m1_after.rb

# app/controllers/sessions_controller.rb
class SessionsController < ApplicationController
  def login
    if current_user
      redirect_to root_path
      return
    end
    @redirect_path = { path: "/auth/facebook", message: { notice: "Logged in successfully" } }
    parse_to_path if params[:to]
    redirect_to @redirect_path[:path], @redirect_path[:message]
  end
  
protected  
  def invalid_to_path
    @redirect_path = { path: new_story_path, message: { alert: "Invalid URL" } }
  end

  def parse_to_path
    begin
      uri = URI.parse(params[:to])
      unless ENV['HOST'].include? uri.host
        invalid_to_path
      else
        session[:from] = uri.to_s
      end
    rescue URI::InvalidURIError
      invalid_to_path
    end
  end
end