{
  "model":       "gpt-4o-mini",       // โมเดลที่ต้องการใช้
  "messages": [
    { "role": "system",    "content": "You are a helpful assistant." },
    { "role": "user",      "content": "สรุปบทความนี้ให้หน่อย..." }
  ],
  "max_tokens":  500,              // จำกัด output token
  "temperature": 0.7,              // 0 = deterministic, 2 = wild
  "stream":      false             // true = ส่งแบบ chunk
}

<?php

namespace App\Services;

use CodeIgniter\HTTP\CURLRequest;

class LlmService
{
    private CURLRequest $client;
    private string      $apiKey;

    public function __construct()
    {
        $this->apiKey = env('OPENAI_API_KEY');
        $this->client = service('curlrequest', [
            'baseURI' => 'https://api.openai.com/v1/',
            'timeout' => 30,
        ]);
    }

    public function chat(string $userMessage): string
    {
        $payload = [
            'model'      => 'gpt-4o-mini',
            'messages'  => [
                ['role' => 'system', 'content' => 'ตอบเป็นภาษาไทย กระชับ และถูกต้อง'],
                ['role' => 'user',   'content' => $userMessage],
            ],
            'max_tokens' => 500,
        ];

        $response = $this->client->post('chat/completions', [
            'headers' => [
                'Authorization' => 'Bearer ' . $this->apiKey,
                'Content-Type'  => 'application/json',
            ],
            'json' => $payload,
        ]);

        $data = json_decode($response->getBody(), true);

        // ดึงคำตอบจาก response structure
        return $data['choices'][0]['message']['content'] ?? '';
    }
}

public function ask()
{
    $question = $this->request->getPost('question');

    if (empty($question)) {
        return $this->response
            ->setStatusCode(422)
            ->setJSON(['error' => 'กรุณาระบุคำถาม']);
    }

    $llm    = new LlmService();
    $answer = $llm->chat($question);

    return $this->response->setJSON([
        'answer' => $answer,
    ]);
}

<?php

namespace App\Services;

use Illuminate\Support\Facades\Http;
use Illuminate\Http\Client\RequestException;

class LlmService
{
    public function chat(string $userMessage, string $systemPrompt = ''): string
    {
        $messages = [];

        if ($systemPrompt) {
            $messages[] = ['role' => 'system', 'content' => $systemPrompt];
        }
        $messages[] = ['role' => 'user', 'content' => $userMessage];

        $response = Http::withToken(config('services.openai.key'))
            ->timeout(30)
            ->retry(2, 1000)           // retry 2 ครั้ง รอ 1 วิ
            ->post('https://api.openai.com/v1/chat/completions', [
                'model'      => 'gpt-4o-mini',
                'messages'  => $messages,
                'max_tokens' => 500,
            ])
            ->throw();                  // โยน exception ถ้า 4xx/5xx

        return $response->json('choices.0.message.content', '');
    }
}

// ต้องปิด output buffering ก่อน
ob_end_clean();
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');

$ch = curl_init('https://api.openai.com/v1/chat/completions');
curl_setopt_array($ch, [
    CURLOPT_POST          => true,
    CURLOPT_HTTPHEADER    => [
        'Authorization: Bearer ' . $apiKey,
        'Content-Type: application/json',
    ],
    CURLOPT_POSTFIELDS    => json_encode([
        'model'    => 'gpt-4o-mini',
        'messages' => [['role' => 'user', 'content' => $prompt]],
        'stream'   => true,  // <-- ตรงนี้สำคัญ!
    ]),
    CURLOPT_WRITEFUNCTION => function($ch, $chunk) {
        echo $chunk;
        ob_flush();
        flush();
        return strlen($chunk);
    },
]);

curl_exec($ch);
curl_close($ch);