import type { Metadata, MetadataRoute } from "next";
import {
  ASSETS,
  CONTENT_CATALOG_SLUG_ORDER,
  contentBlogOgPath,
  getAssetPath,
} from "./assetUtils";
import metadataMessages from "../messages/en/metadata.json";

/**
 * Production origin. Sitemap URLs and prerendered canonicals use this when
 * no request host and no `CLOUDRON_APP_ORIGIN` are available.
 */
export const PRODUCTION_SITE_ORIGIN = "https://communityrule.info";

/** Open Graph / Twitter large-card raster size. */
const OG_IMAGE_SIZE = { width: 1200, height: 630 } as const;

const INDEXABLE_HOSTS = new Set([
  "communityrule.com",
  "www.communityrule.com",
  "communityrule.info",
  "www.communityrule.info",
]);

export const NO_INDEX_ROBOTS = { index: false, follow: false } as const;

/** Unlisted (guest-claim) rule pages stay shareable but must not be indexed. */
export function robotsForPublishedRule(isListed: boolean):
  | {
      index: false;
      follow: false;
    }
  | undefined {
  return isListed ? undefined : NO_INDEX_ROBOTS;
}

function hostnameFromHostHeader(host: string | null | undefined): string {
  if (!host) return "";
  return host.split(",")[0]?.trim().split(":")[0]?.toLowerCase() ?? "";
}

function isLoopbackHost(hostname: string): boolean {
  return (
    hostname === "localhost" ||
    hostname === "127.0.0.1" ||
    hostname === "0.0.0.0" ||
    hostname === "::1"
  );
}

/**
 * Prefer the public hostname Cloudron's proxy forwards. Standalone binds
 * `0.0.0.0`, which is not a crawlable host — fall back to `CLOUDRON_APP_ORIGIN`.
 */
export function resolveRequestHost(
  forwardedHost: string | null,
  host: string | null,
): string | null {
  if (forwardedHost) {
    const first = forwardedHost.split(",")[0]?.trim();
    if (first) return first;
  }

  if (host) {
    const hostname = hostnameFromHostHeader(host);
    if (!isLoopbackHost(hostname)) return host;
  }

  const origin = process.env.CLOUDRON_APP_ORIGIN?.trim();
  if (origin) {
    try {
      return new URL(origin).host;
    } catch {
      return host;
    }
  }

  return host;
}

/**
 * Absolute origin for canonical / `og:url` resolution. Uses the public
 * hostname of this instance (`CLOUDRON_APP_ORIGIN`, the same source
 * `resolveRequestHost` uses when the process binds to a loopback address)
 * so staging shares do not advertise production.
 */
export function originFromHost(host: string | null | undefined): string {
  const fromEnv = (): string | undefined => {
    const origin = process.env.CLOUDRON_APP_ORIGIN?.trim();
    if (!origin) return undefined;
    try {
      return new URL(origin).origin;
    } catch {
      return undefined;
    }
  };

  if (!host) {
    return fromEnv() ?? PRODUCTION_SITE_ORIGIN;
  }

  const hostname = hostnameFromHostHeader(host);
  if (!hostname || isLoopbackHost(hostname)) {
    if (hostname === "localhost") {
      const port = host.includes(":")
        ? host.slice(host.indexOf(":") + 1).split("/")[0]
        : "";
      return port ? `http://localhost:${port}` : "http://localhost:3000";
    }
    return fromEnv() ?? PRODUCTION_SITE_ORIGIN;
  }

  return `https://${hostname}`;
}

export function metadataBaseUrl(): URL {
  return new URL(originFromHost(null));
}

/** Origin baked into prerendered pages: app origin when set, otherwise production. */
export function configuredSiteOrigin(): string {
  return originFromHost(null);
}

/** Absolute URL for canonicals and JSON-LD. Same origin as `metadataBase`. */
export function absoluteSiteUrl(
  pathname: string,
  origin: string = configuredSiteOrigin(),
): string {
  const path = canonicalPath(pathname);
  if (path === "/") return origin;
  return `${origin}${path}`;
}

