implemented basis of login, missing database connection.

app/__init__.py

@@ -1,18 +1,30 @@
 from flask import Flask
+from flask_sqlalchemy import SQLAlchemy
+from flask_login import LoginManager
+
+db = SQLAlchemy()
+login_manager = LoginManager()
 
 def create_app():
     app = Flask(__name__)
 
-    # Basic config
+    app.config["SQLALCHEMY_DATABASE_URI"] = ""
     app.config["SECRET_KEY"] = "dev-secret-key"
 
-    # # ---- Register Blueprints (Routes) ----
-    # from .routes.auth_routes import auth_bp
-    # from .routes.solver_routes import solver_bp
+    db.init_app(app)
+    login_manager.init_app(app)
+    login_manager.login_view = "login.login"
+
+    from .models.user import User
+
+    @login_manager.user_loader
+    def load_user(user_id):
+        return db.session.get(User, int(user_id))
+
+    from .routes.login_routes import login_bp
     from .routes.main_routes import main_bp
 
-    # app.register_blueprint(auth_bp)
-    # app.register_blueprint(solver_bp)
+    app.register_blueprint(login_bp)
     app.register_blueprint(main_bp)
 
     return app

app/models/user.py

@@ -0,0 +1,14 @@
+from .. import db
+from flask_login import UserMixin
+
+class User(UserMixin, db.Model):
+    __tablename__ = "users"
+
+    id = db.Column(db.Integer, primary_key=True)
+    username = db.Column(db.String(20), unique=True, nullable=False)
+    password = db.Column(db.String(255), nullable=False)  # <- größer!
+    email = db.Column(db.String(120), unique=True, nullable=False)
+    created_at = db.Column(db.DateTime, server_default=db.func.now())
+
+    def __repr__(self):
+        return f"<User {self.username}>"

app/routes/login_routes.py

@@ -0,0 +1,49 @@
+from flask import Blueprint, render_template, request, url_for, redirect
+from werkzeug.security import generate_password_hash, check_password_hash
+from flask_login import login_user
+from ..models.user import User
+from .. import db
+
+login_bp = Blueprint("login", __name__)
+
+@login_bp.route("/register", methods=["GET", "POST"])
+def register():
+    if request.method == "POST":
+        username = request.form.get("username")
+        password = request.form.get("password")
+        email = request.form.get("email")
+
+        if User.query.filter_by(username=username).first():
+            return render_template("sign_up.html", error="Username already taken!")
+
+        hashed_password = generate_password_hash(password)
+
+        new_user = User(
+            username=username,
+            password=hashed_password,
+            email=email
+        )
+
+        db.session.add(new_user)
+        db.session.commit()
+
+        return redirect(url_for("login.login"))
+
+    return render_template("sign_up.html")
+
+
+@login_bp.route("/login", methods=["GET", "POST"])
+def login():
+    if request.method == "POST":
+        username = request.form.get("username")
+        password = request.form.get("password")
+
+        user = User.query.filter_by(username=username).first()
+
+        if user and check_password_hash(user.password, password):
+            login_user(user)
+            return redirect(url_for("main.dashboard"))
+
+        return render_template("login.html", error="Invalid username or password")
+
+    return render_template("login.html")

app/templates/login.html

@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Login</title>
+    <style>
+        h1 {
+            color: green;
+        }
+
+        .error {
+            color: red;
+        }
+    </style>
+</head>
+
+<body>
+    <nav>
+        <ul>
+            <li><a href="/login">Login</a></li>
+            <li><a href="/register">Create account</a></li>
+        </ul>
+    </nav>
+    <h1>Login to your account</h1>
+
+    {% if error %}
+    <p class="error">{{ error }}</p>
+    {% endif %}
+
+    <form action="/login" method="post">
+        <label for="username">Username:</label>
+        <input type="text" name="username" required />
+        <label for="password">Password:</label>
+        <input type="password" name="password" required />
+        <button type="submit">Login</button>
+    </form>
+</body>
+
+</html>

app/templates/sign_up.html

@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<html lang="en">
+
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Sign Up</title>
+    <style>
+        h1 {
+            color: green;
+        }
+
+        .error {
+            color: red;
+        }
+    </style>
+</head>
+
+<body>
+    <nav>
+        <ul>
+            <li><a href="/login">Login</a></li>
+            <li><a href="/register">Create account</a></li>
+        </ul>
+    </nav>
+    <h1>Create an account</h1>
+
+    {% if error %}
+    <p class="error">{{ error }}</p>
+    {% endif %}
+
+    <form action="/register" method="post">
+        <label for="username">Username:</label>
+        <input type="text" name="username" required />
+        <label for="password">Password:</label>
+        <input type="password" name="password" required />
+        <button type="submit">Sign Up</button>
+    </form>
+</body>
+
+</html>