from decimal import Decimal

from django.db.models.functions import Power
from django.test import TestCase

from ..models import DecimalModel, FloatModel, IntegerModel


class PowerTests(TestCase):

    def test_null(self):
        IntegerModel.objects.create(big=100)
        obj = IntegerModel.objects.annotate(
            null_power_small=Power('small', 'normal'),
            null_power_normal=Power('normal', 'big'),
        ).first()
        self.assertIsNone(obj.null_power_small)
        self.assertIsNone(obj.null_power_normal)

    def test_decimal(self):
        DecimalModel.objects.create(n1=Decimal('1.0'), n2=Decimal('-0.6'))
        obj = DecimalModel.objects.annotate(n_power=Power('n1', 'n2')).first()
        self.assertIsInstance(obj.n_power, Decimal)
        self.assertAlmostEqual(obj.n_power, Decimal(obj.n1 ** obj.n2))

    def test_float(self):
        FloatModel.objects.create(f1=2.3, f2=1.1)
        obj = FloatModel.objects.annotate(f_power=Power('f1', 'f2')).first()
        self.assertIsInstance(obj.f_power, float)
        self.assertAlmostEqual(obj.f_power, obj.f1 ** obj.f2)

    def test_integer(self):
        IntegerModel.objects.create(small=-1, normal=20, big=3)
        obj = IntegerModel.objects.annotate(
            small_power=Power('small', 'normal'),
            normal_power=Power('normal', 'big'),
            big_power=Power('big', 'small'),
        ).first()
        self.assertIsInstance(obj.small_power, float)
        self.assertIsInstance(obj.normal_power, float)
        self.assertIsInstance(obj.big_power, float)
        self.assertAlmostEqual(obj.small_power, obj.small ** obj.normal)
        self.assertAlmostEqual(obj.normal_power, obj.normal ** obj.big)
        self.assertAlmostEqual(obj.big_power, obj.big ** obj.small)