1import argparse
2import collections
3from typing import Dict
4from typing import Optional
5from typing import Sequence
6
7
8CRLF = b'\r\n'
9LF = b'\n'
10CR = b'\r'
11# Prefer LF to CRLF to CR, but detect CRLF before LF
12ALL_ENDINGS = (CR, CRLF, LF)
13FIX_TO_LINE_ENDING = {'cr': CR, 'crlf': CRLF, 'lf': LF}
14
15
16def _fix(filename: str, contents: bytes, ending: bytes) -> None:
17    new_contents = b''.join(
18        line.rstrip(b'\r\n') + ending for line in contents.splitlines(True)
19    )
20    with open(filename, 'wb') as f:
21        f.write(new_contents)
22
23
24def fix_filename(filename: str, fix: str) -> int:
25    with open(filename, 'rb') as f:
26        contents = f.read()
27
28    counts: Dict[bytes, int] = collections.defaultdict(int)
29
30    for line in contents.splitlines(True):
31        for ending in ALL_ENDINGS:
32            if line.endswith(ending):
33                counts[ending] += 1
34                break
35
36    # Some amount of mixed line endings
37    mixed = sum(bool(x) for x in counts.values()) > 1
38
39    if fix == 'no' or (fix == 'auto' and not mixed):
40        return mixed
41
42    if fix == 'auto':
43        max_ending = LF
44        max_lines = 0
45        # ordering is important here such that lf > crlf > cr
46        for ending_type in ALL_ENDINGS:
47            # also important, using >= to find a max that prefers the last
48            if counts[ending_type] >= max_lines:
49                max_ending = ending_type
50                max_lines = counts[ending_type]
51
52        _fix(filename, contents, max_ending)
53        return 1
54    else:
55        target_ending = FIX_TO_LINE_ENDING[fix]
56        # find if there are lines with *other* endings
57        # It's possible there's no line endings of the target type
58        counts.pop(target_ending, None)
59        other_endings = bool(sum(counts.values()))
60        if other_endings:
61            _fix(filename, contents, target_ending)
62        return other_endings
63
64
65def main(argv: Optional[Sequence[str]] = None) -> int:
66    parser = argparse.ArgumentParser()
67    parser.add_argument(
68        '-f', '--fix',
69        choices=('auto', 'no') + tuple(FIX_TO_LINE_ENDING),
70        default='auto',
71        help='Replace line ending with the specified. Default is "auto"',
72    )
73    parser.add_argument('filenames', nargs='*', help='Filenames to fix')
74    args = parser.parse_args(argv)
75
76    retv = 0
77    for filename in args.filenames:
78        if fix_filename(filename, args.fix):
79            if args.fix == 'no':
80                print(f'{filename}: mixed line endings')
81            else:
82                print(f'{filename}: fixed mixed line endings')
83            retv = 1
84    return retv
85
86
87if __name__ == '__main__':
88    exit(main())
89