const Datastore = require('@google-cloud/datastore');

const datastore = new Datastore();

const datastoreLoader = new DataLoader(
  async keys => {
    const results = await datastore.get(keys);
    // Sort resulting entities by the keys they were requested with.
    const entities = results[0];
    const entitiesByKey = {};
    entities.forEach(entity => {
      entitiesByKey[JSON.stringify(entity[datastore.KEY])] = entity;
    });
    return keys.map(key => entitiesByKey[JSON.stringify(key)] || null);
  },
  {
    // Datastore complex keys need to be converted to a string for use as cache keys
    cacheKeyFn: key => JSON.stringify(key),
  },
);