PHP

<?php

final class Silvertext
{
    private const BASE = 'https://api.silvertext.com';
    private const FINAL = ['done', 'rejected', 'failed', 'cancelled'];

    private readonly string $key;

    public function __construct(string $key = '')
    {
        $this->key = $key !== '' ? $key : (string) getenv('SILVERTEXT_API_KEY');
    }

    /** @return array<string,mixed>|null */
    public function request(string $method, string $path, ?array $json = null, array $headers = [], int $attempts = 4): ?array
    {
        $delay = 1.0;
        for ($attempt = 1; ; $attempt++) {
            $ch = curl_init(self::BASE . $path);
            $hdrs = array_merge(['Authorization: Bearer ' . $this->key, 'Content-Type: application/json'], $headers);
            curl_setopt_array($ch, [
                CURLOPT_CUSTOMREQUEST => $method,
                CURLOPT_RETURNTRANSFER => true,
                CURLOPT_HEADER => true,
                CURLOPT_HTTPHEADER => $hdrs,
                CURLOPT_POSTFIELDS => $json === null ? null : json_encode($json),
                CURLOPT_TIMEOUT => 60,
            ]);
            $raw = curl_exec($ch);
            $status = (int) curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
            $headerSize = (int) curl_getinfo($ch, CURLINFO_HEADER_SIZE);
            curl_close($ch);

            if ($raw !== false && $status < 400) {
                $body = substr($raw, $headerSize);
                return $body === '' ? null : json_decode($body, true);
            }
            $retryable = $raw === false || $status === 429 || $status >= 500;
            if (!$retryable || $attempt >= $attempts) {
                $error = $raw === false ? null : (json_decode(substr($raw, $headerSize), true)['error'] ?? null);
                throw new RuntimeException(($error['code'] ?? 'network') . ': ' . ($error['message'] ?? 'request failed'), $status);
            }
            $retryAfter = 0;
            if ($raw !== false && preg_match('/^Retry-After:\s*(\d+)/mi', substr($raw, 0, $headerSize), $m)) {
                $retryAfter = (int) $m[1];
            }
            usleep((int) (($retryAfter > 0 ? $retryAfter : $delay + mt_rand(0, 500) / 1000) * 1_000_000));
            $delay = min($delay * 2, 30);
        }
    }

    public function createCheck(array $body, ?string $idempotencyKey = null): string
    {
        // Always idempotent: request() retries, and a retry must never start a second check.
        $headers = ['Idempotency-Key: ' . ($idempotencyKey ?? bin2hex(random_bytes(16)))];
        return $this->request('POST', '/v1/checks', $body, $headers)['id'];
    }

    public function getCheck(string $id, ?string $view = null, ?array $include = null): array
    {
        $q = $include ? '?include=' . implode(',', $include) : ($view ? '?view=' . $view : '');
        return $this->request('GET', '/v1/checks/' . $id . $q);
    }

    public function cancelCheck(string $id): void
    {
        $this->request('POST', '/v1/checks/' . $id . '/cancel');
    }

    public function waitForCheck(string $id, int $deadlineSeconds = 600): array
    {
        $started = time();
        $delay = 3;
        while (true) {
            $check = $this->getCheck($id, 'summary');
            if (in_array($check['status'], self::FINAL, true)) {
                return $check;
            }
            if (time() - $started > $deadlineSeconds) {
                $this->cancelCheck($id);
                throw new RuntimeException("check $id did not finish in time");
            }
            sleep($delay);
            if (time() - $started > 60) {
                $delay = min($delay + 2, 10);
            }
        }
    }
}

$st = new Silvertext();

$id = $st->createCheck(
    ['title' => 'Q3 launch post', 'text' => $draft, 'options' => ['citations' => false]],
    "post:$postId:v$version",
);
$summary = $st->waitForCheck($id);
if ($summary['status'] !== 'done') {
    throw new RuntimeException($summary['rejection']['message'] ?? $summary['status']);
}
$report = $st->getCheck($id, include: ['issues', 'sources'])['report'];