from typing import Optional

ATTACHMENT_EXTENSIONS = (
    ".pdf",
    ".docx",
    ".doc",
    ".xlsx",
    ".xls",
    ".zip",
    ".rar",
    ".7z",
    ".tar",
    ".gz",
)

ANTI_CRAWLER_KEYWORDS = (
    "环境异常",
    "完成验证",
    "访问过于频繁",
    "请进行验证",
    "滑动验证",
    "安全验证",
    "robot check",
    "access denied",
)

MIN_BODY_LENGTH = 60
MAX_ATTACHMENT_FILENAME_LENGTH = 120
MAX_ANTI_CRAWLER_TEXT_LENGTH = 300


def is_attachment_name(text: str) -> bool:
    s = text.strip()
    if not s or len(s) >= MAX_ATTACHMENT_FILENAME_LENGTH:
        return False
    return s.lower().endswith(ATTACHMENT_EXTENSIONS)


def is_anti_crawler(text: str) -> bool:
    s = text.strip()
    if not s or len(s) >= MAX_ANTI_CRAWLER_TEXT_LENGTH:
        return False
    return any(kw in s for kw in ANTI_CRAWLER_KEYWORDS)


def sanitize_body_text(raw_text: Optional[str]) -> Optional[str]:
    if not raw_text:
        return None
    cleaned = raw_text.strip()
    if len(cleaned) < MIN_BODY_LENGTH:
        return None
    if is_anti_crawler(cleaned):
        return None
    if is_attachment_name(cleaned):
        return None
    return cleaned