from flask import Flask, request, session, redirect, url_for, render_template
import sqlite3, bcrypt

app = Flask(name)
app.secret_key = "supersecretkey" # Use env variable in production

Database setup

def init_db():
conn = sqlite3.connect("users.db")
c = conn.cursor()
c.execute("CREATE TABLE IF NOT EXISTS users (id INTEGER PRIMARY KEY, username TEXT, password TEXT)")
conn.commit()
conn.close()

@app.route("/register", methods=["GET", "POST"])
def register():
if request.method == "POST":
username = request.form["username"]
password = request.form["password"].encode("utf-8")
hashed = bcrypt.hashpw(password, bcrypt.gensalt())

    conn = sqlite3.connect("users.db")
    c = conn.cursor()
    c.execute("INSERT INTO users (username, password) VALUES (?, ?)", (username, hashed))
    conn.commit()
    conn.close()
    return "Registration successful!"
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"].encode("utf-8")

    conn = sqlite3.connect("users.db")
    c = conn.cursor()
    c.execute("SELECT password FROM users WHERE username=?", (username,))
    result = c.fetchone()
    conn.close()
    
    if result and bcrypt.checkpw(password, result[0]):
        session["user"] = username
        return "Login successful!"
    else:
        return "Invalid credentials."
return render_template("login.html")

@app.route("/logout")
def logout():
session.pop("user", None)
return "Logged out successfully!"

if name == "main":
init_db()