twitter.rb

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  gem "rails"
  gem "puma"
  gem "twitter"
  gem "omniauth-twitter"
end

require "action_controller/railtie"

class TwitterApp < Rails::Application
  secrets.secret_token    = "secret_token"
  secrets.secret_key_base = "secret_key_base"

  config.logger = Logger.new($stdout)
  Rails.logger = config.logger

  config.session_store :cookie_store, key: "cookie_store_key"
  config.middleware.use OmniAuth::Builder do
    provider :twitter, ENV.fetch("TWITTER_API_KEY"), ENV.fetch("TWITTER_API_SECRET")
  end
  OmniAuth.config.allowed_request_methods = [:post, :get]

  routes.draw do
    get '/auth/:provider/callback', to: 'sessions#create'
  end
end

class SessionsController < ActionController::Base
  include Rails.application.routes.url_helpers

  def create
    auth = request.env['omniauth.auth']

    client = Twitter::REST::Client.new do |config|
      config.consumer_key    = ENV.fetch('TWITTER_API_KEY')
      config.consumer_secret = ENV.fetch('TWITTER_API_SECRET')
      config.access_token        = auth.dig(:credentials, :token)
      config.access_token_secret = auth.dig(:credentials, :secret)
    end

    client.update("Tweeting this from a Rails app")

    render plain: "All good"
  end
end

require "rails/command"
require "rails/commands/server/server_command"

options = {
  app: TwitterApp,
  Host: '0.0.0.0'
}
Rails::Server.new(options).start