from django.db import connection

from django.db.models import CharField

from django.db.models.functions import Length, Reverse, Trim

from django.test import TestCase

from django.test.utils import register_lookup

from ..models import Author

class ReverseTests(TestCase):

    @classmethod

    def setUpTestData(cls):

        cls.john = Author.objects.create(name="John Smith", alias="smithj")

        cls.elena = Author.objects.create(name="Élena Jordan", alias="elena")

        cls.python = Author.objects.create(name="パイソン")

    def test_null(self):

        author = Author.objects.annotate(backward=Reverse("alias")).get(

            pk=self.python.pk

        )

        self.assertEqual(

            author.backward,

            "" if connection.features.interprets_empty_strings_as_nulls else None,

        )

    def test_basic(self):

        authors = Author.objects.annotate(backward=Reverse("name"))

        self.assertQuerysetEqual(

            authors,

            [

                ("John Smith", "htimS nhoJ"),

                ("Élena Jordan", "nadroJ anelÉ"),

                ("パイソン", "ンソイパ"),

            ],

            lambda a: (a.name, a.backward),

            ordered=False,

        )

    def test_transform(self):

        with register_lookup(CharField, Reverse):

            authors = Author.objects.all()

            self.assertCountEqual(

                authors.filter(name__reverse=self.john.name[::-1]), [self.john]

            )

            self.assertCountEqual(

                authors.exclude(name__reverse=self.john.name[::-1]),

                [self.elena, self.python],

            )

    def test_expressions(self):

        author = Author.objects.annotate(backward=Reverse(Trim("name"))).get(

            pk=self.john.pk

        )

        self.assertEqual(author.backward, self.john.name[::-1])

        with register_lookup(CharField, Reverse), register_lookup(CharField, Length):

            authors = Author.objects.all()

            self.assertCountEqual(

                authors.filter(name__reverse__length__gt=7), [self.john, self.elena]

            )

            self.assertCountEqual(

                authors.exclude(name__reverse__length__gt=7), [self.python]

            )