<?php
/**
 * FuturePay Official PHP SDK Helper
 * 
 * Lightweight, zero-dependency client class for interacting with the FuturePay Payment Gateway API.
 * 
 * @package FuturePay
 * @version 1.0.0
 */

class FuturePayClient
{
    private string $apiKey;
    private string $baseUrl;
    private int $timeout;

    /**
     * @param string $apiKey Your Merchant Secret API Key from the FuturePay dashboard
     * @param string $baseUrl Base URL of your FuturePay instance (e.g. https://payment.futureitlab.com)
     * @param int $timeout Request timeout in seconds
     */
    public function __construct(string $apiKey, string $baseUrl = 'https://payment.futureitlab.com', int $timeout = 30)
    {
        $this->apiKey = trim($apiKey);
        $this->baseUrl = rtrim($baseUrl, '/');
        $this->timeout = $timeout;
    }

    /**
     * Create a new hosted checkout payment session
     *
     * @param array $params Required keys: amount, currency, success_url, cancel_url, brand_id. Optional: cus_name, cus_email, cus_phone, webhook_url, metadata.
     * @return array Decoded JSON API response
     * @throws Exception On cURL error or network failure
     */
    public function createPayment(array $params): array
    {
        $payload = array_merge([
            'api_key' => $this->apiKey,
        ], $params);

        return $this->request('/api/create-payment', $payload);
    }

    /**
     * Verify payment status by Transaction Reference ID
     *
     * @param string $transactionId FuturePay Transaction ID (e.g. FPTRX...)
     * @return array Decoded JSON API response
     * @throws Exception
     */
    public function verifyPayment(string $transactionId): array
    {
        $payload = [
            'api_key' => $this->apiKey,
            'transaction_id' => $transactionId,
        ];

        return $this->request('/api/verify-payment', $payload);
    }

    /**
     * Helper to verify and decode incoming webhook notification
     *
     * @return array|null Decoded payload or null if invalid
     */
    public static function readWebhookPayload(): ?array
    {
        $raw = file_get_contents('php://input');
        if (empty($raw)) {
            return null;
        }
        $data = json_decode($raw, true);
        return is_array($data) ? $data : null;
    }

    /**
     * Execute internal HTTP POST request using cURL
     */
    private function request(string $endpoint, array $data): array
    {
        $url = $this->baseUrl . $endpoint;

        $ch = curl_init();
        curl_setopt_array($ch, [
            CURLOPT_URL => $url,
            CURLOPT_POST => true,
            CURLOPT_POSTFIELDS => json_encode($data),
            CURLOPT_RETURNTRANSFER => true,
            CURLOPT_TIMEOUT => $this->timeout,
            CURLOPT_HTTPHEADER => [
                'Content-Type: application/json',
                'Accept: application/json',
                'X-API-KEY: ' . $this->apiKey,
            ],
            CURLOPT_SSL_VERIFYPEER => true,
        ]);

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

        if ($curlError) {
            throw new Exception("FuturePay cURL Error: " . $curlError);
        }

        $decoded = json_decode($response, true);
        if ($decoded === null) {
            return [
                'status' => 'error',
                'http_code' => $httpCode,
                'raw_body' => $response,
            ];
        }

        return $decoded;
    }
}