#!/usr/bin/python3

"""Rename 'bad' characters to underscores in a filesystem hierarchy."""

import os
import sys

# We map these to underscores, for the sake of my Android phone which is probably using a FAT filesystem
BAD_CHARACTERS = set(':()[]&!?"\'\\*')


def contains_bad_char(filename):
    """Return True iff filename contains one of the 'bad characters'."""
    return bool(set(filename) & BAD_CHARACTERS)


def obtain_dirnames(root):
    """Get the troublesome directories in root."""
    # Note that this sometimes needs to be run more than once, but it gets where we're going after a run or two
    troublesome_paths = []
    for root, directories, filenames in os.walk(root, topdown=False):
        for dirname in directories:
            path = os.path.join(root, dirname)
            if contains_bad_char(path):
                sys.stderr.write('Got bad path {}\n'.format(path))
                troublesome_paths.append(path)
    troublesome_paths.sort()
    return troublesome_paths


def obtain_filenames(root):
    """Get the troublesome regular (non-directory) filenames in root."""
    troublesome_paths = []
    for root, directories, filenames in os.walk(root):
        for filename in filenames:
            path = os.path.join(root, filename)
            if contains_bad_char(path):
                sys.stderr.write('Got bad path {}\n'.format(path))
                troublesome_paths.append(path)
    troublesome_paths.sort()
    return troublesome_paths


def replace(old_filename):
    """Replace bad characters with underscore."""
    new_filename = old_filename
    for bad_char in BAD_CHARACTERS:
        new_filename = new_filename.replace(bad_char, '_')
    return new_filename


def main():
    """Kick off replacement in each directory hierarchy specified in argv[1:]."""
    for directory in sys.argv[1:]:
        # We do directories first.
        dirnames = obtain_dirnames(directory)
        for old_dirname in dirnames:
            new_dirname = replace(old_dirname)
            sys.stderr.write('Renaming directory {} to {}\n'.format(old_dirname, new_dirname))
            os.rename(old_dirname, new_dirname)

        # Then we re-traverse to get filenames
        filenames = obtain_filenames(directory)
        for old_filename in filenames:
            new_filename = replace(old_filename)
            sys.stderr.write('Renaming {} to {}\n'.format(old_filename, new_filename))
            os.rename(old_filename, new_filename)


main()