import http from 'k6/http';
import { check, fail } from 'k6';

const baseUrl = required('BENCH_BASE_URL').replace(/\/$/, '');
const path = required('BENCH_PATH');
const method = (__ENV.BENCH_METHOD || 'GET').toUpperCase();
const rate = positiveInteger('BENCH_RATE', 100);
const expectedStatus = positiveInteger('BENCH_EXPECTED_STATUS', 200);
const duration = __ENV.BENCH_DURATION || '30s';
const cacheBust = (__ENV.BENCH_CACHE_BUST || 'false').toLowerCase() === 'true';

export const options = {
  discardResponseBodies: true,
  summaryTrendStats: ['avg', 'med', 'p(90)', 'p(95)', 'p(99)', 'max'],
  scenarios: {
    fairComparison: {
      executor: 'constant-arrival-rate',
      rate,
      timeUnit: '1s',
      duration,
      preAllocatedVUs: positiveInteger('BENCH_PRE_ALLOCATED_VUS', Math.max(20, Math.ceil(rate / 20))),
      maxVUs: positiveInteger('BENCH_MAX_VUS', Math.max(100, Math.ceil(rate / 5))),
    },
  },
  thresholds: {
    checks: ['rate>0.99'],
    http_req_failed: ['rate<0.01'],
    dropped_iterations: ['count==0'],
  },
};

export function setup() {
  const readinessPath = __ENV.BENCH_READINESS_PATH;
  if (!readinessPath) return;
  const response = http.get(`${baseUrl}${readinessPath}`, { headers: headers() });
  if (response.status !== 200) fail(`readiness failed: ${response.status}`);
}

export default function () {
  const separator = path.includes('?') ? '&' : '?';
  const requestPath = cacheBust ? `${path}${separator}loadProbe=${__VU}-${__ITER}` : path;
  const response = http.request(method, `${baseUrl}${requestPath}`, __ENV.BENCH_BODY || null, { headers: headers() });
  check(response, { [`status is ${expectedStatus}`]: (value) => value.status === expectedStatus });
}

function headers() {
  const values = { Accept: 'application/json' };
  if (__ENV.BENCH_HOST_HEADER) values.Host = __ENV.BENCH_HOST_HEADER;
  if (__ENV.BENCH_AUTHORIZATION) values.Authorization = __ENV.BENCH_AUTHORIZATION;
  if (__ENV.BENCH_TENANT_HEADER) values['x-tenant-code'] = __ENV.BENCH_TENANT_HEADER;
  if (__ENV.BENCH_BODY) values['Content-Type'] = 'application/json';
  return values;
}

function required(name) {
  const value = __ENV[name];
  if (!value) throw new Error(`${name} is required`);
  return value;
}

function positiveInteger(name, fallback) {
  const value = Number(__ENV[name] || fallback);
  if (!Number.isInteger(value) || value <= 0) throw new Error(`${name} must be a positive integer`);
  return value;
}