/**
 * Router Rate Limiting Load Test Suite (k6)
 * Reference: SPRINT_1200_001_005 (RRL-05-003)
 *
 * Goals:
 * - Validate 429 + Retry-After behavior under load (instance and/or environment limits).
 * - Measure overhead (latency) while rate limiting is enabled.
 * - Exercise route-level matching via mixed-path traffic.
 *
 * Notes:
 * - This test suite is environment-config driven. Ensure Router rate limiting is configured
 *   for the targeted route(s) in the environment under test.
 * - "Scenario B" (environment multi-instance) is achieved by running the same test
 *   concurrently from multiple machines/agents.
 */

import http from 'k6/http';
import { check, sleep } from 'k6';
import { Rate, Trend } from 'k6/metrics';

const BASE_URL = (__ENV.BASE_URL || 'http://localhost:5000').replace(/\/+$/, '');
const METHOD = (__ENV.METHOD || 'GET').toUpperCase();
const PATH = __ENV.PATH || '/api/test';
const PATHS_JSON = __ENV.PATHS_JSON || '';
const TENANT_ID = __ENV.TENANT_ID || 'load-test-tenant';
const AUTH_TOKEN = __ENV.AUTH_TOKEN || '';
const RESULTS_DIR = __ENV.RESULTS_DIR || 'results';

function parsePaths() {
  if (!PATHS_JSON) {
    return [PATH];
  }
  try {
    const parsed = JSON.parse(PATHS_JSON);
    if (Array.isArray(parsed) && parsed.length > 0) {
      return parsed.map((p) => (typeof p === 'string' ? p : PATH)).filter((p) => !!p);
    }
  } catch {
    // Ignore parse errors; fall back to single PATH.
  }
  return [PATH];
}

const PATHS = parsePaths();

// Custom metrics
const rateLimitDenied = new Rate('router_rate_limit_denied');
const retryAfterSeconds = new Trend('router_rate_limit_retry_after_seconds');
const status429MissingRetryAfter = new Rate('router_rate_limit_429_missing_retry_after');

// Scenario configuration (defaults can be overridden via env vars)
const BELOW_RPS = parseInt(__ENV.BELOW_RPS || '50', 10);
const ABOVE_RPS = parseInt(__ENV.ABOVE_RPS || '500', 10);

export const options = {
  scenarios: {
    // Scenario A: baseline below configured limits
    below_limit: {
      executor: 'constant-arrival-rate',
      rate: BELOW_RPS,
      timeUnit: '1s',
      duration: __ENV.BELOW_DURATION || '2m',
      preAllocatedVUs: parseInt(__ENV.BELOW_VUS || '50', 10),
      maxVUs: parseInt(__ENV.BELOW_MAX_VUS || '200', 10),
      tags: { scenario: 'below_limit' },
    },

    // Scenario B: above configured limits (expect some 429s)
    above_limit: {
      executor: 'ramping-arrival-rate',
      startRate: BELOW_RPS,
      timeUnit: '1s',
      stages: [
        { duration: __ENV.ABOVE_RAMP_UP || '20s', target: ABOVE_RPS },
        { duration: __ENV.ABOVE_HOLD || '40s', target: ABOVE_RPS },
        { duration: __ENV.ABOVE_RAMP_DOWN || '20s', target: BELOW_RPS },
      ],
      preAllocatedVUs: parseInt(__ENV.ABOVE_VUS || '100', 10),
      maxVUs: parseInt(__ENV.ABOVE_MAX_VUS || '500', 10),
      startTime: __ENV.ABOVE_START || '2m10s',
      tags: { scenario: 'above_limit' },
    },

    // Scenario C: route mix (exercise route-specific limits/matching)
    route_mix: {
      executor: 'constant-arrival-rate',
      rate: parseInt(__ENV.MIX_RPS || '100', 10),
      timeUnit: '1s',
      duration: __ENV.MIX_DURATION || '2m',
      preAllocatedVUs: parseInt(__ENV.MIX_VUS || '75', 10),
      maxVUs: parseInt(__ENV.MIX_MAX_VUS || '300', 10),
      startTime: __ENV.MIX_START || '3m30s',
      tags: { scenario: 'route_mix' },
    },

