from __future__ import annotations

from datetime import date, datetime
from decimal import Decimal

from sqlalchemy import (
    BigInteger,
    Date,
    DateTime,
    ForeignKey,
    Integer,
    UniqueConstraint,
    func,
)
from sqlalchemy.orm import Mapped, mapped_column

from app.core.config import settings
from app.db.base import Base
from app.db.types import AuditMixin, IdMixin, Rate, qualified


class ExchangeRate(IdMixin, AuditMixin, Base):
    """Официальный курс ЦБ на дату.

    rate — курс за `nominal` единиц валюты, как публикует ЦБ (<Value>).
    Курс за одну единицу = rate / nominal (для CNY nominal = 1).
    """

    __tablename__ = "exchange_rate"
    __table_args__ = (
        UniqueConstraint(
            "currency_id", "rate_date", name="uq_exchange_rate_currency_date"
        ),
        {"schema": settings.DATABASE_SCHEMA} if settings.DATABASE_SCHEMA else {},
    )

    currency_id: Mapped[int] = mapped_column(
        BigInteger, ForeignKey(qualified("currency.id")), nullable=False
    )
    rate_date: Mapped[date] = mapped_column(Date, nullable=False)
    nominal: Mapped[int] = mapped_column(Integer, nullable=False)
    rate: Mapped[Decimal] = mapped_column(Rate, nullable=False)
    loaded_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), server_default=func.now(), nullable=False
    )