/**
 * relayProbe — lightweight connectivity check for an arbitrary Nostr relay.
 * ─────────────────────────────────────────────────────────────────────────────
 * Adapted from the Citrine probe: opening a socket alone is not enough to prove
 * a relay is alive and speaking Nostr, so we complete a minimal handshake —
 * open → tiny bounded REQ → require a protocol-shaped reply (EVENT / EOSE /
 * NOTICE / CLOSED) referencing our subscription id. This gives the Relays UI an
 * honest green "connected" dot instead of an optimistic one.
 *
 * Never throws, never rejects — always resolves to a boolean-plus-reason so the
 * caller can render a status without try/catch noise.
 */

export interface RelayProbeResult {
  ok: boolean;
  /** Short diagnostic for the outcome (useful for debugging / tooltips). */
  reason: string;
}

/**
 * Probe whether a relay at `url` is reachable and answering as a Nostr relay.
 *
 * Mirrors the Citrine handshake: a bare "socket opened" is treated as NOT ok —
 * we require a real protocol reply so a non-Nostr process squatting on the port
 * doesn't show a misleading green dot.
 */
export function probeRelay(url: string, timeoutMs = 4000): Promise<RelayProbeResult> {
  return new Promise<RelayProbeResult>((resolve) => {
    let settled = false;
    let opened = false;
    let ws: WebSocket | undefined;
    const timers: ReturnType<typeof setTimeout>[] = [];

    const done = (ok: boolean, reason: string) => {
      if (settled) return;
      settled = true;
      for (const t of timers) clearTimeout(t);
      try {
        ws?.close();
      } catch {
        // ignore close errors
      }
      resolve({ ok, reason });
    };

    try {
      ws = new WebSocket(url);
    } catch (err) {
      resolve({
        ok: false,
        reason: `blocked: ${err instanceof Error ? err.message : String(err)}`,
      });
      return;
    }

    const subId = `probe-${Math.random().toString(36).slice(2, 10)}`;

    timers.push(setTimeout(() => {
      done(false, opened ? 'opened-but-no-nostr-reply' : 'timeout-no-open');
    }, timeoutMs));

    ws.onopen = () => {
      opened = true;
      try {
        ws!.send(JSON.stringify(['REQ', subId, { limit: 1 }]));
      } catch (err) {
        done(false, `send-failed: ${err instanceof Error ? err.message : String(err)}`);
      }
    };

    ws.onmessage = (ev) => {
      try {
        const data = JSON.parse(typeof ev.data === 'string' ? ev.data : '');
        if (Array.isArray(data) && typeof data[0] === 'string') {
          const verb = data[0];
          const matchesSub = data[1] === subId;
          if (
            ((verb === 'EVENT' || verb === 'EOSE' || verb === 'CLOSED') && matchesSub) ||
            verb === 'NOTICE'
          ) {
            done(true, 'ok');
            return;
          }
        }
      } catch {
        // Non-JSON frame → keep waiting for a valid reply until timeout.
      }
    };

    ws.onerror = () => {
      done(false, opened ? 'error-after-open' : 'connect-error');
    };
    ws.onclose = (ev) => {
      done(false, opened ? 'closed-after-open' : `closed-before-open (code ${ev.code})`);
    };
  });
}

/**
 * True if a relay URL points at the local machine (loopback / localhost / *.local
 * / LAN address). Used to badge local relays (e.g. Citrine, a self-hosted relay)
 * distinctly in the UI, matching the reference "Local" chip.
 */
export function isLocalRelay(url: string): boolean {
  let host = '';
  try {
    host = new URL(url).hostname.toLowerCase();
  } catch {
    // Fall back to a loose match on the raw string.
    const lower = url.toLowerCase();
    return (
      lower.includes('127.0.0.1') ||
      lower.includes('localhost') ||
      lower.startsWith('ws://')
    );
  }

  if (host === 'localhost' || host === '127.0.0.1' || host === '::1' || host === '[::1]') {
    return true;
  }
  if (host.endsWith('.local')) return true;
  // Private LAN ranges.
  if (host.startsWith('10.')) return true;
  if (host.startsWith('192.168.')) return true;
  const m = host.match(/^172\.(\d+)\./);
  if (m) {
    const second = Number(m[1]);
    if (second >= 16 && second <= 31) return true;
  }
  return false;
}