import type { MetadataRoute } from "next";
import { unstable_noStore as noStore } from "next/cache";

import { routing } from "@/i18n/routing";
import { getMaintenanceMode, getSeoSettings, getSiteSettings } from "@/lib/app-config";
import { getLocalizedPath, type AppLocale } from "@/lib/locale";
import { toAbsoluteUrl } from "@/lib/metadata";
import { getActivePortfolioCategories, getPublishedPortfolioProjects } from "@/lib/portfolio";

export const dynamic = "force-dynamic";

type EntryOptions = Pick<MetadataRoute.Sitemap[number], "changeFrequency" | "priority" | "lastModified">;

/**
 * One entry per locale for a path, each carrying hreflang alternates so search
 * engines link the three language versions together.
 */
export function buildLocalizedEntries(
  pathname: string,
  defaultLocale: AppLocale,
  options?: EntryOptions,
): MetadataRoute.Sitemap {
  const languages = Object.fromEntries(
    routing.locales.map((locale) => [locale, toAbsoluteUrl(getLocalizedPath(locale, pathname, defaultLocale))]),
  ) as Record<AppLocale, string>;

  return routing.locales.map((locale) => ({
    url: languages[locale],
    lastModified: options?.lastModified,
    changeFrequency: options?.changeFrequency,
    priority: options?.priority,
    alternates: {
      languages: {
        ...languages,
        "x-default": languages[defaultLocale],
      },
    },
  }));
}

export default async function sitemap(): Promise<MetadataRoute.Sitemap> {
  noStore();
  const [siteSettings, seo, maintenanceEnabled] = await Promise.all([
    getSiteSettings(),
    getSeoSettings(),
    getMaintenanceMode(),
  ]);

  // While the site is hidden (maintenance) or indexing is off, publish an
  // empty sitemap instead of advertising URLs that redirect or are noindex.
  if (maintenanceEnabled || !seo.allowIndexing) {
    return [];
  }

  const defaultLocale = siteSettings.defaultLocale;

  let projects: Awaited<ReturnType<typeof getPublishedPortfolioProjects>> = [];
  let categories: Awaited<ReturnType<typeof getActivePortfolioCategories>> = [];

  try {
    [projects, categories] = await Promise.all([
      getPublishedPortfolioProjects(),
      getActivePortfolioCategories(),
    ]);
  } catch {
    projects = [];
    categories = [];
  }

  // Only categories that actually have published work get a landing URL;
  // an empty category page has nothing to index.
  const categoriesWithProjects = categories.filter((category) =>
    projects.some((project) => project.category.slug === category.slug),
  );

  const latestProjectDate = projects.reduce<Date | undefined>((latest, project) => {
    const date = project.publishedAt ?? undefined;

    return date && (!latest || date > latest) ? date : latest;
  }, undefined);

  return [
    ...buildLocalizedEntries("/", defaultLocale, {
      changeFrequency: "weekly",
      priority: 1,
      lastModified: latestProjectDate,
    }),
    ...buildLocalizedEntries("/about", defaultLocale, {
      changeFrequency: "monthly",
      priority: 0.8,
    }),
    ...buildLocalizedEntries("/portfolio", defaultLocale, {
      changeFrequency: "weekly",
      priority: 0.9,
      lastModified: latestProjectDate,
    }),
    ...categoriesWithProjects.flatMap((category) =>
      buildLocalizedEntries(`/portfolio/${category.slug}`, defaultLocale, {
        changeFrequency: "weekly",
        priority: 0.8,
        lastModified: latestProjectDate,
      }),
    ),
    ...buildLocalizedEntries("/contact", defaultLocale, {
      changeFrequency: "monthly",
      priority: 0.7,
    }),
    ...projects.flatMap((project) =>
      buildLocalizedEntries(`/portfolio/${project.slug}`, defaultLocale, {
        lastModified: project.publishedAt ?? undefined,
        changeFrequency: "monthly",
        priority: 0.8,
      }),
    ),
  ];
}