icepay client in python

icepay.py

import json
import hashlib
import datetime
import requests

class IcepayClient:

    BASE_API_URL = 'https://connect.icepay.com/webservice/api/v1/'

    def __init__(self, merchant_id, secret_code):
        self.merchant_id = merchant_id
        self.secret_code = secret_code


    def calc_checksum(self, url, method, body):

        assert isinstance(body, str), 'body must be a string'

        parts = [
            url,
            method,
            self.merchant_id,
            self.secret_code,
            body
        ]

        sig = ''.join([str(x) for x in parts])

        m = hashlib.sha256()
        m.update(sig.encode('utf8'))
        return m.hexdigest()

    def format_timestamp(self, time=None):
        #returns timestamp formatted as per icepay specs. must be utc.
        #returns now() if specific time not provided
        time = time or datetime.datetime.utcnow()
        return time.isoformat()[:19]

    def call_api(self, method, endpoint, data={}):
        assert method in ['POST', 'GET'], 'invalid method: %s, expected POST or GET' % method

        if 'Timestamp' not in data:
            data['Timestamp'] = self.format_timestamp()

        full_url = self.BASE_API_URL + endpoint

        data = json.dumps(data, separators=(',', ':'))

        headers = {
            "MerchantID": self.merchant_id,
            "Checksum": self.calc_checksum(full_url, method, data)
        }

        if method == 'POST':
            r = requests.post(full_url, headers=headers, data=data)
        else:
            r = requests.get(full_url, headers=headers, data=data)

        if r.status_code == requests.codes.ok:
            return r.json()
        else:
            print('body %s' % r.text)
            print(r.headers)
            r.raise_for_status()


    def GetMyPaymentMethods(self):
        return self.call_api('POST', 'payment/getmypaymentmethods')