How do I check whether a mobile device has already been registered

Question

I'm using the Amazon AWS Ruby SDK for Amazon SNS but I'm having some trouble with devices already being registered. Sometimes when a device gets registered again I get an error like AWS::SNS::Errors::InvalidParameter Invalid parameter: Token Reason: Endpoint arn:aws:sns:us-east-1:**** already exists with the same Token, but different attributes.. How do I check whether an endpoint already exists and more importantly, how do I get the endpoint for a given token?

Answer 1

Credit to BvdBijl's idea, I made an extension method to delete the existing one if found and then add it.

using System;
using System.Text.RegularExpressions;
using Amazon.SimpleNotificationService;
using Amazon.SimpleNotificationService.Model;

namespace Amazon.SimpleNotificationService
{
    public static class AmazonSimpleNotificationServiceClientExtensions
    {
        private const string existingEndpointRegexString = "Reason: Endpoint (.+) already exists with the same Token";
        private static Regex existingEndpointRegex = new Regex(existingEndpointRegexString);
        public static CreatePlatformEndpointResponse CreatePlatformEndpointIdempotent(
            this AmazonSimpleNotificationServiceClient client,
            CreatePlatformEndpointRequest request)
        {
            try
            {
                var result = client.CreatePlatformEndpoint(request);
                return result;
            }
            catch (AmazonSimpleNotificationServiceException e)
            {
                if (e.ErrorCode == "InvalidParameter")
                {
                    var match = existingEndpointRegex.Match(e.Message);
                    if (match.Success) {
                        string arn = match.Groups[1].Value;
                        client.DeleteEndpoint(new DeleteEndpointRequest
                        {
                             EndpointArn = arn,
                        });
                        return client.CreatePlatformEndpoint(request);
                    }
                }
                throw;
            }
        }
    }
}