login error message/alert

login_check.rb

def authenticate
  if params[:username].present? && params[:password].present?
    inn = Inn.find_by(username: params[:username])
    
    if inn
      authenticated = inn.authenticate(params[:password])
      
      if authenticated
        redirect_to inns_url, notice: 'You are now logged in.'
        return
      else
        flash[:notice] = 'Wrong password. Please try again.'
      end
    else
      flash[:notice] = 'No username found. Please try again.'
    end
  else
    flash[:notice] = 'Fields cannot be blank. Please input both username and password.'
  end

  render 'login'
end