from django.db.models import Value as V

from django.db.models.functions import Lower, StrIndex, Substr, Upper

from django.test import TestCase

from ..models import Author

class SubstrTests(TestCase):

    def test_basic(self):

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

        Author.objects.create(name="Rhonda")

        authors = Author.objects.annotate(name_part=Substr("name", 5, 3))

        self.assertQuerysetEqual(

            authors.order_by("name"), [" Sm", "da"], lambda a: a.name_part

        )

        authors = Author.objects.annotate(name_part=Substr("name", 2))

        self.assertQuerysetEqual(

            authors.order_by("name"), ["ohn Smith", "honda"], lambda a: a.name_part

        )

        # If alias is null, set to first 5 lower characters of the name.

        Author.objects.filter(alias__isnull=True).update(

            alias=Lower(Substr("name", 1, 5)),

        )

        self.assertQuerysetEqual(

            authors.order_by("name"), ["smithj", "rhond"], lambda a: a.alias

        )

    def test_start(self):

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

        a = Author.objects.annotate(

            name_part_1=Substr("name", 1),

            name_part_2=Substr("name", 2),

        ).get(alias="smithj")

        self.assertEqual(a.name_part_1[1:], a.name_part_2)

    def test_pos_gt_zero(self):

        with self.assertRaisesMessage(ValueError, "'pos' must be greater than 0"):

            Author.objects.annotate(raises=Substr("name", 0))

    def test_expressions(self):

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

        Author.objects.create(name="Rhonda")

        substr = Substr(Upper("name"), StrIndex("name", V("h")), 5)

        authors = Author.objects.annotate(name_part=substr)

        self.assertQuerysetEqual(

            authors.order_by("name"), ["HN SM", "HONDA"], lambda a: a.name_part

        )