/**
 * Dev launcher — runs `next dev` bound to all interfaces (so the site is
 * reachable from other devices on your LAN) and rewrites Next's
 * "http://0.0.0.0:3000" line to the machine's real LAN IP, so the terminal
 * shows a usable Network URL right next to Local:
 *
 *   - Local:        http://localhost:3000
 *   - Network:      http://192.168.x.x:3000
 *
 * It also auto-increments the port (3000 → 3001 → …) when the desired port is
 * already in use — including by another project bound only to localhost, which
 * a plain `next dev -H 0.0.0.0` fails to detect on Windows. Override the base
 * port with PORT=4000 npm run dev.
 */
import { spawn } from "node:child_process";
import net from "node:net";
import os from "node:os";
import path from "node:path";

const BASE_PORT = Number(process.env.PORT) || 3000;
const nextBin = path.join(process.cwd(), "node_modules", "next", "dist", "bin", "next");

/** First non-internal IPv4 address (skips loopback + link-local). */
function lanIp() {
  for (const ifaces of Object.values(os.networkInterfaces())) {
    for (const net of ifaces || []) {
      const isV4 = net.family === "IPv4" || net.family === 4;
      if (isV4 && !net.internal && !net.address.startsWith("169.254.")) return net.address;
    }
  }
  return null;
}

/**
 * True if something is already listening on the port. We *connect* (rather
 * than try to bind) so we catch listeners on any address — including a project
 * bound only to 127.0.0.1, which a 0.0.0.0 bind test would miss on Windows.
 */
function portInUse(port) {
  return new Promise((resolve) => {
    const socket = net.connect({ host: "127.0.0.1", port, timeout: 500 });
    const finish = (inUse) => {
      socket.destroy();
      resolve(inUse);
    };
    socket.once("connect", () => finish(true));
    socket.once("timeout", () => finish(false));
    socket.once("error", () => finish(false)); // ECONNREFUSED → free
  });
}

async function findFreePort(base) {
  let port = base;
  while (await portInUse(port)) port += 1;
  return port;
}

const ip = lanIp();
const port = await findFreePort(BASE_PORT);
if (port !== BASE_PORT) {
  console.log(`\n  ⚠ Port ${BASE_PORT} is in use — using ${port} instead.`);
}

const child = spawn(process.execPath, [nextBin, "dev", "-H", "0.0.0.0", "-p", String(port)], {
  stdio: ["inherit", "pipe", "inherit"],
  env: process.env,
});

// Swap Next's "0.0.0.0" for the real LAN IP so the Network URL is clickable.
child.stdout.on("data", (chunk) => {
  const text = chunk.toString();
  process.stdout.write(ip ? text.split("0.0.0.0").join(ip) : text);
});

const forward = (sig) => child.kill(sig);
process.on("SIGINT", () => forward("SIGINT"));
process.on("SIGTERM", () => forward("SIGTERM"));
child.on("exit", (code) => process.exit(code ?? 0));