Translation Class

<?php

declare(strict_types=1);

interface TranslationProviderInterface
{
    /**
     * @param string      $text       Text to translate
     * @param string      $targetLang Target language code (format depends on provider)
     * @param string|null $sourceLang Source language code, or null for auto-detect
     * @return string Translated text
     * @throws RuntimeException on request failure
     */
    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string;
}

// ---------------------------------------------------------------------
// Small shared HTTP helper (cURL) so providers don't duplicate this
// ---------------------------------------------------------------------
final class HttpClient
{
    /**
     * @param array<string> $headers
     * @param string|array  $body    Raw string (JSON/form-encoded) or array for multipart
     */
    public static function post(string $url, array $headers, $body): array
    {
        $ch = curl_init($url);
        curl_setopt_array($ch, [
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_POST => true,
            CURLOPT_HTTPHEADER => $headers,
            CURLOPT_POSTFIELDS => $body,
            CURLOPT_TIMEOUT => 15,
            CURLOPT_CONNECTTIMEOUT => 10,
        ]);

        $response = curl_exec($ch);

        if ($response === false) {
            $error = curl_error($ch);
            curl_close($ch);
            throw new RuntimeException("cURL error: {$error}");
        }

        $statusCode = curl_getinfo($ch, CURLINFO_HTTP_CODE);
        curl_close($ch);

        if ($statusCode < 200 || $statusCode >= 300) {
            throw new RuntimeException("HTTP error {$statusCode}: {$response}");
        }

        $decoded = json_decode($response, true);
        if (json_last_error() !== JSON_ERROR_NONE) {
            throw new RuntimeException('Failed to decode JSON response: ' . json_last_error_msg());
        }

        return $decoded ?? [];
    }
}

// ---------------------------------------------------------------------
// Provider: DeepL (https://www.deepl.com/docs-api)
// Target lang example: 'DE', 'ES', 'FR' (uppercase)
// ---------------------------------------------------------------------
final class DeepLProvider implements TranslationProviderInterface
{
    private string $apiKey;
    private string $endpoint;

    public function __construct(string $apiKey, bool $useFreeTier = false)
    {
        $this->apiKey = $apiKey;
        $this->endpoint = $useFreeTier
            ? 'https://api-free.deepl.com/v2/translate'
            : 'https://api.deepl.com/v2/translate';
    }

    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string
        {
            $params = [
                'text'        => $text,
                'target_lang' => strtoupper($targetLang),
            ];

            if ($sourceLang !== null) {
                $params['source_lang'] = strtoupper($sourceLang);
            }

            $result = HttpClient::post(
                $this->endpoint,
                [
                    'Authorization: DeepL-Auth-Key ' . $this->apiKey,
                    'Content-Type: application/x-www-form-urlencoded',
                ],
                http_build_query($params)
            );

            return $result['translations'][0]['text'] ?? '';
        }
}

// ---------------------------------------------------------------------
// Provider: Google Cloud Translation API v2
// Target lang example: 'es', 'fr', 'de' (lowercase ISO 639-1)
// ---------------------------------------------------------------------
final class GoogleTranslateProvider implements TranslationProviderInterface
{
    private string $apiKey;
    private string $endpoint = 'https://translation.googleapis.com/language/translate/v2';

    public function __construct(string $apiKey)
    {
        $this->apiKey = $apiKey;
    }

    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string
    {
        $params = [
            'key' => $this->apiKey,
            'q' => $text,
            'target' => $targetLang,
            'format' => 'text',
        ];
        if ($sourceLang !== null) {
            $params['source'] = $sourceLang;
        }

        $result = HttpClient::post(
            $this->endpoint,
            ['Content-Type: application/x-www-form-urlencoded'],
            http_build_query($params)
        );

        return $result['data']['translations'][0]['translatedText'] ?? '';
    }
}

// ---------------------------------------------------------------------
// Provider: Microsoft Translator (Azure Cognitive Services)
// Target lang example: 'es', 'fr', 'de'
// ---------------------------------------------------------------------
final class MicrosoftTranslatorProvider implements TranslationProviderInterface
{
    private string $apiKey;
    private string $region;
    private string $endpoint = 'https://api.cognitive.microsofttranslator.com/translate?api-version=3.0';

    public function __construct(string $apiKey, string $region)
    {
        $this->apiKey = $apiKey;
        $this->region = $region;
    }

