class ApiError(Exception):

    def __init__(self, request, response):
        super().__init__(f"{repr(request)} -> {repr(response)}")
        self.request = request
        self.response = response


class Api:

    API_URL = "api.exmo.com"
    API_VERSION = "v1"
    REQUESTS_PER_MINUTE = 180

    def __init__(self, key, secret, timeout):
        self._key = key
        self._secret = secret.encode("utf-8")
        self._timeout = timeout
        self._last_call = None

    def _sha512(self, data):
        h = hmac.new(key=self._secret, digestmod=hashlib.sha512)
        h.update(data.encode("utf-8"))
        return h.hexdigest()

    def __getattr__(self, name):
        return functools.partial(self._call, name)

    def _call(self, name, **params):
        now = time.monotonic()
        if self._last_call:
            delta = 60 / self.REQUESTS_PER_MINUTE + self._last_call - now
            time.sleep(max(0, delta))
        self._last_call = now
        params["nonce"] = int(round(time.time() * 1000))
        encoded_params = urllib.parse.urlencode(params)
        headers = {
            "Content-type": "application/x-www-form-urlencoded",
            "Key": self._key,
            "Sign": self._sha512(encoded_params),
        }
        conn = http.client.HTTPSConnection(self.API_URL, timeout=self._timeout)
        conn.request("POST", f"/{self.API_VERSION}/{name}/", encoded_params, headers)
        response = Dict(json.loads(conn.getresponse().read().decode("utf-8")))
        conn.close()
        if response.result is False:
            raise ApiError(params, response)
        return response