KISSmetrics' use of Help Scout's dynamic apps. http://developer.helpscout.net/custom-apps/

helpscout.rb

require 'json'
require 'base64'
require 'hmac-sha1'
require 'httparty'
require 'models/user'
require 'app_config'

class HelpScout
  def initialize(auth_options={:basic_auth => {:username => AppConfig.default.helpscout["api_key"],
                                               :password => "X"}})
    @auth_options = auth_options
  end

  # Takes the conversation object that Help Scout posts and returns the User with the given email
  # http://developer.helpscout.net/objects/conversation/
  # http://developer.helpscout.net/custom-apps/
  #
  # @param body [String] a JSON message containing conversation data
  # @return [User] the User corresponding to the email address found, if any
  def parse_message_for_user(body)
    content = JSON.parse(body)
    
    if content['customer'] && content['customer']['email']
      customer_email = content['customer']['email']
    end
    User[:login => customer_email]
  end

  # Compares X-HelpScout-Signature against the signature generated from the secret key and request body
  # http://developer.helpscout.net/webhooks/
  #
  # @param body [String] a JSON message containing conversation data
  # @param header_signature [String] the computed X-HelpScout-Signature header
  # @return [Boolean] whether the signatures match
  def valid_signature?(body, header_signature)
    generate_body_signature(body) == header_signature.strip
  end

  private
  def generate_body_signature(body)
    hmac = HMAC::SHA1.new( AppConfig.default.helpscout["webhook_secret"] )
    hmac.update(body)
    signature = Base64.encode64(hmac.digest).strip
  end

  def build_helpscout_convo_request(number)
    HTTParty.get("https://api.helpscout.net/v1/conversations/#{number}.json", @auth_options)
  end
end

helpscout.routes.rb

require 'models/helpscout'

post '/admin.helpscout.dynamic' do
  body = request.body.read
  helpscout = HelpScout.new

  if helpscout.valid_signature?(body, env['HTTP_X_HELPSCOUT_SIGNATURE'])
    if @user = helpscout.parse_message_for_user(body)
      response = {:html => erubis(:'admin/support_issues/_helpscout_sidebar.html', :layout => false)}
    else
      response = {:html => "Can't find this user."}
    end
    status(200)
    body(response.to_json)
  else
    response = {:html => "Signature not verified."}
    status(403)
    body(response.to_json)
  end
end