/* ============================================================================
   ROOT LOADER DATA, READ FROM `meta`
   ----------------------------------------------------------------------------
   `buildMeta` needs the locale, the pathname and the site origin, and all
   three are resolved once per request by the root loader. A `meta` function
   reaches them through its `matches`.

   React Router 8 names that property `loaderData` on every match (see
   `CreateMetaArgs` in react-router/lib/types/route-module-annotations.d.ts and
   the `Meta` component that builds the array). Version 7 called it `data`, and
   plenty of examples still do, so both are read here.

   Defensive rather than indexed: `matches[0]` has no data at all while the
   root loader is in flight or on an error render, and a `meta` that throws
   takes the whole document down with it.
   ========================================================================= */

import { DEFAULT_LOCALE, isLocale, localizedPath, type Locale } from "~/i18n";

export interface RootSeo {
  readonly locale: Locale;
  /** Pathname INCLUDING the locale prefix. */
  readonly pathname: string;
  /** Site origin without a trailing slash. */
  readonly siteUrl: string;
}

/** Matches the default in ~/lib/env.server, for the case root data is absent. */
const FALLBACK_SITE_URL = "https://sharper.ly";

function readMatchData(match: unknown): Record<string, unknown> | undefined {
  if (!match || typeof match !== "object") return undefined;

  const { id, loaderData, data } = match as {
    id?: unknown;
    loaderData?: unknown;
    data?: unknown;
  };
  if (id !== "root") return undefined;

  const payload = loaderData ?? data;
  return payload && typeof payload === "object"
    ? (payload as Record<string, unknown>)
    : undefined;
}

/** The root loader's `{ locale, pathname, siteUrl }`, with safe fallbacks. */
export function readRootSeo(matches: readonly unknown[]): RootSeo {
  for (const match of matches) {
    const record = readMatchData(match);
    if (!record) continue;

    const locale = isLocale(record.locale) ? record.locale : DEFAULT_LOCALE;

    return {
      locale,
      pathname:
        typeof record.pathname === "string"
          ? record.pathname
          : localizedPath("/", locale),
      siteUrl:
        typeof record.siteUrl === "string" ? record.siteUrl : FALLBACK_SITE_URL,
    };
  }

  return {
    locale: DEFAULT_LOCALE,
    pathname: localizedPath("/", DEFAULT_LOCALE),
    siteUrl: FALLBACK_SITE_URL,
  };
}