from django.conf import settings
from django.db import models

from apps.catalog.models import Brand, Product, Service


class OrderStatus(models.TextChoices):
    NEW = 'new', 'Новый'
    CONFIRMED = 'confirmed', 'Подтверждён'
    PAID = 'paid', 'Оплачен'          # этап 2
    ASSEMBLED = 'assembled', 'Собран'
    SHIPPED = 'shipped', 'Передан в доставку'  # этап 2
    DONE = 'done', 'Выполнен'
    CANCELLED = 'cancelled', 'Отменён'
    REFUNDED = 'refunded', 'Возврат'   # этап 2


class DeliveryMethod(models.TextChoices):
    PICKUP = 'pickup', 'Самовывоз'
    COURIER = 'courier', 'Доставка по договорённости'  # этап 1
    CDEK = 'cdek', 'СДЭК'                               # этап 2


class PaymentMethod(models.TextChoices):
    BY_AGREEMENT = 'by_agreement', 'По договорённости (напрямую продавцу)'
    ONLINE = 'online', 'Онлайн через агрегатор'  # этап 2


class PickupPoint(models.Model):
    """Пункт выдачи (ТЗ §4: PickupPoint)."""

    name = models.CharField('Название', max_length=200)
    address = models.CharField('Адрес', max_length=300)
    working_hours = models.CharField('Часы работы', max_length=200, blank=True)
    partner = models.CharField('Партнёр', max_length=200, blank=True)
    is_active = models.BooleanField('Активен', default=True)

    class Meta:
        verbose_name = 'Пункт выдачи'
        verbose_name_plural = 'Пункты выдачи'
        ordering = ('name',)

    def __str__(self):
        return f'{self.name} ({self.address})'


class Order(models.Model):
    """Заказ / заявка (ТЗ §4: Order)."""

    buyer = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.PROTECT,
        related_name='orders', verbose_name='Покупатель',
    )
    status = models.CharField(
        'Статус', max_length=20, choices=OrderStatus.choices,
        default=OrderStatus.NEW,
    )
    delivery_method = models.CharField(
        'Способ получения', max_length=20,
        choices=DeliveryMethod.choices, default=DeliveryMethod.PICKUP,
    )
    address = models.CharField('Адрес доставки', max_length=300, blank=True)
    pickup_point = models.ForeignKey(
        PickupPoint, null=True, blank=True, on_delete=models.SET_NULL,
        related_name='orders', verbose_name='Пункт выдачи',
    )
    payment_method = models.CharField(
        'Способ оплаты', max_length=20,
        choices=PaymentMethod.choices, default=PaymentMethod.BY_AGREEMENT,
    )
    customer_comment = models.TextField('Комментарий покупателя', blank=True)

    total = models.DecimalField('Сумма', max_digits=12, decimal_places=2, default=0)
    commission = models.DecimalField(
        'Комиссия площадки', max_digits=12, decimal_places=2, default=0,
    )

    created_at = models.DateTimeField('Создан', auto_now_add=True)
    updated_at = models.DateTimeField('Обновлён', auto_now=True)

    class Meta:
        verbose_name = 'Заказ'
        verbose_name_plural = 'Заказы'
        ordering = ('-created_at',)

    def __str__(self):
        return f'Заказ №{self.pk}'

    def recalculate_total(self):
        self.total = sum((item.line_total for item in self.items.all()), start=0)
        self.save(update_fields=['total'])


class OrderItem(models.Model):
    """Позиция заказа. Может относиться к товару или к услуге (ТЗ §4)."""

    order = models.ForeignKey(
        Order, on_delete=models.CASCADE, related_name='items',
        verbose_name='Заказ',
    )
    brand = models.ForeignKey(
        Brand, on_delete=models.PROTECT, related_name='order_items',
        verbose_name='Бренд',
    )
    product = models.ForeignKey(
        Product, null=True, blank=True, on_delete=models.SET_NULL,
        related_name='order_items', verbose_name='Товар',
    )
    service = models.ForeignKey(
        Service, null=True, blank=True, on_delete=models.SET_NULL,
        related_name='order_items', verbose_name='Услуга',
    )
    name = models.CharField('Название позиции', max_length=255)
    price = models.DecimalField('Цена за единицу', max_digits=12, decimal_places=2)
    quantity = models.PositiveIntegerField('Количество', default=1)

    class Meta:
        verbose_name = 'Позиция заказа'
        verbose_name_plural = 'Позиции заказа'

    def __str__(self):
        return f'{self.name} × {self.quantity}'

    @property
    def line_total(self):
        return self.price * self.quantity


class Favorite(models.Model):
    """Избранное покупателя (ТЗ §3.2, §3.3)."""

    user = models.ForeignKey(
        settings.AUTH_USER_MODEL, on_delete=models.CASCADE,
        related_name='favorites', verbose_name='Пользователь',
    )
    product = models.ForeignKey(
        Product, null=True, blank=True, on_delete=models.CASCADE,
        related_name='favorited_by', verbose_name='Товар',
    )
    service = models.ForeignKey(
        Service, null=True, blank=True, on_delete=models.CASCADE,
        related_name='favorited_by', verbose_name='Услуга',
    )
    created_at = models.DateTimeField('Добавлено', auto_now_add=True)

    class Meta:
        verbose_name = 'Избранное'
        verbose_name_plural = 'Избранное'
        constraints = [
            models.UniqueConstraint(
                fields=('user', 'product'),
                condition=models.Q(product__isnull=False),
                name='uniq_favorite_user_product',
            ),
            models.UniqueConstraint(
                fields=('user', 'service'),
                condition=models.Q(service__isnull=False),
                name='uniq_favorite_user_service',
            ),
        ]

    def __str__(self):
        return f'{self.user} → {self.product or self.service}'