using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Collections;
using MQTTnet.Client;
using MQTTnet.Client.Options;
using MQTTnet;
using System.Reflection;
using MQTTnet.Client.Connecting;
using Tango.Core;
using MQTTnet.Packets;

namespace Tango.Telemetry.Destinations
{
    public class TelemetryMqttDestination : ExtendedObject, ITelemetryDestination
    {
        private IMqttClient _mqttClient;
        private IMqttClientOptions _mqttOptions;
        private DateTime _nextRealAvailabilityCheck;

        public string Name { get; set; } = "MQTT";
        public String Address { get; private set; }
        public int Port { get; private set; }
        public String Topic { get; private set; }

        public IReadOnlyList<TelemetrySourceTypes> SupportedSourceTypes { get; private set; }

        /// <summary>
        /// 
        /// </summary>
        /// <param name="topic">e.g machie/telemetry/serial number</param>
        /// <param name="address">Default localhost</param>
        /// <param name="port">Default 1883</param>
        public TelemetryMqttDestination(String topic, String address = "localhost", int port = 1883)
        {
            _nextRealAvailabilityCheck = DateTime.Now;
            Topic = topic;
            Address = address;
            Port = port;
            SupportedSourceTypes = new List<TelemetrySourceTypes>() { TelemetrySourceTypes.Streaming };
        }

        public async Task<bool> IsAvailable()
        {
            if (_mqttClient == null)
            {
                return await EnsureConnection();
            }
            else
            {
                if (DateTime.Now > _nextRealAvailabilityCheck)
                {
                    _nextRealAvailabilityCheck = DateTime.Now.AddMinutes(5);
                    return await EnsureConnection();
                }
                else
                {
                    return _mqttClient.IsConnected;
                } 
            }
        }

        private async Task<bool> EnsureConnection()
        {
            if (_mqttClient == null || !_mqttClient.IsConnected)
            {
                try
                {
                    var factory = new MqttFactory();
                    _mqttClient = factory.CreateMqttClient();

                    String exeName = Assembly.GetEntryAssembly().GetName().Name;
                    _mqttOptions = new MqttClientOptionsBuilder()
                        .WithClientId(exeName)
                        .WithTcpServer(Address, Port)
                        .WithCleanSession()
                        .Build();

                    var result = await _mqttClient.ConnectAsync(_mqttOptions);
                    if (result.ResultCode != MqttClientConnectResultCode.Success)
                    {
                        LogManager.Log(new Exception($"Error connecting to MQTT broker. {result.ResultCode}"));
                        return false;
                    }
                }
                catch (Exception ex)
                {
                    LogManager.Log(ex, "Error connecting to MQTT broker.");
                    return false;
                }
            }

            return true;
        }

        public async Task Publish(TelemetryPublishPackage package, List<KeyValuePair<String, String>> properties)
        {
            if (await EnsureConnection())
            {
                var message = new MqttApplicationMessageBuilder()
                       .WithTopic($"{Topic}/{package.PendingTelemetry.TelemetryObject.ToTelemetryName()}")
                       .WithPayload(package.ToPayload())
                       .WithExactlyOnceQoS()
                       .WithRetainFlag(false)
                       .Build();

                message.UserProperties = new List<MqttUserProperty>();

                foreach (var prop in properties)
                {
                    message.UserProperties.Add(new MqttUserProperty(prop.Key, prop.Value ?? String.Empty));
                }


                await _mqttClient.PublishAsync(message);
            }
        }

        public void Dispose()
        {
            _mqttClient?.Dispose();
        }

        public override string ToString()
        {
            return $"{Name} -> {Address}:{Port}";
        }
    }
}