MQTTnet/Source/MQTTnet/TopicFilterBuilder.cs

using MQTTnet.Exceptions;
using MQTTnet.Protocol;

namespace MQTTnet
{
    public class TopicFilterBuilder
    {
        private MqttQualityOfServiceLevel _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
        private string _topic;

        public TopicFilterBuilder WithTopic(string topic)
        {
            _topic = topic;
            return this;
        }

        public TopicFilterBuilder WithQualityOfServiceLevel(MqttQualityOfServiceLevel qualityOfServiceLevel)
        {
            _qualityOfServiceLevel = qualityOfServiceLevel;
            return this;
        }

        public TopicFilterBuilder WithAtLeastOnceQoS()
        {
            _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtLeastOnce;
            return this;
        }

        public TopicFilterBuilder WithAtMostOnceQoS()
        {
            _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
            return this;
        }

        public TopicFilterBuilder WithExactlyOnceQoS()
        {
            _qualityOfServiceLevel = MqttQualityOfServiceLevel.ExactlyOnce;
            return this;
        }

        public TopicFilter Build()
        {
            if (string.IsNullOrEmpty(_topic))
            {
                throw new MqttProtocolViolationException("Topic is not set.");
            }

            return new TopicFilter { Topic = _topic, QualityOfServiceLevel = _qualityOfServiceLevel };
        }
    }
}