import { execFileSync } from "node:child_process";
import { existsSync, readFileSync, rmSync } from "node:fs";
import { resolve } from "node:path";

const lockPath = ".next/dev/lock";
const devDirPath = ".next/dev";
const webpackRuntimePath = ".next/dev/server/webpack-runtime.js";
const vendorChunkPath = ".next/dev/server/vendor-chunks/next.js";
const projectRoot = process.cwd();

function run(cmd, args) {
  try {
    return execFileSync(cmd, args, { encoding: "utf8" }).trim();
  } catch {
    return "";
  }
}

function pidExists(pid) {
  try {
    process.kill(pid, 0);
    return true;
  } catch {
    return false;
  }
}

function getProcessCwd(pid) {
  const output = run("lsof", ["-a", "-p", String(pid), "-d", "cwd", "-Fn"]);
  const cwdLine = output
    .split("\n")
    .find((line) => line.startsWith("n"));
  return cwdLine ? cwdLine.slice(1) : "";
}

function getListeningPids(port) {
  const output = run("lsof", ["-ti", `tcp:${port}`, "-sTCP:LISTEN"]);
  if (!output) return [];
  return output
    .split("\n")
    .map((line) => Number(line.trim()))
    .filter((v) => Number.isInteger(v) && v > 0);
}

function removeLock(reason) {
  rmSync(lockPath, { force: true });
  console.log(`Removed stale ${lockPath}: ${reason}`);
}

function resetDevCache(reason) {
  rmSync(devDirPath, { force: true, recursive: true });
  console.log(`Reset ${devDirPath}: ${reason}`);
}

if (existsSync(webpackRuntimePath) && !existsSync(vendorChunkPath)) {
  resetDevCache("missing vendor-chunks/next.js");
  process.exit(0);
}

if (!existsSync(lockPath)) process.exit(0);

let lock;
try {
  lock = JSON.parse(readFileSync(lockPath, "utf8"));
} catch {
  removeLock("invalid JSON");
  process.exit(0);
}

const pid = Number(lock?.pid ?? 0);
const port = Number(lock?.port ?? 3000);
if (!pid) {
  removeLock("missing pid");
  process.exit(0);
}

if (!pidExists(pid)) {
  removeLock(`pid ${pid} not running`);
  process.exit(0);
}

const processCwd = getProcessCwd(pid);
if (!processCwd) {
  removeLock(`cannot resolve cwd for pid ${pid}`);
  process.exit(0);
}

if (resolve(processCwd) !== resolve(projectRoot)) {
  removeLock(`pid ${pid} belongs to another directory`);
  process.exit(0);
}

const portPids = getListeningPids(port);
if (portPids.length > 0 && !portPids.includes(pid)) {
  removeLock(`pid ${pid} is not listening on port ${port}`);
}