accounts-frontend/packages/app/components/i18n/actions.ts

import { Action as ReduxAction } from 'redux';
import i18n from 'app/services/i18n';
import { ThunkAction } from 'app/reducers';

export function setLocale(desiredLocale: string): ThunkAction<Promise<string>> {
  return async (dispatch) => {
    const locale = i18n.detectLanguage(desiredLocale);

    dispatch(_setLocale(locale));

    return locale;
  };
}

interface SetAction extends ReduxAction {
  type: 'i18n:setLocale';
  payload: {
    locale: string;
  };
}

function _setLocale(locale: string): SetAction {
  return {
    type: 'i18n:setLocale',
    payload: {
      locale,
    },
  };
}

export type Action = SetAction;