How to integrate SHIFT API (https://shift.com) to your Rails App. You should read SHIFT API Docs to understand the flow before implementing this.

omniauth.rb

# config/omniauth.rb
# this is OPTIONAL if you want user to login not through SHIFT Website
# Register our provider with the OmniAuth Gem

module OmniAuth
  module Strategies
    # tell OmniAuth to load our strategy
    autoload :Shift, 'shift_strategy'
  end
end

Rails.application.config.middleware.use OmniAuth::Builder do
  provider :facebook, ENV['FB_APP'], ENV['FB_SECRET'], {:scope => 'publish_actions, email, user_interests, user_groups, user_likes, publish_stream, offline_access, user_birthday, create_event, manage_pages'}
  provider :twitter, ENV['TWITTER_KEY'], ENV['TWITTER_SECRET']
  provider :shift, ENV['SHIFT_APP_ID'], ENV['SHIFT_APP_SECRET'], {}
end

sessions_controller.rb

#----------------------------------------------------------------------#
# function: app_install
# summary:  when user authenticate through shift website, this is where
# the redirect_uri settings from shift pointed to
# author:   Duy
#----------------------------------------------------------------------#
  def app_install
    
    # uri
    uri = URI.parse("https://shift.com")
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE
    
    # prepare data
    data = {'code' => params["code"], 
      'client_id' => ENV['SHIFT_APP_ID'], 
      'client_secret' => ENV['SHIFT_APP_SECRET'], 
      'grant_type' => 'authorization_code',
      'redirect_uri' => ENV['SHIFT_REDIRECT_URL']
    }

    # grab the path if available
    path = params['path'] || '/'
    
    # post request
    request = Net::HTTP::Post.new("/v1/oauth2/token")
    request.add_field('Content-Type', 'application/json')
    request.set_form_data(data)
    response = http.request(request)
    
    # get the token from the response
    result = JSON(response.body)
    
    @access_token = result["access_token"]
    @refresh_token = response["refresh_token"]
    
    # obtain user information and put into a hash
    
    user_uri = URI.parse("https://shift.com/v1/users/me")
    user_request = Net::HTTP::Get.new(user_uri.request_uri)
    user_request.add_field('Authorization', "Bearer #{@access_token}")
    user_response = http.request(user_request)
    
    user_data = JSON(user_response.body)
    
    #send_test_message(@access_token)
    
    shift_check_and_login(user_data, @access_token, path)
    
  end
  
  #----------------------------------------------------------------------#
  # function: shift_check_and_login
  # summary:  prepares data hash for user to sign in
  # author:   Duy
  #----------------------------------------------------------------------#
  def shift_check_and_login(user_hash, access_token, path = '/')
    auth_hash = {}
    data_hash = user_hash["data"][0]
    uid = data_hash["id"]
    user = User.where("providers.provider" => 'shift', "providers.uid" =>  uid).first
    
    # provider hash
    provider = {"provider" => "shift", "uid" => uid}
    
    # info hash
    info = {
      "info" => {
        'username' => data_hash['username'],
        'first_name' => data_hash['first_name'],
        'last_name' => data_hash['last_name'],
        'email' => data_hash['primary_email']['address'],
        'image' => data_hash['images'][0]['sizes']['default']
      }
    }
    
    # credentials hash
    credentials = {
      "credentials" => {
        "token" => access_token
      }
    }
    
    # extra info
    extra = {
      "extra" => {
        "title" => data_hash['title'],
        "company" => data_hash['company']
      }
    }
    
    # prepare data
    auth_hash = auth_hash.merge(provider)
    auth_hash = auth_hash.merge(info)
    auth_hash = auth_hash.merge(credentials)
    auth_hash = auth_hash.merge(extra)
    
    # authenticate user and redirect to the right path
    # this function is customized with your authentication system eg. Devise
    authenticate(auth_hash, path)
    
  end

shift_object_creation_worker.rb

# app/workers/shift_object_creation_worker.rb
# To create an SHIFT Object and Post the message to team feed via background job (Resque)

require "uri"
require "net/https"
require "json"


class ShiftCampaignCreateApi
  @queue = :shift_api
  def self.perform(campaign_id, access_token)
    
    campaign = Campaign.find(campaign_id)
    
    link = "campaigns/#{ campaign.slug }"
    
