app/models/session.py

# app/models/session.py
"""UserSession model for tracking active multi-device selector-verifier tokens, metadata, and security versions."""

from datetime import datetime, timezone
from sqlalchemy import Column, Integer, String, DateTime, Boolean, ForeignKey
from app.core.database import Base


class UserSession(Base):
    __tablename__ = "user_sessions"

    id = Column(Integer, primary_key=True, index=True)
    user_id = Column(String(100), ForeignKey("users.user_id", ondelete="CASCADE"), index=True, nullable=False)
    
    # Selector-Verifier splits
    selector = Column(String(32), unique=True, index=True, nullable=False)
    verifier_hash = Column(String(64), nullable=False)
    
    # Invalidation Versioning
    session_version = Column(Integer, default=1, nullable=False)
    
    # Metadata for fraud detection
    ip_address = Column(String(45), nullable=True)
    user_agent = Column(String(512), nullable=True)
    
    is_compromised = Column(Boolean, default=False, nullable=False)
    created_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
    last_active_at = Column(DateTime, default=lambda: datetime.now(timezone.utc), nullable=False)
    expires_at = Column(DateTime, nullable=False)

    def __repr__(self) -> str:
        return f"<UserSession {self.user_id}:{self.selector}>"