USAGE = '''
Usage example:

python tabs2spaces.py . 4 ".*\.py$"

'''

import io
import argparse
import os
import re

parser = argparse.ArgumentParser(description='Replace tabs with spaces.'+USAGE)
parser.add_argument('root_directory', type=str,
                   help='directory to run the script in')
parser.add_argument('spaces_for_tab', type=int, default=4, nargs='?',
                   help='number of spaces for one tab')
parser.add_argument('file_mask_regex', default=".*", nargs='?',
                   help='file name mask regex')
parser.add_argument("--head-only", action='store_true', default=True,
                   help='only change the tab in the head of each line.')

args = parser.parse_args()
file_mask_regex = re.compile(args.file_mask_regex)
replacement_spaces = ' ' * args.spaces_for_tab

print('Starting tab replacement. \
directory {0}, spaces number {1}, file mask {2}'.format(args.root_directory, args.spaces_for_tab, args.file_mask_regex))

found_files = []
for path, subdirs, files in os.walk(args.root_directory):
    for name in files:
        found_files.append(os.path.join(path, name));

matched_files = [name for name in found_files if file_mask_regex.match(name)]

for file_path in matched_files:
    print('Replacing tabs in {0}'.format(file_path))

    file_contents = ''
    with open(file_path) as f:
        file_contents = f.read()

    if args.head_only:
        file_lines = file_contents.split("\n")
        file_lines_out = []
        for line in file_lines:
            if not line.startswith("\t"):
                file_lines_out.append(line)
                continue
            else:
                head_tabs = re.findall("^\t+", line)[0]
                head_spaces = head_tabs.replace("\t", replacement_spaces)
                line = re.sub('^'+head_tabs, head_spaces, line)
                file_lines_out.append(line)
        file_contents = "\n".join(file_lines_out)
    else:
        file_contents = re.sub('\t', replacement_spaces, file_contents)


    with open(file_path, "w") as f:
        f.write(file_contents)

print('Done')