/* ============================================================================
   SEO
   ----------------------------------------------------------------------------
   One function builds the whole `meta` descriptor array for a page: title,
   description, robots, canonical, the en/ar/x-default hreflang set, Open Graph,
   Twitter, and any JSON-LD the route wants to attach.

   Pure and client-safe: `meta` also runs in the browser on a client-side
   navigation, so nothing here may touch `process.env`. The origin arrives as
   `siteUrl`, which the root loader resolves once per request via
   `getSiteUrl(request)` from ~/lib/env.server.
   ========================================================================= */

import type { MetaDescriptor } from "react-router";

import {
  DEFAULT_LOCALE,
  INTL_LOCALE,
  OG_LOCALE,
  SUPPORTED_LOCALES,
  type Locale,
} from "~/i18n/config";
import { getCounterpartLocale, localizedPath, stripLocale } from "~/i18n/paths";
import { getMessages } from "~/i18n/t";

export const SITE_NAME = "SHARP-ER";

/** Separator between the page title and the site name. */
const TITLE_SEPARATOR = " | ";

/** A JSON-LD node. Kept structural - schema.org has no useful TS type. */
export type JsonLd = Readonly<Record<string, unknown>>;

export interface SeoImage {
  /** Absolute URL, or a path rooted at the site (e.g. "/assets/og.png"). */
  readonly url: string;
  readonly alt?: string;
  readonly width?: number;
  readonly height?: number;
  /** MIME type, e.g. "image/png". */
  readonly type?: string;
}

export interface SeoArticle {
  readonly publishedTime?: string;
  readonly modifiedTime?: string;
  readonly authors?: readonly string[];
  readonly section?: string;
  readonly tags?: readonly string[];
}

export interface SeoInput {
  readonly locale: Locale;
  /** Pathname of the page INCLUDING its locale prefix, e.g. "/ar/contact". */
  readonly pathname: string;
  /** Site origin without a trailing slash, from the root loader. */
  readonly siteUrl: string;
  /** Page title without the site name - it is appended for you. */
  readonly title: string;
  readonly description?: string;
  readonly image?: SeoImage;
  readonly type?: "website" | "article";
  /** Emit `robots: noindex, nofollow`. Use on search and filter result pages. */
  readonly noIndex?: boolean;
  readonly keywords?: readonly string[];
  readonly article?: SeoArticle;
  /** Append " | SHARP-ER" to the title. Default true. */
  readonly appendSiteName?: boolean;
  /**
   * Also emit `<link rel="canonical">` and the hreflang set from THIS page's
   * meta. Default false, and it should normally stay false: the app shell
   * emits both for every route from `root.tsx`'s `Layout`, so a page that
   * writes its own `meta` cannot accidentally drop them. Turn it on only when
   * rendering a document outside that shell.
   */
  readonly alternates?: boolean;
  /** JSON-LD to embed, from the builders below or hand-written. */
  readonly jsonLd?: JsonLd | readonly JsonLd[];
}

/* ---------------------------------------------------------------------------
   URLS
   ------------------------------------------------------------------------ */

const ABSOLUTE_URL = /^(?:[a-z][a-z\d+\-.]*:|\/\/)/i;

/** Join a site origin and a path into an absolute URL. */
export function absoluteUrl(siteUrl: string, path: string): string {
  if (ABSOLUTE_URL.test(path)) return path;
  return `${siteUrl.replace(/\/+$/, "")}/${path.replace(/^\/+/, "")}`;
}

/** The canonical URL of a page. Trailing slashes are normalised away. */
export function canonicalUrl(siteUrl: string, pathname: string): string {
  const path = pathname.replace(/\/+$/, "") || "/";
  return absoluteUrl(siteUrl, path);
}

export interface LocaleAlternate {
  readonly locale: Locale;
  readonly hrefLang: string;
  readonly href: string;
}

/**
 * The hreflang set for a page: one entry per locale plus `x-default`, which
 * points at the default-locale URL because that is what a bare "/" resolves
 * to when no locale can be negotiated.
 */
export function alternateUrls(
  siteUrl: string,
  pathname: string,
): LocaleAlternate[] {
  const unprefixed = stripLocale(pathname);

  const alternates: LocaleAlternate[] = SUPPORTED_LOCALES.map((locale) => ({
    locale,
    hrefLang: locale,
    href: canonicalUrl(siteUrl, localizedPath(unprefixed, locale)),
  }));

  return [
    ...alternates,
    {
      locale: DEFAULT_LOCALE,
      hrefLang: "x-default",
      href: canonicalUrl(siteUrl, localizedPath(unprefixed, DEFAULT_LOCALE)),
    },
  ];
}

