from datetime import UTC, datetime

from app import db


class CardLink(db.Model):
    """CardLink model for bidirectional card-to-card relationships"""

    __tablename__ = "card_links"

    id = db.Column(db.Integer, primary_key=True)
    parent_card_id = db.Column(
        db.Integer,
        db.ForeignKey("cards.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    child_card_id = db.Column(
        db.Integer,
        db.ForeignKey("cards.id", ondelete="CASCADE"),
        nullable=False,
        index=True,
    )
    created_by = db.Column(
        db.Integer, db.ForeignKey("users.id"), nullable=True, index=True
    )

    # Timestamps
    created_at = db.Column(db.DateTime, default=lambda: datetime.now(UTC))

    # Relationships
    parent_card = db.relationship(
        "Card",
        foreign_keys=[parent_card_id],
        back_populates="child_links",
    )
    child_card = db.relationship(
        "Card",
        foreign_keys=[child_card_id],
        back_populates="parent_links",
    )

    def to_dict(self, include_cards=False):
        """Convert card link to dictionary"""
        result = {
            "id": self.id,
            "parent_card_id": self.parent_card_id,
            "child_card_id": self.child_card_id,
            "created_by": self.created_by,
            "created_at": self.created_at.isoformat() if self.created_at else None,
        }
        if include_cards:
            result["parent_card"] = (
                self.parent_card.to_dict() if self.parent_card else None
            )
            result["child_card"] = (
                self.child_card.to_dict() if self.child_card else None
            )
        return result

    def __repr__(self):
        return f"<CardLink {self.parent_card_id} -> {self.child_card_id}>"

    __table_args__ = (
        db.UniqueConstraint("parent_card_id", "child_card_id", name="unique_card_link"),
    )