todos-contra-el-fuego-web/test/server/calcUnionAsync.test.js

/* eslint-env mocha */
/* eslint-disable func-names, prefer-arrow-callback */
/* eslint-disable import/no-absolute-path */

import fs from 'fs';
import path from 'path';
import { Worker } from 'worker_threads';
import { expect } from 'chai';
import calcUnionAsync from '/imports/startup/server/calcUnionAsync';

// These run the real worker thread against the real @turf modules. The point is
// not the geometry (turf is not ours to test) but the plumbing that broke twice
// in production: the worker script and the turf packages live in sibling
// directories of the built bundle that a bare require() can never find
// (3249362), and one attempt at fixing that doubled the programs/server prefix
// so nothing resolved at all (570cb49).

const subAt = (lat, lon, distance = 10) => ({ location: { lat, lon }, distance });

describe('calcUnionAsync worker plumbing', function () {
  this.timeout(60000);

  it('resolves the worker script and the turf packages from the bundle layout', function () {
    const worker = path.resolve(process.cwd(), 'assets/app/workers/unionWorker.js');
    expect(fs.existsSync(worker), `worker script missing at ${worker}`).to.equal(true);

    ['circle', 'union', 'truncate'].forEach((mod) => {
      const turf = path.resolve(process.cwd(), 'npm/node_modules/@turf', mod);
      expect(fs.existsSync(turf), `@turf/${mod} missing at ${turf}`).to.equal(true);
      // The doubled-prefix regression: this path must NOT be under programs/server
      // twice, which is what silently produced "Cannot find module" at runtime.
      expect(turf).to.not.match(/programs\/server\/programs\/server/);
    });
  });

  it('computes a union of one circle', async function () {
    const union = await calcUnionAsync([subAt(43.5, -5.9)]);
    expect(union).to.be.an('object');
    expect(union.geometry.type).to.equal('Polygon');
    expect(union.geometry.coordinates[0].length).to.be.above(3);
  });

  it('returns null when there is nothing to unite', async function () {
    expect(await calcUnionAsync([])).to.equal(null);
  });

  it('merges two overlapping circles into a single polygon', async function () {
    const union = await calcUnionAsync([subAt(43.5, -5.9, 20), subAt(43.55, -5.9, 20)]);
    expect(union.geometry.type).to.equal('Polygon');
  });

  it('keeps two far-apart circles as a MultiPolygon', async function () {
    const union = await calcUnionAsync([subAt(43.5, -5.9, 10), subAt(28.1, -15.4, 10)]);
    expect(union.geometry.type).to.equal('MultiPolygon');
    expect(union.geometry.coordinates).to.have.lengthOf(2);
  });

  it('merges into a given base union instead of starting over', async function () {
    const base = await calcUnionAsync([subAt(43.5, -5.9, 10)]);
    const merged = await calcUnionAsync([subAt(28.1, -15.4, 10)], base);

    expect(merged.geometry.type).to.equal('MultiPolygon');
    expect(merged.geometry.coordinates).to.have.lengthOf(2);
  });

  it('truncates coordinates to 6 decimals so the stored union stays small', async function () {
    const union = await calcUnionAsync([subAt(43.5, -5.9)]);
    union.geometry.coordinates[0].forEach(([lon, lat]) => {
      expect(String(lon).split('.')[1] || '').to.have.length.at.most(6);
      expect(String(lat).split('.')[1] || '').to.have.length.at.most(6);
    });
  });

  // Regression 50ca9cc's other half: the caller must be able to tell a failure
  // apart from an empty union, so a worker error has to reject, never resolve.
  it('rejects when the worker throws instead of resolving to null', async function () {
    let rejected = false;
    try {
      // A subscription with no location makes tcircle throw inside the worker.
      await calcUnionAsync([{ distance: 10 }]);
    } catch (e) {
      rejected = true;
      expect(e).to.be.an('error');
    }
    expect(rejected, 'calcUnionAsync resolved instead of rejecting').to.equal(true);
  });

  it('rejects when the worker script itself cannot be loaded', async function () {
    let rejected = false;
    try {
      await new Promise((resolve, reject) => {
        const worker = new Worker(path.resolve(process.cwd(), 'assets/app/workers/doesNotExist.js'));
        worker.once('message', resolve);
        worker.once('error', reject);
      });
    } catch (e) {
      rejected = true;
    }
    expect(rejected).to.equal(true);
  });

  // The whole reason the worker exists (b4e5511 / fbb746f): a union big enough to
  // take real CPU time must not stop the event loop from running timers, because
  // that is what froze DDP and disconnected every browser.
  it('leaves the event loop free while it computes', async function () {
    const subs = [];
    for (let i = 0; i < 120; i += 1) subs.push(subAt(40 + (i * 0.02), -4 + (i * 0.02), 25));

    let ticks = 0;
    const timer = setInterval(() => { ticks += 1; }, 10);
    const started = Date.now();
    try {
      await calcUnionAsync(subs);
    } finally {
      clearInterval(timer);
    }
    const elapsed = Date.now() - started;

    // If the union ran on the main thread the interval would barely fire at all.
    // Half the theoretical ticks is a wide margin against a loaded CI runner.
    expect(ticks, `only ${ticks} timer ticks in ${elapsed}ms`).to.be.at.least(Math.floor(elapsed / 10 / 2));
  });
});