from sqlalchemy import Column, Integer, String, Float, Boolean, DateTime, ForeignKey, Table
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy.sql import func
from datetime import datetime

Base = declarative_base()

# Association table for many-to-many relationship between shopping events and groceries
shopping_event_groceries = Table(
    'shopping_event_groceries',
    Base.metadata,
    Column('shopping_event_id', Integer, ForeignKey('shopping_events.id'), primary_key=True),
    Column('grocery_id', Integer, ForeignKey('groceries.id'), primary_key=True),
    Column('amount', Float, nullable=False)  # Amount of this grocery bought in this event
)

class Grocery(Base):
    __tablename__ = "groceries"
    
    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, nullable=False, index=True)
    price = Column(Float, nullable=False)
    category = Column(String, nullable=False)
    organic = Column(Boolean, default=False)
    weight = Column(Float, nullable=True)  # in grams or kg
    weight_unit = Column(String, default="piece")  # "g", "kg", "ml", "l", "piece"
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    updated_at = Column(DateTime(timezone=True), onupdate=func.now())
    
    # Relationships
    shopping_events = relationship("ShoppingEvent", secondary=shopping_event_groceries, back_populates="groceries")

class Shop(Base):
    __tablename__ = "shops"
    
    id = Column(Integer, primary_key=True, index=True)
    name = Column(String, nullable=False, index=True)
    city = Column(String, nullable=False)
    address = Column(String, nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    
    # Relationships
    shopping_events = relationship("ShoppingEvent", back_populates="shop")

class ShoppingEvent(Base):
    __tablename__ = "shopping_events"
    
    id = Column(Integer, primary_key=True, index=True)
    shop_id = Column(Integer, ForeignKey("shops.id"), nullable=False)
    date = Column(DateTime(timezone=True), nullable=False, default=datetime.utcnow)
    total_amount = Column(Float, nullable=True)  # Total cost of the shopping event
    notes = Column(String, nullable=True)
    created_at = Column(DateTime(timezone=True), server_default=func.now())
    
    # Relationships
    shop = relationship("Shop", back_populates="shopping_events")
    groceries = relationship("Grocery", secondary=shopping_event_groceries, back_populates="shopping_events")