"""Ground explicit discussion-group bounds only from direct user messages."""
from __future__ import annotations

import re


def requested_mode(messages: object) -> str | None:
    mode = None
    if not isinstance(messages, list):
        return mode
    for message in messages:
        if not isinstance(message, dict) or message.get("role") != "user" or not isinstance(message.get("text"), str):
            continue
        text = re.sub(r"```[\s\S]*?```|https?://\S+", "", message["text"])
        text = re.sub(r'“[^”]*”|‘[^’]*’|「[^」]*」|『[^』]*』|"[^"\n]*"|`[^`\n]*`', "", text)
        current = None
        changed = False
        for clause in re.split(r"[，,。；;！？!?\n]", text):
            if clause.lstrip().startswith(">") or re.search(r"例如|比如|示例|(?:网页|页面|原文)(?:上)?(?:说|写|显示)|引用", clause):
                continue
            if re.search(r"不限(?:制)?(?:讨论组|评论组)|不限制(?:讨论组|评论组)(?:数|数量|范围)?|(?:不再只|不要只|改为全部|改为所有)[^。；\n]{0,18}(?:讨论|评论)", clause):
                current, changed = None, True
                continue
            first = re.search(r"(?:只|仅|限定)[^。；;\n]{0,18}(?:(?:第一|第1|首)(?:组|个)(?:讨论|评论)|(?:讨论|评论)(?:区)?(?:的)?(?:第一|第1)组)", clause)
            one = re.search(r"(?:只|仅|限定)[^。；;\n]{0,16}(?:(?:一|1)(?:个|组)(?:讨论|评论)(?:组)?|(?:讨论|评论)组(?:只|仅)?(?:一|1)个)", clause)
            found = first or one
            if found and not re.search(r"(?:不要|不用|别|不必|不需要|不是|不)[^，,]{0,4}$", clause[:found.start()]):
                current = "first" if first else current or "one"
                changed = True
        if changed:
            mode = current
    return mode