/**
 * Proxmox preflight reachability check.
 *
 * The Proxmox Terraform provider, when given an unreachable api_url,
 * sits in TCP `SYN_SENT` until the kernel-level connect timeout fires
 * — typically 30–75s on macOS. During that window the user sees a
 * frozen progress display and no clue what's wrong (common cause: VPN
 * is down). We probe the api_url's host:port with a short timeout
 * before invoking terraform so we can fail fast with an actionable
 * message instead of letting the provider hang.
 *
 * Scoped intentionally to the proxmox container-service deploy path —
 * other terraform invocations (DigitalOcean, system audit) talk to
 * different endpoints with their own failure modes.
 */

import { Socket } from 'node:net';

export interface ProxmoxReachabilityResult {
  reachable: boolean;
  host: string;
  port: number;
  /** Populated when `reachable` is false. */
  error?: string;
}

/**
 * Probe `host:port` with a TCP connect attempt. Resolves on connect,
 * timeout, or socket error — never rejects. Caller decides what to do
 * with the result.
 */
export async function checkProxmoxReachable(
  apiUrl: string,
  timeoutMs = 3000,
): Promise<ProxmoxReachabilityResult> {
  let host: string;
  let port: number;
  try {
    const url = new URL(apiUrl);
    host = url.hostname;
    port = url.port ? Number(url.port) : url.protocol === 'https:' ? 443 : 80;
  } catch {
    return {
      reachable: false,
      host: apiUrl,
      port: 0,
      error: `Invalid Proxmox API URL: ${apiUrl}`,
    };
  }

  return await new Promise<ProxmoxReachabilityResult>((resolve) => {
    const socket = new Socket();
    let settled = false;

    const finish = (result: ProxmoxReachabilityResult) => {
      if (settled) return;
      settled = true;
      socket.destroy();
      resolve(result);
    };

    socket.setTimeout(timeoutMs);
    socket.once('connect', () => finish({ reachable: true, host, port }));
    socket.once('timeout', () =>
      finish({
        reachable: false,
        host,
        port,
        error: `Connection to ${host}:${port} timed out after ${timeoutMs}ms`,
      }),
    );
    socket.once('error', (err) =>
      finish({
        reachable: false,
        host,
        port,
        error: err.message,
      }),
    );

    socket.connect(port, host);
  });
}

/**
 * Format an unreachable result into a multi-line error message
 * suitable for display in the deploy progress panel.
 */
export function formatProxmoxUnreachableError(result: ProxmoxReachabilityResult): string {
  return [
    `Proxmox unreachable at ${result.host}:${result.port}`,
    '',
    'Check:',
    '  - VPN connection (if Proxmox is on a private network)',
    '  - Is the Proxmox host running and reachable from this machine?',
    `  - Try: nc -zv ${result.host} ${result.port}`,
    '',
    `(${result.error ?? 'no further detail'})`,
  ].join('\n');
}