#!/bin/zsh
DNS_SERVER="45.8.173.221"
printf "应用桥：1 设置热点 DNS；2 恢复原设置\n"
read -r choice
/usr/bin/sudo /usr/bin/python3 - "$choice" "$DNS_SERVER" <<'APPLICATION_BRIDGE_PY'
"""Standalone macOS Internet Sharing DHCP DNS helper, embedded in a download."""
import copy
import ipaddress
import json
import os
from pathlib import Path
import plistlib
import pwd
import re
import subprocess
import sys
import tempfile


def main():
    if os.geteuid()!=0:raise ValueError('需要管理员权限修改热点 DHCP 配置')
    uid=int(os.environ.get('SUDO_UID','0'))
    account=pwd.getpwuid(uid)
    folder=Path(account.pw_dir)/'Library/Application Support/ApplicationBridge'
    folder.mkdir(parents=True,exist_ok=True,mode=0o700)
    os.chown(folder,uid,account.pw_gid)
    record=folder/'hotspot-dns.json'
    config_file=Path('/etc/bootpd.plist')
    config=plistlib.loads(config_file.read_bytes())
    action=sys.argv[1]
    if action=='1':
        if record.exists():raise ValueError('已有未恢复设置，请先选择 2 恢复；未覆盖恢复记录')
        resolver=str(ipaddress.IPv4Address(sys.argv[2]))
        if not ipaddress.ip_address(resolver).is_global:
            raise ValueError('此工具需要实际公网 DNS 地址；本机开发预览地址不能用于车机热点')
        matches=[x for x in config.get('Subnets',[]) if x.get('_creator')=='com.apple.NetworkSharing'
                 and x.get('interface') in config.get('dhcp_enabled',[])]
        if len(matches)!=1:raise ValueError('请先开启唯一的 Wi-Fi 互联网共享热点')
        subnet=matches[0]
        state={'interface':subnet['interface'],'network':subnet['net_address'],
               'present':'dhcp_domain_name_server' in subnet,
               'original':copy.deepcopy(subnet.get('dhcp_domain_name_server')),'resolver':resolver}
        with record.open('x') as f:
            os.fchmod(f.fileno(),0o600);os.fchown(f.fileno(),uid,account.pw_gid)
            json.dump(state,f)
        subnet['dhcp_domain_name_server']=[resolver]
    elif action=='2':
        if not record.exists():print('没有待恢复的热点 DNS 设置');return
        state=json.loads(record.read_text())
        if not re.fullmatch(r'bridge[0-9]+',state['interface']):raise ValueError('恢复记录接口无效')
        ipaddress.IPv4Address(state['network']);ipaddress.IPv4Address(state['resolver'])
        for value in state.get('original') or []:ipaddress.ip_address(value)
        matches=[x for x in config.get('Subnets',[]) if x.get('_creator')=='com.apple.NetworkSharing'
                 and x.get('interface')==state['interface'] and x.get('net_address')==state['network']]
        if len(matches)!=1:raise ValueError('共享子网已变化，未覆盖当前配置')
        subnet=matches[0]
        if subnet.get('dhcp_domain_name_server') not in ([state['resolver']],state['original']):
            raise ValueError('DNS 已被其他操作改动，未覆盖当前设置')
        if state['present']:subnet['dhcp_domain_name_server']=state['original']
        else:subnet.pop('dhcp_domain_name_server',None)
    else:raise ValueError('请选择 1 或 2')
    info=config_file.stat();fd,name=tempfile.mkstemp(prefix='.appbridge-',dir=str(config_file.parent))
    try:
        with os.fdopen(fd,'wb') as f:
            os.fchmod(f.fileno(),info.st_mode&0o777);os.fchown(f.fileno(),info.st_uid,info.st_gid)
            plistlib.dump(config,f);f.flush();os.fsync(f.fileno())
        os.replace(name,config_file)
    finally:
        if os.path.exists(name):os.unlink(name)
    running=subprocess.run(['/bin/launchctl','print','system/com.apple.bootpd'],capture_output=True,text=True)
    if running.returncode==0 and 'state = running' in running.stdout:
        subprocess.run(['/bin/launchctl','kill','SIGHUP','system/com.apple.bootpd'],check=True,capture_output=True)
    if action=='2':record.unlink()
    print('热点 DHCP DNS 已更新；Mac 自身上联 DNS 保持原样。请让车机重新连接热点。')


if __name__=='__main__':
    try:main()
    except Exception as error:
        print('操作未完成：'+str(error),file=sys.stderr)
        sys.exit(1)

APPLICATION_BRIDGE_PY
printf "\n请让车机断开重连热点。按回车关闭。"
read -r