import { useQuery } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';
import { Link } from 'react-router';

import { fetchReadiness, readyQueryKey } from '@/api/health';
import { fetchMeta, metaQueryKey } from '@/api/meta';
import { Badge, Button, Card } from '@/components/ui/primitives';
import { StatBytes, StatRow } from '@/components/ui/StatRow';
import { supportedLanguages, type SupportedLanguage } from '@/i18n';
import { useApiErrorMessage } from '@/lib/useApiErrorMessage';
import { useUiStore } from '@/stores/ui';

/** Публичная страница состояния инстанса: мета, healthz/readyz, тема и язык. */
export default function StatusPage() {
  const { t, i18n } = useTranslation();
  const describeError = useApiErrorMessage();
  const theme = useUiStore((state) => state.theme);
  const toggleTheme = useUiStore((state) => state.toggleTheme);
  const locale = i18n.resolvedLanguage ?? 'ru';

  const meta = useQuery({
    queryKey: metaQueryKey,
    queryFn: ({ signal }) => fetchMeta(signal),
    retry: 1,
  });

  const readiness = useQuery({
    queryKey: readyQueryKey,
    queryFn: ({ signal }) => fetchReadiness(signal),
    retry: 1,
    refetchInterval: 30_000,
  });

  const online = readiness.isSuccess || meta.isSuccess;
  const schemaReady = readiness.data?.checks['database'] === 'ok';

  const changeLanguage = (language: SupportedLanguage): void => {
    window.localStorage.setItem('glchat.language', language);
    void i18n.changeLanguage(language);
  };

  return (
    <div className="mx-auto flex min-h-full w-full max-w-3xl flex-col gap-6 px-4 py-10">
      <header className="flex flex-wrap items-center justify-between gap-4">
        <div>
          <h1 className="text-2xl font-semibold tracking-tight">{t('app.name')}</h1>
          <p className="mt-1 text-fg-muted">{t('app.tagline')}</p>
        </div>
        <div className="flex items-center gap-2">
          <Badge aria-live="polite" data-testid="connection-state">
            <span
              aria-hidden="true"
              className={`h-2 w-2 rounded-full ${online ? 'bg-success' : 'bg-danger'}`}
            />
            {t(online ? 'health.online' : 'health.offline')}
          </Badge>
          <Button variant="ghost" onClick={toggleTheme}>
            {t(theme === 'dark' ? 'theme.switchToLight' : 'theme.switchToDark')}
          </Button>
          <label className="flex items-center gap-1 text-sm text-fg-muted">
            <span className="sr-only">{t('language.label')}</span>
            <select
              className="rounded-[var(--radius-sm)] border border-border/60 bg-surface-2 px-2 py-1 text-fg"
              value={locale.startsWith('en') ? 'en' : 'ru'}
              onChange={(event) => changeLanguage(event.target.value === 'en' ? 'en' : 'ru')}
            >
              {supportedLanguages.map((language) => (
                <option key={language} value={language}>
                  {t(`language.${language}`)}
                </option>
              ))}
            </select>
          </label>
        </div>
      </header>

      <Card>
        <h2 className="text-lg font-semibold">{t('status.title')}</h2>
        <p className="mt-1 text-fg-muted">{t('status.description')}</p>

        {meta.isPending ? (
          <p className="mt-4 text-fg-muted" role="status">
            {t('status.connecting')}
          </p>
        ) : null}

        {meta.isError ? (
          <div className="mt-4 flex items-center justify-between gap-4" role="alert">
            <p className="text-danger">{describeError(meta.error)}</p>
            <Button variant="ghost" onClick={() => void meta.refetch()}>
              {t('status.retry')}
            </Button>
          </div>
        ) : null}

        {meta.data ? (
          <dl className="mt-4 text-sm">
            <StatRow label={t('status.instance')} value={meta.data.name} />
            <StatRow label={t('status.version')} value={meta.data.version} />
            <StatRow label={t('status.apiVersion')} value={meta.data.api_version} />
            <StatRow
              label={t('status.schemaReady')}
              value={schemaReady ? t('status.schemaOk') : (readiness.data?.status ?? '…')}
            />
            <StatRow
              label={t('status.maxUpload')}
              value={<StatBytes bytes={meta.data.max_upload_size} locale={locale} />}
            />
          </dl>
        ) : null}
      </Card>

      <div className="flex flex-wrap gap-3">
        <Link className="text-sm text-accent underline" to="/login">
          {t('auth.login.title')}
        </Link>
        <Link className="text-sm text-accent underline" to="/register">
          {t('auth.register.title')}
        </Link>
      </div>

      <footer className="mt-auto flex items-center justify-between text-xs text-fg-muted">
        <span>
          {t('app.name')} · {t('footer.license')}
        </span>
        <span className="tabular-nums">{meta.data?.commit ?? ''}</span>
      </footer>
    </div>
  );
}