#!/usr/bin/env python3
"""
Decode base64 file names inside the Chinese celeb dataset directory.

Default target: /Users/chenchaoyun/Downloads/chinese_celeb_dataset.
Use --root to override; --dry-run only prints the plan.
"""
import argparse
import base64
from pathlib import Path
import sys

DEFAULT_ROOT = Path("/Users/chenchaoyun/Downloads/chinese_celeb_dataset")


def _decode_basename(encoded: str) -> str:
    padding = "=" * ((4 - len(encoded) % 4) % 4)
    try:
        return base64.urlsafe_b64decode(
            (encoded + padding).encode("ascii")).decode("utf-8")
    except Exception:
        return encoded


def rename_dataset(root: Path, dry_run: bool = False) -> int:
    if not root.exists():
        print(f"Directory does not exist: {root}", file=sys.stderr)
        return 1
    if not root.is_dir():
        print(f"Not a directory: {root}", file=sys.stderr)
        return 1

    renamed = 0
    for file_path in sorted(root.rglob("*")):
        if not file_path.is_file():
            continue
        decoded = _decode_basename(file_path.stem)
        if decoded == file_path.stem:
            continue

        new_path = file_path.with_name(f"{decoded}{file_path.suffix}")
        if new_path == file_path:
            continue

        # Append a counter if the decoded target already exists
        counter = 1
        while new_path.exists() and new_path != file_path:
            new_path = file_path.with_name(
                f"{decoded}_{counter}{file_path.suffix}"
            )
            counter += 1

        print(f"{file_path} -> {new_path}")
        if dry_run:
            continue
        file_path.rename(new_path)
        renamed += 1

    print(f"Renamed {renamed} files")
    return 0


def parse_args() -> argparse.Namespace:
    parser = argparse.ArgumentParser(
        description="Decode chinese_celeb_dataset file names")
    parser.add_argument(
        "--root",
        type=Path,
        default=DEFAULT_ROOT,
        help="Dataset root directory (default: %(default)s)",
    )
    parser.add_argument(
        "--dry-run",
        action="store_true",
        help="Only print planned renames without applying them",
    )
    return parser.parse_args()


def main() -> int:
    args = parse_args()
    return rename_dataset(args.root.expanduser().resolve(), args.dry_run)


if __name__ == "__main__":
    sys.exit(main())