// -----------------------------------------------------------------------------
// spike-test.js
// Sprint: SPRINT_5100_0005_0001_router_chaos_suite
// Task: T1 - Load Test Harness
// Description: k6 load test for router spike testing and backpressure validation.
// -----------------------------------------------------------------------------

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

// Custom metrics for throttle behavior
const throttledRate = new Rate('throttled_requests');
const retryAfterTrend = new Trend('retry_after_seconds');
const recoveryTime = new Trend('recovery_time_ms');
const throttle429Count = new Counter('throttle_429_count');
const throttle503Count = new Counter('throttle_503_count');
const successCount = new Counter('success_count');

export const options = {
  scenarios: {
    // Phase 1: Baseline load (normal operation)
    baseline: {
      executor: 'constant-arrival-rate',
      rate: 100,
      timeUnit: '1s',
      duration: '1m',
      preAllocatedVUs: 50,
      maxVUs: 100,
    },
    // Phase 2: 10x spike
    spike_10x: {
      executor: 'constant-arrival-rate',
      rate: 1000,
      timeUnit: '1s',
      duration: '30s',
      startTime: '1m',
      preAllocatedVUs: 500,
      maxVUs: 1000,
    },
    // Phase 3: 50x spike
    spike_50x: {
      executor: 'constant-arrival-rate',
      rate: 5000,
      timeUnit: '1s',
      duration: '30s',
      startTime: '2m',
      preAllocatedVUs: 2000,
      maxVUs: 5000,
    },
    // Phase 4: Recovery observation
    recovery: {
      executor: 'constant-arrival-rate',
      rate: 100,
      timeUnit: '1s',
      duration: '2m',
      startTime: '3m',
      preAllocatedVUs: 50,
      maxVUs: 100,
    },
  },
  thresholds: {
    // At least 95% of requests should succeed OR return proper throttle response
    'http_req_failed{expected_response:true}': ['rate<0.05'],
    // Throttled requests should have Retry-After header
    'throttled_requests': ['rate>0'],  // We expect some throttling during spike
    // Recovery should happen within reasonable time
    'recovery_time_ms': ['p(95)<30000'],  // 95% recover within 30s
    // Response time should be bounded even under load
    'http_req_duration{expected_response:true}': ['p(95)<5000'],
  },
};

const ROUTER_URL = __ENV.ROUTER_URL || 'http://localhost:8080';
const API_ENDPOINT = __ENV.API_ENDPOINT || '/api/v1/scan';

export function setup() {
  console.log(`Testing router at: ${ROUTER_URL}${API_ENDPOINT}`);

  // Verify router is reachable
  const healthCheck = http.get(`${ROUTER_URL}/health`);
  if (healthCheck.status !== 200) {
    console.warn(`Router health check returned ${healthCheck.status}`);
  }

  return {
    startTime: new Date().toISOString(),
    routerUrl: ROUTER_URL,
  };
}

export default function () {
  const payload = JSON.stringify({
    image: 'alpine:latest',
    requestId: `spike-test-${__VU}-${__ITER}`,
    timestamp: new Date().toISOString(),
  });

  const params = {
    headers: {
      'Content-Type': 'application/json',
      'X-Request-ID': `${__VU}-${__ITER}`,
    },
    tags: { expected_response: 'true' },
    timeout: '10s',
  };

  const response = http.post(`${ROUTER_URL}${API_ENDPOINT}`, payload, params);

  // Handle throttle responses (429 Too Many Requests)
  if (response.status === 429) {
    throttledRate.add(1);
    throttle429Count.add(1);

