import python_http_client

region_host_dict = {'eu':'https://api.eu.sendgrid.com','global':'https://api.sendgrid.com'}

class BaseInterface(object):
    def __init__(self, auth, host, impersonate_subuser):
        """
        Construct the Twilio SendGrid v3 API object.
        Note that the underlying client is being set up during initialization,
        therefore changing attributes in runtime will not affect HTTP client
        behaviour.

        :param auth: the authorization header
        :type auth: string
        :param impersonate_subuser: the subuser to impersonate. Will be passed
                                    by "On-Behalf-Of" header by underlying
                                    client. See
                                    https://sendgrid.com/docs/User_Guide/Settings/subusers.html
                                    for more details
        :type impersonate_subuser: string
        :param host: base URL for API calls
        :type host: string
        """
        from . import __version__
        self.auth = auth
        self.impersonate_subuser = impersonate_subuser
        self.version = __version__
        self.useragent = 'sendgrid/{};python'.format(self.version)
        self.host = host

        self.client = python_http_client.Client(
            host=self.host,
            request_headers=self._default_headers,
            version=3)

    @property
    def _default_headers(self):
        """Set the default header for a Twilio SendGrid v3 API call"""
        headers = {
            "Authorization": self.auth,
            "User-Agent": self.useragent,
            "Accept": 'application/json'
        }
        if self.impersonate_subuser:
            headers['On-Behalf-Of'] = self.impersonate_subuser

        return headers

    def reset_request_headers(self):
        self.client.request_headers = self._default_headers

    def send(self, message):
        """Make a Twilio SendGrid v3 API request with the request body generated by
           the Mail object

        :param message: The Twilio SendGrid v3 API request body generated by the Mail
                        object
        :type message: Mail
        """
        if not isinstance(message, dict):
            message = message.get()

        return self.client.mail.send.post(request_body=message)

    def set_sendgrid_data_residency(self, region):
        """
        Client libraries contain setters for specifying region/edge.
        This supports global and eu regions only. This set will likely expand in the future.
        Global is the default residency (or region)
        Global region means the message will be sent through https://api.sendgrid.com
        EU region means the message will be sent through https://api.eu.sendgrid.com
        :param region: string
        :return:
        """
        if region in region_host_dict.keys():
            self.host = region_host_dict[region]
            if self._default_headers is not None:
                self.client = python_http_client.Client(
                    host=self.host,
                    request_headers=self._default_headers,
                    version=3)
        else:
            raise ValueError("region can only be \"eu\" or \"global\"")