from sqlalchemy import create_engine, Column, Integer, String, Float, DateTime
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()  # Define base class for ORM models

class Product(Base):
    __tablename__ = "products"
    id = Column(Integer, primary_key=True)  # Primary key for products
    name = Column(String, nullable=False)
    current_stock = Column(Float, nullable=False)
    safety_stock = Column(Float, nullable=False)
    lead_time = Column(Float, nullable=False)
    monthly_demand = Column(Float, nullable=False)
    product_class = Column(String, nullable=False)

class Transaction(Base):
    __tablename__ = "transactions"
    id = Column(Integer, primary_key=True)  # Primary key for transactions
    product_id = Column(Integer, nullable=False)
    quantity = Column(Float, nullable=False)
    transaction_type = Column(String, nullable=False)
    timestamp = Column(DateTime, server_default="CURRENT_TIMESTAMP")

engine = create_engine("sqlite:///:memory:")  # In-memory SQLite database
SessionLocal = sessionmaker(bind=engine)  # Session factory for database access

def initialize_database():
    Base.metadata.create_all(engine)  # Create all tables

def get_db():
    db = SessionLocal()
    try:
        yield db
    finally:
        db.close()  # Ensure database session is closed