Web Push Package in Rails.

Gemfile

# The rubygems.org grocer-pushpackager needs a bump. Ride that <del>dragon</del> master.
gem 'grocer-pushpackager', git: 'git@github.com:layervault/grocer-pushpackager.git'

# Houston will help us send the notifications themselves.
gem 'houston'

push_notification_service_base.rb

# You're going to want to subclass this base class and override
# #payload, #custom_data, and #user.
# 
# We have something called a PushNotificationService::RepliedComment for
# example, which handles sending out the push notification when someone 
# replies to a comment on Designer News.
module PushNotificationService
  class Base
    def send!
      validate_payload!(payload)
      validate_custom_data!(custom_data)

      user.device_tokens.map do |device_token|
        notification = Houston::Notification.new(device: device_token.token)
        notification.alert = payload
        notification.custom_data = custom_data
        houston.push(notification)
        notification
      end
    end

    # { "title"=>"Hello, Doge!", "body"=>"Welcome to Designer News!", "action"=>"See More" }
    def payload
      raise "Attempted to call an abstract method!"
    end

    # { "aps" => { "url-args" => [@action, @object_id] } }
    def custom_data
      raise "Attempted to call an abstract method!"
    end

    def user
      raise "Attempted to call an abstract method!"
    end

    private

    def houston
      return @apn if @apn

      # So the annoying thing is, you'll need a .p12 certificate and a 
      # .pem-style certificate with my setup. If you're down with the OpenSSL,
      # you can get things down to a single certificate.
      @apn ||= Houston::Client.production
      @apn.certificate = File.read("/home/user/cert.pem")
      @apn.passphrase = "hellapassword!"
      @apn
    end

    def validate_payload!(payload)
      raise "'title' is required" unless payload['title']
      raise "'body' is required" unless payload['body']
    end

    def validate_custom_data!(custom_data)
      raise "['aps'] is required" unless custom_data['aps']
      raise "['aps']['url-args'] is required" unless custom_data['aps']['url-args']
      raise "url-ags must be of size 2" unless custom_data['aps']['url-args'].size == 2
      raise "url-args can only be strings" unless custom_data['aps']['url-args'][0].is_a?(String) && custom_data['aps']['url-args'][1].is_a?(String)
    end
  end
end

push_notifications_controller.rb

class PushNotificationsController < ApplicationController
  respond_to :html

  def validate
    respond_to do |format|
      format.html { send_data builder.buffer }
    end
  end
  
  def log
    logger.info params[:logs]

    respond_to do |format|
      format.html { head :ok }
    end
  end

  def register_device
    @user = aps_user || not_found

    unless DeviceToken.where(user_id: @user.id, token: params[:token]).exists?
      DeviceToken.create({
        user: @user,
        token: params[:token]
      })
    end

    respond_to do |format|
      format.html { head :ok }
    end
  end
  
  def unregister_device
    DeviceToken.where(user_id: aps_user.id, token: params[:token]).destroy

    respond_to do |format|
      format.html { head :ok }
    end
  end

  private

  def builder
    test_icon16   = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/16.png'))
    test_icon16r  = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/32.png'))
    test_icon32   = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/32.png'))
    test_icon32r  = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/64.png'))
    test_icon128  = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/128.png'))
    test_icon128r = File.open(File.join(Rails.root, 'app/assets/images/push_notification_badges/256.png'))
    @user = User.first
    @p12 = OpenSSL::PKCS12.new File.open(File.join(Rails.root, 'lib/designer_news.p12'), 'rb').read, "passwordyeahyeah"

    builder = Grocer::Pushpackager::Package.new({
      websiteName: 'Designer News',
      websitePushID: Rails.application.config.website_push_id,
      allowedDomains: ["https://news.layervault.com"],
      urlFormatString: "https://news.layervault.com/push_link/%@/%@",
      authenticationToken: user.push_notification_auth_token,
      webServiceURL: "https://news.layervault.com",
      certificate: @p12.certificate,
      key: @p12.key,
      iconSet: {
        :'16x16'      => test_icon16,
        :'16x16@2x'   => test_icon16r,
        :'32x32'      => test_icon32,
        :'32x32@2x'   => test_icon32r,
        :'128x128'    => test_icon128,
        :'128x128@2x' => test_icon128r
      }
    })
  end
  
  # This is pulling the user_id out of the user_info submitted with your
  # window.safari.pushNotification.requestPermission call. I use the following dictionary 
  # on the client-side: { "user_id": "1" }
  #
  # NOTE: Apple hates integers, so you should .toString() things in JS and .to_s things
  # in Rubby.
  def user
    User.find JSON.parse(request.body.read)['user_id']
  end

  # Apple includes an Authorization header that looks like this in their requests:
  #    Authorization: ApplePushNotifications <16-char auth_token>
  def aps_user
    User.find_by_cached_push_notification_auth_token request.headers["Authorization"].split(' ')[1]
  end
end

routes.rb

# Apple requires your endpoint to be /v1/...
scope controller: 'push_notifications', path: 'v1', format: :html, constraints: { website_push_id: /\w+\.\w+\.\w+\.\w+/ } do
  post    'pushPackages/:website_push_id', action: :validate
  post    'log', action: :log
  post    'devices/:token/registrations/:website_push_id', action: :register_device
  delete  'devices/:token/registrations/:website_push_id', action: :unregister_device
end

user.rb

class User
  def push_notification_auth_token
    return cached_push_notification_auth_token if cached_push_notification_auth_token

    # Apple requires auth tokens be at least 16-characters
    self.cached_push_notification_auth_token = SecureRandom.hex(16)
    save!

    self.cached_push_notification_auth_token
  end
end