# -*- coding: utf-8 -*-
r'''在设备上测 Cloudflare 隧道边缘 IP 的 TCP 握手延迟，挑优选 IP。

为什么要这么干：
    cloudflared 连 region1.v2.argotunnel.com，这个域名由 GeoDNS 决定 ——
    国内 4G 常被解析到美西（实测 lax13），单程 200ms+，
    往返加丢包重传能到 4 秒（用户实测 4141ms）。

    Cloudflare 是 anycast，同一批 IP 从不同网络过去落点不同。
    做法：测各候选 IP 的 7844（隧道端口）握手延迟，
    把最快的写进 /etc/hosts 覆盖 GeoDNS。

⚠ 关键教训：
    7844 **只对 Cloudflare 的隧道专用段开放**，不是所有 anycast IP 都行。
    专用段是 198.41.192.0/24 和 198.41.200.0/24（实测 198.41.192.107 通）。
    我第一次拿 104.16.x.x 测，56 个全不通，就是选错段了。
'''
from __future__ import annotations

import socket
import sys
import time

PORT = 7844          # cloudflared 的 HTTP/2 隧道端口

# 已知能用的几个放前面：先确认能通，再放大范围扫
KNOWN = [
    "198.41.192.107", "198.41.192.7", "198.41.192.167",
    "198.41.200.13", "198.41.200.33", "198.41.200.53", "198.41.200.63",
]


def build_candidates() -> list[str]:
    ips = list(KNOWN)
    for third in range(1, 255, 3):
        ips.append("198.41.192." + str(third))
    for third in range(1, 255, 3):
        ips.append("198.41.200." + str(third))
    seen = set()
    out = []
    for ip in ips:
        if ip not in seen:
            seen.add(ip)
            out.append(ip)
    return out


def probe(ip: str, timeout: float = 2.5):
    """返回 TCP 握手耗时（毫秒），不通返回 None。"""
    sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    sock.settimeout(timeout)
    start = time.perf_counter()
    try:
        sock.connect((ip, PORT))
        return (time.perf_counter() - start) * 1000
    except OSError:
        return None
    finally:
        sock.close()


def main() -> int:
    candidates = build_candidates()
    print("  候选 %d 个（Cloudflare 隧道专用段）" % len(candidates))
    print("  测 %d 端口，每个 2 次取最快" % PORT)
    print()

    results = []
    reachable = 0
    for index, ip in enumerate(candidates, 1):
        best = None
        for _ in range(2):
            ms = probe(ip)
            if ms is not None and (best is None or ms < best):
                best = ms
        if best is not None:
            reachable += 1
            results.append((best, ip))
        if index % 40 == 0:
            print("    已测 %d/%d，通了 %d 个" % (index, len(candidates), reachable))

    print()
    if not results:
        print("  一个都不通")
        return 1

    results.sort()
    print("  通了 %d 个，最快的 15 个：" % reachable)
    for ms, ip in results[:15]:
        print("    %7.1f ms  %s" % (ms, ip))

    print()
    print("  默认 GeoDNS 解析：")
    for host in ("region1.v2.argotunnel.com", "region2.v2.argotunnel.com"):
        try:
            infos = socket.getaddrinfo(host, PORT)
            v4 = sorted({i[4][0] for i in infos if i[0] == socket.AF_INET})
            print("    %s: %s" % (host, v4 or "（只有 IPv6）"))
        except OSError as exc:
            print("    %s: 解析失败 %s" % (host, exc))

    with open("/root/cf_best.txt", "w") as fh:
        for ms, ip in results[:5]:
            fh.write("%s %.0f\n" % (ip, ms))
    print()
    print("  最快 5 个 -> /root/cf_best.txt")
    return 0


if __name__ == "__main__":
    sys.exit(main())