"""Allow running transmutate_app as a module: python -m transmutate_app <file>."""

import sys
import os
from .gui import open_file


def main():
    """CLI entry point for ``python -m transmutate_app <file>``."""
    if len(sys.argv) < 2:
        print("Usage: python -m transmutate_app <path/to/file>")
        sys.exit(1)

    filepath = sys.argv[1]
    if not os.path.isfile(filepath):
        print(f"Error: File does not exist: {filepath}", file=sys.stderr)
        sys.exit(1)

    open_file(filepath)