import { constants } from "node:fs";
import { access, readFile } from "node:fs/promises";
import { spawnSync } from "node:child_process";

const failures: string[] = [];

async function requireExecutable(path: string, label: string): Promise<void> {
  try {
    await access(path, constants.X_OK);
  } catch {
    failures.push(`${label} is required at ${path}`);
  }
}

await Promise.all([
  requireExecutable("/usr/bin/bwrap", "bubblewrap"),
  requireExecutable("/usr/bin/systemctl", "systemctl"),
  requireExecutable("/usr/bin/tar", "tar"),
]);

try {
  const controllers = await readFile("/sys/fs/cgroup/cgroup.controllers", "utf8");
  if (controllers.trim().length === 0) {
    failures.push("cgroup v2 controllers are unavailable");
  }
} catch {
  failures.push("cgroup v2 is required at /sys/fs/cgroup/cgroup.controllers");
}

if (!failures.some((failure) => failure.includes("systemctl"))) {
  const probe = spawnSync("/usr/bin/systemctl", ["show-environment"], {
    encoding: "utf8",
    timeout: 3_000,
  });
  if (probe.error || probe.status !== 0) {
    failures.push("a reachable systemd manager bus is required");
  }
}

if (failures.length > 0) {
  process.stderr.write(
    [
      "System/CI-runner test prerequisites are unavailable:",
      ...failures.map((failure) => ` - ${failure}`),
      "",
      "Run test:unit/test:contract/test:component/test:integration for the",
      "developer loop. test:system is intentionally reserved for a compatible",
      "Linux CI-runner host.",
      "",
    ].join("\n"),
  );
  process.exit(1);
}

process.stdout.write("System test prerequisites: PASS\n");