import datetime
import decimal
import unittest

from django.db import connection, models
from django.db.models import Avg
from django.db.models.expressions import Value
from django.db.models.functions import Cast
from django.test import (
    TestCase, ignore_warnings, override_settings, skipUnlessDBFeature,
)

from ..models import Author, DTModel, Fan


class CastTests(TestCase):
    @classmethod
    def setUpTestData(self):
        Author.objects.create(name='Bob', age=1, alias='1')

    def test_cast_from_value(self):
        numbers = Author.objects.annotate(cast_integer=Cast(Value('0'), models.IntegerField()))
        self.assertEqual(numbers.get().cast_integer, 0)

    def test_cast_from_field(self):
        numbers = Author.objects.annotate(cast_string=Cast('age', models.CharField(max_length=255)),)
        self.assertEqual(numbers.get().cast_string, '1')

    def test_cast_to_char_field_without_max_length(self):
        numbers = Author.objects.annotate(cast_string=Cast('age', models.CharField()))
        self.assertEqual(numbers.get().cast_string, '1')

    # Silence "Truncated incorrect CHAR(1) value: 'Bob'".
    @ignore_warnings(module='django.db.backends.mysql.base')
    @skipUnlessDBFeature('supports_cast_with_precision')
    def test_cast_to_char_field_with_max_length(self):
        names = Author.objects.annotate(cast_string=Cast('name', models.CharField(max_length=1)))
        self.assertEqual(names.get().cast_string, 'B')

    def test_cast_to_integer(self):
        for field_class in (
            models.AutoField,
            models.BigAutoField,
            models.IntegerField,
            models.BigIntegerField,
            models.SmallIntegerField,
            models.PositiveIntegerField,
            models.PositiveSmallIntegerField,
        ):
            with self.subTest(field_class=field_class):
                numbers = Author.objects.annotate(cast_int=Cast('alias', field_class()))
                self.assertEqual(numbers.get().cast_int, 1)

    def test_cast_from_db_datetime_to_date(self):
        dt_value = datetime.datetime(2018, 9, 28, 12, 42, 10, 234567)
        DTModel.objects.create(start_datetime=dt_value)
        dtm = DTModel.objects.annotate(
            start_datetime_as_date=Cast('start_datetime', models.DateField())
        ).first()
        self.assertEqual(dtm.start_datetime_as_date, datetime.date(2018, 9, 28))

    def test_cast_from_db_datetime_to_time(self):
        dt_value = datetime.datetime(2018, 9, 28, 12, 42, 10, 234567)
        DTModel.objects.create(start_datetime=dt_value)
        dtm = DTModel.objects.annotate(
            start_datetime_as_time=Cast('start_datetime', models.TimeField())
        ).first()
        rounded_ms = int(round(.234567, connection.features.time_cast_precision) * 10**6)
        self.assertEqual(dtm.start_datetime_as_time, datetime.time(12, 42, 10, rounded_ms))

    def test_cast_from_db_date_to_datetime(self):
        dt_value = datetime.date(2018, 9, 28)
        DTModel.objects.create(start_date=dt_value)
        dtm = DTModel.objects.annotate(start_as_datetime=Cast('start_date', models.DateTimeField())).first()
        self.assertEqual(dtm.start_as_datetime, datetime.datetime(2018, 9, 28, 0, 0, 0, 0))

    def test_cast_from_db_datetime_to_date_group_by(self):
        author = Author.objects.create(name='John Smith', age=45)
        dt_value = datetime.datetime(2018, 9, 28, 12, 42, 10, 234567)
        Fan.objects.create(name='Margaret', age=50, author=author, fan_since=dt_value)
        fans = Fan.objects.values('author').annotate(
            fan_for_day=Cast('fan_since', models.DateField()),
            fans=models.Count('*')
        ).values()
        self.assertEqual(fans[0]['fan_for_day'], datetime.date(2018, 9, 28))
        self.assertEqual(fans[0]['fans'], 1)

    def test_cast_from_python_to_date(self):
        today = datetime.date.today()
        dates = Author.objects.annotate(cast_date=Cast(today, models.DateField()))
        self.assertEqual(dates.get().cast_date, today)

    def test_cast_from_python_to_datetime(self):
        now = datetime.datetime.now()
        dates = Author.objects.annotate(cast_datetime=Cast(now, models.DateTimeField()))
        time_precision = datetime.timedelta(
            microseconds=10**(6 - connection.features.time_cast_precision)
        )
        self.assertAlmostEqual(dates.get().cast_datetime, now, delta=time_precision)

    def test_cast_from_python(self):
        numbers = Author.objects.annotate(cast_float=Cast(decimal.Decimal(0.125), models.FloatField()))
        cast_float = numbers.get().cast_float
        self.assertIsInstance(cast_float, float)
        self.assertEqual(cast_float, 0.125)

    @unittest.skipUnless(connection.vendor == 'postgresql', 'PostgreSQL test')
    @override_settings(DEBUG=True)
    def test_expression_wrapped_with_parentheses_on_postgresql(self):
        """
        The SQL for the Cast expression is wrapped with parentheses in case
        it's a complex expression.
        """
        list(Author.objects.annotate(cast_float=Cast(Avg('age'), models.FloatField())))
        self.assertIn('(AVG("db_functions_author"."age"))::double precision', connection.queries[-1]['sql'])

    def test_cast_to_text_field(self):
        self.assertEqual(Author.objects.values_list(Cast('age', models.TextField()), flat=True).get(), '1')
