import { execFileSync } from "node:child_process";
import { openSync, closeSync, readFileSync, writeFileSync } from "node:fs";
import { CONFIG } from "./config.js";

function run(cmd: string, args: string[]) {
  execFileSync(cmd, args, { stdio: "pipe" });
}

function sudo(args: string[]) {
  run("sudo", args);
}

export function ensureBridge() {
  try {
    execFileSync("ip", ["link", "show", CONFIG.bridge.name], {
      stdio: "pipe",
    });
  } catch {
    sudo(["ip", "link", "add", CONFIG.bridge.name, "type", "bridge"]);
    sudo([
      "ip",
      "addr",
      "add",
      `${CONFIG.bridge.ip}/24`,
      "dev",
      CONFIG.bridge.name,
    ]);
    sudo(["ip", "link", "set", CONFIG.bridge.name, "up"]);
    sudo(["sysctl", "-w", "net.ipv4.ip_forward=1"]);
  }
}

export function ensureNat() {
  // Check if rule already exists
  try {
    execFileSync(
      "sudo",
      [
        "iptables",
        "-t",
        "nat",
        "-C",
        "POSTROUTING",
        "-s",
        CONFIG.bridge.subnet,
        "-j",
        "MASQUERADE",
      ],
      { stdio: "pipe" }
    );
  } catch {
    // Find the default route interface
    const routeOut = execFileSync("ip", ["route", "show", "default"], {
      encoding: "utf-8",
    });
    const extIface = routeOut.match(/dev\s+(\S+)/)?.[1] ?? "eno2";

    sudo([
      "iptables",
      "-t",
      "nat",
      "-A",
      "POSTROUTING",
      "-s",
      CONFIG.bridge.subnet,
      "-o",
      extIface,
      "-j",
      "MASQUERADE",
    ]);
    sudo([
      "iptables",
      "-A",
      "FORWARD",
      "-i",
      CONFIG.bridge.name,
      "-o",
      extIface,
      "-j",
      "ACCEPT",
    ]);
    sudo([
      "iptables",
      "-A",
      "FORWARD",
      "-i",
      extIface,
      "-o",
      CONFIG.bridge.name,
      "-m",
      "state",
      "--state",
      "RELATED,ESTABLISHED",
      "-j",
      "ACCEPT",
    ]);
  }
}

export function createTap(tapName: string) {
  sudo(["ip", "tuntap", "add", tapName, "mode", "tap"]);
  sudo(["ip", "link", "set", tapName, "master", CONFIG.bridge.name]);
  sudo(["ip", "link", "set", tapName, "up"]);
}

export function deleteTap(tapName: string) {
  try {
    sudo(["ip", "tuntap", "del", tapName, "mode", "tap"]);
  } catch {
    // Already gone
  }
}

export type NetworkPolicy = "full" | "local" | "none";

export function applyNetworkPolicy(ip: string, policy: NetworkPolicy) {
  if (policy === "full") return; // Default, no restrictions

  // Block outbound internet — only allow LAN, bridge, Ollama, IRC
  const allowedDests = [
    CONFIG.bridge.subnet,   // bridge network (other VMs, IRC, Ollama)
    "192.168.0.0/16",       // LAN
  ];

  if (policy === "none") {
    // Only allow bridge subnet (IRC + Ollama)
    allowedDests.length = 1; // keep only bridge subnet
  }

  // Allow established connections back
  sudo([
    "iptables", "-I", "FORWARD",
    "-s", ip,
    "-m", "state", "--state", "ESTABLISHED,RELATED",
    "-j", "ACCEPT",
  ]);

  // Allow specific destinations
  for (const dest of allowedDests) {
    sudo([
      "iptables", "-I", "FORWARD",
      "-s", ip, "-d", dest,
      "-j", "ACCEPT",
    ]);
  }

  // Drop everything else from this IP
  sudo([
    "iptables", "-A", "FORWARD",
    "-s", ip,
    "-j", "DROP",
  ]);
}

export function removeNetworkPolicy(ip: string) {
  // Remove all FORWARD rules mentioning this IP
  // Run in a loop since there may be multiple rules
  for (let i = 0; i < 10; i++) {
    try {
      sudo([
        "iptables", "-D", "FORWARD",
        "-s", ip,
        "-j", "DROP",
      ]);
    } catch {
      break;
    }
  }
  for (let i = 0; i < 10; i++) {
    try {
      sudo([
        "iptables", "-D", "FORWARD",
        "-s", ip,
        "-j", "ACCEPT",
      ]);
    } catch {
      break;
    }
  }
}

export function macFromOctet(octet: number): string {
  return `AA:FC:00:00:00:${octet.toString(16).padStart(2, "0").toUpperCase()}`;
}

interface IpPool {
  allocated: number[];
}

function readPool(): IpPool {
  try {
    return JSON.parse(readFileSync(CONFIG.ipPoolFile, "utf-8"));
  } catch {
    return { allocated: [] };
  }
}

function writePool(pool: IpPool) {
  writeFileSync(CONFIG.ipPoolFile, JSON.stringify(pool));
}

export function allocateIp(): { ip: string; octet: number } {
  const fd = openSync(CONFIG.ipPoolLock, "w");
  try {
    // Simple flock via child process
    const pool = readPool();
    for (
      let octet = CONFIG.bridge.minHost;
      octet <= CONFIG.bridge.maxHost;
      octet++
    ) {
      if (!pool.allocated.includes(octet)) {
        pool.allocated.push(octet);
        writePool(pool);
        return { ip: `${CONFIG.bridge.prefix}.${octet}`, octet };
      }
    }
    throw new Error("No free IPs in pool");
  } finally {
    closeSync(fd);
  }
}

export function releaseIp(octet: number) {
  const fd = openSync(CONFIG.ipPoolLock, "w");
  try {
    const pool = readPool();
    pool.allocated = pool.allocated.filter((o) => o !== octet);
    writePool(pool);
  } finally {
    closeSync(fd);
  }
}