import { Link } from "react-router";

import {
  getCounterpartLocale,
  getCounterpartPath,
  getDirection,
  LOCALE_ENDONYM,
  LOCALE_SHORT_LABEL,
  type Locale,
} from "./locale-path";

/* Reinforces the global :focus-visible rule in app.css with the same tier-2
   focus tokens, so the ring is visible even if a caller overrides `outline`. */
const FOCUS_RING =
  "focus-visible:outline-[color:var(--focus-ring-color)] " +
  "focus-visible:outline-[length:var(--focus-ring-width)] " +
  "focus-visible:outline-offset-[var(--focus-ring-offset)]";

export interface LanguageToggleProps {
  /** The locale the reader is currently on. */
  locale: Locale;
  /** Current pathname, e.g. "/en/news-and-updates". */
  pathname: string;
  /** Query string to carry across the switch. Usually `location.search`. */
  search?: string;
  /** Fragment to carry across the switch. Usually `location.hash`. */
  hash?: string;
  /** Accessible name of the pair ("Language"), in the reader's language. */
  label: string;
  /** Navigate with a full document request instead of a client transition. */
  reloadDocument?: boolean;
  className?: string;
}

/**
 * Both languages, side by side: the current locale in an accent chip, and the
 * other locale as a link to the same page under that locale.
 *
 * One tap to switch and no state to open, which is why the draft prefers it;
 * the drawer still uses <LanguageSwitcher />.
 * The current language is marked with `aria-current`, not by colour alone. The
 * link carries its own lang/hrefLang/dir and is named with the target
 * language's endonym ("العربية"), so a screen reader switches voice for it
 * while the visible "AR" stays a two-letter code.
 */
export function LanguageToggle({
  locale,
  pathname,
  search,
  hash,
  label,
  reloadDocument = false,
  className,
}: LanguageToggleProps) {
  const target = getCounterpartLocale(locale);
  const href = getCounterpartPath(pathname, locale, { search, hash });

  return (
    <div
      role="group"
      aria-label={label}
      className={[
        "flex shrink-0 items-center gap-xs text-[var(--text-secondary)]",
        className,
      ]
        .filter(Boolean)
        .join(" ")}
    >
      <span className="flex items-center">
        <span
          aria-current="true"
          lang={locale}
          dir={getDirection(locale)}
          className="label-md rounded-control bg-[var(--surface-accent)] px-xs py-2xs text-[var(--text-on-accent)]"
        >
          {LOCALE_SHORT_LABEL[locale]}
        </span>

        <Link
          to={href}
          reloadDocument={reloadDocument}
          hrefLang={target}
          lang={target}
          dir={getDirection(target)}
          aria-label={LOCALE_ENDONYM[target]}
          title={LOCALE_ENDONYM[target]}
          data-language-switcher={target}
          className={[
            "label-md rounded-control px-xs py-2xs no-underline",
            "text-[var(--text-secondary)]",
            "transition-colors duration-[var(--motion-duration-fast)]",
            "ease-[var(--motion-ease-standard)]",
            "hover:text-[var(--text-primary)]",
            FOCUS_RING,
          ].join(" ")}
        >
          <span aria-hidden="true">{LOCALE_SHORT_LABEL[target]}</span>
        </Link>
      </span>
    </div>
  );
}

export default LanguageToggle;

/* ---------------------------------------------------------------------------
   USAGE
   ---------------------------------------------------------------------------
   // Reading English at /en/news-and-updates -> "EN" chipped, "AR" links to
   // /ar/news-and-updates.
   <LanguageToggle locale="en" pathname="/en/news-and-updates" label="Language" />
   ------------------------------------------------------------------------ */