// k6 load test — POST /v1/track against the local cdp-ingest service.
//
// Usage:
//   brew install k6                # one-time
//   k6 run tests/k6/track.js       # defaults: 50 CCU, 1m
//
// Override at the CLI:
//   k6 run -e WRITE_KEY=xxx -e BASE=http://localhost:3049 \
//          -e VUS=100 -e DURATION=2m tests/k6/track.js

import http from 'k6/http';
import { check } from 'k6';
import encoding from 'k6/encoding';

const BASE       = __ENV.BASE       ?? 'http://localhost:3049';
const WRITE_KEY  = __ENV.WRITE_KEY  ?? 'cdp_dev_writekey_1234567890';
const VUS        = parseInt(__ENV.VUS      ?? '50', 10);
const DURATION   = __ENV.DURATION   ?? '1m';

// Segment-compatible auth: Basic base64(writeKey + ":")
const AUTH = 'Basic ' + encoding.b64encode(`${WRITE_KEY}:`);

export const options = {
  scenarios: {
    constant_load: {
      executor: 'constant-vus',
      vus: VUS,
      duration: DURATION,
    },
  },
  thresholds: {
    http_req_failed:   ['rate<0.01'],            // < 1% errors
    http_req_duration: ['p(95)<300', 'p(99)<800'],
    checks:            ['rate>0.99'],
  },
};

export default function () {
  const now = new Date().toISOString();
  const messageId = `k6_${__VU}_${__ITER}_${Date.now()}`;

  const payload = JSON.stringify({
    type: 'track',
    messageId,
    anonymousId: `anon_${__VU}`,
    userId: `user_${__VU}@example.com`,
    event: 'k6 Test Event',
    properties: {
      testProp: 'load test',
      vu: __VU,
      iter: __ITER,
      price: 42.5,
    },
    timestamp: now,
    sentAt: now,
    context: {
      library_name: 'k6',
      library_version: '0.1.0',
      ip: '127.0.0.1',
      userAgent: 'k6/loadtest',
      locale: 'en-US',
      page: {
        path: '/',
        host: 'example.com',
        title: 'Example page',
        url: 'https://example.com/',
      },
    },
  });

  const res = http.post(`${BASE}/v1/track`, payload, {
    headers: {
      'Content-Type': 'application/json',
      Authorization: AUTH,
    },
  });

  check(res, {
    'status 200':    (r) => r.status === 200,
    'body ok':       (r) => r.json('ok') === true,
    'fast (<500ms)': (r) => r.timings.duration < 500,
  });
}