Add numbering mode to nn

bin/nn

@@ -100,6 +100,35 @@ def plan_parse_rename(filepath):
     return new_name, STATUS_RENAME
 
 
+def get_date_for_file(filepath, parse_mode):
+    """Resolve a date string for a file, or None if unavailable."""
+    if parse_mode:
+        date_str = None
+        if shutil.which('exiftool') is not None:
+            date_str = get_exif_date(filepath)
+        if not date_str:
+            date_str = get_file_date(filepath)
+        return date_str
+
+    # Default pattern mode: extract date from filename
+    stem = filepath.stem
+
+    # Check if already normalized (e.g. "2024-06-01 breakfast.jpg")
+    norm_match = re.match(r'^(\d{4})-(\d{2})-(\d{2}) ', filepath.name)
+    if norm_match:
+        return f'{norm_match.group(1)}-{norm_match.group(2)}-{norm_match.group(3)}'
+
+    # Try the standard pattern
+    match = PATTERN.match(stem)
+    if not match:
+        match = PATTERN.match(filepath.name)
+    if match:
+        year, month, day, _ = match.groups()
+        return f'{year}-{month}-{day}'
+
+    return None
+
+
 def collect_files(paths):
     """Resolve the list of files to process."""
     if not paths:
@@ -144,6 +173,49 @@ def build_plan(files, parse_mode):
     return plan
 
 
+def build_number_plan(files, parse_mode):
+    """Build a rename plan using sequential numbering per day."""
+    entries = []
+    for file_path in files:
+        date_str = get_date_for_file(file_path, parse_mode)
+        entries.append((file_path, date_str))
+
+    day_counter = {}
+    plan = []
+    seen_targets = {}
+
+    for file_path, date_str in entries:
+        if date_str is None:
+            plan.append((file_path, None, STATUS_NO_MATCH))
+            continue
+
+        day_counter[date_str] = day_counter.get(date_str, 0) + 1
+        seq = day_counter[date_str]
+        ext = file_path.suffix
+        new_name = f'{date_str} {seq:02d}{ext}'
+
+        if new_name == file_path.name:
+            plan.append((file_path, None, STATUS_ALREADY))
+            continue
+
+        status = STATUS_RENAME
+        target = file_path.parent / new_name
+        target_key = str(target).casefold()
+
+        if target.exists() and target.resolve() != file_path.resolve():
+            status = STATUS_CONFLICT
+        elif target_key in seen_targets:
+            prev_idx = seen_targets[target_key]
+            plan[prev_idx] = (plan[prev_idx][0], plan[prev_idx][1], STATUS_CONFLICT)
+            status = STATUS_CONFLICT
+        else:
+            seen_targets[target_key] = len(plan)
+
+        plan.append((file_path, new_name, status))
+
+    return plan
+
+
 def print_preview(plan):
     """Print a formatted preview table."""
     if not plan:
@@ -194,6 +266,15 @@ def main():
         action='store_true',
         help='Use EXIF data or file dates instead of pattern matching.',
     )
+    parser.add_argument(
+        '-n',
+        '--number',
+        action='store_true',
+        help=(
+            'Discard original filename stems and number files sequentially '
+            'per day. Combines with --parse to select the date source.'
+        ),
+    )
     parser.add_argument(
         'files',
         nargs='*',
@@ -207,7 +288,10 @@ def main():
         print('No files found.')
         sys.exit(0)
 
-    plan = build_plan(files, args.parse)
+    if args.number:
+        plan = build_number_plan(files, args.parse)
+    else:
+        plan = build_plan(files, args.parse)
     print_preview(plan)
 
     renames = sum(1 for _, _, status in plan if status == STATUS_RENAME)