from django.db import connection

from django.db.models import Value

from django.db.models.functions import Length, Repeat

from django.test import TestCase

from ..models import Author

class RepeatTests(TestCase):

    def test_basic(self):

        Author.objects.create(name="John", alias="xyz")

        none_value = (

            "" if connection.features.interprets_empty_strings_as_nulls else None

        )

        tests = (

            (Repeat("name", 0), ""),

            (Repeat("name", 2), "JohnJohn"),

            (Repeat("name", Length("alias")), "JohnJohnJohn"),

            (Repeat(Value("x"), 3), "xxx"),

            (Repeat("name", None), none_value),

            (Repeat(Value(None), 4), none_value),

            (Repeat("goes_by", 1), none_value),

        )

        for function, repeated_text in tests:

            with self.subTest(function=function):

                authors = Author.objects.annotate(repeated_text=function)

                self.assertQuerysetEqual(

                    authors, [repeated_text], lambda a: a.repeated_text, ordered=False

                )

    def test_negative_number(self):

        with self.assertRaisesMessage(

            ValueError, "'number' must be greater or equal to 0."

        ):

            Repeat("name", -1)