import uuid
from decimal import Decimal

from django.db import models
from django.db.models import Q


class CostType(models.TextChoices):
    COMMISSION = "commission", "Комиссия"
    DELIVERY = "delivery", "Доставка"
    STORAGE = "storage", "Хранение"
    ADVERTISING = "advertising", "Реклама"
    ACQUIRING = "acquiring", "Эквайринг"
    RETURN = "return", "Возврат"
    OTHER = "other", "Прочее"


class Cost(models.Model):
    """Additional product- or sale-line-level expense."""

    id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
    project = models.ForeignKey(
        "commerce.ExternalProject", null=True, blank=True, on_delete=models.PROTECT
    )
    source = models.ForeignKey(
        "commerce.SourceSystem",
        on_delete=models.PROTECT,
        related_name="costs",
        verbose_name="Источник",
    )
    product = models.ForeignKey(
        "commerce.Product",
        on_delete=models.PROTECT,
        null=True,
        blank=True,
        related_name="costs",
        verbose_name="Товар",
    )
    sale_line = models.ForeignKey(
        "commerce.SaleLine",
        on_delete=models.CASCADE,
        null=True,
        blank=True,
        related_name="costs",
        verbose_name="Позиция продажи",
    )
    external_id = models.CharField("Внешний ID", max_length=255, blank=True)
    channel = models.CharField("Канал продаж", max_length=64, blank=True, db_index=True)
    cost_type = models.CharField("Тип расхода", max_length=32, choices=CostType.choices)
    amount = models.DecimalField(
        "Сумма", max_digits=18, decimal_places=2, default=Decimal("0")
    )
    currency = models.CharField("Валюта", max_length=3, default="RUB")
    occurred_at = models.DateTimeField("Дата расхода", db_index=True)
    metadata = models.JSONField("Дополнительные данные", default=dict, blank=True)
    created_at = models.DateTimeField("Создано", auto_now_add=True)

    class Meta:
        verbose_name = "Расход"
        verbose_name_plural = "Расходы"
        constraints = [
            models.CheckConstraint(
                condition=Q(product__isnull=False)
                | Q(sale_line__isnull=False)
                | Q(project__isnull=False),
                name="commerce_cost_has_target",
            ),
            models.UniqueConstraint(
                fields=["source", "external_id", "cost_type"],
                condition=~Q(external_id=""),
                name="commerce_cost_source_external_type",
            ),
        ]
        indexes = [
            models.Index(
                fields=["product", "occurred_at"], name="commerce_cost_product_date"
            )
        ]

    def __str__(self):
        return f"{self.get_cost_type_display()}: {self.amount} {self.currency}"