import os
import argparse

parser = argparse.ArgumentParser("LibEmpty", "Generates a list of the empty folders in a library.")


def is_folder_empty(folder_path):
    num_files = len(os.listdir(folder_path))
    return num_files == 0


def list_empty_folders(library_root):
    result = []
    for folder in os.listdir(library_root):
        folder = os.path.join(library_root, folder)
        if os.path.isfile(folder):
            continue
        if is_folder_empty(folder):
            result.append(folder)
    return result


def main(lib_dir, out_file):
    empty_folders = list_empty_folders(lib_dir)

    with open(out_file, 'w+') as writer:
        for folder in empty_folders:
            writer.write(folder+'\n')


def check_args(lib, out):
    fatal_errors = False
    if not os.path.exists(lib):
        print('Error: The library root does not exist %s' % lib)
        fatal_errors = True
    if os.path.exists(out):
        print('The file %s will be overwritten.' % out)
    if fatal_errors:
        parser.print_help()
        print('Exiting...')
        exit(-1)


if __name__ == '__main__':
    parser.add_argument('-l', '--lib_root', required=True, help='The root directory of the library.')
    parser.add_argument('-o', '--output', required=True, help='The path to the output file.')

    args = parser.parse_args()

    lib_root = args.lib_root
    out_path = args.output

    check_args(lib_root, out_path)
    main(lib_root, out_path)