"""PAC 数据文件的网络传输与安全落盘。"""

import json
import os
import urllib.request
from pathlib import Path


def read_version(path):
    """读取 PAC JSON 的 version/date；无效文件返回空字符串。"""
    try:
        data = json.loads(Path(path).read_text("utf-8"))
        return str(data.get("version") or ""), str(data.get("date") or "")
    except Exception:
        return "", ""


def no_proxy_opener():
    """创建忽略环境/系统代理的直连 HTTP opener。"""
    return urllib.request.build_opener(urllib.request.ProxyHandler({}))


def fetch_json(url, timeout=15, tries=2):
    """以直连方式拉取 JSON；最后一次失败时保留原始异常。"""
    opener = no_proxy_opener()
    for attempt in range(tries):
        try:
            with opener.open(url, timeout=timeout) as response:
                return json.loads(response.read().decode("utf-8"))
        except Exception:
            if attempt == tries - 1:
                raise


def validate_document(name, data):
    """校验各 PAC 文件的最小结构，避免错误响应覆盖有效缓存。"""
    if not isinstance(data, dict):
        return False
    if name in ("pac_domains", "pac_direct_domains"):
        return isinstance(data.get("domains"), list)
    if name == "pac_ip_cn":
        return isinstance(data.get("cidrs"), list)
    return False


def atomic_write(directory, name, data):
    """将 PAC JSON 以 tmp + replace 原子写入指定用户目录。"""
    directory = Path(directory)
    directory.mkdir(parents=True, exist_ok=True)
    target = directory / f"{name}.json"
    temporary_path = directory / f"{name}.json.tmp"
    temporary_path.write_text(json.dumps(data, ensure_ascii=False), "utf-8")
    os.replace(temporary_path, target)