import { createContext, useContext, useEffect, useMemo, useState, type ReactNode } from 'react';
import { createT, formatAmd, formatDateTime, isLocale, type Locale, type TFunction } from '@barev/i18n';
import { reportClientError } from './telegram.ts';

interface I18nValue {
  locale: Locale;
  t: TFunction;
  setLocale: (l: Locale) => void;
  amd: (n: number) => string;
  dt: (d: Date, opts?: Intl.DateTimeFormatOptions) => string;
}

const Ctx = createContext<I18nValue | null>(null);

export function pickLocale(...candidates: (string | null | undefined)[]): Locale {
  for (const c of candidates) {
    const base = c?.split('-')[0]?.toLowerCase();
    if (isLocale(base)) return base;
  }
  return 'ru';
}

export function I18nProvider({ initial, children }: { initial: Locale; children: ReactNode }) {
  const [locale, setLocale] = useState<Locale>(initial);
  useEffect(() => setLocale(initial), [initial]);
  useEffect(() => {
    document.documentElement.lang = locale;
  }, [locale]);
  const value = useMemo<I18nValue>(
    () => ({
      locale,
      t: createT(locale),
      setLocale,
      amd: (n) => formatAmd(locale, n),
      dt: (d, opts) => formatDateTime(locale, d, opts),
    }),
    [locale],
  );
  return <Ctx.Provider value={value}>{children}</Ctx.Provider>;
}

export function useI18n(): I18nValue {
  const v = useContext(Ctx);
  if (!v) throw new Error('I18nProvider missing');
  return v;
}

/** Текст ошибки API: errors.<код бизнес-ошибки> или общий */
export function errorText(t: TFunction, err: unknown): string {
  reportClientError(err, 'errorText');
  const e = err as { data?: { domainCode?: string | null; code?: string }; message?: string } | null;
  const code = e?.data?.domainCode ?? e?.message;
  if (code && /^[A-Z0-9_]+$/.test(code)) {
    const s = t(`errors.${code}`);
    if (s !== `errors.${code}`) return s;
  }
  return t('errors.generic');
}