from datetime import date
from decimal import Decimal

from sqlalchemy import Date, ForeignKey, Numeric
from sqlalchemy.orm import Mapped, mapped_column, relationship

from src.models.common import BaseModelDb


class CategoryBudgetDb(BaseModelDb):
    """Budget amount for a category, optionally bounded to a time window.

    Satellite table to ``category``: one category may have several budgets
    (e.g. one per month). ``valid_from``/``valid_to`` are nullable; ``None``
    means unbounded on that side.
    """

    __tablename__ = "category_budget"

    id: Mapped[int] = mapped_column(primary_key=True, autoincrement=True)
    category_id: Mapped[int] = mapped_column(ForeignKey("category.id"), nullable=False)
    amount_eur: Mapped[Decimal] = mapped_column(Numeric(12, 2), nullable=False)
    valid_from: Mapped[date | None] = mapped_column(Date, nullable=True, default=None)
    valid_to: Mapped[date | None] = mapped_column(Date, nullable=True, default=None)

    # relationship
    category = relationship("CategoryDb", back_populates="budgets")