/**
 * Featured ("Pro") ranking verification.
 *
 * SECURITY: a `["featured", <expiry>]` tag is SELF-ASSERTED — anyone can add it
 * and get top placement, and `useFeaturedVerification` only downgrades the badge,
 * never the ordering. This helper resolves which featured coordinates are backed
 * by a **provider-authored NIP-57 zap receipt** so list hooks can rank only those.
 *
 * Availability over strictness: if the provider pubkey can't be resolved or the
 * receipt query fails, it returns `null` and the caller keeps the self-asserted
 * ordering (so a provider outage never blanks paid placement).
 */
import { PRO_LIGHTNING_ADDRESS } from '@/lib/sasquatchPro';
import { getZapProviderPubkey } from '@/lib/lightningAddress';
import { PLATFORM_OWNER_PUBKEYS } from '@/hooks/useListingRestrictions';
import type { NostrEvent, NostrFilter } from '@nostrify/nostrify';

let providerPromise: Promise<string | null> | null = null;

function cachedProvider(): Promise<string | null> {
  if (!providerPromise) {
    providerPromise = getZapProviderPubkey(PRO_LIGHTNING_ADDRESS).catch(() => null);
  }
  return providerPromise;
}

/**
 * @returns the set of featured coords with a verified provider receipt, or
 *          `null` when verification is unavailable (caller should not demote).
 */
export async function verifiedFeaturedCoords(
  coords: string[],
  query: (filter: NostrFilter) => Promise<NostrEvent[]>,
): Promise<Set<string> | null> {
  if (coords.length === 0) return null;
  const provider = await cachedProvider();
  if (!provider) return null;
  try {
    const receipts = await query({
      kinds: [9735],
      authors: [provider],
      '#a': coords,
      '#p': PLATFORM_OWNER_PUBKEYS,
      limit: coords.length * 4,
    });
    const set = new Set<string>();
    for (const r of receipts) {
      for (const [n, v] of r.tags) if (n === 'a' && v) set.add(v);
    }
    return set;
  } catch {
    return null;
  }
}