# from sqlalchemy import Column, Integer, String, Text, DateTime, ForeignKey, func
# from sqlalchemy.orm import relationship
# from src.models.base import BaseModel

# class User(BaseModel):
#     """
#     Represents an application user.
#     """
#     __tablename__ = "users"

#     id = Column(Integer, primary_key=True, index=True)
#     username = Column(String(50), unique=True, nullable=False, index=True)
#     email = Column(String(100), unique=True, nullable=False, index=True)
#     password = Column(String(100), nullable=False)
#     avatar_url = Column(Text, nullable=True)

#     created_at = Column(DateTime(timezone=True), server_default=func.now())
#     updated_at = Column(DateTime(timezone=True), onupdate=func.now(), server_default=func.now())

#     # Relationships
#     questions = relationship(
#         "Question",
#         back_populates="user",
#         cascade="all, delete",
#         passive_deletes=True
#     )
#     comments = relationship(
#         "Comment",
#         back_populates="user",
#         cascade="all, delete",
#         passive_deletes=True
#     )
#     ratings = relationship(
#         "Rating",
#         back_populates="user",
#         cascade="all, delete",
#         passive_deletes=True
#     )
#     exam_attempts = relationship(
#         "ExamAttempt",
#         back_populates="user",
#         cascade="all, delete",
#         passive_deletes=True
#     )
#     exams = relationship(
#         "Exam",
#         back_populates="user",
#         cascade="all, delete",
#         passive_deletes=True
#     )

#     def __repr__(self):
#         return f"<User id={self.id}, username='{self.username}', email='{self.email}'>"