import { getLocaleCodes, isValidLocale } from './helpers.js';
/** Cookie name the template uses to persist a visitor's locale choice. */ /**
 * Cookie name for the persisted locale choice. Uses NEXT_LOCALE — the convention
 * Next.js and its i18n ecosystem expect — so the cookie is interoperable with
 * other libraries that read the active locale (instead of a plugin-specific
 * name). Written only under functional consent; cleared when that consent is
 * withdrawn (see consent cookieMap).
 */ export const LOCALE_COOKIE_NAME = 'NEXT_LOCALE';
/**
 * Resolves which locale to serve, in priority order:
 *   1. Cookie (explicit prior choice)
 *   2. Accept-Language header (best match against configured locales)
 *   3. Configured default locale
 *
 * Pure function — the template feeds it request data and acts on the result
 * (redirect, cookie set). No Next.js or request objects here.
 */ export function negotiateLocale({ acceptLanguage, config, cookieLocale }) {
    // 1. Explicit prior choice wins
    if (cookieLocale && isValidLocale(cookieLocale, config)) {
        return cookieLocale;
    }
    // 2. Best match from Accept-Language
    const fromHeader = matchAcceptLanguage(acceptLanguage, config);
    if (fromHeader) {
        return fromHeader;
    }
    // 3. Fall back to configured default
    return config.defaultLocale;
}
/**
 * Parses an Accept-Language header and returns the best-matching configured
 * locale, or undefined if none match.
 *
 * Matches on the primary subtag (e.g. "en-US" matches configured "en"),
 * respecting the header's quality-value ordering.
 */ export function matchAcceptLanguage(acceptLanguage, config) {
    if (!acceptLanguage) {
        return undefined;
    }
    const available = getLocaleCodes(config);
    const ranked = parseAcceptLanguage(acceptLanguage);
    for (const tag of ranked){
        // Exact match (e.g. "pt-BR" === "pt-BR")
        const exact = available.find((code)=>code.toLowerCase() === tag);
        if (exact) {
            return exact;
        }
        // Primary-subtag match (e.g. "en-us" → "en")
        const primary = tag.split('-')[0];
        const partial = available.find((code)=>code.toLowerCase().split('-')[0] === primary);
        if (partial) {
            return partial;
        }
    }
    return undefined;
}
/**
 * Parses an Accept-Language header into locale tags ordered by descending
 * quality value. Tags are lowercased for comparison.
 *
 * "en-US,en;q=0.9,pl;q=0.8" → ["en-us", "en", "pl"]
 */ function parseAcceptLanguage(header) {
    return header.split(',').map((part)=>{
        const [tag, ...params] = part.trim().split(';');
        const qParam = params.find((p)=>p.trim().startsWith('q='));
        const quality = qParam ? parseFloat(qParam.split('=')[1]) : 1;
        return {
            quality: Number.isNaN(quality) ? 0 : quality,
            tag: tag.trim().toLowerCase()
        };
    }).filter((entry)=>entry.tag && entry.tag !== '*').sort((a, b)=>b.quality - a.quality).map((entry)=>entry.tag);
}

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