app.py

from flask import Flask, render_template, request, redirect, url_for, session, flash
from werkzeug.security import generate_password_hash, check_password_hash
from flask_sqlalchemy import SQLAlchemy
import os

app = Flask(__name__)
app.secret_key = 'supersecretkey'  

app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///todo.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(150), unique=True, nullable=False)
    password_hash = db.Column(db.String(150), nullable=False)

class Task(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    content = db.Column(db.String(200), nullable=False)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)

with app.app_context():
    db.create_all()

def login_required(f):
    def decorated_function(*args, **kwargs):
        if 'user_id' not in session:
            return redirect(url_for('login'))
        return f(*args, **kwargs)
    decorated_function.__name__ = f.__name__
    return decorated_function

@app.route('/')
@login_required
def index():
    user_id = session['user_id']
    user_tasks = Task.query.filter_by(user_id=user_id).all()
    return render_template('index.html', tasks=user_tasks)

@app.route('/register', methods=['GET', 'POST'])
def register():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        
        existing_user = User.query.filter_by(username=username).first()
        if existing_user:
            flash("Username already exists!")
            return redirect(url_for('register'))
        
        password_hash = generate_password_hash(password)
        new_user = User(username=username, password_hash=password_hash)
        db.session.add(new_user)
        db.session.commit()
        
        flash("Registration successful, please log in.")
        return redirect(url_for('login'))
    return render_template('register.html')

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        
        user = User.query.filter_by(username=username).first()
        if user and check_password_hash(user.password_hash, password):
            session['user_id'] = user.id
            return redirect(url_for('index'))
        
        flash("Invalid username or password")
    return render_template('login.html')

@app.route('/logout')
def logout():
    session.pop('user_id', None)
    flash("You have been logged out.")
    return redirect(url_for('login'))

@app.route('/add', methods=['POST'])
@login_required
def add_task():
    task_content = request.form.get('content')
    if task_content:
        user_id = session['user_id']
        new_task = Task(content=task_content, user_id=user_id)
        db.session.add(new_task)
        db.session.commit()
    return redirect(url_for('index'))

@app.route('/delete/<int:task_id>')
@login_required
def delete_task(task_id):
    task = Task.query.get_or_404(task_id)
    if task.user_id == session['user_id']:
        db.session.delete(task)
        db.session.commit()
    return redirect(url_for('index'))

if __name__ == '__main__':
    app.run(debug=True)