import { buildLocalizedPath, getLocaleCodes } from '../i18n/index.js';
/**
 * Builds a map of locale → URL for hreflang alternate links, suitable for
 * Next.js Metadata `alternates.languages`.
 *
 * Bridges SEO and i18n: for each configured locale that the document has a
 * slug in, it produces the locale-aware path (via buildLocalizedPath),
 * optionally prefixed with an absolute origin.
 *
 * @example
 * buildHreflangAlternates({
 *   slugs: { pl: 'o-nas', en: 'about' },
 *   config,
 *   baseUrl: 'https://example.com',
 * })
 * // → { pl: 'https://example.com/pl/o-nas', en: 'https://example.com/en/about' }
 */ export function buildHreflangAlternates({ slugs, config, baseUrl, homeSlug = 'home', prefix }) {
    const origin = baseUrl?.replace(/\/$/, '') ?? '';
    const alternates = {};
    // Single-locale sites have no language alternatives — hreflang describes
    // relationships BETWEEN language versions, and there's only one. Emitting
    // hreflang (or x-default) here would be wrong, so return empty: the page keeps
    // its canonical, but no alternate-language links.
    if (config.locales.length === 1) {
        return alternates;
    }
    for (const locale of getLocaleCodes(config)){
        const path = buildLocalizedPath({
            slugs,
            locale,
            config,
            homeSlug,
            prefix
        });
        if (path) {
            alternates[locale] = `${origin}${path}`;
        }
    }
    // x-default: the version Google serves when the user's language/region doesn't
    // match any hreflang — and, crucially here, the fallback when the root ('/')
    // redirect is ambiguous (Googlebot with no/foreign Accept-Language). Point it
    // at the default locale (the primary market) so search shows that version by
    // default instead of guessing. Only set when the default locale has a URL.
    const defaultLocalePath = alternates[config.defaultLocale];
    if (defaultLocalePath) {
        alternates['x-default'] = defaultLocalePath;
    }
    return alternates;
}

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