graphbrainz/src/extensions/cover-art-archive/loaders.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/cover-art-archive');

export default function createLoaders(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;

  return {
    coverArtArchive: new DataLoader(
      (keys) => {
        return Promise.all(
          keys.map((key) => {
            const [entityType, id] = key;
            return client
              .images(entityType, id)
              .catch((err) => {
                if (err.response.statusCode === 404) {
                  return { images: [] };
                }
                throw err;
              })
              .then((coverArt) => ({
                ...coverArt,
                _entityType: entityType,
                _id: id,
                _releaseID:
                  coverArt.release && coverArt.release.split('/').pop(),
              }));
          })
        );
      },
      {
        cacheKeyFn: ([entityType, id]) => `${entityType}/${id}`,
        cacheMap: cache,
      }
    ),
    coverArtArchiveURL: new DataLoader(
      (keys) => {
        return Promise.all(
          keys.map((key) => {
            const [entityType, id, type, size] = key;
            return client.imageURL(entityType, id, type, size);
          })
        );
      },
      {
        batch: false,
        cacheKeyFn: ([entityType, id, type, size]) => {
          const key = `${entityType}/${id}/${type}`;
          return size ? `${key}-${size}` : key;
        },
        cacheMap: cache,
      }
    ),
  };
}