using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using MQTTnet.Core.Exceptions;
using MQTTnet.Core.Protocol;

namespace MQTTnet.Core
{
    public class MqttApplicationMessageBuilder
    {
        private MqttQualityOfServiceLevel _qualityOfServiceLevel = MqttQualityOfServiceLevel.AtMostOnce;
        private string _topic;
        private byte[] _payload;
        private bool _retain;
        
        public MqttApplicationMessageBuilder WithTopic(string topic)
        {
            _topic = topic;
            return this;
        }

        public MqttApplicationMessageBuilder WithPayload(IEnumerable<byte> payload)
        {
            if (payload == null)
            {
                _payload = null;
                return this;
            }

            _payload = payload.ToArray();
            return this;
        }

        public MqttApplicationMessageBuilder WithPayload(MemoryStream payload)
        {
            if (payload == null)
            {
                _payload = null;
                return this;
            }

            if (payload.Length == 0)
            {
                _payload = new byte[0];
            }
            else
            {
                _payload = new byte[payload.Length - payload.Position];
                payload.Read(_payload, 0, _payload.Length);
            }

            return this;
        }

        public MqttApplicationMessageBuilder WithPayload(string payload)
        {
            if (payload == null)
            {
                _payload = null;
                return this;
            }

            _payload = string.IsNullOrEmpty(payload) ? new byte[0] : Encoding.UTF8.GetBytes(payload);
            return this;
        }

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

        public MqttApplicationMessageBuilder WithRetainFlag(bool value = true)
        {
            _retain = value;
            return this;
        }

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

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

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

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

            return new MqttApplicationMessage(_topic, _payload ?? new byte[0], _qualityOfServiceLevel, _retain);
        }
    }
}