    // Verify Retry-After header
    const retryAfter = response.headers['Retry-After'];
    check(response, {
      '429 has Retry-After header': (r) => r.headers['Retry-After'] !== undefined,
      'Retry-After is valid number': (r) => {
        const val = r.headers['Retry-After'];
        return val && !isNaN(parseInt(val));
      },
      'Retry-After is reasonable (1-300s)': (r) => {
        const val = parseInt(r.headers['Retry-After']);
        return val >= 1 && val <= 300;
      },
    });

    if (retryAfter) {
      retryAfterTrend.add(parseInt(retryAfter));
    }
  }
  // Handle overload responses (503 Service Unavailable)
  else if (response.status === 503) {
    throttledRate.add(1);
    throttle503Count.add(1);

    check(response, {
      '503 has Retry-After header': (r) => r.headers['Retry-After'] !== undefined,
    });

    const retryAfter = response.headers['Retry-After'];
    if (retryAfter) {
      retryAfterTrend.add(parseInt(retryAfter));
    }
  }
  // Handle success responses
  else {
    throttledRate.add(0);
    successCount.add(1);

    check(response, {
      'status is 200 or 202': (r) => r.status === 200 || r.status === 202,
      'response has body': (r) => r.body && r.body.length > 0,
      'response time < 5s': (r) => r.timings.duration < 5000,
    });
  }

  // Track any errors
  if (response.status >= 500 && response.status !== 503) {
    check(response, {
      'no unexpected 5xx errors': () => false,
    });
  }
}

export function teardown(data) {
  console.log(`Test completed. Started at: ${data.startTime}`);
  console.log(`Router URL: ${data.routerUrl}`);
}

export function handleSummary(data) {
  const summary = {
    testRun: {
      startTime: new Date().toISOString(),
      routerUrl: ROUTER_URL,
    },
    metrics: {
      totalRequests: data.metrics.http_reqs ? data.metrics.http_reqs.values.count : 0,
      throttled429: data.metrics.throttle_429_count ? data.metrics.throttle_429_count.values.count : 0,
      throttled503: data.metrics.throttle_503_count ? data.metrics.throttle_503_count.values.count : 0,
      successful: data.metrics.success_count ? data.metrics.success_count.values.count : 0,
      throttleRate: data.metrics.throttled_requests ? data.metrics.throttled_requests.values.rate : 0,
      retryAfterAvg: data.metrics.retry_after_seconds ? data.metrics.retry_after_seconds.values.avg : null,
      retryAfterP95: data.metrics.retry_after_seconds ? data.metrics.retry_after_seconds.values['p(95)'] : null,
    },
    thresholds: data.thresholds,
    checks: data.metrics.checks ? {
      passes: data.metrics.checks.values.passes,
      fails: data.metrics.checks.values.fails,
      rate: data.metrics.checks.values.rate,
    } : null,
  };

  return {
    'results/spike-test-summary.json': JSON.stringify(summary, null, 2),
    stdout: textSummary(data, { indent: ' ', enableColors: true }),
  };
}

function textSummary(data, options) {
  let output = '\n=== Router Spike Test Summary ===\n\n';

  const totalReqs = data.metrics.http_reqs ? data.metrics.http_reqs.values.count : 0;
  const throttled429 = data.metrics.throttle_429_count ? data.metrics.throttle_429_count.values.count : 0;
  const throttled503 = data.metrics.throttle_503_count ? data.metrics.throttle_503_count.values.count : 0;
  const successful = data.metrics.success_count ? data.metrics.success_count.values.count : 0;

  output += `Total Requests: ${totalReqs}\n`;
  output += `Successful (2xx): ${successful}\n`;
  output += `Throttled (429): ${throttled429}\n`;
  output += `Overloaded (503): ${throttled503}\n`;
  output += `Throttle Rate: ${((throttled429 + throttled503) / totalReqs * 100).toFixed(2)}%\n`;

  if (data.metrics.retry_after_seconds) {
    output += `\nRetry-After Header:\n`;
    output += `  Avg: ${data.metrics.retry_after_seconds.values.avg.toFixed(2)}s\n`;
    output += `  P95: ${data.metrics.retry_after_seconds.values['p(95)'].toFixed(2)}s\n`;
  }

  output += '\nThreshold Results:\n';
  for (const [name, result] of Object.entries(data.thresholds || {})) {
    output += `  ${result.ok ? 'PASS' : 'FAIL'}: ${name}\n`;
  }

  return output;
}