import merge from 'lodash/merge';
import { DEFAULT_LOCALE } from './index';

interface AllNavigatorLanguage extends NavigatorLanguage {
    browserLanguage?: string;
    userLanguage?: string;
}

/**
 * Resolve the browser locale according to the value of the global window.navigator
 *
 * Use it to determine the <Admin> locale at runtime.
 *
 * @example
 *     import React from 'react';
 *     import { Admin, Resource, resolveBrowserLocale } from 'react-admin';
 *     import englishMessages from 'ra-language-english';
 *     import frenchMessages from 'ra-language-french';
 *     const messages = {
 *        fr: frenchMessages,
 *        en: englishMessages,
 *     };
 *     const App = () => (
 *         <Admin locale={resolveBrowserLocale()} messages={messages}>
 *             ...
 *         </Admin>
 *     );
 *
 * @param {String} defaultLocale Defaults to 'en'
 */
export const resolveBrowserLocale = (defaultLocale = DEFAULT_LOCALE) => {
    // from http://blog.ksol.fr/user-locale-detection-browser-javascript/
    // Rely on the window.navigator object to determine user locale
    const {
        language,
        browserLanguage,
        userLanguage,
    } = window.navigator as AllNavigatorLanguage;
    return (language || browserLanguage || userLanguage || defaultLocale).split(
        '-'
    )[0];
};

/**
 * Compose translations from multiple packages for a single language (eg: 'english').
 *
 * Use it to merge translations from addons with the main react-admin translations.
 *
 * @example
 *     import React from 'react';
 *     import { Admin, Resource, mergeTranslations } from 'react-admin';
 *     import englishMessages from 'ra-language-english';
 *     import englishTreeMessages from 'ra-tree-language-english';
 *     const messages = {
 *        en: mergeTranslations(englishMessages, englishTreeMessages),
 *     };
 *     const App = () => (
 *         <Admin locale="en" messages={messages}>
 *             ...
 *         </Admin>
 *     );
 */
export const mergeTranslations = (...translationsModules: object[]) =>
    merge({}, ...translationsModules);