refactor: Phase C — découpe scanner.rs et analyzer.rs en sous-fonctions

scanner.rs:
- Extrait should_skip_deletions() — logique pure de sécurité anti-suppression (testable)
- Extrait handle_stale_deletions() — gestion des fichiers disparus du disque
- Extrait upsert_directory_mtimes() — sauvegarde des mtimes pour scan incrémental
- 6 tests unitaires pour should_skip_deletions (volume démonté, DB vide, cas normal, etc.)

analyzer.rs:
- Extrait spawn_cancellation_poller() — polling d'annulation de job réutilisable

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/indexer/src/analyzer.rs

@@ -353,22 +353,7 @@ pub async fn analyze_library_books(
         total, thumbnail_only, concurrency
     );
 
-    let cancelled_flag = Arc::new(AtomicBool::new(false));
+    let (cancelled_flag, cancel_handle) = spawn_cancellation_poller(state.pool.clone(), job_id);
-    let cancel_pool = state.pool.clone();
-    let cancel_flag_for_poller = cancelled_flag.clone();
-    let cancel_handle = tokio::spawn(async move {
-        loop {
-            tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
-            match is_job_cancelled(&cancel_pool, job_id).await {
-                Ok(true) => {
-                    cancel_flag_for_poller.store(true, Ordering::Relaxed);
-                    break;
-                }
-                Ok(false) => {}
-                Err(_) => break,
-            }
-        }
-    });
 
     #[derive(Clone)]
     struct BookTask {
@@ -845,3 +830,27 @@ pub async fn cleanup_orphaned_thumbnails(state: &AppState) -> Result<()> {
     info!("[ANALYZER] Deleted {} orphaned thumbnail files", deleted_count);
     Ok(())
 }
+
+/// Spawn a background task that polls for job cancellation every 2 seconds.
+/// Returns the shared cancellation flag and the task handle.
+fn spawn_cancellation_poller(
+    pool: sqlx::PgPool,
+    job_id: Uuid,
+) -> (Arc<AtomicBool>, tokio::task::JoinHandle<()>) {
+    let flag = Arc::new(AtomicBool::new(false));
+    let flag_clone = flag.clone();
+    let handle = tokio::spawn(async move {
+        loop {
+            tokio::time::sleep(tokio::time::Duration::from_secs(2)).await;
+            match is_job_cancelled(&pool, job_id).await {
+                Ok(true) => {
+                    flag_clone.store(true, Ordering::Relaxed);
+                    break;
+                }
+                Ok(false) => {}
+                Err(_) => break,
+            }
+        }
+    });
+    (flag, handle)
+}

apps/indexer/src/scanner.rs

@@ -501,20 +501,38 @@ pub async fn scan_library_discovery(
         library_id, library_processed_count, stats.indexed_files, stats.errors
     );
 
-    // Handle deletions — with safety check against volume mount failures
+    handle_stale_deletions(state, library_id, root, &existing, &seen, stats).await?;
+    upsert_directory_mtimes(state, library_id, &new_dir_mtimes).await;
+
+    Ok(())
+}
+
+/// Determine whether file deletions should be skipped based on safety heuristics.
+/// Returns true if deletions should be skipped (e.g., volume not mounted).
+fn should_skip_deletions(root_accessible: bool, seen_count: usize, existing_count: usize, stale_count: usize) -> bool {
+    !root_accessible
+        || (seen_count == 0 && existing_count > 0)
+        || (stale_count > 0 && stale_count == existing_count)
+}
+
+/// Handle deletion of stale files (files in DB but no longer on disk).
+/// Includes safety checks to prevent mass deletion if volume is unmounted.
+async fn handle_stale_deletions(
+    state: &AppState,
+    library_id: Uuid,
+    root: &Path,
+    existing: &HashMap<String, (Uuid, Uuid, String)>,
+    seen: &HashMap<String, bool>,
+    stats: &mut JobStats,
+) -> Result<()> {
     let existing_count = existing.len();
     let seen_count = seen.len();
     let stale_count = existing.iter().filter(|(p, _)| !seen.contains_key(p.as_str())).count();
 
-    // Safety: if the library root is not accessible, or if we found zero files
-    // but the DB had many, the volume is probably not mounted correctly.
-    // Do NOT delete anything in that case.
     let root_accessible = root.is_dir() && std::fs::read_dir(root).is_ok();
-    let skip_deletions = !root_accessible
-        || (seen_count == 0 && existing_count > 0)
-        || (stale_count > 0 && stale_count == existing_count);
 
-    if skip_deletions && stale_count > 0 {
+    if should_skip_deletions(root_accessible, seen_count, existing_count, stale_count) {
+        if stale_count > 0 {
             warn!(
                 "[SCAN] Skipping deletion of {} stale files for library {} — \
                  root accessible={}, seen={}, existing={}. \
@@ -522,9 +540,12 @@ pub async fn scan_library_discovery(
                 stale_count, library_id, root_accessible, seen_count, existing_count
             );
             stats.warnings += stale_count;
-    } else {
+        }
+        return Ok(());
+    }
+
     let mut removed_count = 0usize;
-        for (abs_path, (file_id, book_id, _)) in &existing {
+    for (abs_path, (file_id, book_id, _)) in existing {
         if seen.contains_key(abs_path) {
             continue;
         }
@@ -543,15 +564,22 @@ pub async fn scan_library_discovery(
     }
 
     if removed_count > 0 {
-            info!(
+        info!("[SCAN] Removed {} stale files from database", removed_count);
-                "[SCAN] Removed {} stale files from database",
+    }
-                removed_count
+
-            );
+    Ok(())
-        }
+}
+
+/// Save directory modification times to DB for incremental scan optimization.
+async fn upsert_directory_mtimes(
+    state: &AppState,
+    library_id: Uuid,
+    new_dir_mtimes: &[(String, DateTime<Utc>)],
+) {
+    if new_dir_mtimes.is_empty() {
+        return;
     }
 
-    // Upsert directory mtimes for next incremental scan
-    if !new_dir_mtimes.is_empty() {
     let dir_paths_db: Vec<String> = new_dir_mtimes
         .iter()
         .map(|(local, _)| utils::unmap_libraries_path(local))
@@ -575,7 +603,43 @@ pub async fn scan_library_discovery(
     {
         warn!("[SCAN] Failed to upsert directory mtimes: {}", e);
     }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn skip_deletions_when_root_not_accessible() {
+        assert!(should_skip_deletions(false, 10, 10, 5));
     }
 
-    Ok(())
+    #[test]
+    fn skip_deletions_when_no_files_seen_but_existing() {
+        // Volume probably not mounted — saw 0 files but DB has 50
+        assert!(should_skip_deletions(true, 0, 50, 50));
+    }
+
+    #[test]
+    fn skip_deletions_when_all_existing_are_stale() {
+        // Every DB file is stale — suspicious, skip
+        assert!(should_skip_deletions(true, 5, 10, 10));
+    }
+
+    #[test]
+    fn allow_deletions_normal_case() {
+        // Some stale files but most are still present — normal
+        assert!(!should_skip_deletions(true, 45, 50, 5));
+    }
+
+    #[test]
+    fn allow_deletions_no_stale() {
+        assert!(!should_skip_deletions(true, 50, 50, 0));
+    }
+
+    #[test]
+    fn allow_deletions_empty_db() {
+        // No existing files in DB — nothing to delete anyway
+        assert!(!should_skip_deletions(true, 10, 0, 0));
+    }
 }