import { execFileSync } from "node:child_process";
import { Builder } from "selenium-webdriver";
import firefox from "selenium-webdriver/firefox.js";

/**
 * Resolve the geckodriver path from $PATH.
 *
 * @returns {string}
 */
function findGeckodriver() {
  try {
    return execFileSync("which", ["geckodriver"], { encoding: "utf-8" }).trim();
  } catch {
    throw new Error(
      "geckodriver not found on $PATH. Install it (e.g. via Nix or your package manager).",
    );
  }
}

/**
 * Create a Firefox WebDriver instance.
 *
 * @param {object} opts
 * @param {boolean} [opts.headless=false] - Run Firefox in headless mode.
 * @param {string}  [opts.existingUrl]    - Connect to an already-running
 *   WebDriver server (e.g. "http://localhost:4444").
 * @returns {Promise<import("selenium-webdriver").WebDriver>}
 */
export async function createDriver({ headless = false, existingUrl } = {}) {
  const options = new firefox.Options();

  // Configure Headless
  if (headless) {
    options.addArguments("--headless");
  }

  const builder = new Builder().forBrowser("firefox").setFirefoxOptions(options);

  // Connect to Existing Server
  if (existingUrl) {
    builder.usingServer(existingUrl);
  } else {
    // Use System Geckodriver - Bypasses the bundled selenium-manager which
    // is x86-64 only and doesn't work on aarch64.
    const service = new firefox.ServiceBuilder(findGeckodriver());
    builder.setFirefoxService(service);
  }

  return builder.build();
}