from __future__ import unicode_literals

import six

from openid.yadis.discover import DiscoveryFailure, discover
from openid.yadis.etxrd import XRDSError, iterServices, parseXRDS
from openid.yadis.filters import mkFilter


def getServiceEndpoints(input_url, flt=None):
    """Perform the Yadis protocol on the input URL and return an
    iterable of resulting endpoint objects.

    @param flt: A filter object or something that is convertable to
        a filter object (using mkFilter) that will be used to generate
        endpoint objects. This defaults to generating BasicEndpoint
        objects.

    @param input_url: The URL on which to perform the Yadis protocol

    @return: The normalized identity URL and an iterable of endpoint
        objects generated by the filter function.

    @rtype: (six.text_type, [endpoint])

    @raises DiscoveryFailure: when Yadis fails to obtain an XRDS document.
    """
    result = discover(input_url)
    try:
        endpoints = applyFilter(result.normalized_uri,
                                result.response_text, flt)
    except XRDSError as err:
        raise DiscoveryFailure(six.text_type(err), None)
    return (result.normalized_uri, endpoints)


def applyFilter(normalized_uri, xrd_data, flt=None):
    """Generate an iterable of endpoint objects given this input data,
    presumably from the result of performing the Yadis protocol.

    @param normalized_uri: The input URL, after following redirects,
        as in the Yadis protocol.

    @param xrd_data: The XML text the XRDS file fetched from the
        normalized URI.
    @type xrd_data: six.binary_type
    """
    flt = mkFilter(flt)
    et = parseXRDS(xrd_data)

    endpoints = []
    for service_element in iterServices(et):
        endpoints.extend(
            flt.getServiceEndpoints(normalized_uri, service_element))

    return endpoints