/* ---------------------------------------------------------------------------
   META
   ------------------------------------------------------------------------ */

function formatTitle(input: SeoInput): string {
  const { title, appendSiteName = true } = input;
  if (!appendSiteName) return title;
  if (title === SITE_NAME || title.includes(SITE_NAME)) return title;
  return `${title}${TITLE_SEPARATOR}${SITE_NAME}`;
}

/**
 * The full `meta` descriptor array for a page.
 *
 *   export function meta({ matches }: Route.MetaArgs) {
 *     const root = matches[0].data;
 *     return buildMeta({
 *       locale: root.locale, pathname: root.pathname, siteUrl: root.siteUrl,
 *       title: "Contact", description: "...",
 *     });
 *   }
 */
export function buildMeta(input: SeoInput): MetaDescriptor[] {
  const {
    locale,
    pathname,
    siteUrl,
    description,
    image,
    type = "website",
    noIndex = false,
    keywords,
    article,
    alternates = false,
    jsonLd,
  } = input;

  const messages = getMessages(locale);
  const title = formatTitle(input);
  const url = canonicalUrl(siteUrl, pathname);
  const descriptionText = description ?? messages.site.description;
  const counterpart = getCounterpartLocale(locale);

  const descriptors: MetaDescriptor[] = [
    { title },
    { name: "description", content: descriptionText },
  ];

  if (keywords && keywords.length > 0) {
    descriptors.push({ name: "keywords", content: keywords.join(", ") });
  }

  descriptors.push({
    name: "robots",
    content: noIndex ? "noindex, nofollow" : "index, follow",
  });

  if (alternates) {
    descriptors.push({ tagName: "link", rel: "canonical", href: url });

    for (const alternate of alternateUrls(siteUrl, pathname)) {
      descriptors.push({
        tagName: "link",
        rel: "alternate",
        hrefLang: alternate.hrefLang,
        href: alternate.href,
      });
    }
  }

  descriptors.push(
    { property: "og:type", content: type },
    { property: "og:site_name", content: SITE_NAME },
    { property: "og:title", content: title },
    { property: "og:description", content: descriptionText },
    { property: "og:url", content: url },
    { property: "og:locale", content: OG_LOCALE[locale] },
    { property: "og:locale:alternate", content: OG_LOCALE[counterpart] },
  );

  if (image) {
    const imageUrl = absoluteUrl(siteUrl, image.url);
    descriptors.push({ property: "og:image", content: imageUrl });
    if (image.alt) {
      descriptors.push({ property: "og:image:alt", content: image.alt });
    }
    if (image.width) {
      descriptors.push({
        property: "og:image:width",
        content: String(image.width),
      });
    }
    if (image.height) {
      descriptors.push({
        property: "og:image:height",
        content: String(image.height),
      });
    }
    if (image.type) {
      descriptors.push({ property: "og:image:type", content: image.type });
    }
  }

  if (type === "article" && article) {
    if (article.publishedTime) {
      descriptors.push({
        property: "article:published_time",
        content: article.publishedTime,
      });
    }
    if (article.modifiedTime) {
      descriptors.push({
        property: "article:modified_time",
        content: article.modifiedTime,
      });
    }
    if (article.section) {
      descriptors.push({
        property: "article:section",
        content: article.section,
      });
    }
    for (const author of article.authors ?? []) {
      descriptors.push({ property: "article:author", content: author });
    }
    for (const tag of article.tags ?? []) {
      descriptors.push({ property: "article:tag", content: tag });
    }
  }

  descriptors.push(
    {
      name: "twitter:card",
      content: image ? "summary_large_image" : "summary",
    },
    { name: "twitter:title", content: title },
    { name: "twitter:description", content: descriptionText },
  );

  if (image) {
    descriptors.push({
      name: "twitter:image",
      content: absoluteUrl(siteUrl, image.url),
    });
    if (image.alt) {
      descriptors.push({ name: "twitter:image:alt", content: image.alt });
    }
  }

  for (const node of toArray(jsonLd)) {
    descriptors.push({ "script:ld+json": node });
  }

  return descriptors;
}

function toArray(value: JsonLd | readonly JsonLd[] | undefined): JsonLd[] {
  if (!value) return [];
  return Array.isArray(value) ? [...value] : [value as JsonLd];
}

