import re
import sys
from pathlib import Path

MEDIA = re.compile(r'@media([^{;]*prefers-reduced-motion[^{;]*)\{')
MOTION = re.compile(r'\(\s*prefers-reduced-motion\s*:\s*(reduce|no-preference)\s*\)')


def block_end(css, start):
    depth, i, quote = 1, start, None
    while depth:
        ch = css[i]
        if quote:
            if ch == '\\':
                i += 1
            elif ch == quote:
                quote = None
        elif ch in '"\'':
            quote = ch
        elif ch == '{':
            depth += 1
        elif ch == '}':
            depth -= 1
        i += 1
    return i


def without_motion(prelude):
    if ',' in prelude or re.search(r'\b(or|not|only)\b', prelude):
        raise ValueError(f'@media{prelude}')
    parts = [part.strip() for part in re.split(r'\band\b', prelude)]
    wanted = [MOTION.fullmatch(part).group(1) for part in parts if MOTION.fullmatch(part)]
    if len(wanted) != 1 or any('prefers-reduced-motion' in part and not MOTION.fullmatch(part) for part in parts):
        raise ValueError(f'@media{prelude}')
    return wanted[0], ' and '.join(part for part in parts if not MOTION.fullmatch(part))


def everyone_moves(css):
    out, i = [], 0
    while match := MEDIA.search(css, i):
        out.append(css[i:match.start()])
        end = block_end(css, match.end())
        wanted, rest = without_motion(match.group(1))
        if wanted == 'no-preference':
            inner = everyone_moves(css[match.end():end - 1])
            if not rest and inner.strip() and not inner.rstrip().endswith((';', '}')):
                inner += ';'
            out.append(f'@media {rest}{{{inner}}}' if rest else inner)
        i = end
    out.append(css[i:])
    return ''.join(out)


failed = False
for name in sys.argv[1:]:
    path = Path(name)
    before = path.read_text(encoding='utf-8')
    try:
        after = everyone_moves(before)
    except ValueError as query:
        print(f'{name}: cannot rewrite {query}', file=sys.stderr)
        failed = True
        continue
    if 'prefers-reduced-motion' in after:
        print(f'{name}: a prefers-reduced-motion query is still there', file=sys.stderr)
        failed = True
        continue
    if after != before:
        path.write_text(after, encoding='utf-8')
        print(f'{name}: motion now plays for everyone')
sys.exit(1 if failed else 0)