SNS.rb

class Notification
  require 'aws-sdk'
  require 'httparty'

  attr_accessor :message_info, :verifier, :message_body
  def initialize(message_body, logger)
    @message_info = JSON.parse(message_body)
    @message_body = message_body
    @verifier = ::Aws::SNS::MessageVerifier.new
    @logger = logger
  end

  def confirm!
    response = ::HTTParty.get(self.SubscribeURL)
    response.code == 200
  end

  def valid?
    @valid ||= @verifier.authentic?(@message_body)
  end

  def message
    @message ||= case JSON.parse(@message_info["Message"])["notificationType"]
    when "TYPE_A"
      CustomANotification.new(@message_info["Message"])
    when "Delivery"
      CustomBNotification.new(@message_info["Message"])
    else
      ""
    end
  end

  def method_missing(method_sym, *arguments, &block)
    @message_info.try(:[], method_sym.to_s)
  end

  def process
    case self.Type
    when "SubscriptionConfirmation"
      @logger.debug "Subscription Request - #{self.SubscribeURL}"
      self.confirm!
    when "Notification"
      self.message.process
    else
      @logger.debug "Unknown type: #{self.Type}"
    end
  end
end

class CustomANotification
  def initialize(message)
    @info = JSON.parse(message)
    @logger = Rails.configuration.aws_logger
  end

  def method_missing(method_sym, *arguments, &block)
    @info.try(:[], method_sym.to_s)
  end

  def process
    # Custom logic goes here (send a notification?)
  end
end