feat(watch): add opt-in --backfill flag for existing archives

Co-authored-by: Belphemur <197810+Belphemur@users.noreply.github.com>

cmd/cbzoptimizer/commands/watch_command.go

@@ -41,6 +41,9 @@ func init() {
 	// Setup common flags (format, quality, override, split, timeout) with viper binding
 	setupCommonFlags(command, &converterType, 85, true, false, true)
 
+	command.Flags().Bool("backfill", false, "Optimize CBZ/CBR files that already exist in the watched folder at startup, before watching for new changes")
+	_ = viper.BindPFlag("backfill", command.Flags().Lookup("backfill"))
+
 	AddCommand(command)
 }
 func WatchCommand(_ *cobra.Command, args []string) error {
@@ -64,6 +67,8 @@ func WatchCommand(_ *cobra.Command, args []string) error {
 
 	timeout := viper.GetDuration("timeout")
 
+	backfill := viper.GetBool("backfill")
+
 	converterType := constant.FindConversionFormat(viper.GetString("format"))
 	chapterConverter, err := converter.Get(converterType)
 	if err != nil {
@@ -74,7 +79,7 @@ func WatchCommand(_ *cobra.Command, args []string) error {
 	if err != nil {
 		return fmt.Errorf("failed to prepare converter: %w", err)
 	}
-	log.Info().Str("path", path).Bool("override", override).Uint8("quality", quality).Str("format", converterType.String()).Bool("split", split).Msg("Watching directory")
+	log.Info().Str("path", path).Bool("override", override).Uint8("quality", quality).Str("format", converterType.String()).Bool("split", split).Bool("backfill", backfill).Msg("Watching directory")
 
 	watcher, err := fsnotify.NewWatcher()
 	if err != nil {
@@ -101,15 +106,18 @@ func WatchCommand(_ *cobra.Command, args []string) error {
 	defer debouncer.Stop()
 
 	// Note: existing archives already present under path when the watch
-	// starts are intentionally left untouched. Watch mode only reacts to
-	// filesystem events going forward; use the `optimize` command to process
-	// a library's existing contents. Archives inside a directory that is
-	// created/moved into the watched tree *after* startup are still
-	// back-filled below, since only the directory itself generates an
-	// fsnotify event.
+	// starts are left untouched unless --backfill is set. Watch mode only
+	// reacts to filesystem events going forward by default; use the
+	// `optimize` command (or pass --backfill) to process a library's
+	// existing contents. Archives inside a directory that is created/moved
+	// into the watched tree *after* startup are always back-filled below,
+	// since only the directory itself generates an fsnotify event.
 	if err := addRecursiveWatch(watcher, path); err != nil {
 		return fmt.Errorf("failed to watch path %s: %w", path, err)
 	}
+	if backfill {
+		backfillExistingArchives(path, debouncer.Trigger)
+	}
 
 	for {
 		select {

cmd/cbzoptimizer/commands/watch_command_test.go

@@ -170,3 +170,37 @@ func TestOptimizeQueueSkipsMissingPath(t *testing.T) {
 
 	assert.EqualValues(t, 1, atomic.LoadInt32(&calls))
 }
+
+func TestWatchCommandBackfillFlagDefaultsToFalse(t *testing.T) {
+	watchCmd, _, err := rootCmd.Find([]string{"watch"})
+	require.NoError(t, err)
+
+	flag := watchCmd.Flags().Lookup("backfill")
+	require.NotNil(t, flag, "watch command should register a --backfill flag")
+	assert.Equal(t, "false", flag.DefValue)
+	assert.Equal(t, "bool", flag.Value.Type())
+}
+
+func TestBackfillExistingArchivesOnlyInvokedWhenRequested(t *testing.T) {
+	root := t.TempDir()
+	require.NoError(t, os.WriteFile(filepath.Join(root, "chapter1.cbz"), []byte("data"), 0o644))
+
+	runBackfill := func(backfill bool) []string {
+		var found []string
+		var mu sync.Mutex
+		process := func(path string) {
+			mu.Lock()
+			defer mu.Unlock()
+			found = append(found, path)
+		}
+		// Mirrors the gating logic in WatchCommand: backfillExistingArchives
+		// must only run when the --backfill flag is set.
+		if backfill {
+			backfillExistingArchives(root, process)
+		}
+		return found
+	}
+
+	assert.Empty(t, runBackfill(false), "no pre-existing archive should be processed when backfill is disabled")
+	assert.Len(t, runBackfill(true), 1, "pre-existing archives should be processed when backfill is enabled")
+}