/** WebSite block. No SearchAction — the site has no search page. */
export function websiteJsonLd(origin: string) {
  return {
    "@context": "https://schema.org" as const,
    "@type": "WebSite" as const,
    name: "CommunityRule",
    url: origin,
  };
}

type ShareImage = {
  url: string;
  width: number;
  height: number;
  alt: string;
};

function shareImage(url: string, alt: string): ShareImage {
  return {
    url,
    width: OG_IMAGE_SIZE.width,
    height: OG_IMAGE_SIZE.height,
    alt,
  };
}

export function defaultShareImages(): ShareImage[] {
  return [
    shareImage(
      getAssetPath(ASSETS.OG_IMAGE),
      metadataMessages.shareImage.defaultAlt,
    ),
  ];
}

export function templatesShareImages(): ShareImage[] {
  return [
    shareImage(
      getAssetPath(ASSETS.OG_IMAGE_TEMPLATES),
      metadataMessages.shareImage.templatesAlt,
    ),
  ];
}

export function articleShareImages(
  slug: string,
  alt: string,
): ShareImage[] | undefined {
  if (!(CONTENT_CATALOG_SLUG_ORDER as readonly string[]).includes(slug)) {
    return undefined;
  }
  return [shareImage(contentBlogOgPath(slug), alt)];
}

function twitterImageUrls(images: ShareImage[]): string[] {
  return images.map((image) => image.url);
}

/**
 * Staging, restore-drill hosts, and local dev are not indexed. Override with
 * `SITE_INDEXING=true` / `false` when the hostname check is not enough.
 */
function isIndexableHost(host: string | null | undefined): boolean {
  const override = process.env.SITE_INDEXING?.trim().toLowerCase();
  if (override === "true") return true;
  if (override === "false") return false;
  return INDEXABLE_HOSTS.has(hostnameFromHostHeader(host));
}

function canonicalPath(pathname: string): string {
  const trimmed = pathname.trim();
  if (trimmed === "" || trimmed === "/") return "/";
  const withLeading = trimmed.startsWith("/") ? trimmed : `/${trimmed}`;
  const withoutQuery = withoutQueryOrHash(withLeading);
  if (withoutQuery.length > 1 && withoutQuery.endsWith("/")) {
    return withoutQuery.slice(0, -1);
  }
  return withoutQuery;
}

function withoutQueryOrHash(pathname: string): string {
  const q = pathname.indexOf("?");
  const h = pathname.indexOf("#");
  let end = pathname.length;
  if (q !== -1) end = Math.min(end, q);
  if (h !== -1) end = Math.min(end, h);
  return pathname.slice(0, end) || "/";
}

/**
 * Merge path canonical + `og:url` (resolved against `metadataBase`) and a
 * default 1200×630 share image. Callers override `openGraph.images` /
 * `twitter.images` for templates and articles.
 */
export function routeMetadata(
  pathname: string,
  metadata: Metadata = {},
): Metadata {
  const path = canonicalPath(pathname);
  const defaultImages = defaultShareImages();
  const openGraph = metadata.openGraph ?? {};
  const twitter = metadata.twitter ?? {};
  const pageTitle = typeof metadata.title === "string" ? metadata.title : undefined;
  const pageDescription =
    typeof metadata.description === "string" ? metadata.description : undefined;
  const mergedOpenGraph = {
    images: defaultImages,
    ...(pageTitle ? { title: pageTitle } : {}),
    ...(pageDescription ? { description: pageDescription } : {}),
    ...openGraph,
    url: openGraph.url ?? path,
  };
  const ogImages = mergedOpenGraph.images;
  const derivedTwitterImages = Array.isArray(ogImages)
    ? ogImages
        .map((image) => {
          if (typeof image === "string") return image;
          if (image instanceof URL) return image.href;
          const url = image.url;
          return typeof url === "string" ? url : url.href;
        })
        .filter((url) => url.length > 0)
    : twitterImageUrls(defaultImages);

  return {
    ...metadata,
    alternates: {
      ...metadata.alternates,
      canonical: path,
    },
    openGraph: mergedOpenGraph,
    twitter: {
      card: "summary_large_image" as const,
      ...(pageTitle ? { title: pageTitle } : {}),
      ...(pageDescription ? { description: pageDescription } : {}),
      images: derivedTwitterImages,
      ...twitter,
    },
  };
}

/**
 * Link unfurlers. Staging stays out of search indexes, and these agents can
 * still fetch the page so a shared link can show its image.
 */
const UNFURL_USER_AGENTS = [
  "Twitterbot",
  "facebookexternalhit",
  "Slackbot",
  "Discordbot",
  "LinkedInBot",
  "TelegramBot",
  "WhatsApp",
  "Bluesky",
] as const;

export function buildRobots(
  host: string | null | undefined,
): MetadataRoute.Robots {
  if (!isIndexableHost(host)) {
    return {
      rules: [
        { userAgent: "*", disallow: "/" },
        { userAgent: [...UNFURL_USER_AGENTS], allow: "/" },
      ],
    };
  }

  return {
    rules: {
      userAgent: "*",
      allow: "/",
    },
    sitemap: `${PRODUCTION_SITE_ORIGIN}/sitemap.xml`,
  };
}

export function sitemapUrl(pathname: string): string {
  return absoluteSiteUrl(pathname, PRODUCTION_SITE_ORIGIN);
}