sanity.js

import {
    createClient
} from "next-sanity";
import createImageUrlBuilder from '@sanity/image-url'

import {suspend} from 'suspend-react'
import {_checkAuth} from '@sanity/preview-kit'

export const config = {
    /**
     * Find your project ID and dataset in `sanity.json` in your studio project.
     * These are considered “public”, but you can use environment variables
     * if you want differ between local  dev and production. 
     * 
     * https://nextjs.org/docs/basic-features/environment-variables
     */
    dataset: process.env.NEXT_PUBLIC_SANITY_DATASET || "production",
    projectId: process.env.NEXT_PUBLIC_SANITY_PROJECT_ID,
    apiVersion: "2021-03-25",

    /**
     * set useCdn to `false` if your application require the freshest possible
     * data always (potentially slightly slower and a bit more expensive).
     * Authenticated request (like preview) will always bypass the CDN
    */
    useCdn: process.env.NODE_ENV === "production"
}

const useCheckAuth = () =>
  suspend(() => _checkAuth(projectId, null), ['@sanity/preview-kit', 'checkAuth', projectId])



// Set up the client for fetching data in the getProps page functions
export const sanityClient = createClient(config);

/**
 * Set up a helper function for generating Image URLs with only the asset reference data
 * in your documents.
 * Read more: https://www.sanity.io/docs/image-url
 */
export const urlFor = (source) => createImageUrlBuilder(config).image(source);

// Helper function for using the current logged in user account
// export const useCurrentUser = createCurrentUserHook(config); 
export default function Page() {
    const isAuthenticated = useCheckAuth()
}