from django import forms
from django.contrib.auth import get_user_model
from django.contrib.auth.models import Permission
from django.contrib.contenttypes.models import ContentType
from django.test import TestCase

from utils.forms import KeepUnselectableModelFormMixin

User = get_user_model()


class KeepUnselectableModelFormMixinTests(TestCase):

    def _get_form_cls(self):
        """
        We recreate a new form class for each test, because `queryset` may not
        be reevaluated and may lack the permissions created by `setUp`.
        """
        class ExampleForm(KeepUnselectableModelFormMixin, forms.ModelForm):
            user_permissions = forms.ModelMultipleChoiceField(
                queryset=Permission.objects.filter(
                    codename__startswith='selec'),
            )

            keep_unselectable_fields = ['user_permissions']

            class Meta:
                model = User
                fields = ('username', 'user_permissions')
        return ExampleForm

    def setUp(self):
        ct = ContentType.objects.get_for_model(Permission)

        self.unselec_perm1 = Permission.objects.create(
            content_type=ct, codename='unselec_perm1', name='Unselectable 1')
        self.unselec_perm2 = Permission.objects.create(
            content_type=ct, codename='unselec_perm2', name='Unselectable 2')

        # These two perms are the only selectable permissions from
        # 'permissions' field of ExampleForm.
        self.selec_perm1 = Permission.objects.create(
            content_type=ct, codename='selec_perm1', name='Selectable 1')
        self.selec_perm2 = Permission.objects.create(
            content_type=ct, codename='selec_perm2', name='Selectable 2')

    def test_creation(self):
        """
        The mixin functions properly when instance is being created.
        """
        ExampleForm = self._get_form_cls()
        data = {
            'username': 'user',
            'user_permissions': [self.selec_perm1.pk],
        }
        form = ExampleForm(data)

        instance = form.save()

        self.assertQuerysetEqual(
            instance.user_permissions.all(),
            map(repr, [self.selec_perm1]),
        )

    def test_creation_commit_false(self):
        """
        When instance is being created and 'save' method is called with
        'commit=False', 'save_m2m' method functions properly.

        https://docs.djangoproject.com/en/1.11/topics/forms/modelforms/#the-save-method
        """
        ExampleForm = self._get_form_cls()
        data = {
            'username': 'user',
            'user_permissions': [self.selec_perm1.pk],
        }
        form = ExampleForm(data)

        instance = form.save(commit=False)

        with self.assertRaises(User.DoesNotExist):
            User.objects.get(username='user')

        instance.save()
        form.save_m2m()

        self.assertQuerysetEqual(
            instance.user_permissions.all(),
            map(repr, [self.selec_perm1]),
        )

    def test_existing(self):
        """
        Unselectable items of an instance are kept.
        """
        instance = User.objects.create(username='user')
        # Link instance with an unselectable and a selectable permissions.
        instance.user_permissions.add(self.unselec_perm1, self.selec_perm2)

        ExampleForm = self._get_form_cls()
        data = {
            'username': 'user',
            'user_permissions': [self.selec_perm1.pk],
        }
        form = ExampleForm(data, instance=instance)

        instance = form.save()

        self.assertQuerysetEqual(
            instance.user_permissions.all(),
            map(repr, [self.selec_perm1, self.unselec_perm1]),
        )

    def test_existing_commit_false(self):
        """
        When 'save' is called with 'commit=False', unselectable items of an
        instance are kept by 'save_m2m'.
        """
        instance = User.objects.create(username='user')
        # Link instance with an unselectable and a selectable permissions.
        instance.user_permissions.add(self.unselec_perm1, self.selec_perm2)

        ExampleForm = self._get_form_cls()
        data = {
            'username': 'changed',
            'user_permissions': [self.selec_perm1.pk],
        }
        form = ExampleForm(data, instance=instance)

        instance = form.save(commit=False)

        with self.assertRaises(User.DoesNotExist):
            User.objects.get(username='changed')

        instance.save()
        form.save_m2m()

        self.assertQuerysetEqual(
            instance.user_permissions.all(),
            map(repr, [self.selec_perm1, self.unselec_perm1]),
        )