from sqlalchemy.orm import Mapped
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from typing import AsyncIterator, Optional

from .base import Base, CommonMixin


class Product(Base, CommonMixin):
    """Product."""

    name: Mapped[str]

    protein: Mapped[float]
    carb: Mapped[float]
    fat: Mapped[float]

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

        :rtype: float
        """
        return self.protein * 4 + self.carb * 4 + self.fat * 9

    @classmethod
    async def list_all(
        cls, session: AsyncSession, offset: int, limit: int, q: Optional[str] = None
    ) -> AsyncIterator["Product"]:
        query = select(cls)

        if q:
            query = query.filter(cls.name.ilike(f"%{q.lower()}%"))

        query = query.offset(offset).limit(limit)
        stream = await session.stream_scalars(query.order_by(cls.id))
        async for row in stream:
            yield row

    @classmethod
    async def create(
        cls, session: AsyncSession, name: str, carb: float, protein: float, fat: float
    ) -> "Product":
        # validation here
        assert carb <= 100, "carb must be less than 100"
        assert protein <= 100, "protein must be less than 100"
        assert fat <= 100, "fat must be less than 100"
        assert carb >= 0, "carb must be greater than 0"
        assert protein >= 0, "protein must be greater than 0"
        assert fat >= 0, "fat must be greater than 0"
        assert carb + protein + fat <= 100, "total must be less than 100"

        # to avoid duplicates in the database keep name as lower
        name = name.lower()

        # check if product already exists
        query = select(cls).where(cls.name == name)
        existing_product = await session.scalar(query)
        assert existing_product is None, "product already exists"

        product = Product(
            name=name,
            protein=protein,
            carb=carb,
            fat=fat,
        )
        session.add(product)
        await session.flush()
        return product