import "server-only";

import {
  type AnyVariables,
  type TypedDocumentNode,
  cacheExchange,
  createClient,
  fetchExchange,
  stringifyDocument,
} from "@urql/core";
import { registerUrql } from "@urql/next/rsc";

import { cmsCache, cmsCacheForToday } from "@/lib/cmsCache";

const wagtailBaseUrl = process.env.WAGTAIL_BASE_URL;
if (!wagtailBaseUrl) {
  throw new Error("WAGTAIL_BASE_URL is not set");
}
const graphqlEndpoint = `${wagtailBaseUrl.replace(/\/$/, "")}/api/graphql/`;

const makeClient = () => {
  return createClient({
    url: graphqlEndpoint,
    exchanges: [cacheExchange, fetchExchange],
  });
};

// Uncached. Only for per-user (search) and token-scoped (preview) queries,
// together with the `uncached` context; everything else goes through cmsQuery
export const { getClient } = registerUrql(makeClient);

// Throws on GraphQL and network errors, which keeps them out of the cache
async function runQuery(query: string, variables: AnyVariables) {
  const { data, error } = await getClient().query(query, variables);
  if (error) throw new Error(error.message);
  return data;
}

// The cached functions take the query as text: their arguments are the cache
// key, and urql adds bookkeeping properties to document objects it has seen
async function cachedQuery(query: string, variables: AnyVariables) {
  "use cache";
  cmsCache();
  return runQuery(query, variables);
}

async function cachedQueryForToday(query: string, variables: AnyVariables) {
  "use cache";
  cmsCacheForToday();
  return runQuery(query, variables);
}

// Every cacheable CMS read goes through one of the two functions below, so
// all of them carry the tag the CMS webhook purges

// Cached until the content is edited in the CMS
export function cmsQuery<Data, Variables extends AnyVariables>(
  document: TypedDocumentNode<Data, Variables>,
  variables: Variables
): Promise<Data | undefined> {
  return cachedQuery(stringifyDocument(document), variables);
}

// For queries where the CMS decides by today's date what to return
// (futureEvents): also purged at Oslo midnight
export function cmsQueryForToday<Data, Variables extends AnyVariables>(
  document: TypedDocumentNode<Data, Variables>,
  variables: Variables
): Promise<Data | undefined> {
  return cachedQueryForToday(stringifyDocument(document), variables);
}