A2U payments: Protect against double-paying (#5)

lib/errors.rb

@@ -17,5 +17,15 @@ def initialize(message, payment_id)
         @payment_id = payment_id
       end
     end
+
+    class TxidAlreadyLinkedError < StandardError
+      attr_reader :payment_id
+      attr_reader :txid
+
+      def initialize(message, payment_id, txid)
+        super(message)
+        @payment_id = payment_id
+        @txid = txid
+    end
   end
 end

lib/pi_network.rb

@@ -59,8 +59,10 @@ def create_payment(payment_data)
   def submit_payment(payment_id)
     payment = @open_payments[payment_id]
 
-    if payment.nil?
+    if payment.nil? || payment["identifier"] != payment_id
       payment = get_payment(payment_id)
+      txid = payment["transaction"]["txid"]
+      raise Errors::TxidAlreadyLinkedError.new("This payment already has a linked txid", payment_id, txid) if txid.present?
     end
 
     set_horizon_client(payment["network"])
@@ -89,6 +91,7 @@ def complete_payment(identifier, txid)
       http_headers
     )
 
+    @open_payments.delete(identifier)
     handle_http_response(response, "An unknown error occurred while completing the payment")
   end
 
@@ -99,6 +102,7 @@ def cancel_payment(identifier)
       http_headers,
     )
 
+    @open_payments.delete(identifier)
     handle_http_response(response, "An unknown error occurred while cancelling the payment")
   end