t2s.rb

require 'bundler'
Bundler.require

Slack.configure do |config|
  config.token = 'xxx'
end
slack = Slack::Web::Client.new

twitter = Twitter::Streaming::Client.new do |config|
  config.consumer_key = 'xxx'
  config.consumer_secret = 'xxx'
  config.access_token = 'xxx'
  config.access_token_secret = 'xxx'
end

options = {
  twitter: twitter,
  slack: slack,
  channel: '#twitter',
}

class TwitterToSlack
  BASE_URL = 'https://twitter.com'

  def initialize(options)
    @twitter = options[:twitter]
    @slack = options[:slack]
    @channel = options[:channel]
  end

  def run
    loop do
      begin
        @twitter.user do |obj|
          case obj
          when Twitter::Tweet
            on_tweet obj
          end
        end
      rescue => e
        p e
        sleep 10
      end
    end
  end

  private

  def on_tweet(t)
    options = {
      channel: @channel,
      text: text(t),
      attachments: attachments(t),
      as_user: false,
      icon_url: t.user.profile_image_url_https.to_s,
      username: t.user.screen_name,
    }
    puts "[#{t.created_at}] #{t.user.screen_name}: #{t.full_text}"
    @slack.chat_postMessage options
  end

  def text(t)
    make_links t.text
  end

  def make_links(text)
    [:mention_links, :hashtag_links].inject(text) do |text, meth|
      method(meth).call(text)
    end
  end

  def mention_links(text)
    text.gsub /@([a-zA-Z0-9_]+)/ do |mention|
      "<#{BASE_URL}/#{$1}|#{mention}>"
    end
  end

  def hashtag_links(text)
    text.gsub /#([^#\s]+)/ do |hashtag|
      "<#{BASE_URL}/hashtag/#{$1}|#{hashtag}>"
    end
  end

  def attachments(t)
    unless t.in_reply_to_status_id.nil?
      [{
        title: "In reply to @#{t.in_reply_to_screen_name}",
        title_link: "#{BASE_URL}/#{t.in_reply_to_screen_name}/statuses/#{t.in_reply_to_status_id}",
        footer: 'Twitter',
      }]
    end
  end
end

begin
  t2s = TwitterToSlack.new options
  t2s.run
rescue Interrupt
end