Verifies a payment that is being generated with PayPal's Mobile SDKs.

Verify payment

require 'paypal-sdk-rest'
require 'sinatra'

include PayPal::SDK::REST

get '/verify/:payment_id/:total/:currency' do
  payment_id = params[:payment_id]
  total = params[:total]
  currency = params[:currency]
  
  begin
    payment = Payment.find(payment_id)
    
    if payment.state == 'approved'
      transaction = payment.transactions.find{ |txn| txn.amount.total == total && txn.amount.currency == currency }
      if transaction
        sale = transaction.related_resources.find{ |res| res.sale.state == 'completed' }
        if sale
          "OK"
        else
          "ERROR - no sale"
        end
      else
        "ERROR - no transaction"
      end  
    else
      "ERROR - wrong state"
    end
  rescue
    "ERROR - no payment"
  end
end