from django.db import DEFAULT_DB_ALIAS, router
from django.test import TestCase

from djadmin2.utils import NestedObjects
from ..models import Count, Event, EventGuide


class NestedObjectsTests(TestCase):
    """
    Tests for ``NestedObject`` utility collection.

    This is adopted from the Django core. django-admin2 mandates that code
    doesn't depend on imports from django.contrib.admin.

    https://github.com/django/django/blob/1.5.1/tests/regressiontests/admin_util/tests.py
    """
    def setUp(self):
        self.n = NestedObjects(using=DEFAULT_DB_ALIAS)
        self.objs = [Count.objects.create(num=i) for i in range(5)]

    def _check(self, target):
        self.assertEqual(self.n.nested(lambda obj: obj.num), target)

    def _connect(self, i, j):
        self.objs[i].parent = self.objs[j]
        self.objs[i].save()

    def _collect(self, *indices):
        self.n.collect([self.objs[i] for i in indices])

    def test_unrelated_roots(self):
        self._connect(2, 1)
        self._collect(0)
        self._collect(1)
        self._check([0, 1, [2]])

    def test_siblings(self):
        self._connect(1, 0)
        self._connect(2, 0)
        self._collect(0)
        self._check([0, [1, 2]])

    def test_non_added_parent(self):
        self._connect(0, 1)
        self._collect(0)
        self._check([0])

    def test_cyclic(self):
        self._connect(0, 2)
        self._connect(1, 0)
        self._connect(2, 1)
        self._collect(0)
        self._check([0, [1, [2]]])

    def test_queries(self):
        self._connect(1, 0)
        self._connect(2, 0)
        # 1 query to fetch all children of 0 (1 and 2)
        # 1 query to fetch all children of 1 and 2 (none)
        # Should not require additional queries to populate the nested graph.
        self.assertNumQueries(2, self._collect, 0)

    def test_on_delete_do_nothing(self):
        """
        Check that the nested collector doesn't query for DO_NOTHING objects.
        """
        objs = [Event.objects.create()]
        using = router.db_for_write(Event._meta.model)
        n = NestedObjects(using=using)
        EventGuide.objects.create(event=objs[0])
        with self.assertNumQueries(2):
            # One for Location, one for Guest, and no query for EventGuide
            n.collect(objs)
