import type { MetadataRoute } from 'next';
import { getCanonicalSiteUrl } from '@/core/lib/site-url';

/**
 * robots.txt with an explicit AI-crawler policy.
 *
 * Merchants WANT to be recommended by AI assistants, so the bots that power
 * AI search/answers are allowed by name — an explicit allow survives any
 * future tightening of the `*` rule and documents intent to auditors:
 *
 *   - OAI-SearchBot / ChatGPT-User  → ChatGPT search + shopping visibility
 *   - Claude-SearchBot / Claude-User → Claude search + user-requested reads
 *   - PerplexityBot / Perplexity-User → Perplexity shopping visibility
 *   - Bingbot → also feeds Microsoft Copilot answers
 *   - Applebot → Siri / Apple search surfaces
 *   - Amazonbot → Alexa / Amazon shopping surfaces
 *
 * TRAINING bots (GPTBot, ClaudeBot, CCBot, Google-Extended, Meta-
 * ExternalAgent, Applebot-Extended) are also allowed by default: model-weight
 * familiarity with the store feeds zero-shot recommendations, which is what a
 * store wants. A merchant who objects to AI training on their content can
 * move those user-agents to a `disallow: '/'` rule — that does NOT affect
 * search visibility (Google-Extended, for example, has no effect on Google
 * Search or AI Overviews; it only gates Gemini training).
 *
 * Checkout/account/API paths stay disallowed for every agent.
 */
const DISALLOWED_PATHS = ['/api/', '/auth/', '/checkout/', '/account/'];

const AI_SEARCH_BOTS = [
  'OAI-SearchBot',
  'ChatGPT-User',
  'Claude-SearchBot',
  'Claude-User',
  'PerplexityBot',
  'Perplexity-User',
  'Bingbot',
  'Applebot',
  'Amazonbot',
];

const AI_TRAINING_BOTS = [
  'GPTBot',
  'ClaudeBot',
  'CCBot',
  'Google-Extended',
  'Meta-ExternalAgent',
  'Applebot-Extended',
];

export default async function robots(): Promise<MetadataRoute.Robots> {
  const baseUrl = await getCanonicalSiteUrl();

  return {
    rules: [
      {
        userAgent: '*',
        allow: '/',
        disallow: DISALLOWED_PATHS,
      },
      {
        userAgent: AI_SEARCH_BOTS,
        allow: '/',
        disallow: DISALLOWED_PATHS,
      },
      {
        userAgent: AI_TRAINING_BOTS,
        allow: '/',
        disallow: DISALLOWED_PATHS,
      },
    ],
    sitemap: `${baseUrl}/sitemap.xml`,
  };
}