<?php

declare(strict_types=1);

namespace Tests\Performance\LoadTests;

use App\Framework\Core\ValueObjects\Duration;

/**
 * Load test runner for simulating concurrent requests
 *
 * Simulates multiple concurrent users hitting the application
 * to test performance under load
 */
final readonly class LoadTestRunner
{
    public function __construct(
        private string $baseUrl = 'https://localhost'
    ) {}

    /**
     * Run load test with specified parameters
     *
     * @param string $endpoint Endpoint to test
     * @param int $concurrentUsers Number of concurrent users
     * @param int $requestsPerUser Requests each user makes
     * @param Duration|null $rampUpTime Time to ramp up to full concurrency
     * @return LoadTestResult
     */
    public function run(
        string $endpoint,
        int $concurrentUsers = 10,
        int $requestsPerUser = 100,
        ?Duration $rampUpTime = null
    ): LoadTestResult {
        $startTime = microtime(true);
        $results = [];
        $errors = [];

        // Calculate ramp-up delay per user
        $rampUpDelay = $rampUpTime
            ? $rampUpTime->toMilliseconds() / $concurrentUsers
            : 0;

        // Spawn concurrent user processes
        $userProcesses = [];
        for ($i = 0; $i < $concurrentUsers; $i++) {
            // Ramp-up delay
            if ($rampUpDelay > 0) {
                usleep((int) ($rampUpDelay * 1000));
            }

            $userProcesses[] = $this->spawnUserProcess(
                userId: $i,
                endpoint: $endpoint,
                requestCount: $requestsPerUser
            );
        }

        // Wait for all user processes to complete
        foreach ($userProcesses as $userId => $process) {
            $userResults = $this->waitForUserProcess($process);
            $results[$userId] = $userResults;

            foreach ($userResults['errors'] ?? [] as $error) {
                $errors[] = $error;
            }
        }

        $endTime = microtime(true);
        $totalTime = ($endTime - $startTime) * 1000; // milliseconds

        return $this->analyzeResults($results, $errors, $totalTime);
    }

    /**
     * Spawn a user process that makes requests
     *
     * @return array Process information
     */
    private function spawnUserProcess(
        int $userId,
        string $endpoint,
        int $requestCount
    ): array {
        $responseTimes = [];
        $statusCodes = [];
        $errors = [];

        for ($i = 0; $i < $requestCount; $i++) {
            $requestStart = microtime(true);

            try {
                $result = $this->makeRequest($endpoint);

                $requestEnd = microtime(true);
                $responseTime = ($requestEnd - $requestStart) * 1000;

                $responseTimes[] = $responseTime;
                $statusCodes[] = $result['status_code'];

                if ($result['status_code'] >= 400) {
                    $errors[] = [
                        'user_id' => $userId,
                        'request_num' => $i,
                        'status_code' => $result['status_code'],
                        'error' => $result['error'] ?? 'HTTP error'
                    ];
                }
            } catch (\Exception $e) {
                $errors[] = [
                    'user_id' => $userId,
                    'request_num' => $i,
                    'error' => $e->getMessage()
                ];
            }
        }

        return [
            'user_id' => $userId,
            'response_times' => $responseTimes,
            'status_codes' => $statusCodes,
            'errors' => $errors
        ];
    }

    /**
     * Make HTTP request to endpoint
     */
    private function makeRequest(string $endpoint): array
    {
        $url = $this->baseUrl . $endpoint;

        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_SSL_VERIFYPEER => false,
            CURLOPT_SSL_VERIFYHOST => false,
            CURLOPT_HTTPHEADER => [
                'User-Agent: Mozilla/5.0 (Load Test)',
                'Accept: application/json'
            ],
            CURLOPT_TIMEOUT => 30
        ]);

        $response = curl_exec($ch);
        $statusCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $error = curl_error($ch);

        curl_close($ch);

        return [
            'response' => $response,
            'status_code' => $statusCode,
            'error' => $error ?: null
        ];
    }

    /**
     * Wait for user process to complete (placeholder for actual process handling)
     */
    private function waitForUserProcess(array $process): array
    {
        return $process;
    }

    /**
     * Analyze results from all users
     */
    private function analyzeResults(array $results, array $errors, float $totalTime): LoadTestResult
    {
        $allResponseTimes = [];
        $allStatusCodes = [];

        foreach ($results as $userResult) {
            $allResponseTimes = array_merge($allResponseTimes, $userResult['response_times']);
            $allStatusCodes = array_merge($allStatusCodes, $userResult['status_codes']);
        }

        sort($allResponseTimes);

        $totalRequests = count($allResponseTimes);
        $avgResponseTime = array_sum($allResponseTimes) / $totalRequests;
        $minResponseTime = min($allResponseTimes);
        $maxResponseTime = max($allResponseTimes);
        $medianResponseTime = $this->calculateMedian($allResponseTimes);
        $p95ResponseTime = $this->calculatePercentile($allResponseTimes, 95);
        $p99ResponseTime = $this->calculatePercentile($allResponseTimes, 99);

        $requestsPerSecond = ($totalRequests / $totalTime) * 1000;

        $successfulRequests = count(array_filter($allStatusCodes, fn($code) => $code >= 200 && $code < 300));
        $errorRate = ($totalRequests - $successfulRequests) / $totalRequests * 100;

        return new LoadTestResult(
            totalRequests: $totalRequests,
            totalTimeMs: $totalTime,
            avgResponseTimeMs: $avgResponseTime,
            minResponseTimeMs: $minResponseTime,
            maxResponseTimeMs: $maxResponseTime,
            medianResponseTimeMs: $medianResponseTime,
            p95ResponseTimeMs: $p95ResponseTime,
            p99ResponseTimeMs: $p99ResponseTime,
            requestsPerSecond: $requestsPerSecond,
            successfulRequests: $successfulRequests,
            errorRate: $errorRate,
            errors: $errors
        );
    }

    private function calculateMedian(array $values): float
    {
        $count = count($values);
        $middle = floor($count / 2);

        if ($count % 2 === 0) {
            return ($values[$middle - 1] + $values[$middle]) / 2;
        }

        return $values[$middle];
    }

    private function calculatePercentile(array $values, int $percentile): float
    {
        $count = count($values);
        $index = ceil($count * ($percentile / 100)) - 1;

        return $values[(int) max(0, min($index, $count - 1))];
    }
}