server.py

@@ -2586,7 +2586,10 @@ class MetadataDB:
                 self.conn.executemany("DELETE FROM songs WHERE filename = ?", [(f,) for f in stale])
                 self.conn.commit()
                 self._work_display_dirty = True   # membership changed → regroup
-            return len(stale)
+            # Report both deltas from the one query we already ran: rows pruned,
+            # and how many current files are genuinely new (not yet in the DB),
+            # so a scan can surface an "N added / M removed" summary.
+            return {"removed": len(stale), "added": len(current_filenames - db_files)}
 
     # ── Metadata enrichment (P7 — plumbing; the matcher itself is the next
     # slice) ─────────────────────────────────────────────────────────────────
@@ -5034,7 +5037,7 @@ def _stat_for_cache(f: Path) -> tuple[float, int]:
     return st.st_mtime, st.st_size
 
 
-_SCAN_STATUS_INIT = {"running": False, "stage": "idle", "total": 0, "done": 0, "current": "", "error": None, "is_first_scan": False}
+_SCAN_STATUS_INIT = {"running": False, "stage": "idle", "total": 0, "done": 0, "current": "", "error": None, "is_first_scan": False, "added": 0, "removed": 0}
 _scan_status = dict(_SCAN_STATUS_INIT)
 
 _STARTUP_STATUS_INIT = {
@@ -5364,10 +5367,12 @@ def _background_scan():
 
     current_files = {_relpath(f, dlc) for f in all_songs}
 
-    # Clean up stale DB entries
+    # Clean up stale DB entries. delete_missing reports both deltas (rows pruned
-    stale = meta_db.delete_missing(current_files)
+    # + genuinely-new files) so the scan can surface an added/removed summary.
-    if stale:
+    _delta = meta_db.delete_missing(current_files)
-        log.info("Removed %d stale DB entries", stale)
+    removed, added = _delta["removed"], _delta["added"]
+    if removed:
+        log.info("Removed %d stale DB entries", removed)
 
     # Figure out which need scanning
     to_scan = []
@@ -5405,7 +5410,7 @@ def _background_scan():
             to_scan.append((f, mtime, size, dlc))
 
     if not to_scan:
-        _scan_status = {**_SCAN_STATUS_INIT, "running": True, "stage": "complete"}
+        _scan_status = {**_SCAN_STATUS_INIT, "running": True, "stage": "complete", "added": added, "removed": removed}
         log.info("Scan: nothing new to scan (%d songs, all cached)", len(all_songs))
         return
 
@@ -5430,7 +5435,7 @@ def _background_scan():
             _scan_status["current"] = fname
 
     log.info("Scan complete: %d songs cached", len(to_scan))
-    _scan_status = {**_SCAN_STATUS_INIT, "running": True, "stage": "complete"}
+    _scan_status = {**_SCAN_STATUS_INIT, "running": True, "stage": "complete", "added": added, "removed": removed}
 
 
 _scan_kick_lock = threading.Lock()

static/v3/songs.js

@@ -2795,13 +2795,20 @@
         }
     }
     // Show a completion toast (reuses the shared fbNotify surface), suppressed
-    // while in a song. Honest + never-punishing copy; the precise "N added" count
+    // while in a song. Honest + never-punishing copy: shows the "N added / M
-    // arrives with the background-scan delta work — until then this is a generic,
+    // removed" delta from the scan when there is one, else "up to date".
-    // truthful confirmation.
     function _scanCompleteToast(sd) {
         if (document.querySelector('.screen.active') && document.querySelector('.screen.active').id === 'player') return;
         if (!window.fbNotify) return;
-        const msg = (sd && sd.error) ? 'Scan finished with an error' : 'Your library is up to date';
+        const added = (sd && sd.added) || 0, removed = (sd && sd.removed) || 0;
+        let msg;
+        if (sd && sd.error) msg = 'Scan finished with an error';
+        else if (added || removed) {
+            const parts = [];
+            if (added) parts.push(added + ' song' + (added === 1 ? '' : 's') + ' added');
+            if (removed) parts.push(removed + ' removed');
+            msg = parts.join(' · ');
+        } else msg = 'Your library is up to date';
         try { window.fbNotify.show({ title: 'Library scan complete', message: msg, icon: '🔄', accent: '#22C55E' }); } catch (e) { /* */ }
     }
     // Poll scan-status until the scan finishes, driving the button state. On
@@ -2824,8 +2831,12 @@
             if ((sawRunning && sd && !sd.running) || noopDone || ticks >= 180) {
                 clearInterval(_refreshPoll); _refreshPoll = null;
                 _setRefreshState(null);
-                if (sawRunning && window.feedBack) { try { window.feedBack.emit('library:changed', { reason: 'rescan' }); } catch (e) { /* */ } }
+                const hasDelta = sd && (((sd.added || 0) > 0) || ((sd.removed || 0) > 0));
-                if (announce) _scanCompleteToast(sd);
+                if (sawRunning && window.feedBack) { try { window.feedBack.emit('library:changed', { reason: 'rescan', added: (sd && sd.added) || 0, removed: (sd && sd.removed) || 0 }); } catch (e) { /* */ } }
+                // A user-initiated refresh always confirms; a scan we only attached
+                // to (background / Settings) toasts just when it changed something,
+                // so a periodic no-op pass stays silent.
+                if (announce || hasDelta) _scanCompleteToast(sd);
             }
         }, 1000);
     }