/**
 * Priority 14: Load & Stress Benchmark Runner
 *
 * Simulates high concurrency scenarios:
 * 1. Concurrent Job Discovery searches
 * 2. Concurrent Readiness probe checks
 * 3. Concurrent AI Matching calculations
 *
 * Measures: Requests per second (RPS), Error rate %, and p50, p95, p99 latencies.
 */

const http = require("http");

function makeRequest(url, options = {}) {
  return new Promise((resolve) => {
    const start = Date.now();
    const parsed = new URL(url);
    const req = http.request(
      {
        hostname: parsed.hostname,
        port: parsed.port,
        path: parsed.pathname + parsed.search,
        method: options.method || "GET",
        headers: options.headers || {},
      },
      (res) => {
        let body = "";
        res.on("data", (chunk) => (body += chunk));
        res.on("end", () => {
          resolve({
            statusCode: res.statusCode,
            latencyMs: Date.now() - start,
            success: res.statusCode >= 200 && res.statusCode < 400,
          });
        });
      }
    );

    req.on("error", (err) => {
      resolve({
        statusCode: 0,
        latencyMs: Date.now() - start,
        success: false,
        error: err.message,
      });
    });

    if (options.body) {
      req.write(options.body);
    }
    req.end();
  });
}

function calculatePercentiles(latencies) {
  if (latencies.length === 0) return { p50: 0, p95: 0, p99: 0, min: 0, max: 0 };
  const sorted = [...latencies].sort((a, b) => a - b);
  const count = sorted.length;
  return {
    count,
    p50: Math.round(sorted[Math.floor(count * 0.5)]),
    p95: Math.round(sorted[Math.floor(count * 0.95)] || sorted[count - 1]),
    p99: Math.round(sorted[Math.floor(count * 0.99)] || sorted[count - 1]),
    min: Math.round(sorted[0]),
    max: Math.round(sorted[count - 1]),
  };
}

async function runScenario(name, url, totalRequests = 200, concurrency = 20) {
  console.log(`\n--- Running Scenario: ${name} (${totalRequests} requests, ${concurrency} concurrency) ---`);
  const latencies = [];
  let successCount = 0;
  let failCount = 0;

  const startTime = Date.now();
  let completed = 0;

  async function worker() {
    while (completed < totalRequests) {
      completed++;
      const res = await makeRequest(url);
      latencies.push(res.latencyMs);
      if (res.success) {
        successCount++;
      } else {
        failCount++;
      }
    }
  }

  const workers = Array.from({ length: concurrency }, () => worker());
  await Promise.all(workers);

  const durationSec = (Date.now() - startTime) / 1000;
  const rps = Math.round(totalRequests / durationSec);
  const p = calculatePercentiles(latencies);
  const errorRate = ((failCount / totalRequests) * 100).toFixed(1);

  console.log(`  Requests Completed: ${totalRequests}`);
  console.log(`  Duration: ${durationSec.toFixed(2)}s | Throughput: ${rps} req/sec`);
  console.log(`  Error Rate: ${errorRate}% (Success: ${successCount}, Failed: ${failCount})`);
  console.log(`  Latency (ms): p50=${p.p50}ms | p95=${p.p95}ms | p99=${p.p99}ms (min=${p.min}ms, max=${p.max}ms)`);

  return { name, totalRequests, rps, errorRate, ...p };
}

async function main() {
  console.log("=================================================");
  console.log("  JOBSBOARD PRODUCTION LOAD & STRESS BENCHMARK   ");
  console.log("=================================================");

  // Scenario 1: Readiness Health Check (high-frequency load balancer probe)
  const healthResult = await runScenario(
    "Load Balancer Readiness Probe",
    "http://localhost:3000/api/health?type=readiness",
    300,
    30
  );

  // Scenario 2: Public Job Discovery Search (with filters)
  const searchResult = await runScenario(
    "Marketplace Job Discovery (/api/jobs?search=engineer&remoteOnly=true)",
    "http://localhost:3000/api/jobs?search=engineer&remoteOnly=true&limit=20",
    200,
    20
  );

  // Scenario 3: Metrics Observability Endpoint
  const metricsResult = await runScenario(
    "Metrics Endpoint (/api/metrics)",
    "http://localhost:3000/api/metrics",
    100,
    10
  );

  console.log("\n=================================================");
  console.log("  BENCHMARK SUMMARY MATRIX                       ");
  console.log("=================================================");
  console.log(JSON.stringify({ healthResult, searchResult, metricsResult }, null, 2));
}

main().catch(console.error);