    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string
    {
        $url = $this->endpoint . '&to=' . urlencode($targetLang);
        if ($sourceLang !== null) {
            $url .= '&from=' . urlencode($sourceLang);
        }

        $headers = [
            'Ocp-Apim-Subscription-Key: ' . $this->apiKey,
            'Ocp-Apim-Subscription-Region: ' . $this->region,
            'Content-Type: application/json',
        ];

        $body = json_encode([['Text' => $text]]);

        $result = HttpClient::post($url, $headers, $body);

        return $result[0]['translations'][0]['text'] ?? '';
    }
}

// ---------------------------------------------------------------------
// Provider: LibreTranslate (self-hosted or public instance, no vendor lock-in)
// Target lang example: 'es', 'fr', 'de'
// ---------------------------------------------------------------------
final class LibreTranslateProvider implements TranslationProviderInterface
{
    private string $endpoint;
    private ?string $apiKey;

    public function __construct(string $endpoint = 'https://libretranslate.com/translate', ?string $apiKey = null)
    {
        $this->endpoint = $endpoint;
        $this->apiKey = $apiKey;
    }

    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string
    {
        $payload = [
            'q' => $text,
            'source' => $sourceLang ?? 'auto',
            'target' => $targetLang,
            'format' => 'text',
        ];
        if ($this->apiKey !== null) {
            $payload['api_key'] = $this->apiKey;
        }

        $result = HttpClient::post(
            $this->endpoint,
            ['Content-Type: application/json'],
            json_encode($payload)
        );

        return $result['translatedText'] ?? '';
    }
}

// ---------------------------------------------------------------------
// Facade: what your application code actually talks to
// ---------------------------------------------------------------------
final class Translator
{
    private TranslationProviderInterface $provider;

    public function __construct(TranslationProviderInterface $provider)
    {
        $this->provider = $provider;
    }

    public function translate(string $text, string $targetLang, ?string $sourceLang = null): string
    {
        return $this->provider->translate($text, $targetLang, $sourceLang);
    }

    /**
     * Convenience for translating several strings in one call.
     * (Loops client-side; providers with native batch endpoints could
     * override this for efficiency.)
     *
     * @param string[] $texts
     * @return string[]
     */
    public function translateBatch(array $texts, string $targetLang, ?string $sourceLang = null): array
    {
        $results = [];
        foreach ($texts as $key => $text) {
            $results[$key] = $this->translate($text, $targetLang, $sourceLang);
        }
        return $results;
    }
}

// ---------------------------------------------------------------------
// Usage examples (uncomment the one you need)
// ---------------------------------------------------------------------

// DeepL
// $translator = new Translator(new DeepLProvider('YOUR_DEEPL_API_KEY'));
// echo $translator->translate('Hello, world!', 'DE');

// Google Cloud Translation
// $translator = new Translator(new GoogleTranslateProvider('YOUR_GOOGLE_API_KEY'));
// echo $translator->translate('Hello, world!', 'es');

// Microsoft Translator
// $translator = new Translator(new MicrosoftTranslatorProvider('YOUR_MS_KEY', 'YOUR_REGION'));
// echo $translator->translate('Hello, world!', 'it');

// LibreTranslate (free/self-hosted, no API key required by default)
// $translator = new Translator(new LibreTranslateProvider());
// echo $translator->translate('Hello, world!', 'fr');

// Batch example
// $translator = new Translator(new DeepLProvider('YOUR_DEEPL_API_KEY'));
// $translated = $translator->translateBatch(
//     ['Hello', 'Goodbye', 'Thank you'],
//     'FR'
// );
// print_r($translated);