import type { MetadataRoute } from 'next';
import { locales } from '@/i18n/config';
import { fetchActiveListings } from '@/lib/listings-server';

const siteUrl = process.env['NEXT_PUBLIC_SITE_URL'] || 'https://goodgo.vn';

/**
 * Dynamic sitemap that includes:
 *  - Static pages (home, search, login, register) per locale
 *  - All active property listings per locale
 *
 * ISR: the server-side fetch in fetchActiveListings uses `next: { revalidate: 3600 }`
 * so the sitemap is regenerated roughly every hour.
 */
export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
  // ------------------------------------------------------------------
  // 1. Static pages
  // ------------------------------------------------------------------
  const staticRoutes: MetadataRoute.Sitemap = [];

  for (const locale of locales) {
    staticRoutes.push(
      {
        url: `${siteUrl}/${locale}`,
        lastModified: new Date(),
        changeFrequency: 'daily',
        priority: 1,
      },
      {
        url: `${siteUrl}/${locale}/search`,
        lastModified: new Date(),
        changeFrequency: 'daily',
        priority: 0.9,
      },
      {
        url: `${siteUrl}/${locale}/login`,
        lastModified: new Date(),
        changeFrequency: 'monthly',
        priority: 0.3,
      },
      {
        url: `${siteUrl}/${locale}/register`,
        lastModified: new Date(),
        changeFrequency: 'monthly',
        priority: 0.3,
      },
    );
  }

  // ------------------------------------------------------------------
  // 2. Dynamic listing pages
  // ------------------------------------------------------------------
  const listingRoutes: MetadataRoute.Sitemap = [];

  try {
    // Fetch up to 1000 listings per page, paginate if needed.
    // For very large catalogs this could be split into multiple sitemap
    // indices, but for the current scale (<50k) a single file is fine.
    let page = 1;
    let totalPages = 1;

    do {
      const result = await fetchActiveListings({ page, limit: 1000 });
      totalPages = result.totalPages;

      for (const listing of result.data) {
        for (const locale of locales) {
          listingRoutes.push({
            url: `${siteUrl}/${locale}/listings/${listing.id}`,
            lastModified: listing.publishedAt
              ? new Date(listing.publishedAt)
              : new Date(listing.createdAt),
            changeFrequency: 'weekly',
            priority: 0.8,
          });
        }
      }

      page++;
    } while (page <= totalPages);
  } catch {
    // If the API is unreachable, return static pages only.
    // The sitemap will be retried on the next request (ISR).
  }

  return [...staticRoutes, ...listingRoutes];
}