import { Language, defaultLanguage, isValidLanguage } from './config';

export const getLanguageFromPath = (pathname: string, search?: string): Language => {
    // 首页、产品页面和新闻页面支持 ?lang=xx
    if (
        (pathname === '/' || pathname === '' || pathname === '/products' || pathname === '/news') &&
        search
    ) {
        const params = new URLSearchParams(search);
        const lang = params.get('lang');
        if (lang && isValidLanguage(lang)) {
            return lang as Language;
        }
    }
    const segments = pathname.split('/').filter(Boolean);
    const firstSegment = segments[0];
    if (firstSegment && isValidLanguage(firstSegment)) {
        return firstSegment;
    }
    return defaultLanguage;
};

export const removeLanguageFromPath = (pathname: string): string => {
    const segments = pathname.split('/').filter(Boolean);
    const firstSegment = segments[0];

    if (firstSegment && isValidLanguage(firstSegment)) {
        return '/' + segments.slice(1).join('/');
    }

    return pathname;
};

export const addLanguageToPath = (pathname: string, language: Language): string => {
    if (language === defaultLanguage) {
        return pathname;
    }

    const cleanPath = removeLanguageFromPath(pathname);
    return `/${language}${cleanPath === '/' ? '' : cleanPath}`;
};

export const getStoredLanguage = (): Language => {
    if (typeof window === 'undefined') return defaultLanguage;

    const stored = localStorage.getItem('preferred-language');
    if (stored && isValidLanguage(stored)) {
        return stored;
    }

    return defaultLanguage;
};

export const setStoredLanguage = (language: Language): void => {
    if (typeof window === 'undefined') return;
    localStorage.setItem('preferred-language', language);
};

export const getBrowserLanguage = (): Language => {
    if (typeof window === 'undefined') return defaultLanguage;

    const browserLang = navigator.language.toLowerCase();

    if (browserLang.startsWith('zh-cn') || browserLang.startsWith('zh-hans')) {
        return 'zh-CN';
    }
    if (browserLang.startsWith('zh-tw') || browserLang.startsWith('zh-hant')) {
        return 'zh-TW';
    }
    if (browserLang.startsWith('en')) {
        return 'en';
    }

    return defaultLanguage;
};