from django import newforms as forms
from openid.consumer.discover import discover, DiscoveryFailure
from openid.fetchers import HTTPFetchingError
from openid.yadis import xri


def identifierScheme(identifier):
    """Wrap openid.yadis.xri.identifierScheme to keep URI/URL consistent."""
    scheme = xri.identifierScheme(identifier)
    if scheme == 'XRI':
        return scheme
    return 'URL'


class OpenIDField(forms.CharField):
    """Field to normalize and validate an OpenID.

    Adds 'http://' prefix to URLs that don't have a scheme, appends trailing '/'
    if no path is provided, strips URL fragments and follows HTTP redirects.

    Strips 'xri://' prefix from XRIs.

    http://openid.net/specs/openid-authentication-2_0.html#normalization

    """
    default_error_messages = {
        'discovery': u"This %s doesn't appear to be an OpenID.",
        'invalid': u'Enter a valid OpenID.',
        'invalid_link': u'This URL appears to be a broken link.',
        'required': u'Enter an OpenID.'
    }

    def __init__(self, max_length=255, *args, **kwargs):
        super(OpenIDField, self).__init__(max_length, *args, **kwargs)

    def clean(self, value):
        value = super(OpenIDField, self).clean(value)

        if value in forms.fields.EMPTY_VALUES:
            return u''

        scheme = identifierScheme(value)

        if scheme == 'XRI' and value.startswith('xri://'):
            value = value[6:]

        try:
            claimed_id, endpoints = discover(value)
        except DiscoveryFailure:
            # resource not found
            raise forms.ValidationError(self.error_messages['invalid_link'])
        except HTTPFetchingError:
            # server not found or invalid URL
            raise forms.ValidationError(self.error_messages['invalid'])
        else:
            # valid URL/XRI with no OpenID endpoints
            if not endpoints:
                raise forms.ValidationError(
                    self.error_messages['discovery'] % scheme
                )
            self.endpoints = endpoints

        return claimed_id

    def widget_attrs(self, widget):
        # CSS hook for http://openid.net/logos/
        return {'class': 'openid'}