import requests
import hashlib
import time

class PaymentGatewayClient:
    def __init__(self, api_key, secret_key, base_url):
        self.api_key = api_key
        self.secret_key = secret_key
        self.base_url = base_url
    
    def _generate_signature(self, params):
        param_str = '&'.join([f'{k}={v}' for k,v in sorted(params.items())])
        return hashlib.sha256((param_str + self.secret_key).encode()).hexdigest()
    
    def create_payment(self, amount, currency, order_id, callback_url):
        params = {
            'api_key': self.api_key,
            'amount': amount,
            'currency': currency,
            'order_id': order_id,
            'callback_url': callback_url,
            'timestamp': int(time.time())
        }
        params['signature'] = self._generate_signature(params)
        
        response = requests.post(
            f"{self.base_url}/v1/payments",
            json=params,
            headers={'Content-Type': 'application/json'}
        )
        return response.json()

# 使用示例
client = PaymentGatewayClient(
    api_key="your_api_key",
    secret_key="your_secret_key",
    base_url="https://api.payment-gateway.com"
)

result = client.create_payment(
    amount=100.00,
    currency="USD",
    order_id="ORD123456",
    callback_url="https://your-site.com/callback"
)
print(result)