models.py

from flask_sqlalchemy import SQLAlchemy
from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash
from datetime import datetime

db = SQLAlchemy()

class User(UserMixin, db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(64), unique=True, nullable=False)
    password_hash = db.Column(db.String(128))
    files = db.relationship('File', backref='owner', lazy='dynamic')
    messages = db.relationship('Message', backref='author', lazy='dynamic')

    def set_password(self, password):
        self.password_hash = generate_password_hash(password)

    def check_password(self, password):
        return check_password_hash(self.password_hash, password)

class File(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    filename = db.Column(db.String(256), nullable=False)
    filepath = db.Column(db.String(256), nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    upload_time = db.Column(db.DateTime, default=datetime.utcnow)

    # Names only have to be unique per user, so two users can both send
    # "report.pdf" without blocking (or overwriting) each other.
    __table_args__ = (
        db.UniqueConstraint('user_id', 'filename', name='uq_file_user_filename'),
    )

class Message(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    content = db.Column(db.Text, nullable=False)
    timestamp = db.Column(db.DateTime, index=True, default=datetime.utcnow)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))