import uuid
from datetime import UTC, datetime
from typing import TYPE_CHECKING

from sqlalchemy import DateTime, Enum, Float, ForeignKey, Integer
from sqlalchemy.dialects.postgresql import UUID
from sqlalchemy.orm import Mapped, mapped_column, relationship

from database import Base

from .enums import BitcoinTransferMethod, ExchangeStatus, TradeDirection

if TYPE_CHECKING:
    from .user import User


class Exchange(Base):
    """Bitcoin exchange trades booked by users."""

    __tablename__ = "exchanges"
    # Note: No unique constraint on slot_start to allow cancelled bookings
    # to be replaced. Application-level check in create_exchange ensures only
    # one BOOKED trade per slot. For existing databases, manually drop the
    # constraint: ALTER TABLE exchanges DROP CONSTRAINT IF EXISTS
    # uq_exchange_slot_start;

    id: Mapped[int] = mapped_column(Integer, primary_key=True, autoincrement=True)
    public_id: Mapped[uuid.UUID] = mapped_column(
        UUID(as_uuid=True),
        nullable=False,
        unique=True,
        index=True,
        default=uuid.uuid4,
    )
    user_id: Mapped[int] = mapped_column(
        Integer, ForeignKey("users.id"), nullable=False, index=True
    )
    user: Mapped["User"] = relationship("User", foreign_keys=[user_id], lazy="joined")

    # Slot timing
    slot_start: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), nullable=False, index=True
    )
    slot_end: Mapped[datetime] = mapped_column(DateTime(timezone=True), nullable=False)

    # Trade details
    direction: Mapped[TradeDirection] = mapped_column(
        Enum(TradeDirection), nullable=False
    )
    bitcoin_transfer_method: Mapped[BitcoinTransferMethod] = mapped_column(
        Enum(BitcoinTransferMethod),
        nullable=False,
        default=BitcoinTransferMethod.ONCHAIN,
    )
    eur_amount: Mapped[int] = mapped_column(Integer, nullable=False)  # EUR cents
    sats_amount: Mapped[int] = mapped_column(Integer, nullable=False)  # Satoshis

    # Price information (snapshot at booking time)
    market_price_eur: Mapped[float] = mapped_column(
        Float, nullable=False
    )  # EUR per BTC
    agreed_price_eur: Mapped[float] = mapped_column(
        Float, nullable=False
    )  # EUR per BTC with premium
    premium_percentage: Mapped[int] = mapped_column(
        Integer, nullable=False
    )  # e.g. 5 for 5%

    # Status
    status: Mapped[ExchangeStatus] = mapped_column(
        Enum(ExchangeStatus), nullable=False, default=ExchangeStatus.BOOKED
    )

    # Timestamps
    created_at: Mapped[datetime] = mapped_column(
        DateTime(timezone=True), default=lambda: datetime.now(UTC)
    )
    cancelled_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )
    completed_at: Mapped[datetime | None] = mapped_column(
        DateTime(timezone=True), nullable=True
    )