import re

_TIMESTAMP_RE = re.compile(r'\[\d{2}:\d{2}\.\d{2,3}\]')
_META_TAG_RE = re.compile(r'\[[a-zA-Z]+:[^\]]*\]')


def ensure_newlines(text: str | None) -> str:
    """确保歌词每行之间有换行符，保留时间戳等原始内容"""
    if not text:
        return ''
    # 将字面量 \\n / \\r 转为真正换行符
    text = text.replace('\\n', '\n').replace('\\r', '')
    lines = [line.strip() for line in text.splitlines() if line.strip()]
    return '\n'.join(lines)


def strip_timestamps(text: str | None) -> str:
    if not text:
        return ''
    text = _META_TAG_RE.sub('', text)
    text = _TIMESTAMP_RE.sub('', text)
    lines = [line.strip() for line in text.splitlines() if line.strip()]
    return '\n'.join(lines)