import sys


class AppSettings(object):
    __PREFIX = 'MELLON_'
    __DEFAULTS = {
        'DISCOVERY_SERVICE_URL': None,
        'PUBLIC_KEYS': (),
        'PRIVATE_KEY': None,
        'PRIVATE_KEYS': (),
        'PRIVATE_KEY_PASSWORD': None,
        'NAME_ID_FORMATS': (),
        'NAME_ID_POLICY_FORMAT': None,
        'NAME_ID_POLICY_ALLOW_CREATE': True,
        'FORCE_AUTHN': False,
        'ADAPTER': (
            'mellon.adapters.DefaultAdapter',
        ),
        'REALM': 'saml',
        'PROVISION': True,
        'USERNAME_TEMPLATE': '{attributes[name_id_content]}@{realm}',
        'ATTRIBUTE_MAPPING': {},
        'SUPERUSER_MAPPING': {},
        'AUTHN_CLASSREF': (),
        'GROUP_ATTRIBUTE': None,
        'CREATE_GROUP': True,
        'ERROR_URL': None,
        'ERROR_REDIRECT_AFTER_TIMEOUT': 120,
        'DEFAULT_ASSERTION_CONSUMER_BINDING': 'post',  # or artifact
        'VERIFY_SSL_CERTIFICATE': True,
        'OPENED_SESSION_COOKIE_NAME': None,
        'OPENED_SESSION_COOKIE_DOMAIN': None,
        'ORGANIZATION': None,
        'CONTACT_PERSONS': [],
        'TRANSIENT_FEDERATION_ATTRIBUTE': None,
        'LOGIN_URL': 'mellon_login',
        'LOGOUT_URL': 'mellon_logout',
        'ARTIFACT_RESOLVE_TIMEOUT': 10.0,
        'FEDERATIONS': [],
    }

    @property
    def FEDERATIONS(self):
        from django.conf import settings
        if settings.hasattr('MELLON_FEDERATIONS'):
            federations = settings.MELLON_FEDERATIONS
        if isinstance(federations, dict):
            federations = [federations]
        return federations

    @property
    def IDENTITY_PROVIDERS(self):
        from django.conf import settings
        idps = []
        try:
            if hasattr(settings, 'MELLON_IDENTITY_PROVIDERS'):
                idps = settings.MELLON_IDENTITY_PROVIDERS
            elif not hasattr(settings, 'MELLON_FEDERATIONS'):
                raise AttributeError
        except AttributeError:
            from django.core.exceptions import ImproperlyConfigured
            raise ImproperlyConfigured('Either the MELLON_IDENTITY_PROVIDERS '
                                       'or the MELLON_FEDERATIONS settings '
                                       'are mandatory')
        if isinstance(idps, dict):
            idps = [idps]
        return idps

    def __getattr__(self, name):
        from django.conf import settings
        if name not in self.__DEFAULTS:
            raise AttributeError
        return getattr(settings, self.__PREFIX + name, self.__DEFAULTS[name])

app_settings = AppSettings()
app_settings.__name__ = __name__
sys.modules[__name__] = app_settings