"""链接解析：把用户随手粘的东西还原成 aweme_id。

支持的输入形态：
  7xxxxxxxxxxxxxxxxxx                     裸 id
  https://v.douyin.com/xxxxxxx/           分享短链（需要一次网络跳转）
  4.53 复制打开抖音... https://v.douyin.com/xxx/ ...  整段分享口令
  https://www.douyin.com/video/7xxxxxx
  https://www.douyin.com/note/7xxxxxx     图文
  https://www.douyin.com/?modal_id=7xxxxxx
  https://www.iesdouyin.com/share/video/7xxxxxx/
"""

from __future__ import annotations

import re
from typing import Optional

import requests

# 从一段中文分享口令里把 url 抠出来
URL_RE = re.compile(r"https?://[-\w./?=&%#:]+")

SHORT_HOSTS = ("v.douyin.com", "v.iesdouyin.com")

# 按优先级尝试的 id 提取规则
ID_PATTERNS = (
    re.compile(r"/(?:video|note|slides|share/video|share/note)/(\d{15,25})"),
    re.compile(r"[?&](?:modal_id|aweme_id|item_ids|vid)=(\d{15,25})"),
)

BARE_ID_RE = re.compile(r"^\d{15,25}$")


class ParseError(ValueError):
    """输入里找不到可用的 aweme_id。"""


def _first_url(text: str) -> Optional[str]:
    m = URL_RE.search(text)
    return m.group(0) if m else None


def _extract_id(url: str) -> Optional[str]:
    for pat in ID_PATTERNS:
        m = pat.search(url)
        if m:
            return m.group(1)
    return None


def resolve_short_link(url: str, session: requests.Session, timeout: float = 15.0) -> str:
    """跟随 v.douyin.com 短链跳转，返回落地长链。"""
    resp = session.get(url, timeout=timeout, allow_redirects=True)
    return resp.url


def extract_aweme_id(raw: str, session: Optional[requests.Session] = None) -> str:
    """从任意输入中解析出 aweme_id，必要时联网还原短链。"""
    raw = raw.strip()
    if BARE_ID_RE.match(raw):
        return raw

    url = _first_url(raw)
    if not url:
        raise ParseError(f"输入里没找到链接也不是纯数字 id: {raw[:80]!r}")

    aid = _extract_id(url)
    if aid:
        return aid

    if any(h in url for h in SHORT_HOSTS):
        if session is None:
            session = requests.Session()
            session.headers["User-Agent"] = (
                "Mozilla/5.0 (iPhone; CPU iPhone OS 16_6 like Mac OS X) "
                "AppleWebKit/605.1.15 (KHTML, like Gecko) Version/16.6 "
                "Mobile/15E148 Safari/604.1"
            )
        final = resolve_short_link(url, session)
        aid = _extract_id(final)
        if aid:
            return aid
        raise ParseError(f"短链 {url} 跳转到 {final}，但里面没有 aweme_id")

    raise ParseError(f"无法从 {url} 中解析出 aweme_id")