    # uri
    uri = URI.parse("https://shift.com")
    http = Net::HTTP.new(uri.host, uri.port)
    http.use_ssl = true
    http.verify_mode = OpenSSL::SSL::VERIFY_NONE
    
    # create a test object
    obj_hash = '{
      "url" : "'+link+'",
      "type" : "Campaign",
      "team" : "'+ENV['SHIFT_TEAM_ID']+'",
      "name" : "'+campaign.title+'"
    }'
    
    obj_uri = URI.parse("https://shift.com/v1/applications/#{ENV['SHIFT_APP_ID']}/objects")
    obj_request = Net::HTTP::Post.new(obj_uri.request_uri)
    obj_request.add_field("Content-Type", "application/json")
    obj_request.add_field("Authorization", "Bearer #{access_token}")
    obj_request.body = obj_hash
    
    obj_response = http.request(obj_request)
    
    obj_result = JSON(obj_response.body)
    
    obj_id = obj_result["data"][0]["id"]
    
    # Send a test message
    message_data = '{
    "addressed_users": [],'
    message_data += '
    "text": "Create a new Campaign {0}",'
    message_data += '
    "addressed_teams": [
      "'+ENV['SHIFT_TEAM_ID']+'"
      ],'
      message_data += '
      "mentions": [{"type": "appobject", "id": "'+obj_id+'", "name": "'+campaign.title+'"}]
      }'

    
    msg_uri = URI.parse("https://shift.com/v1/messages")
    msg_request = Net::HTTP::Post.new(msg_uri.request_uri)
    msg_request.add_field('Content-Type', 'application/json')
    msg_request.add_field('Authorization', "Bearer #{access_token}")
    msg_request.body = message_data
    
    msg_response = http.request(msg_request)
    
  end
  
end

shift_strategy.rb

# lib/shift_strategy.rb
# this is OPTIONAL if you want user to login not through SHIFT Website
# creates a omniauth strategry (provider) for OmniAuth

require 'omniauth/strategies/oauth2'
require 'base64'
require 'openssl'
require 'rack/utils'

module OmniAuth
  module Strategies
    class Shift < OmniAuth::Strategies::OAuth2
      class NoAuthorizationCodeError < StandardError; end
      
      option :client_options, {
        :site => 'https://shift.com',
        :authorize_url => "https://shift.com/v1/oauth2/auth",
        :token_url => '/v1/oauth2/token'
      }

      uid { raw_info['data'][0]['id'] }

      info do
        prune!({
          'username' => raw_info['data'][0]['username'],
          'first_name' => raw_info['data'][0]['first_name'],
          'last_name' => raw_info['data'][0]['last_name'],
          'email' => raw_info['data'][0]['primary_email']['address'],
          'image' => raw_info['data'][0]['images'][0]['sizes']['default']
          })
        end

        extra do
          hash = {}
          hash['raw_info'] = raw_info unless skip_info?
          prune! hash
        end

        def raw_info
          @raw_info ||= access_token.get('/v1/users/me').parsed || {}
        end


        def request_phase
          if request.params["access_token"]

            url = callback_url
            url << "?" unless url.match(/\?/)
            url << "&" unless url.match(/[\&\?]$/)
            url << query

            redirect url
          else
            super
          end
        end
        

        # NOTE if we're using code from the signed request
        # then FB sets the redirect_uri to '' during the authorize
        # phase + it must match during the access_token phase:
        # https://github.com/facebook/php-sdk/blob/master/src/base_facebook.php#L348
        def callback_url
          options[:callback_url] || super
        end


        
        private

 

        def prune!(hash)
          hash.delete_if do |_, value|
            prune!(value) if value.is_a?(Hash)
            value.nil? || (value.respond_to?(:empty?) && value.empty?)
          end
        end



      end
    end
  end