73 lines
2.7 KiB
TypeScript
73 lines
2.7 KiB
TypeScript
import type { I18nConfig, LocalizedSlugs } from '../i18n/index.js'
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import { buildLocalizedPath, getLocaleCodes } from '../i18n/index.js'
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type BuildHreflangArgs = {
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/** slug per locale for the current document, e.g. { pl: 'o-nas', en: 'about' } */
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slugs: LocalizedSlugs
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config: I18nConfig
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/** Absolute site origin, e.g. 'https://example.com'. Omit for relative paths. */
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baseUrl?: string
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/** Home slug that collapses to the locale root. Defaults to 'home'. */
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homeSlug?: string | Record<string, string>
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/**
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* Localized segment the document lives under (an archive page's slugs),
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* e.g. { pl: 'artykuly', en: 'articles' }. Locales missing from the prefix
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* are omitted — an entry with no archive in that language has no URL there.
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*/
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prefix?: LocalizedSlugs
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}
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/**
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* Builds a map of locale → URL for hreflang alternate links, suitable for
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* Next.js Metadata `alternates.languages`.
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*
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* Bridges SEO and i18n: for each configured locale that the document has a
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* slug in, it produces the locale-aware path (via buildLocalizedPath),
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* optionally prefixed with an absolute origin.
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*
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* @example
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* buildHreflangAlternates({
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* slugs: { pl: 'o-nas', en: 'about' },
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* config,
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* baseUrl: 'https://example.com',
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* })
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* // → { pl: 'https://example.com/pl/o-nas', en: 'https://example.com/en/about' }
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*/
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export function buildHreflangAlternates({
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slugs,
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config,
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baseUrl,
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homeSlug = 'home',
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prefix,
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}: BuildHreflangArgs): Record<string, string> {
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const origin = baseUrl?.replace(/\/$/, '') ?? ''
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const alternates: Record<string, string> = {}
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// Single-locale sites have no language alternatives — hreflang describes
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// relationships BETWEEN language versions, and there's only one. Emitting
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// hreflang (or x-default) here would be wrong, so return empty: the page keeps
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// its canonical, but no alternate-language links.
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if (config.locales.length === 1) {
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return alternates
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}
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for (const locale of getLocaleCodes(config)) {
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const path = buildLocalizedPath({ slugs, locale, config, homeSlug, prefix })
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if (path) {
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alternates[locale] = `${origin}${path}`
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}
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}
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// x-default: the version Google serves when the user's language/region doesn't
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// match any hreflang — and, crucially here, the fallback when the root ('/')
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// redirect is ambiguous (Googlebot with no/foreign Accept-Language). Point it
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// at the default locale (the primary market) so search shows that version by
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// default instead of guessing. Only set when the default locale has a URL.
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const defaultLocalePath = alternates[config.defaultLocale]
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if (defaultLocalePath) {
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alternates['x-default'] = defaultLocalePath
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}
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return alternates
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}
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