    // Scenario F: activation gate (low traffic then spike)
    activation_gate: {
      executor: 'ramping-arrival-rate',
      startRate: 1,
      timeUnit: '1s',
      stages: [
        { duration: __ENV.GATE_LOW_DURATION || '2m', target: parseInt(__ENV.GATE_LOW_RPS || '5', 10) },
        { duration: __ENV.GATE_SPIKE_DURATION || '30s', target: parseInt(__ENV.GATE_SPIKE_RPS || '200', 10) },
        { duration: __ENV.GATE_RECOVERY_DURATION || '30s', target: parseInt(__ENV.GATE_LOW_RPS || '5', 10) },
      ],
      preAllocatedVUs: parseInt(__ENV.GATE_VUS || '50', 10),
      maxVUs: parseInt(__ENV.GATE_MAX_VUS || '300', 10),
      startTime: __ENV.GATE_START || '5m40s',
      tags: { scenario: 'activation_gate' },
    },
  },
  thresholds: {
    'http_req_failed': ['rate<0.01'],
    'router_rate_limit_429_missing_retry_after': ['rate<0.001'],
  },
};

export default function () {
  const path = PATHS[Math.floor(Math.random() * PATHS.length)];
  const normalizedPath = path.startsWith('/') ? path : `/${path}`;
  const url = `${BASE_URL}${normalizedPath}`;

  const headers = {
    'Accept': 'application/json',
    'X-Tenant-Id': TENANT_ID,
    'X-Correlation-Id': `rl-load-${Date.now()}-${Math.random().toString(36).slice(2, 10)}`,
  };

  if (AUTH_TOKEN) {
    headers['Authorization'] = `Bearer ${AUTH_TOKEN}`;
  }

  const res = http.request(METHOD, url, null, {
    headers,
    tags: { endpoint: normalizedPath },
  });

  const is429 = res.status === 429;
  rateLimitDenied.add(is429);

  if (is429) {
    const retryAfter = res.headers['Retry-After'];
    status429MissingRetryAfter.add(!retryAfter);

    if (retryAfter) {
      const parsed = parseInt(retryAfter, 10);
      if (!Number.isNaN(parsed)) {
        retryAfterSeconds.add(parsed);
      }
    }
  }

  check(res, {
    'status is 2xx or 429': (r) => (r.status >= 200 && r.status < 300) || r.status === 429,
    'Retry-After present on 429': (r) => r.status !== 429 || r.headers['Retry-After'] !== undefined,
  });

  sleep(0.05 + Math.random() * 0.1);
}

export function setup() {
  console.log(`Starting Router rate limiting load test against ${BASE_URL}`);
  console.log(`Method=${METHOD}, paths=${JSON.stringify(PATHS)}`);
}

export function handleSummary(data) {
  const timestamp = new Date().toISOString().replace(/[:.]/g, '-');

  function metricValue(metricName, valueName) {
    const metric = data.metrics && data.metrics[metricName];
    const values = metric && metric.values;
    return values ? values[valueName] : undefined;
  }

  const summary = {
    timestampUtc: new Date().toISOString(),
    baseUrl: BASE_URL,
    method: METHOD,
    paths: PATHS,
    metrics: {
      httpReqFailedRate: metricValue('http_req_failed', 'rate'),
      httpReqDurationP95Ms: metricValue('http_req_duration', 'p(95)'),
      rateLimitDeniedRate: metricValue('router_rate_limit_denied', 'rate'),
      retryAfterP95Seconds: metricValue('router_rate_limit_retry_after_seconds', 'p(95)'),
      missingRetryAfterRate: metricValue('router_rate_limit_429_missing_retry_after', 'rate'),
    },
    notes: [
      `Set RESULTS_DIR to control file output directory (default: ${RESULTS_DIR}).`,
      'Ensure the results directory exists before running if you want JSON artifacts written.',
    ],
  };

  const json = JSON.stringify(data, null, 2);
  const summaryJson = JSON.stringify(summary, null, 2);

  return {
    stdout: `${summaryJson}\n`,
    [`${RESULTS_DIR}/router-rate-limiting-load-test-${timestamp}.json`]: json,
    [`${RESULTS_DIR}/router-rate-limiting-load-test-latest.json`]: json,
  };
}