"""输入防护（F-03 最小实现）。"""

from __future__ import annotations

import re

from app.utils.exceptions import AppError

_INJECTION_PATTERNS = (
    re.compile(r"(?i)ignore\s+previous\s+instructions"),
    re.compile(r"(?i)system\s*:\s*"),
    re.compile(r"(?is)(drop|delete|update|insert|alter|truncate)\s+"),
)


def validate_user_message(message: str, *, max_len: int = 8000) -> str:
    text = message.strip()
    if not text:
        raise AppError(400, "消息不能为空", error_code="INPUT_EMPTY")
    if len(text) > max_len:
        raise AppError(400, "消息过长", error_code="INPUT_OVERSIZE", audit_event="input_guard")
    for pattern in _INJECTION_PATTERNS:
        if pattern.search(text):
            raise AppError(400, "输入包含不允许的内容", error_code="INPUT_BLOCKED", audit_event="input_guard")
    return text