"""
Base model with common fields for all entities.
"""
from datetime import datetime
from sqlalchemy import Column, Integer, DateTime
from sqlalchemy.ext.declarative import declared_attr

from app.database import Base


class BaseModel(Base):
    """
    Abstract base model with common fields.
    All models should inherit from this class.
    """
    __abstract__ = True

    id = Column(Integer, primary_key=True, index=True, autoincrement=True)
    created_at = Column(DateTime, default=datetime.utcnow, nullable=False)
    updated_at = Column(
        DateTime,
        default=datetime.utcnow,
        onupdate=datetime.utcnow,
        nullable=False
    )

    @declared_attr
    def __tablename__(cls) -> str:
        """Generate table name from class name (lowercase with underscores)."""
        import re
        name = cls.__name__
        return re.sub(r'(?<!^)(?=[A-Z])', '_', name).lower() + 's'