from datetime import datetime, date
from decimal import Decimal
from sqlalchemy import String, Boolean, Numeric, ForeignKey, Date, DateTime, UniqueConstraint, func
from sqlalchemy.orm import Mapped, mapped_column, relationship
from app.database import Base


class Currency(Base):
    __tablename__ = "currencies"

    id: Mapped[int] = mapped_column(primary_key=True)
    code: Mapped[str] = mapped_column(String(3), unique=True, nullable=False)   # ISO 4217
    name: Mapped[str] = mapped_column(String(100), nullable=False)
    symbol: Mapped[str | None] = mapped_column(String(10))
    is_active: Mapped[bool] = mapped_column(Boolean, default=True, nullable=False)
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())

    exchange_rates_from: Mapped[list["ExchangeRate"]] = relationship(
        "ExchangeRate", foreign_keys="ExchangeRate.currency_from_id", back_populates="currency_from"
    )
    exchange_rates_to: Mapped[list["ExchangeRate"]] = relationship(
        "ExchangeRate", foreign_keys="ExchangeRate.currency_to_id", back_populates="currency_to"
    )
    accounts: Mapped[list] = relationship("Account", back_populates="currency")
    operations: Mapped[list] = relationship("Operation", back_populates="currency")
    budgets: Mapped[list] = relationship("Budget", back_populates="currency")
    calendar_events: Mapped[list] = relationship("CalendarEvent", back_populates="currency")


class ExchangeRate(Base):
    __tablename__ = "exchange_rates"
    __table_args__ = (
        UniqueConstraint("currency_from_id", "currency_to_id", "rate_date", name="uq_exchange_rate_day"),
    )

    id: Mapped[int] = mapped_column(primary_key=True)
    currency_from_id: Mapped[int] = mapped_column(ForeignKey("currencies.id"), nullable=False)
    currency_to_id: Mapped[int] = mapped_column(ForeignKey("currencies.id"), nullable=False)
    rate: Mapped[Decimal] = mapped_column(Numeric(20, 6), nullable=False)
    rate_date: Mapped[date] = mapped_column(Date, nullable=False)
    source: Mapped[str | None] = mapped_column(String(100))
    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), server_default=func.now())

    currency_from: Mapped["Currency"] = relationship(
        "Currency", foreign_keys=[currency_from_id], back_populates="exchange_rates_from"
    )
    currency_to: Mapped["Currency"] = relationship(
        "Currency", foreign_keys=[currency_to_id], back_populates="exchange_rates_to"
    )