2. Consumo de APIs de LLMs en PHP (cURL/Guzzle) y Node/Browser (Fetch)

<?php
declare(strict_types=1);

namespace App\Services;

class OpenAIService
{
    private string $apiKey;
    private string $baseUrl;

    public function __construct(string $apiKey, string $baseUrl = 'https://api.openai.com/v1')
    {
        $this->apiKey = $apiKey;
        $this->baseUrl = rtrim($baseUrl, '/');
    }

    /**
     * Envía una lista de mensajes al modelo de chat y retorna el texto generado.
     *
     * @param array<int, array{role: string, content: string}> $messages
     * @param string $model
     * @param float $temperature
     * @param int $maxTokens
     * @return array{content: string, prompt_tokens: int, completion_tokens: int, total_tokens: int}
     * @throws \RuntimeException
     */
    public function chatCompletion(
        array $messages,
        string $model = 'gpt-4o-mini',
        float $temperature = 0.2,
        int $maxTokens = 800
    ): array {
        $endpoint = $this->baseUrl . '/chat/completions';

        $payload = [
            'model'       => $model,
            'messages'    => $messages,
            'temperature' => $temperature,
            'max_tokens'  => $maxTokens,
        ];

        $ch = curl_init($endpoint);
        curl_setopt_array($ch, [
            CURLOPT_POST           => true,
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_HTTPHEADER     => [
                'Content-Type: application/json',
                'Authorization: Bearer ' . $this->apiKey,
                'User-Agent: Kilopolis-Web-App/1.0',
            ],
            CURLOPT_POSTFIELDS     => json_encode($payload, JSON_THROW_ON_ERROR),
            CURLOPT_TIMEOUT        => 25,
            CURLOPT_CONNECTTIMEOUT => 5,
        ]);

        $rawResponse = curl_exec($ch);
        $httpCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        $curlError = curl_error($ch);
        curl_close($ch);

        if ($curlError !== '') {
            throw new \RuntimeException("Falla de conexión de red con el LLM: {$curlError}");
        }

        if ($httpCode !== 200 || !is_string($rawResponse)) {
            throw new \RuntimeException("Respuesta de API inválida (HTTP {$httpCode}): {$rawResponse}");
        }

        $decoded = json_decode($rawResponse, true, 512, JSON_THROW_ON_ERROR);

        return [
            'content'           => $decoded['choices'][0]['message']['content'] ?? '',
            'prompt_tokens'     => $decoded['usage']['prompt_tokens'] ?? 0,
            'completion_tokens' => $decoded['usage']['completion_tokens'] ?? 0,
            'total_tokens'      => $decoded['usage']['total_tokens'] ?? 0,
        ];
    }
}