app/models/cart.py

from datetime import datetime, timezone
from sqlalchemy import Column, Integer, String, Float, DateTime, ForeignKey, Boolean
from sqlalchemy.orm import relationship

from app.db.base import Base

class Coupon(Base):
    __tablename__ = "coupons"

    id = Column(Integer, primary_key=True, autoincrement=True)
    code = Column(String(50), unique=True, index=True, nullable=False)
    discount_percent = Column(Float, nullable=False)
    is_active = Column(Boolean, default=True, nullable=False)
    expires_at = Column(DateTime, nullable=True)
    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)

    carts = relationship("Cart", back_populates="coupon")

class Cart(Base):
    __tablename__ = "carts"

    id = Column(Integer, primary_key=True, autoincrement=True)
    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=True)
    session_id = Column(String(255), unique=True, index=True, nullable=True)
    coupon_id = Column(Integer, ForeignKey("coupons.id", ondelete="SET NULL"), nullable=True)
    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
    updated_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc), nullable=False)

    user = relationship("User", backref="cart")
    coupon = relationship("Coupon", back_populates="carts")
    items = relationship("CartItem", back_populates="cart", cascade="all, delete-orphan")

class CartItem(Base):
    __tablename__ = "cart_items"

    id = Column(Integer, primary_key=True, autoincrement=True)
    cart_id = Column(Integer, ForeignKey("carts.id", ondelete="CASCADE"), nullable=False)
    product_id = Column(Integer, ForeignKey("products.id", ondelete="CASCADE"), nullable=False)
    variant_label = Column(String(100), nullable=True)  # Store variant name (e.g. "Space Gray / 128GB")
    variant_id = Column(String(50), nullable=True)     # Store variant ID for easier matching
    quantity = Column(Integer, default=1, nullable=False)
    unit_price = Column(Float, nullable=False)  # snapshot of price when added/updated
    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
    updated_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc), nullable=False)

    cart = relationship("Cart", back_populates="items")
    product = relationship("Product")