```ruby
class SessionsController < ApplicationController
  def new
  end

  def create
  end

  def destroy
  end
end
```

Implement actions for sessions controller
user
```ruby
class SessionsController < ApplicationController
  def new
    @user = User.new
  end

  def create
    user = User.find_by(username: user_params[:username])
    if user && user.authenticate(user_params[:password])
      session[:user_id] = user.id
      redirect_to root_path
    else
      flash[:notice] = "Invalid Username or Password"
      redirect_to login_path
    end
  end

  def destroy
    session[:user_id] = nil
    redirect_to root_path
  end
end
```
assistant