/**
 * agents.md — GET /agents.md
 *
 * The canonical AI-agent discovery file (the convention Shopify made standard
 * in 2026): a machine-readable guide telling shopping agents and AI assistants
 * what this site sells, where its machine surfaces live, and how a purchase
 * works. /llms.txt mirrors the same information in the older convention —
 * keep the two consistent.
 */
import { getServerClient } from '@/core/lib/brainerce.server';
import { getCanonicalSiteUrl } from '@/core/lib/site-url';

export const revalidate = 3600;

interface CategoryNodeLike {
  name: string;
  slug?: string | null;
  children?: CategoryNodeLike[];
}

export async function GET() {
  const baseUrl = await getCanonicalSiteUrl();
  // Machine-readable product feed served by the Brainerce API per channel —
  // the same artifact Google/Microsoft/Perplexity ingest; agents can read the
  // whole catalog in one structured fetch instead of crawling page by page.
  const apiUrl = (process.env.BRAINERCE_API_URL || 'https://api.brainerce.com').replace(/\/+$/, '');
  const channelId =
    process.env.NEXT_PUBLIC_BRAINERCE_SALES_CHANNEL_ID ||
    process.env.NEXT_PUBLIC_BRAINERCE_CONNECTION_ID ||
    '';
  const client = await getServerClient();

  const [info, categoriesRes] = await Promise.all([
    client.getStoreInfo().catch(() => null),
    client.getCategories().catch(() => null),
  ]);

  const topCategories: CategoryNodeLike[] = (
    (categoriesRes?.categories as CategoryNodeLike[] | undefined) ?? []
  ).filter((c) => c.slug);

  const lines: string[] = [
    `# ${info?.name ?? 'Store'} — guide for AI agents`,
    '',
    ...(info?.metaDescription ? [`> ${info.metaDescription}`, ''] : []),
    'This is an e-commerce storefront. Product data, prices, and availability',
    'are rendered server-side into every page (no JavaScript execution needed)',
    'and marked up with schema.org Product / Offer / BreadcrumbList JSON-LD.',
    '',
    '## Machine-readable surfaces',
    '',
    `- Sitemap: ${baseUrl}/sitemap.xml (products, categories, articles, pages)`,
    `- AI summary: ${baseUrl}/llms.txt`,
    `- Blog RSS: ${baseUrl}/blog/rss.xml`,
    ...(channelId
      ? [
          `- Product feed (Google Shopping XML): ${apiUrl}/api/feeds/${channelId}/google-shopping.xml`,
          `- Product feed (JSONL): ${apiUrl}/api/feeds/${channelId}/openai-products.jsonl`,
          `- MCP endpoint (catalog tools, stateless JSON-RPC): ${apiUrl}/api/mcp/storefront/${channelId}`,
          '  Tools: search_products, get_product, list_categories, get_store_info. Read-only;',
          '  to buy, send the shopper to the product `url` — checkout happens on this site.',
        ]
      : []),
    `- IndexNow key: ${baseUrl}/indexnow-key.txt`,
    '',
    '## Key pages',
    '',
    `- [All products](${baseUrl}/products) — full catalog, filterable`,
    ...topCategories
      .slice(0, 20)
      .map((c) => `- [${c.name}](${baseUrl}/category/${c.slug}) — category page`),
    `- [Blog](${baseUrl}/blog) — guides and articles`,
    `- [FAQ](${baseUrl}/faq)`,
    `- [Contact](${baseUrl}/contact)`,
    '',
    '## Buying',
    '',
    `- Currency: ${info?.currency ?? 'see product pages'}`,
    '- Checkout happens on this site (cart → checkout). Carts and checkout',
    '  are session-based; agents should hand the shopper the product URL.',
    ...(info?.contactEmail ? ['', `## Contact`, '', `- Email: ${info.contactEmail}`] : []),
    '',
  ];

  return new Response(lines.join('\n'), {
    headers: { 'Content-Type': 'text/markdown; charset=utf-8' },
  });
}