/**
 * Reachability probe for the machine pool.
 *
 * One implementation, deliberately. This SSH probe previously existed twice —
 * once in `alerting/builtin-source.ts` for the monitor sweep and once in
 * `cli/commands/system-audit.ts` for `celilo system audit` — as identical
 * copy-pasted blocks. Both carried the same bug, and fixing one would have left
 * the other reporting the management server as unreachable forever.
 */

import { execFile } from 'node:child_process';
import { promisify } from 'node:util';
import type { MachineReachableResult } from './audit/machines-reachable';
import { listMachines } from './machine-pool';
import { LOCAL_MACHINE_IP } from './ssh-key-manager';

const execFileAsync = promisify(execFile);

/**
 * Probe every machine in the pool.
 *
 * `BatchMode=yes` prevents a password prompt from hanging the probe forever,
 * and `ConnectTimeout` bounds the wait on an unresponsive host — the exact
 * condition this check exists to detect must not be the one that wedges it.
 *
 * The local management box is reported reachable WITHOUT probing it. celilo
 * runs there as the `celilo` user and deliberately does not materialize an SSH
 * key for itself, so `ssh root@127.0.0.1` fails with `Permission denied
 * (publickey)` on a perfectly healthy host. Left unhandled that produced a
 * permanently firing `machines_reachable` alert against celilo-mgr — and since
 * that monitor is unsuppressible by design, nothing could explain it away.
 *
 * The check is also meaningless there: if the box running this code were
 * unreachable, this code would not be running.
 */
export async function probeMachines(): Promise<MachineReachableResult[]> {
  const machines = await listMachines();
  return Promise.all(
    machines.map(async (m): Promise<MachineReachableResult> => {
      if (m.ipAddress === LOCAL_MACHINE_IP) {
        return { hostname: m.hostname, ipAddress: m.ipAddress, reachable: true };
      }
      try {
        await execFileAsync(
          'ssh',
          [
            '-o',
            'BatchMode=yes',
            '-o',
            'ConnectTimeout=5',
            '-o',
            'StrictHostKeyChecking=no',
            '-o',
            'UserKnownHostsFile=/dev/null',
            `${m.sshUser}@${m.ipAddress}`,
            'true',
          ],
          { timeout: 8000 },
        );
        return { hostname: m.hostname, ipAddress: m.ipAddress, reachable: true };
      } catch (err) {
        const e = err as { stderr?: string; message?: string };
        return {
          hostname: m.hostname,
          ipAddress: m.ipAddress,
          reachable: false,
          message: e.stderr?.trim() || e.message || 'SSH probe failed',
        };
      }
    }),
  );
}