Added support for single localization

src/modules/i18n/localeMiddleware.ts

@@ -1,16 +1,15 @@
-import type { I18nConfig } from './types.js'
-
+import type { I18nConfig } from '../i18n/index.js'
+import { negotiateLocale, isValidLocale, LOCALE_COOKIE_NAME } from '../i18n/index.js'
 import { CONSENT_COOKIE, parseConsent } from '../consent/storage.js'
-import { isValidLocale, LOCALE_COOKIE_NAME, negotiateLocale } from '../i18n/index.js'
 
 /**
  * Minimal request shape the middleware reads. Kept structural so the plugin
  * doesn't hard-depend on next/server types; a Next.js `NextRequest` satisfies it.
  */
 type MiddlewareRequest = {
+  nextUrl: { pathname: string; search: string; clone: () => URL }
   cookies: { get: (name: string) => { value: string } | undefined }
-  headers: { get: (name: string) => null | string }
-  nextUrl: { clone: () => URL; pathname: string; search: string }
+  headers: { get: (name: string) => string | null }
   url: string
 }
 
@@ -20,11 +19,13 @@ type MiddlewareRequest = {
  * `next` means let the request pass through untouched.
  */
 export type LocaleMiddlewareResult =
-  | { cookie?: { name: string; value: string }; location: string; type: 'redirect' }
-  | { cookie?: { name: string; value: string }; type: 'next' }
+  | { type: 'next'; cookie?: { name: string; value: string } }
+  | { type: 'redirect'; location: string; cookie?: { name: string; value: string } }
 
 type CreateLocaleMiddlewareArgs = {
   config: I18nConfig
+  /** Cookie name for the locale choice. Defaults to LOCALE_COOKIE_NAME. */
+  cookieName?: string
   /**
    * Consent category that gates *persisting* the locale cookie. The locale is
    * always detected (routing works regardless), but the choice is only written
@@ -32,11 +33,9 @@ type CreateLocaleMiddlewareArgs = {
    * 'functional'. Pass 'necessary' to always persist (treat locale as strictly
    * necessary), which restores the pre-consent behaviour.
    */
-  consentCategory?: 'functional' | 'necessary'
+  consentCategory?: 'necessary' | 'functional'
   /** Name of the consent cookie to read. Defaults to CONSENT_COOKIE. */
   consentCookieName?: string
-  /** Cookie name for the locale choice. Defaults to LOCALE_COOKIE_NAME. */
-  cookieName?: string
 }
 
 /**
@@ -76,14 +75,14 @@ function firstSegment(pathname: string): string {
  */
 export function createLocaleMiddleware({
   config,
+  cookieName = LOCALE_COOKIE_NAME,
   consentCategory = 'functional',
   consentCookieName = CONSENT_COOKIE,
-  cookieName = LOCALE_COOKIE_NAME,
 }: CreateLocaleMiddlewareArgs) {
   // Whether the locale cookie may be written: 'necessary' is always granted;
   // 'functional' (default) requires the visitor to have consented.
   function mayPersistLocale(request: MiddlewareRequest): boolean {
-    if (consentCategory === 'necessary') {return true}
+    if (consentCategory === 'necessary') return true
     const consent = parseConsent(request.cookies.get(consentCookieName)?.value)
     return consent?.[consentCategory] === true
   }
@@ -91,6 +90,15 @@ export function createLocaleMiddleware({
   return function localeMiddleware(request: MiddlewareRequest): LocaleMiddlewareResult {
     const { pathname } = request.nextUrl
 
+    // Single-locale sites have no /pl, /en prefix and no negotiation — one
+    // language, no redirect. The middleware becomes a pass-through: paths stay
+    // as-is (/o-nas), nothing to detect or persist. (Projects that are truly
+    // single-locale usually don't even mount this middleware, but guarding here
+    // makes it safe if they do.)
+    if (config.locales.length === 1) {
+      return { type: 'next' }
+    }
+
     // Already locale-prefixed (e.g. the visitor switched language by
     // navigating to /en). Routing is fine — but if the URL's locale differs
     // from the stored cookie, the visitor is *choosing* a language, and we
@@ -108,9 +116,9 @@ export function createLocaleMiddleware({
 
