from django.db.models import Subquery, TextField

from django.db.models.functions import Coalesce, Lower

from django.test import TestCase

from django.utils import timezone

from ..models import Article, Author

lorem_ipsum = """

    Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod

    tempor incididunt ut labore et dolore magna aliqua."""

class CoalesceTests(TestCase):

    def test_basic(self):

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

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

        authors = Author.objects.annotate(display_name=Coalesce("alias", "name"))

        self.assertQuerysetEqual(

            authors.order_by("name"), ["smithj", "Rhonda"], lambda a: a.display_name

        )

    def test_gt_two_expressions(self):

        with self.assertRaisesMessage(

            ValueError, "Coalesce must take at least two expressions"

        ):

            Author.objects.annotate(display_name=Coalesce("alias"))

    def test_mixed_values(self):

        a1 = Author.objects.create(name="John Smith", alias="smithj")

        a2 = Author.objects.create(name="Rhonda")

        ar1 = Article.objects.create(

            title="How to Django",

            text=lorem_ipsum,

            written=timezone.now(),

        )

        ar1.authors.add(a1)

        ar1.authors.add(a2)

        # mixed Text and Char

        article = Article.objects.annotate(

            headline=Coalesce("summary", "text", output_field=TextField()),

        )

        self.assertQuerysetEqual(

            article.order_by("title"), [lorem_ipsum], lambda a: a.headline

        )

        # mixed Text and Char wrapped

        article = Article.objects.annotate(

            headline=Coalesce(

                Lower("summary"), Lower("text"), output_field=TextField()

            ),

        )

        self.assertQuerysetEqual(

            article.order_by("title"), [lorem_ipsum.lower()], lambda a: a.headline

        )

    def test_ordering(self):

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

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

        authors = Author.objects.order_by(Coalesce("alias", "name"))

        self.assertQuerysetEqual(authors, ["Rhonda", "John Smith"], lambda a: a.name)

        authors = Author.objects.order_by(Coalesce("alias", "name").asc())

        self.assertQuerysetEqual(authors, ["Rhonda", "John Smith"], lambda a: a.name)

        authors = Author.objects.order_by(Coalesce("alias", "name").desc())

        self.assertQuerysetEqual(authors, ["John Smith", "Rhonda"], lambda a: a.name)

    def test_empty_queryset(self):

        Author.objects.create(name="John Smith")

        tests = [

            Author.objects.none(),

            Subquery(Author.objects.none()),

        ]

        for empty_query in tests:

            with self.subTest(empty_query.__class__.__name__):

                qs = Author.objects.annotate(annotation=Coalesce(empty_query, 42))

                self.assertEqual(qs.first().annotation, 42)