import { getNormalizedTranslations } from '$lib/cms';
import { isCmsAvailable } from '$lib/cms-health.server';
import { maintenanceResponse } from '$lib/maintenance.server';
import { TRANSLATION_BUNDLE_SLUG } from '$lib/constants';
import { env as envPublic } from '$env/dynamic/public';
import { logWarn } from '$lib/log.server';
import { lookupRedirect } from '$lib/redirects.server';
import type { Handle } from '@sveltejs/kit';

/**
 * Page-Routen: kurze Edge-Cache + SWR. Webhook purged App-Cache,
 * Edge läuft via stale-while-revalidate auf den warmen App-Cache.
 */
const PAGE_CACHE_CONTROL =
  'public, max-age=0, s-maxage=30, stale-while-revalidate=300';

const ASSET_EXT_RE = /\.(ico|png|jpe?g|webp|gif|svg|css|js|mjs|map|woff2?|ttf|otf|txt|xml|json|pdf)$/i;

function isCacheablePath(pathname: string): boolean {
  if (pathname.startsWith('/api/')) return false;
  if (pathname.startsWith('/cms-images/')) return false;
  if (pathname.startsWith('/_app/')) return false;
  return true;
}

/** Pfade auf denen wir vor dem Resolve einen CMS-Health-Check machen. */
function shouldHealthCheck(pathname: string): boolean {
  if (pathname.startsWith('/api/')) return false;
  if (pathname.startsWith('/_app/')) return false;
  if (pathname.startsWith('/cms-images/')) return false;
  if (pathname.startsWith('/cms-files/')) return false;
  if (pathname === '/sitemap.xml' || pathname === '/robots.txt') return false;
  if (ASSET_EXT_RE.test(pathname)) return false;
  return true;
}

function isMaintenanceSimulation(pathname: string, search: URLSearchParams): boolean {
  if (pathname === '/maintenance' || pathname === '/maintenance/') return true;
  if (search.has('cms_down')) return true;
  return false;
}

/**
 * Legacy /blog/* + /p/* Pfade auf das neue /posts/* Schema mappen.
 * Liefert Ziel-Pfad oder null. Permanente 301-Redirects → werden vom
 * Browser/CDN gecacht, daher kein Render-Aufruf nötig.
 */
function legacyRedirectTarget(pathname: string): string | null {
  if (pathname === '/blog' || pathname === '/blog/') return '/posts/';
  const m1 = pathname.match(/^\/blog\/page\/([^/]+)\/?$/);
  if (m1) return `/posts/page/${m1[1]}/`;
  const m2 = pathname.match(/^\/blog\/tag\/([^/]+)\/?$/);
  if (m2) return `/posts/tag/${m2[1]}/`;
  const m3 = pathname.match(/^\/p\/([^/]+)\/?$/);
  if (m3) return `/post/${m3[1]}/`;
  return null;
}

export const handle: Handle = async ({ event, resolve }) => {
  // Simulation: erlaubt manuelles Triggern der Maintenance-Seite ohne
  // CMS abzuschalten. /maintenance oder ?cms_down=1.
  if (isMaintenanceSimulation(event.url.pathname, event.url.searchParams)) {
    return maintenanceResponse(200);
  }

  // CMS-verwaltete Redirects (Admin UI → /admin/plugins/redirects).
  // Editor-Regeln gewinnen gegen hardcoded Legacy-Patterns; nur GET, sonst
  // brechen POST-Forms beim Pfadwechsel.
  if (event.request.method === 'GET') {
    const cmsRedirect = await lookupRedirect(event.url.pathname);
    if (cmsRedirect) {
      const search = event.url.search;
      const dest =
        cmsRedirect.to.startsWith('http') || !search
          ? cmsRedirect.to
          : `${cmsRedirect.to}${search}`;
      return new Response(null, {
        status: cmsRedirect.status,
        headers: { location: dest },
      });
    }
  }

  // Legacy-Pfade (/blog, /p) → /posts, /post. Vor Health-Check, weil
  // SvelteKit-Routing/CMS-Calls dafür unnötig.
  const redirectTo = legacyRedirectTarget(event.url.pathname);
  if (redirectTo) {
    const dest = `${redirectTo}${event.url.search}`;
    return new Response(null, { status: 301, headers: { location: dest } });
  }

  // Echter Ausfall: vor dem ersten CMS-Call prüfen ob die API antwortet.
  // Cached, daher kein Roundtrip pro Request.
  if (event.request.method === 'GET' && shouldHealthCheck(event.url.pathname)) {
    const ok = await isCmsAvailable();
    if (!ok) return maintenanceResponse(503);
  }

  try {
    event.locals.translations = await getNormalizedTranslations(
      TRANSLATION_BUNDLE_SLUG,
      { locale: 'de' },
    );
  } catch (err) {
    event.locals.translations = {};
    logWarn('hooks.translations', err);
  }

  const response = await resolve(event, {
    preload: ({ type, path }) => {
      if (type === 'js' || type === 'css') return true;
      if (type === 'font') {
        return /inter-latin-(400|700)-normal\.[a-f0-9]*\.?woff2$/i.test(path);
      }
      return false;
    },
  });

  const isPreview =
    event.url.searchParams.has('preview') ||
    event.url.searchParams.has('preview_draft');
  const isPreviewDraft = event.url.searchParams.has('preview_draft');

  // Vite-versioned assets: content-hashed filenames → safe to cache 1 year.
  if (event.url.pathname.startsWith('/_app/immutable/')) {
    response.headers.set('cache-control', 'public, max-age=31536000, immutable');
  } else if (
    event.request.method === 'GET' &&
    isCacheablePath(event.url.pathname) &&
    !isPreview &&
    !response.headers.has('cache-control')
  ) {
    response.headers.set('cache-control', PAGE_CACHE_CONTROL);
  }

  if (
    event.request.method === 'GET' &&
    !response.headers.has('x-robots-tag') &&
    (response.headers.get('content-type') ?? '').includes('text/html')
  ) {
    response.headers.set(
      'x-robots-tag',
      isPreview
        ? 'noindex, nofollow'
        : 'index, follow, max-image-preview:large, max-snippet:-1',
    );
  }

  // Live-preview: allow the admin iframe to embed this response. The admin
  // origin is configured via PUBLIC_PREVIEW_PARENT_ORIGIN; when unset we fall
  // back to wildcard (dev only). Outside live-preview we leave existing
  // headers alone so production hardening (X-Frame-Options / CSP from Caddy)
  // stays intact.
  if (isPreviewDraft) {
    const parent = (envPublic.PUBLIC_PREVIEW_PARENT_ORIGIN ?? '').trim();
    response.headers.set(
      'content-security-policy',
      `frame-ancestors 'self' ${parent || '*'}`,
    );
    response.headers.delete('x-frame-options');
  }

  return response;
};