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

const debug = createDebug('graphbrainz:extensions/mediawiki');

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;

  return new DataLoader(
    (keys) => {
      return Promise.allSettled(
        keys.map((key) => client.imageInfo(key))
      ).then((results) =>
        results.map((result) => result.reason || result.value)
      );
    },
    { batch: false, cacheMap: cache }
  );
}