from flask import Flask, request, render_template

app = Flask(__name__)

# Define a dictionary with the valid usernames and passwords
users = {
    'user1': 'password1',
    'user2': 'password2'
}

@app.route('/', methods=['GET', 'POST'])
def login():
    # Check if the user is already logged in
    if 'username' in session:
        return f'Logged in as {session["username"]}.'
    
    # Check if the user submitted the login form
    if request.method == 'POST':
        username = request.form['username']
        password = request.form['password']
        
        # Check if the username and password are valid
        if username in users and users[username] == password:
            # Store the username in the session
            session['username'] = username
            return f'Logged in as {username}.'
        else:
            return 'Invalid username or password.'
    
    # Render the login form
    return render_template('login.html')

@app.route('/logout')
def logout():
    # Remove the username from the session if it exists
    session.pop('username', None)
    return 'Logged out.'

if __name__ == '__main__':
    app.secret_key = 'supersecretkey'
    app.run()