/* ---------------------------------------------------------------------------
   JSON-LD BUILDERS
   Facts are taken from the ToR and the approved draft copy: EU-funded,
   December 2025 - December 2027, nationwide Libya, Acted (lead) with UEC and
   SBE. Nothing here is speculative.
   ------------------------------------------------------------------------ */

const SCHEMA_CONTEXT = "https://schema.org";

export const CONSORTIUM_PARTNERS = [
  { name: "Acted", role: "Lead implementing partner" },
  { name: "United Efforts Consultancy", role: "Consortium partner" },
  { name: "Stichting Bureau Ensemble", role: "Consortium partner" },
] as const;

export interface OrganizationJsonLdInput {
  readonly siteUrl: string;
  readonly locale: Locale;
  /** Public profiles, e.g. the project's Facebook page. */
  readonly sameAs?: readonly string[];
  readonly email?: string;
}

/** Organization JSON-LD for the site itself. Emit it once, from the home page. */
export function buildOrganizationJsonLd({
  siteUrl,
  locale,
  sameAs,
  email,
}: OrganizationJsonLdInput): JsonLd {
  const messages = getMessages(locale);

  return {
    "@context": SCHEMA_CONTEXT,
    "@type": "Organization",
    name: messages.site.name,
    alternateName: messages.site.fullName,
    description: messages.site.description,
    url: canonicalUrl(siteUrl, localizedPath("/", locale)),
    logo: absoluteUrl(siteUrl, "/assets/sharp-er-logo.png"),
    inLanguage: INTL_LOCALE[locale],
    areaServed: { "@type": "Country", name: "Libya" },
    funder: { "@type": "Organization", name: "European Union" },
    member: CONSORTIUM_PARTNERS.map((partner) => ({
      "@type": "Organization",
      name: partner.name,
    })),
    ...(email ? { email } : {}),
    ...(sameAs && sameAs.length > 0 ? { sameAs: [...sameAs] } : {}),
  };
}

export interface WebSiteJsonLdInput {
  readonly siteUrl: string;
  readonly locale: Locale;
  /** Path of the site search route, e.g. "/en/search". Omit to skip the action. */
  readonly searchPath?: string;
}

export function buildWebSiteJsonLd({
  siteUrl,
  locale,
  searchPath,
}: WebSiteJsonLdInput): JsonLd {
  const messages = getMessages(locale);

  return {
    "@context": SCHEMA_CONTEXT,
    "@type": "WebSite",
    name: messages.site.name,
    url: canonicalUrl(siteUrl, localizedPath("/", locale)),
    inLanguage: INTL_LOCALE[locale],
    ...(searchPath
      ? {
          potentialAction: {
            "@type": "SearchAction",
            target: {
              "@type": "EntryPoint",
              urlTemplate: `${absoluteUrl(siteUrl, searchPath)}?q={search_term_string}`,
            },
            "query-input": "required name=search_term_string",
          },
        }
      : {}),
  };
}

export interface EventJsonLdInput {
  readonly siteUrl: string;
  readonly locale: Locale;
  readonly name: string;
  /** Path of the event page, including the locale prefix. */
  readonly pathname: string;
  /** ISO 8601. */
  readonly startDate: string;
  readonly endDate?: string;
  readonly description?: string;
  readonly image?: string;
  /** Venue name, e.g. "Tripoli". Omit for an online-only event. */
  readonly locationName?: string;
  readonly addressLocality?: string;
  readonly addressCountry?: string;
  /** Joining URL for an online or hybrid event. */
  readonly onlineUrl?: string;
  readonly isOnline?: boolean;
  readonly registrationUrl?: string;
  readonly status?: "scheduled" | "cancelled" | "postponed" | "rescheduled";
  readonly organizerName?: string;
}

const EVENT_STATUS: Readonly<Record<NonNullable<EventJsonLdInput["status"]>, string>> = {
  scheduled: "https://schema.org/EventScheduled",
  cancelled: "https://schema.org/EventCancelled",
  postponed: "https://schema.org/EventPostponed",
  rescheduled: "https://schema.org/EventRescheduled",
};

