from datetime import datetime

from sqlalchemy import DateTime, ForeignKey, Integer
from sqlalchemy.exc import IntegrityError
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import Mapped, mapped_column, relationship

from .base import Base, CommonMixin
from .entry import Entry
from .product import Product


class PresetEntry(Base, CommonMixin):
    """Entry."""

    grams: Mapped[float]
    product_id: Mapped[int] = mapped_column(Integer, ForeignKey("product.id"))
    product: Mapped[Product] = relationship(lazy="selectin")
    preset_id: Mapped[int] = mapped_column(Integer, ForeignKey("preset.id"))
    last_changed: Mapped[datetime] = mapped_column(
        DateTime, default=datetime.utcnow, onupdate=datetime.utcnow
    )

    @property
    def amount(self) -> float:
        """amount.

        :rtype: float
        """
        return self.grams / 100

    @property
    def calories(self) -> float:
        """calories.

        :rtype: float
        """
        return self.amount * self.product.calories

    @property
    def protein(self) -> float:
        """protein.

        :rtype: float
        """
        return self.amount * self.product.protein

    @property
    def carb(self) -> float:
        """carb.

        :rtype: float
        """
        return self.amount * self.product.carb

    @property
    def fat(self) -> float:
        """fat.

        :rtype: float
        """
        return self.amount * self.product.fat

    @property
    def fiber(self) -> float:
        """fiber.

        :rtype: float
        """
        return self.amount * self.product.fiber

    @classmethod
    async def create(
        self,
        session: AsyncSession,
        preset_id: int,
        entry: Entry,
    ) -> None:
        pentry = PresetEntry(
            preset_id=preset_id,
            product_id=entry.product_id,
            grams=entry.grams,
        )
        session.add(pentry)

        try:
            await session.flush()
        except IntegrityError:
            raise AssertionError("preset or product does not exist")