models.py

from sqlalchemy import Column, Integer, String, DateTime, ForeignKey
from sqlalchemy.orm import relationship
from database import Base
from datetime import datetime


class User(Base):
    """
    User model - represents users who can create tasks
    """
    __tablename__ = "users"
    
    id = Column(Integer, primary_key=True, index=True)
    username = Column(String, unique=True, nullable=False, index=True)
    email = Column(String, unique=True, nullable=False, index=True)
    hashed_password = Column(String, nullable=False)  # NEVER store plain passwords!
    created_at = Column(DateTime, default=datetime.utcnow)
    
    # Relationship: One user has many tasks
    # When you access user.tasks, you get all tasks belonging to this user
    tasks = relationship("Task", back_populates="owner", cascade="all, delete-orphan")


class Task(Base):
    """
    Task model - represents tasks owned by users
    """
    __tablename__ = "tasks"
    
    id = Column(Integer, primary_key=True, index=True)
    title = Column(String, nullable=False)
    description = Column(String, nullable=True)
    status = Column(String, default="todo")  # todo, in_progress, done
    priority = Column(String, default="medium")  # low, medium, high
    created_at = Column(DateTime, default=datetime.utcnow)
    
    # Foreign Key: Links task to user
    user_id = Column(Integer, ForeignKey("users.id"), nullable=False)
    
    # Relationship: Each task belongs to one user
    # When you access task.owner, you get the user who owns this task
    owner = relationship("User", back_populates="tasks")