import { isValidLocale, LOCALE_COOKIE_NAME, negotiateLocale } from '../i18n/index.js';
/**
 * First path segment of a URL pathname, or '' for root.
 * '/pl/o-nas' → 'pl', '/o-nas' → 'o-nas', '/' → ''.
 */ function firstSegment(pathname) {
    return pathname.split('/').filter(Boolean)[0] ?? '';
}
/**
 * Builds locale-routing logic for Next.js middleware.
 *
 * Behavior:
 *  - path already starts with a valid locale (/pl/...) → pass through
 *  - any other path (/, /o-nas) → redirect to /{locale}{path}, where locale
 *    comes from negotiateLocale (cookie → Accept-Language → default)
 *  - the chosen locale is written to a cookie so the next visit is stable
 *
 * The plugin returns a decision; the thin next-middleware.ts in the client project
 * turns it into a NextResponse. This keeps all logic in the plugin while
 * respecting that next-middleware.ts must physically live in the client app.
 *
 * @example
 * // next-middleware.ts (client project) — one wiring file, no logic:
 * import { NextResponse } from 'next/server'
 * import { localeMiddleware } from './ipal.middleware' // created from this factory
 * export function middleware(req) {
 *   const r = localeMiddleware(req)
 *   if (r.type === 'next') return NextResponse.next()
 *   const res = NextResponse.redirect(r.location)
 *   res.cookies.set(r.cookie.name, r.cookie.value)
 *   return res
 * }
 */ export function createLocaleMiddleware({ config, cookieName = LOCALE_COOKIE_NAME }) {
    return function localeMiddleware(request) {
        const { pathname } = request.nextUrl;
        // Already locale-prefixed → nothing to do
        if (isValidLocale(firstSegment(pathname), config)) {
            return {
                type: 'next'
            };
        }
        // Resolve the locale to use
        const locale = negotiateLocale({
            acceptLanguage: request.headers.get('accept-language'),
            config,
            cookieLocale: request.cookies.get(cookieName)?.value ?? null
        });
        // Redirect to the locale-prefixed path, preserving the rest
        const url = request.nextUrl.clone();
        url.pathname = `/${locale}${pathname === '/' ? '' : pathname}`;
        return {
            type: 'redirect',
            cookie: {
                name: cookieName,
                value: locale
            },
            location: url.toString()
        };
    };
}
/**
 * Default Next.js middleware matcher: run on everything except API routes, the
 * admin panel, Next internals, and files with an extension (static assets).
 */ export const DEFAULT_MIDDLEWARE_MATCHER = [
    '/((?!api|admin|_next|.*\\..*).*)'
];

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