import http from 'k6/http';
import { check } from 'k6';
import { Counter } from 'k6/metrics';
import { Trend } from 'k6/metrics';
import exec from 'k6/execution';

const API_URL = __ENV.API_URL || 'http://localhost:8000/api/v1/cdr/raw';
const PROFILE = (__ENV.PROFILE || 'assessment').toLowerCase();
const P95_MS = Number(__ENV.P95_MS || 50);

// Assessment profile directly models the required scenario:
// 500 records in <5s. 125 iterations/s for 4 seconds schedules exactly 500 iterations.
const assessmentScenario = {
  executor: 'constant-arrival-rate',
  rate: 125,
  timeUnit: '1s',
  duration: '4s',
  preAllocatedVUs: 50,
  maxVUs: 250,
  gracefulStop: '5s',
};

// Optional heavier capacity test. Run with PROFILE=stress.
const stressScenario = {
  executor: 'ramping-arrival-rate',
  startRate: 250,
  timeUnit: '1s',
  preAllocatedVUs: 250,
  maxVUs: 1000,
  stages: [
    { duration: '10s', target: 500 },
    { duration: '10s', target: 1000 },
    { duration: '30s', target: 1000 },
    { duration: '5s', target: 0 },
  ],
};

export const options = {
  discardResponseBodies: true,
  scenarios: {
    ingestion: PROFILE === 'stress' ? stressScenario : assessmentScenario,
  },
  thresholds: {
    // 429 is a failure for the assessment burst. k6 also treats 4xx as failed HTTP requests.
    http_req_failed: ['rate==0'],
    checks: ['rate==1'],
    dropped_iterations: ['count==0'],
    ...(PROFILE === 'assessment' ? {
      accepted_202: ['count==500'],
      assessment_completion_ms: ['max<5000'],
    } : {}),

    // This is a project performance guardrail, not an assessment requirement.
    // Override it with P95_MS=100 (etc.) if you want a different SLA.
    http_req_duration: [`p(95)<${P95_MS}`],
  },
};

const accepted202 = new Counter('accepted_202');
const rejected429 = new Counter('rejected_429');
const unexpectedStatus = new Counter('unexpected_status');
const completionTime = new Trend('assessment_completion_ms');

export default function () {
  const now = Date.now();
  const rawId = `k6-${PROFILE}-${__VU}-${__ITER}-${now}`;

  const payload = JSON.stringify({
    raw_id: rawId,
    src_ip: '10.240.1.1',
    device_id: '310410998877665',
    caller_num: '+19875551234',
    svc: '4G_DATA',
    up_bytes: 1048576,
    down_bytes: 4194304,
    rat: 6,
    lac: '4021',
    ci: '8812',
    epoch_start: Math.floor(now / 1000) - 300,
    epoch_end: Math.floor(now / 1000),
  });

  const res = http.post(API_URL, payload, {
    headers: { 'Content-Type': 'application/json' },
    tags: { test_profile: PROFILE },
  });
  completionTime.add(Date.now() - exec.scenario.startTime);

  if (res.status === 202) {
    accepted202.add(1);
  } else if (res.status === 429) {
    rejected429.add(1);
  } else {
    unexpectedStatus.add(1);
  }

  check(res, {
    'accepted with 202': (r) => r.status === 202,
    'not backpressured with 429': (r) => r.status !== 429,
  });
}

export function handleSummary(data) {
  const reqs = data.metrics.http_reqs?.values?.count || 0;
  const failedRate = data.metrics.http_req_failed?.values?.rate || 0;
  const p95 = data.metrics.http_req_duration?.values?.['p(95)'];
  const dropped = data.metrics.dropped_iterations?.values?.count || 0;
  const accepted = data.metrics.accepted_202?.values?.count || 0;
  const rejected = data.metrics.rejected_429?.values?.count || 0;
  const unexpected = data.metrics.unexpected_status?.values?.count || 0;
  const completionMs = data.metrics.assessment_completion_ms?.values?.max;

  const lines = [
    '',
    '=== CDR Ingestion Load-Test Summary ===',
    `Profile:             ${PROFILE}`,
    `Requests attempted:  ${reqs}`,
    `202 Accepted:        ${accepted}`,
    `429 Backpressure:    ${rejected}`,
    `Unexpected statuses: ${unexpected}`,
    `Dropped iterations:  ${dropped}`,
    `HTTP failure rate:   ${(failedRate * 100).toFixed(2)}%`,
    `p95 latency:         ${p95 !== undefined ? p95.toFixed(2) + ' ms' : 'n/a'}`,
  ];

  if (PROFILE === 'assessment') {
    const assessmentPass =
      reqs === 500 &&
      accepted === 500 &&
      rejected === 0 &&
      unexpected === 0 &&
      dropped === 0 &&
      completionMs < 5000;

    lines.push(
      'Assessment target:   500 acknowledged records in <5s, no 429, no dropped iterations',
      `Last completion:     ${completionMs !== undefined ? completionMs.toFixed(2) + ' ms' : 'unavailable'}`,
      `Assessment result:   ${assessmentPass ? 'PASS' : 'FAIL'}`,
      'Note: k6 proves API-side burst handling; run generate_traffic.py',
      '      to verify end-to-end ClickHouse/DLQ/deduplication behavior.'
    );
  } else {
    lines.push(
      'Stress target:       sustain the configured arrival rate without errors/drops.'
    );
  }

  lines.push('=======================================', '');

  return {
    stdout: `${lines.join('\n')}\n`,
  };
}