app.rb

require "rubygems"
require "sinatra/base"
require "json"
require "sendgrid-ruby"
include SendGrid

class App < Sinatra::Base

  before do
    content_type :json
    headers 'Access-Control-Allow-Origin': '*',
            'Access-Control-Allow-Methods': ['OPTIONS', 'GET', 'POST'],
            'Access-Control-Allow-Headers': 'Content-Type'
  end

  set :protection, except: :http_origin

  helpers do

    def send_email(params, user)

      # create variables
      from = Email.new(email: params["email"], name: params["name"])
      to = Email.new(email: user.email, name: user.name)
      subject = params["subject"]
      content = Content.new(type: 'text/html', value: params["message"])

      # create email
      mail = Mail.new(from, subject, to, content)

      # instance sendgrid
      sendgrid = SendGrid::API.new(api_key: ENV['SENDGRID_API_KEY'])

      if ENV['SENDGRID_API_KEY']
        # send email
        response = sendgrid.client.mail._('send').post(request_body: mail.to_json)
        response.body
      else
        puts "Please add an environment variable for Mandrill Key"
      end
    end
  end

  options "/user" do
    200
  end

  post "/user" do
    content_type :json

    params = JSON.parse(request.body.read)

    user = User.first(uuid: params["uuid"])
    unless user
      halt 400, "Bad Request"
    end

    if user and params.keys.length == 5

      status = send_email(params, user)

      if status[0]['status'] != 'sent'
        return { message: "The message could not be sent" }.to_json
      else
        halt 200, {message: "Message Sent!"}.to_json
      end
    else
      halt 400, "Bad Request"
    end
  end

  post "/register" do
    user = User.first(email: params[:email])
    if user
      "The user is already registered"
    else
      @user = User.create(name: params[:name], email: params[:email], url: params[:url], uuid: UUID.generate)
      "Token: #{@user.uuid} "
    end
  end
end