indent-replace

#!/usr/bin/env python

import os, sys, re, base64, pathlib as pl


def indent_replace(p_list, to_tabs, n, verbose):
	p_tmp_rm, pre_src, pre_dst = None, ' '*n, '\t'
	if not to_tabs: pre_src, pre_dst = pre_dst, pre_src
	pre_sub = re.compile(fr'^({pre_src})+')
	try:
		for p in p_list:
			src_old, src_new = p.read_text(), list()
			for line in src_old.split('\n'):
				if m := pre_sub.search(line):
					line = m.group().replace(pre_src, pre_dst) + line[m.end():]
				src_new.append(line)
			src_new = '\n'.join(src_new)
			if src_old == src_new: continue

			if verbose: print(p)
			p_tmp = p.parent / (p.name + '.tmp')
			while p_tmp.exists():
				suffix = base64.urlsafe_b64encode(os.urandom(3)).decode()
				p_tmp = p.parent / (p.name + f'.tmp.{suffix}')
			p_tmp_rm = p_tmp
			p_tmp.touch(p.stat().st_mode)
			p_tmp.write_text(src_new)
			p_tmp.rename(p)
			p_tmp_rm = None
	finally:
		if p_tmp_rm: p_tmp_rm.unlink(missing_ok=True)


def main(args=None):
	import argparse
	parser = argparse.ArgumentParser(
		description='Replace tabs with spaces in all files and back.')
	parser.add_argument('files', nargs='+', help='File(s) to process.')
	parser.add_argument('-t', '--tabs',
		action='store_true', help='Replace spaces with tabs (default).')
	parser.add_argument('-s', '--spaces',
		action='store_true', help='Replace tabs with spaces.')
	parser.add_argument('-n', '--space-count',
		type=int, metavar='n', default=4,
		help='Number of spaces to replace in either direction (default: %(default)s)')
	parser.add_argument('-q', '--quiet',
		action='store_true', help='Do not print processed filenames to stdout.')
	opts = parser.parse_args(sys.argv[1:] if args is None else args)

	if opts.tabs and opts.spaces:
		parser.error( 'Both -t/--tabs or -s/--spaces'
			' options cannot be used at the same time' )

	p_list = list(map(pl.Path, opts.files))
	for p in p_list:
		if not p.is_file(): parser.error(f'Not a file: {p}')

	indent_replace( p_list,
		to_tabs=not opts.spaces,
		n=opts.space_count, verbose=not opts.quiet )

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