graphbrainz/src/extensions/fanart-tv/loader.js

A GraphQL schema, Express server, and middleware for querying the MusicBrainz.

import createDebug from 'debug';
import DataLoader from 'dataloader';
import LRUCache from 'lru-cache';

const debug = createDebug('graphbrainz:extensions/fanart-tv');

export default function createLoader(options) {
  const { client } = options;
  const cache = new LRUCache({
    max: options.cacheSize,
    maxAge: options.cacheTTL,
    dispose(key) {
      debug(`Removed from cache. key=${key}`);
    },
  });
  // Make the cache Map-like.
  cache.delete = cache.del;
  cache.clear = cache.reset;

  const loader = new DataLoader(
    (keys) => {
      return Promise.all(
        keys.map((key) => {
          const [entityType, id] = key;
          return client
            .musicEntity(entityType, id)
            .catch((err) => {
              if (err.statusCode === 404) {
                // 404s are OK, just return empty data.
                return {
                  artistbackground: [],
                  artistthumb: [],
                  musiclogo: [],
                  hdmusiclogo: [],
                  musicbanner: [],
                  musiclabel: [],
                  albums: {},
                };
              }
              throw err;
            })
            .then((body) => {
              if (entityType === 'artist') {
                const releaseGroupIDs = Object.keys(body.albums || {});
                debug(
                  `Priming album cache with ${releaseGroupIDs.length} album(s).`
                );
                releaseGroupIDs.forEach((key) =>
                  loader.prime(['release-group', key], body)
                );
              }
              return body;
            });
        })
      );
    },
    {
      batch: false,
      cacheKeyFn: ([entityType, id]) => `${entityType}/${id}`,
      cacheMap: cache,
    }
  );

  return loader;
}