service_wopi/lib/Preview/ConversionClient.php

<?php
declare(strict_types=1);
namespace KTXM\ServiceWopi\Preview;

use CURLStringFile;
use KTXF\Preview\PreviewGenerationException;
use KTXM\ServiceWopi\Discovery\ServerAddress;

class ConversionClient
{
    public const MAX_RESPONSE_BYTES = 32 * 1024 * 1024;

    public function pdf(ServerAddress $server, string $content, string $extension, string $mimeType): string
    {
        $curl = curl_init($server->url . '/cool/convert-to/pdf');
        $pdf = '';
        curl_setopt_array($curl, [
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => ['data' => new CURLStringFile($content, 'document.' . $extension, $mimeType)],
            CURLOPT_CONNECTTIMEOUT => 5,
            CURLOPT_TIMEOUT => 30,
            CURLOPT_FOLLOWLOCATION => false,
            CURLOPT_PROTOCOLS => CURLPROTO_HTTPS,
            CURLOPT_SSL_VERIFYPEER => true,
            CURLOPT_SSL_VERIFYHOST => 2,
            CURLOPT_HTTPHEADER => ['Accept: application/pdf'],
            CURLOPT_WRITEFUNCTION => static function ($handle, string $chunk) use (&$pdf): int {
                if (strlen($pdf) + strlen($chunk) > self::MAX_RESPONSE_BYTES) { return 0; }
                $pdf .= $chunk;
                return strlen($chunk);
            },
        ]);
        try {
            if (curl_exec($curl) === false) {
                throw new PreviewGenerationException('WOPI conversion failed (cURL ' . curl_errno($curl) . ')');
            }
            if (curl_getinfo($curl, CURLINFO_RESPONSE_CODE) !== 200 || !str_starts_with($pdf, '%PDF-')) {
                throw new PreviewGenerationException('WOPI conversion did not return a PDF');
            }
            return $pdf;
        } finally {
            curl_close($curl);
        }
    }
}