/** Event JSON-LD for an event detail page or an events listing. */
export function buildEventJsonLd(input: EventJsonLdInput): JsonLd {
  const {
    siteUrl,
    locale,
    name,
    pathname,
    startDate,
    endDate,
    description,
    image,
    locationName,
    addressLocality,
    addressCountry = "LY",
    onlineUrl,
    isOnline = false,
    registrationUrl,
    status = "scheduled",
    organizerName = SITE_NAME,
  } = input;

  const hasPhysicalLocation = Boolean(locationName ?? addressLocality);
  const attendanceMode = isOnline
    ? hasPhysicalLocation
      ? "https://schema.org/MixedEventAttendanceMode"
      : "https://schema.org/OnlineEventAttendanceMode"
    : "https://schema.org/OfflineEventAttendanceMode";

  const physicalLocation = hasPhysicalLocation
    ? {
        "@type": "Place",
        name: locationName ?? addressLocality,
        address: {
          "@type": "PostalAddress",
          ...(addressLocality ? { addressLocality } : {}),
          addressCountry,
        },
      }
    : undefined;

  const virtualLocation = onlineUrl
    ? { "@type": "VirtualLocation", url: onlineUrl }
    : undefined;

  const locations = [physicalLocation, virtualLocation].filter(Boolean);

  return {
    "@context": SCHEMA_CONTEXT,
    "@type": "Event",
    name,
    startDate,
    ...(endDate ? { endDate } : {}),
    ...(description ? { description } : {}),
    ...(image ? { image: absoluteUrl(siteUrl, image) } : {}),
    url: canonicalUrl(siteUrl, pathname),
    inLanguage: INTL_LOCALE[locale],
    eventAttendanceMode: attendanceMode,
    eventStatus: EVENT_STATUS[status],
    ...(locations.length === 1
      ? { location: locations[0] }
      : locations.length > 1
        ? { location: locations }
        : {}),
    organizer: { "@type": "Organization", name: organizerName },
    ...(registrationUrl
      ? {
          offers: {
            "@type": "Offer",
            url: registrationUrl,
            price: "0",
            priceCurrency: "LYD",
            availability: "https://schema.org/InStock",
          },
        }
      : {}),
  };
}

export interface ArticleJsonLdInput {
  readonly siteUrl: string;
  readonly locale: Locale;
  readonly headline: string;
  /** Path of the article, including the locale prefix. */
  readonly pathname: string;
  readonly datePublished: string;
  readonly dateModified?: string;
  readonly description?: string;
  readonly image?: string;
  readonly authorName?: string;
  readonly section?: string;
  readonly keywords?: readonly string[];
}

/** Article JSON-LD for a news item, a publication or a knowledge-hub page. */
export function buildArticleJsonLd(input: ArticleJsonLdInput): JsonLd {
  const {
    siteUrl,
    locale,
    headline,
    pathname,
    datePublished,
    dateModified,
    description,
    image,
    authorName,
    section,
    keywords,
  } = input;

  const url = canonicalUrl(siteUrl, pathname);

  return {
    "@context": SCHEMA_CONTEXT,
    "@type": "Article",
    headline,
    ...(description ? { description } : {}),
    ...(image ? { image: absoluteUrl(siteUrl, image) } : {}),
    datePublished,
    dateModified: dateModified ?? datePublished,
    inLanguage: INTL_LOCALE[locale],
    url,
    mainEntityOfPage: { "@type": "WebPage", "@id": url },
    author: { "@type": "Organization", name: authorName ?? SITE_NAME },
    publisher: {
      "@type": "Organization",
      name: SITE_NAME,
      logo: {
        "@type": "ImageObject",
        url: absoluteUrl(siteUrl, "/assets/sharp-er-logo.png"),
      },
    },
    ...(section ? { articleSection: section } : {}),
    ...(keywords && keywords.length > 0 ? { keywords: keywords.join(", ") } : {}),
  };
}

export interface BreadcrumbItem {
  readonly name: string;
  /** Path including the locale prefix. */
  readonly pathname: string;
}

/** BreadcrumbList JSON-LD. Pass the trail from the home page to this page. */
export function buildBreadcrumbJsonLd(
  siteUrl: string,
  items: readonly BreadcrumbItem[],
): JsonLd {
  return {
    "@context": SCHEMA_CONTEXT,
    "@type": "BreadcrumbList",
    itemListElement: items.map((item, index) => ({
      "@type": "ListItem",
      position: index + 1,
      name: item.name,
      item: canonicalUrl(siteUrl, item.pathname),
    })),
  };
}