     // Resolve the locale to use
     const locale = negotiateLocale({
+      cookieLocale: request.cookies.get(cookieName)?.value ?? null,
       acceptLanguage: request.headers.get('accept-language'),
       config,
-      cookieLocale: request.cookies.get(cookieName)?.value ?? null,
     })
 
     // Redirect to the locale-prefixed path, preserving the rest

src/modules/i18n/localizedPath.ts

@@ -71,6 +71,13 @@ export function buildLocalizedPath({
     return undefined
   }
 
+  // Single-locale sites have no /pl, /en prefix — the language segment is
+  // dropped entirely (path is /o-nas, not /pl/o-nas). Detected automatically:
+  // one configured locale means one language, so no prefix is needed. The
+  // project's folder structure matches (app/[[...slug]] without [locale]).
+  const singleLocale = config.locales.length === 1
+  const localeSegment = singleLocale ? '' : `/${locale}`
+
   if (prefix) {
     const segment = prefix[locale]
     // No archive slug in this locale means the entry is unreachable there —
@@ -79,14 +86,15 @@ export function buildLocalizedPath({
     if (!segment) {
       return undefined
     }
-    return `/${locale}/${segment}/${slug}`
+    return `${localeSegment}/${segment}/${slug}`
   }
 
   if (slug === homeSlug) {
-    return `/${locale}`
+    // Home collapses to the root: '/' for single-locale, '/pl' otherwise.
+    return localeSegment || '/'
   }
 
-  return `/${locale}/${slug}`
+  return `${localeSegment}/${slug}`
 }
 
 type SwitchLocaleArgs = {

src/modules/seo/hreflang.ts

@@ -1,11 +1,12 @@
 import type { I18nConfig, LocalizedSlugs } from '../i18n/index.js'
-
-import { buildLocalizedPath, getDefaultLocale, getLocaleCodes } from '../i18n/index.js'
+import { buildLocalizedPath, getLocaleCodes } from '../i18n/index.js'
 
 type BuildHreflangArgs = {
+  /** slug per locale for the current document, e.g. { pl: 'o-nas', en: 'about' } */
+  slugs: LocalizedSlugs
+  config: I18nConfig
   /** Absolute site origin, e.g. 'https://example.com'. Omit for relative paths. */
   baseUrl?: string
-  config: I18nConfig
   /** Home slug that collapses to the locale root. Defaults to 'home'. */
   homeSlug?: string
   /**
@@ -14,46 +15,44 @@ type BuildHreflangArgs = {
    * are omitted — an entry with no archive in that language has no URL there.
    */
   prefix?: LocalizedSlugs
-  /** slug per locale for the current document, e.g. { pl: 'o-nas', en: 'about' } */
-  slugs: LocalizedSlugs
 }
 
 /**
+ * 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.
  *
- * Also emits `x-default` pointing at the default locale — the version Google
- * serves when the user's language/region matches no hreflang, and the fallback
- * when the root ('/') redirect is ambiguous (Googlebot with no/foreign
- * Accept-Language).
- *
  * @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',
- * //   'x-default': 'https://example.com/pl/o-nas',
- * // }
+ * // → { pl: 'https://example.com/pl/o-nas', en: 'https://example.com/en/about' }
  */
 export function buildHreflangAlternates({
-  baseUrl,
+  slugs,
   config,
+  baseUrl,
   homeSlug = 'home',
   prefix,
-  slugs,
 }: BuildHreflangArgs): Record<string, string> {
   const origin = baseUrl?.replace(/\/$/, '') ?? ''
   const alternates: Record<string, string> = {}
 
+  // 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({ config, homeSlug, locale, prefix, slugs })
+    const path = buildLocalizedPath({ slugs, locale, config, homeSlug, prefix })
     if (path) {
       alternates[locale] = `${origin}${path}`
     }
@@ -64,7 +63,7 @@ export function buildHreflangAlternates({
   // 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[getDefaultLocale(config)]
+  const defaultLocalePath = alternates[config.defaultLocale]
   if (defaultLocalePath) {
     alternates['x-default'] = defaultLocalePath
   }