<?php
/**
 * 支付宝支付网关（电脑网站支付 / 当面付）
 *
 * 配置项（settings 表）：
 *   pay_alipay_enabled  - 是否启用 (1/0)
 *   pay_alipay_appid    - 应用 APPID
 *   pay_alipay_private_key - 应用私钥
 *   pay_alipay_public_key  - 支付宝公钥
 *
 * 使用 RSA2 签名方式。
 */
if (!defined('IN_APP')) exit('Forbidden');

class AlipayGateway implements PaymentGatewayInterface
{
    private $appId;
    private $privateKey;
    private $publicKey;
    private $gatewayUrl = 'https://openapi.alipay.com/gateway.do';
    private $sandboxUrl = 'https://openapi-sandbox.dl.alipaydev.com/gateway.do';

    public function __construct()
    {
        $this->appId       = getSetting('pay_alipay_appid', '');
        $this->privateKey  = getSetting('pay_alipay_private_key', '');
        $this->publicKey   = getSetting('pay_alipay_public_key', '');
        // 沙箱模式（开发测试用）
        if (getSetting('pay_alipay_sandbox', '0') === '1') {
            $this->gatewayUrl = $this->sandboxUrl;
        }
    }

    public function getName()
    {
        return '支付宝';
    }

    /**
     * 创建支付宝电脑网站支付订单。
     */
    public function createOrder(array $order)
    {
        $params = [
            'app_id'      => $this->appId,
            'method'      => 'alipay.trade.page.pay',
            'format'      => 'JSON',
            'return_url'  => $order['return_url'],
            'notify_url'  => $order['notify_url'],
            'charset'     => 'utf-8',
            'sign_type'   => 'RSA2',
            'timestamp'   => date('Y-m-d H:i:s'),
            'version'     => '1.0',
            'biz_content' => json_encode([
                'out_trade_no' => $order['order_no'],
                'total_amount' => sprintf('%.2f', $order['amount']),
                'subject'      => $order['subject'],
                'product_code' => 'FAST_INSTANT_TRADE_PAY',
            ], JSON_UNESCAPED_UNICODE),
        ];

        $params['sign'] = $this->sign($params);

        // 构建跳转 URL（GET 方式）
        $url = $this->gatewayUrl . '?' . http_build_query($params);

        return ['url' => $url, 'form' => ''];
    }

    public function verifyNotify(array $params)
    {
        if (empty($params['sign'])) return false;
        $sign = $params['sign'];
        unset($params['sign'], $params['sign_type']);
        return $this->rsaVerify($this->buildSignData($params), $sign);
    }

    public function getTradeNo(array $params)
    {
        return $params['trade_no'] ?? '';
    }

    public function isPaid(array $params)
    {
        return ($params['trade_status'] ?? '') === 'TRADE_SUCCESS';
    }

    public function respondSuccess()
    {
        echo 'success';
    }

    // ─── 签名相关 ───

    private function sign($params)
    {
        ksort($params);
        $data = $this->buildSignData($params);
        $res = openssl_sign($data, $signature, $this->loadPrivateKey(), OPENSSL_ALGO_SHA256);
        return base64_encode($signature);
    }

    private function rsaVerify($data, $sign)
    {
        $result = openssl_verify($data, base64_decode($sign), $this->loadPublicKey(), OPENSSL_ALGO_SHA256);
        return $result === 1;
    }

    private function buildSignData($params)
    {
        $pairs = [];
        foreach ($params as $k => $v) {
            if ($v === '' || is_array($v)) continue;
            $pairs[] = $k . '=' . $v;
        }
        return implode('&', $pairs);
    }

    private function loadPrivateKey()
    {
        $key = trim($this->privateKey);
        $key = preg_replace('/-----BEGIN RSA PRIVATE KEY-----/', '', $key);
        $key = preg_replace('/-----END RSA PRIVATE KEY-----/', '', $key);
        $key = str_replace(["\r", "\n", " "], '', $key);
        return "-----BEGIN RSA PRIVATE KEY-----\n" .
               chunk_split($key, 64, "\n") .
               "-----END RSA PRIVATE KEY-----";
    }

    private function loadPublicKey()
    {
        $key = trim($this->publicKey);
        $key = preg_replace('/-----BEGIN PUBLIC KEY-----/', '', $key);
        $key = preg_replace('/-----END PUBLIC KEY-----/', '', $key);
        $key = str_replace(["\r", "\n", " "], '', $key);
        return "-----BEGIN PUBLIC KEY-----\n" .
               chunk_split($key, 64, "\n") .
               "-----END PUBLIC KEY-----";
    }
}