// Concurrent durable-write benchmark: N clients each do M sequential
// insertOne ({w:1, j:true} by default) into their own collection, reporting
// aggregate docs/s. Exercises the group-commit path under real contention.
//
//   node tests/e2e/concurrent.js --url mongodb://127.0.0.1:27019 --label multiforadb
//                                 [--clients 8] [--per-client 2000] [--wc j|none]
//
// Output (stdout, tab-separated, one line):
//   <label>	clients=N	<docs/s>	(M docs in S s)
const { MongoClient, ObjectId } = require('mongodb');

let opt = { url: null, label: null, clients: 8, perClient: 2000, wc: 'j' };
for (let i = 2; i < process.argv.length; i++) {
  const a = process.argv[i];
  if (a === '--url') opt.url = process.argv[++i];
  else if (a === '--label') opt.label = process.argv[++i];
  else if (a === '--clients') opt.clients = Number(process.argv[++i]);
  else if (a === '--per-client') opt.perClient = Number(process.argv[++i]);
  else if (a === '--wc') opt.wc = process.argv[++i];
  else { console.error(`unknown option ${a}`); process.exit(2); }
}
if (!opt.url) { console.error('--url required'); process.exit(2); }
opt.label = opt.label || opt.url.replace(/^mongodb:\/\//, '');
const WC = opt.wc === 'j' ? { writeConcern: { w: 1, j: true } } : {};

async function worker(i) {
  const c = new MongoClient(opt.url, { maxPoolSize: 4, serverSelectionTimeoutMS: 15000 });
  await c.connect();
  // One collection per worker in a scratch db, so no cross-worker contention
  // beyond the engine's own commit path.
  const coll = c.db(`cc${Date.now() % 100000}`).collection(`w${i}`);
  for (let j = 0; j < opt.perClient; j++) {
    await coll.insertOne({ _id: new ObjectId(), k: j, payload: 'x'.repeat(256) }, WC);
  }
  await c.close();
}

(async () => {
  const t0 = process.hrtime.bigint();
  await Promise.all(Array.from({ length: opt.clients }, (_, i) => worker(i)));
  const s = Number(process.hrtime.bigint() - t0) / 1e9;
  const total = opt.clients * opt.perClient;
  console.log(`${opt.label}\tclients=${opt.clients}\t${(total / s).toFixed(0)} docs/s\t(${total} docs in ${s.toFixed(2)} s)`);
  process.exit(0);
})().catch((e) => { console.error('FAIL', e); process.exit(1); });