"""Windows 系统代理模式：注册表切换、原状态保存与异常退出恢复。"""

from __future__ import annotations

import ctypes
import re
from typing import Callable


PROXY_REG = r"HKCU\Software\Microsoft\Windows\CurrentVersion\Internet Settings"
BACKUP_KEY = "prev_proxy_state"
_VALUE_NAMES = ("ProxyEnable", "ProxyServer", "ProxyOverride", "AutoConfigURL")


def is_our_pac_url(value: str) -> bool:
    return bool(re.fullmatch(r"http://127\.0\.0\.1:\d+/proxy\.pac", str(value).strip()))


def notify_proxy_change() -> None:
    """通知 WinINET 和顶层窗口重新读取系统代理。"""
    try:
        ctypes.windll.Wininet.InternetSetOptionW(None, 39, None, 0)
        ctypes.windll.Wininet.InternetSetOptionW(None, 37, None, 0)
        result = ctypes.c_ulong()
        ctypes.windll.user32.SendMessageTimeoutW(
            0xFFFF, 0x001A, 0, ctypes.c_wchar_p("InternetSettings"),
            0x0002, 5000, ctypes.byref(result))
    except Exception:
        pass


class SystemProxyMode:
    def __init__(self, *, run: Callable, settings_load: Callable,
                 settings_save: Callable, log: Callable,
                 endpoint: Callable[[], tuple[str, int]],
                 proxy_override: Callable[[bool], str]):
        self.run = run
        self.settings_load = settings_load
        self.settings_save = settings_save
        self.log = log
        self.endpoint = endpoint
        self.proxy_override = proxy_override
        self._previous = None

    def reg_query(self, name: str):
        result = self.run(["reg", "query", PROXY_REG, "/v", name], warn=False)
        if result.returncode:
            return None
        for line in (result.stdout or "").splitlines():
            parts = line.strip().split(None, 2)
            if len(parts) >= 3 and parts[0].lower() == name.lower():
                return parts[1], parts[2]
        return None

    def _backup(self):
        if self._previous is not None:
            return
        state = {name: list(value) if (value := self.reg_query(name)) else None
                 for name in _VALUE_NAMES}
        self._previous = state
        try:
            self.settings_save({**self.settings_load(), BACKUP_KEY: state})
        except Exception:
            pass

    def _restore(self):
        state = self._previous
        if state is None:
            state = self.settings_load().get(BACKUP_KEY)
        if isinstance(state, dict):
            for name in _VALUE_NAMES:
                value = state.get(name)
                if value:
                    self.run(["reg", "add", PROXY_REG, "/v", name, "/t", value[0],
                              "/d", value[1], "/f"], warn=False)
                else:
                    self.run(["reg", "delete", PROXY_REG, "/v", name, "/f"], warn=False)
            self.log("已恢复开启代理前的系统代理设置")
        else:
            for name in ("ProxyServer", "ProxyOverride", "AutoConfigURL"):
                self.run(["reg", "delete", PROXY_REG, "/v", name, "/f"], warn=False)
            self.run(["reg", "add", PROXY_REG, "/v", "ProxyEnable", "/t",
                      "REG_DWORD", "/d", "0", "/f"])
        self._previous = None
        try:
            data = self.settings_load()
            if BACKUP_KEY in data:
                del data[BACKUP_KEY]
                self.settings_save(data)
        except Exception:
            pass

    def enable(self, pac_url=None, bypass_lan=False):
        self._backup()
        if pac_url:
            self.run(["reg", "add", PROXY_REG, "/v", "ProxyEnable", "/t",
                      "REG_DWORD", "/d", "0", "/f"])
            for name in ("ProxyServer", "ProxyOverride"):
                self.run(["reg", "delete", PROXY_REG, "/v", name, "/f"], warn=False)
            self.run(["reg", "add", PROXY_REG, "/v", "AutoConfigURL", "/t",
                      "REG_SZ", "/d", pac_url, "/f"])
            self.log("系统代理已设置 (PAC)")
        else:
            host, port = self.endpoint()
            address = f"{host}:{port}"
            self.run(["reg", "add", PROXY_REG, "/v", "ProxyEnable", "/t",
                      "REG_DWORD", "/d", "1", "/f"])
            self.run(["reg", "add", PROXY_REG, "/v", "ProxyServer", "/t",
                      "REG_SZ", "/d", address, "/f"])
            self.run(["reg", "add", PROXY_REG, "/v", "ProxyOverride", "/t",
                      "REG_SZ", "/d", self.proxy_override(bypass_lan), "/f"])
            self.log(f"系统代理已设置: {address}")
        notify_proxy_change()

    def disable(self):
        self._restore()
        notify_proxy_change()

    def is_on(self):
        host, port = self.endpoint()
        enabled = self.reg_query("ProxyEnable")
        try:
            fixed_enabled = bool(enabled and int(str(enabled[1]).strip(), 0) == 1)
        except (TypeError, ValueError):
            fixed_enabled = False
        if fixed_enabled:
            server = self.reg_query("ProxyServer")
            return bool(server and (server[1] or "").strip() == f"{host}:{port}")
        pac = self.reg_query("AutoConfigURL")
        return bool(pac) and is_our_pac_url(pac[1] or "")

    def is_stale(self):
        host, port = self.endpoint()
        server = self.reg_query("ProxyServer")
        pac = self.reg_query("AutoConfigURL")
        return (bool(server) and (server[1] or "").strip() == f"{host}:{port}") or \
               (bool(pac) and is_our_pac_url(pac[1] or ""))