@netlify/next-runtime/dist/run/headers.js

Run Next.js seamlessly on Netlify

const generateNetlifyVaryValues = ({ headers, languages, cookies }) => {
    const values = [];
    if (headers.length !== 0) {
        values.push(`header=${headers.join(`|`)}`);
    }
    if (languages.length !== 0) {
        values.push(`language=${languages.join(`|`)}`);
    }
    if (cookies.length !== 0) {
        values.push(`cookie=${cookies.join(`|`)}`);
    }
    return values.join(',');
};
const getHeaderValueArray = (header) => {
    return header.split(',').map((value) => value.trim());
};
const removeHeaderValues = (header, values) => {
    const headerValues = getHeaderValueArray(header);
    const filteredValues = headerValues.filter((value) => !values.some((val) => value.startsWith(val)));
    return filteredValues.join(', ');
};
/**
 * Ensure the Netlify CDN varies on things that Next.js varies on,
 * e.g. i18n, preview mode, etc.
 */
export const setVaryHeaders = (headers, request, { basePath, i18n }) => {
    const netlifyVaryValues = {
        headers: [],
        languages: [],
        cookies: ['__prerender_bypass', '__next_preview_data'],
    };
    const vary = headers.get('vary');
    if (vary !== null) {
        netlifyVaryValues.headers.push(...getHeaderValueArray(vary));
    }
    const path = new URL(request.url).pathname;
    const locales = i18n && i18n.localeDetection !== false ? i18n.locales : [];
    if (locales.length > 1 && (path === '/' || path === basePath)) {
        netlifyVaryValues.languages.push(...locales);
        netlifyVaryValues.cookies.push(`NEXT_LOCALE`);
    }
    headers.set(`netlify-vary`, generateNetlifyVaryValues(netlifyVaryValues));
};
/**
 * Ensure stale-while-revalidate and s-maxage don't leak to the client, but
 * assume the user knows what they are doing if CDN cache controls are set
 */
export const setCacheControlHeaders = (headers) => {
    const cacheControl = headers.get('cache-control');
    if (cacheControl !== null &&
        !headers.has('cdn-cache-control') &&
        !headers.has('netlify-cdn-cache-control')) {
        const clientCacheControl = removeHeaderValues(cacheControl, [
            's-maxage',
            'stale-while-revalidate',
        ]);
        headers.set('cache-control', clientCacheControl || 'public, max-age=0, must-revalidate');
        headers.set('netlify-cdn-cache-control', cacheControl);
    }
};
export const setCacheTagsHeaders = (request, headers, cacheEntry) => {
    const pageData = cacheEntry?.value?.pageData;
    const cacheHeaders = cacheEntry?.value?.headers;
    const path = new URL(request.url).pathname;
    // Page Data for app chould be a string, Pages should be an obj
    if (pageData && typeof pageData === 'string' && cacheHeaders?.['x-next-cache-tags']) {
        console.debug('Cache values for app routes:', cacheHeaders['x-next-cache-tags']);
        headers.set('cache-tag', cacheHeaders['x-next-cache-tags']);
    }
    if (pageData && typeof pageData === 'object') {
        console.debug('Cache values for Page routes', cacheEntry);
        headers.set('cache-tag', path);
    }
};