/**
 * /sitemap.xml.ts — Custom sitemap with per-type priority/changefreq.
 *
 * Generates a sitemap by:
 *   1. Listing all static .astro pages (excluding 404 + dynamic [slug])
 *   2. Walking content collections (blog) for dynamic routes
 *   3. Classifying each URL into a category to assign priority + changefreq
 *
 * Per Astro 6, the file lives in src/pages/ and exports a GET handler.
 */
import type { APIRoute } from 'astro';
import { getCollection } from 'astro:content';

const SITE = 'https://dealplustech.com';

// ---------------------------------------------------------------------------
// URL classification
// ---------------------------------------------------------------------------

const NOINDEX_PAGES = new Set([
  'privacy-policy',
  'terms-and-conditions',
  '404',
]);

const PRODUCT_SLUGS = new Set([
  'aeroflex', 'armflex', 'durgo-avvs', 'grilles', 'maxflex',
  'pipe-coupling', 'realflex', 'water-pump', 'water-treatment',
  'ตู้ดับเพลิง',
  'ท่อ-hdpe', 'ท่อ-ppr-scg', 'ท่อ-ppr-thai-ppr', 'ท่อ-syler',
  'ท่อ-upvc', 'ท่อ-xy-lent',
  'ระบบรั้วไวน์แมน', 'รั้วเทวดา',
  'วาล์ว-valve', 'หัวจ่าย-ball-jet',
  'เครื่องเชื่อม-hdpe', 'เครื่องเชื่อม-ppr',
  'เทอร์โมเบรค-thermobreak', 'เม็กกรู๊ฟ-คับปลิ้ง',
]);

const HOMEPAGE_SLUGS = new Set(['index', 'all-products']);
const CATEGORY_SLUGS = new Set(['ระบบน้ำ']);
const STATIC_SLUGS = new Set(['about-us', 'contact-us', 'portfolio']);

type Entry = {
  loc: string;
  priority: number;
  changefreq: 'daily' | 'weekly' | 'monthly' | 'yearly';
  lastmod?: string;
};

function classify(slug: string): { priority: number; changefreq: Entry['changefreq'] } {
  if (slug === 'index') return { priority: 1.0, changefreq: 'weekly' };
  if (slug === 'all-products') return { priority: 0.9, changefreq: 'weekly' };
  if (PRODUCT_SLUGS.has(slug)) return { priority: 0.9, changefreq: 'monthly' };
  if (CATEGORY_SLUGS.has(slug)) return { priority: 0.8, changefreq: 'monthly' };
  if (STATIC_SLUGS.has(slug)) return { priority: 0.6, changefreq: 'yearly' };
  return { priority: 0.5, changefreq: 'monthly' };
}

function urlFromSlug(slug: string): string {
  if (slug === 'index') return `${SITE}/`;
  return `${SITE}/${slug}`;
}

// ---------------------------------------------------------------------------
// Build entries
// ---------------------------------------------------------------------------

async function buildEntries(): Promise<Entry[]> {
  // 1. Static pages — discovered via Vite's import.meta.glob
  const modules = import.meta.glob<true>('./*.astro');
  const pageFiles = Object.keys(modules)
    .map(p => p.replace(/^\.\//, '').replace(/\.astro$/, ''))
    .filter(slug => !slug.startsWith('[') && !NOINDEX_PAGES.has(slug));

  const entries: Entry[] = pageFiles.map(slug => {
    const { priority, changefreq } = classify(slug);
    return { loc: urlFromSlug(slug), priority, changefreq };
  });

  // 2. Blog posts (dynamic [slug] route)
  const articles = await getCollection('blog');
  for (const article of articles) {
    entries.push({
      loc: `${SITE}/${encodeURI('บทความ')}/${encodeURIComponent(article.id)}`,
      priority: 0.7,
      changefreq: 'yearly',
      lastmod: article.data.published_at.toISOString(),
    });
  }

  // 3. Blog index
  entries.push({
    loc: `${SITE}/${encodeURI('บทความ')}`,
    priority: 0.7,
    changefreq: 'weekly',
  });

  // Sort: homepage first, then by priority desc, then by URL asc
  entries.sort((a, b) => {
    if (a.loc === `${SITE}/`) return -1;
    if (b.loc === `${SITE}/`) return 1;
    if (a.priority !== b.priority) return b.priority - a.priority;
    return a.loc.localeCompare(b.loc);
  });

  return entries;
}

// ---------------------------------------------------------------------------
// XML serialiser
// ---------------------------------------------------------------------------

function escapeXml(s: string): string {
  return s
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;')
    .replace(/'/g, '&apos;');
}

function toXml(entries: Entry[]): string {
  const urls = entries.map(e => {
    const lastmod = e.lastmod ? `\n    <lastmod>${e.lastmod}</lastmod>` : '';
    return `  <url>
    <loc>${escapeXml(e.loc)}</loc>${lastmod}
    <changefreq>${e.changefreq}</changefreq>
    <priority>${e.priority.toFixed(1)}</priority>
  </url>`;
  }).join('\n');

  return `<?xml version="1.0" encoding="UTF-8"?>
<urlset xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
${urls}
</urlset>
`;
}

// ---------------------------------------------------------------------------
// Handler
// ---------------------------------------------------------------------------

export const GET: APIRoute = async () => {
  const entries = await buildEntries();
  const xml = toXml(entries);

  return new Response(xml, {
    status: 200,
    headers: {
      'Content-Type': 'application/xml; charset=utf-8',
      'Cache-Control': 'public, max-age=3600',
    },
  });
};