import logging

from django.core.exceptions import PermissionDenied
from django.contrib import auth
from django.contrib.auth.models import Group

from . import utils, app_settings, models


class DefaultAdapter(object):
    def __init__(self, *args, **kwargs):
        self.logger = logging.getLogger(__name__)

    def get_idp(self, entity_id):
        '''Find the first IdP definition matching entity_id'''
        for idp in app_settings.IDENTITY_PROVIDERS:
            if entity_id == idp['ENTITY_ID']:
                return idp

    def get_idps(self):
        return [idp for idp in app_settings.IDENTITY_PROVIDERS]

    def authorize(self, idp, saml_attributes):
        if not idp:
            return False
        required_classref = utils.get_setting(idp, 'AUTHN_CLASSREF')
        if required_classref:
            given_classref = saml_attributes['authn_context_class_ref']
            if given_classref is None or \
                    given_classref not in required_classref:
                raise PermissionDenied
        return True

    def format_username(self, idp, saml_attributes):
        realm = utils.get_setting(idp, 'REALM')
        username_template = utils.get_setting(idp, 'USERNAME_TEMPLATE')
        try:
            username = unicode(username_template).format(
                realm=realm, attributes=saml_attributes, idp=idp)[:30]
        except ValueError:
            self.logger.error(u'invalid username template %r', username_template)
        except (AttributeError, KeyError, IndexError), e:
            self.logger.error(u'invalid reference in username template %r: %s',
                    username_template, e)
        except Exception, e:
            self.logger.exception(u'unknown error when formatting username')
        else:
            return username

    def lookup_user(self, idp, saml_attributes):
        User = auth.get_user_model()
        name_id = saml_attributes['name_id_content']
        issuer = saml_attributes['issuer']
        try:
            return User.objects.get(saml_identifiers__name_id=name_id,
                    saml_identifiers__issuer=issuer)
        except User.DoesNotExist:
            if not utils.get_setting(idp, 'PROVISION'):
                return None
            username = self.format_username(idp, saml_attributes)
            if not username:
                return None
            user = User(username=username)
            user.save()
            self.provision_name_id(user, idp, saml_attributes)
        return user

    def provision(self, user, idp, saml_attributes):
        self.provision_attribute(user, idp, saml_attributes)
        self.provision_superuser(user, idp, saml_attributes)
        self.provision_groups(user, idp, saml_attributes)

    def provision_name_id(self, user, idp, saml_attributes):
        models.UserSAMLIdentifier.objects.get_or_create(
                user=user,
                issuer=saml_attributes['issuer'],
                name_id=saml_attributes['name_id_content'])

    def provision_attribute(self, user, idp, saml_attributes):
        realm = utils.get_setting(idp, 'REALM')
        attribute_mapping = utils.get_setting(idp, 'ATTRIBUTE_MAPPING')
        attribute_set = False
        for field, tpl in attribute_mapping.iteritems():
            try:
                value = unicode(tpl).format(realm=realm, attributes=saml_attributes, idp=idp)
            except ValueError:
                self.logger.warning(u'invalid attribute mapping template %r', tpl)
            except (AttributeError, KeyError, IndexError, ValueError), e:
                self.logger.warning(u'invalid reference in attribute mapping template %r: %s', tpl, e)
            else:
                attribute_set = True
                model_field = user._meta.get_field(field)
                if hasattr(model_field, 'max_length'):
                    value = value[:model_field.max_length]
                setattr(user, field, value)
        if attribute_set:
            user.save()

    def provision_superuser(self, user, idp, saml_attributes):
        superuser_mapping = utils.get_setting(idp, 'SUPERUSER_MAPPING')
        if not superuser_mapping:
            return
        for key, values in superuser_mapping.iteritems():
            if key in saml_attributes:
                if not isinstance(values, (tuple, list)):
                    values = [values]
                values = set(values)
                attribute_values = saml_attributes[key]
                if not isinstance(attribute_values, (tuple, list)):
                    attribute_values = [attribute_values]
                attribute_values = set(attribute_values)
                if attribute_values & values:
                    user.is_staff = True
                    user.is_superuser = True
                    user.save()
                    break
        else:
            if user.is_superuser:
                user.is_superuser = False
                user.save()

    def provision_groups(self, user, idp, saml_attributes):
        User = user.__class__
        group_attribute = utils.get_setting(idp, 'GROUP_ATTRIBUTE')
        create_group = utils.get_setting(idp, 'CREATE_GROUP')
        if group_attribute in saml_attributes:
            values = saml_attributes[group_attribute]
            if not isinstance(values, (list, tuple)):
                values = [values]
            groups = []
            for value in set(values):
                if create_group:
                    group, created = Group.objects.get_or_create(name=value)
                else:
                    try:
                        group = Group.objects.get(name=value)
                    except Group.DoesNotExist:
                        continue
                groups.append(group)
            for group in Group.objects.filter(pk__in=[g.pk for g in groups]).exclude(user=user):
                self.logger.info(u'adding group %s (%s) to user %s (%s)', group, group.pk, user, user.pk)
                User.groups.through.objects.get_or_create(group=group, user=user)
            qs = User.groups.through.objects.exclude(group__pk__in=[g.pk for g in groups]).filter(user=user)
            for rel in qs:
                self.logger.info(u'removing group %s (%s) from user %s (%s)', rel.group,
                                 rel.group.pk, rel.user, rel.user.pk)
            qs.delete()
