#!/usr/bin/env python3
"""
auto_socat_bind.py
──────────────────
在本机 10.1.1.2:3333-3337 (utun0) 上监听 TCP，
并将流量转发到 127.0.0.1:同端口（已有服务监听）。
若 socat 异常退出则 5 秒后自动重启。
"""

import subprocess
import threading
import signal
import time
import shutil
import logging
from typing import List

# ─── 配置区域 ────────────────────────────────────────────────────────────────
TARGET_BIND = "10.1.1.8"            # 监听地址（utun0）
FORWARD_DST = "127.0.0.1"           # 目标地址（旧服务）
PORTS       = range(4445, 4447)     # 3333-3337
RETRY_DELAY = 5                     # 子进程异常后延迟重启秒数
SOCAT_OPTS  = "reuseaddr,fork,keepalive,nodelay"      # socat 监听选项
# ────────────────────────────────────────────────────────────────────────────

logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s [%(threadName)s] %(levelname)s: %(message)s",
)

if shutil.which("socat") is None:
    raise SystemExit("❌ 未找到 socat，可通过 brew / apt 等安装后再运行")

stop_evt = threading.Event()        # 线程间退出信号


def guard_port(port: int) -> None:
    """守护单个 socat 进程"""
    cmd = [
        "socat",
        f"TCP4-LISTEN:{port},bind={TARGET_BIND},{SOCAT_OPTS}",
        f"TCP4:{FORWARD_DST}:{port}",
    ]
    cmd_str = " ".join(cmd)

    while not stop_evt.is_set():
        logging.info("启动 socat: %s", cmd_str)
        try:
            proc = subprocess.Popen(cmd)
            proc.wait()
            code = proc.returncode
            logging.warning("port %d socat 退出，code=%d", port, code)
        except Exception as exc:
            logging.exception("port %d socat 异常: %s", port, exc)
            code = -1

        if stop_evt.is_set() or code == 0:
            break  # 收到退出信号或正常退出，不再重启

        logging.info("port %d %d 秒后重启", port, RETRY_DELAY)
        time.sleep(RETRY_DELAY)

    logging.info("port %d 守护线程结束", port)


def main() -> None:
    # 捕获 Ctrl-C / SIGTERM
    def _signal_handler(signum, _frm):
        logging.info("收到信号 %s，准备退出…", signum)
        stop_evt.set()

    signal.signal(signal.SIGINT, _signal_handler)
    signal.signal(signal.SIGTERM, _signal_handler)

    threads: List[threading.Thread] = []
    for p in PORTS:
        t = threading.Thread(
            target=guard_port,
            args=(p,),
            name=f"port-{p}",
            daemon=True,
        )
        t.start()
        threads.append(t)

    # 等待所有守护线程退出
    for t in threads:
        t.join()

    logging.info("全部端口守护线程已退出")


if __name__ == "__main__":
    main()