eager-resolve/lib/index.js

"use strict";

Object.defineProperty(exports, "__esModule", {
  value: true
});
exports.eager = eager;
exports.mapByProperty = mapByProperty;
exports.one = one;
exports.many = many;
function eager(batchFn, mapFn) {
  let entriesOfContext = new Map(),
      scheduled = false;

  return (source, args, context, info) => {
    if (!scheduled) {
      scheduled = true;
      process.nextTick(() => {
        const entries = entriesOfContext.get(context);

        const { sources, resolves, rejects } = entries.reduce(({ sources, resolves, rejects }, [source, resolve, reject]) => ({
          sources: [...sources, source],
          resolves: [...resolves, resolve],
          rejects: [...rejects, reject]
        }), { sources: [], resolves: [], rejects: [] });

        Promise.resolve(batchFn(sources, args, context, info)).then(results => mapFn(sources, results).forEach((r, idx) => resolves[idx](r))).catch(err => rejects.forEach(reject => reject(err)));

        entriesOfContext.delete(context);
        scheduled = false;
      });
    }

    return new Promise((resolve, reject) => {
      let entries = entriesOfContext.get(context);
      entries = [...(entries || []), [source, resolve, reject]];

      entriesOfContext.set(context, entries);
    });
  };
}

function mapByProperty(sourceProperty, resultProperty = sourceProperty) {
  return (source, result) => result && source[sourceProperty] === result[resultProperty];
}

const mapById = mapByProperty("id");

function one(fn = val => val, map = mapById) {
  return (sources, results) => sources.map(s => {
    return fn(results.find(r => map(s, r)));
  });
}

function many(fn = val => val, map = mapById) {
  return (sources, results) => {
    return fn(sources.map(source => results.filter(result => map(source, result))));
  };
}