using MQTTnet;
using MQTTnet.Client;
using System;
using System.Security.Authentication;
using System.Text;
using System.Threading;
using System.Threading.Tasks;

namespace HighWayIot.Mqtt
{
    public sealed class MqttClient
    {

        public delegate void PrintMessageReceived(string message);
        public event PrintMessageReceived PrintMessageReceivedEvent;

        private IMqttClient client;

        private static readonly Lazy<MqttClient> lazy = new Lazy<MqttClient>(() => new MqttClient());

        public static MqttClient Instance
        {
            get
            {
                return lazy.Value;
            }
        }

        private MqttClient() { }

        /// <summary>
        /// 链接服务器
        /// </summary>
        /// <param name="ip"></param>
        /// <param name="port"></param>
        /// <param name="clientId"></param>
        /// <param name="username"></param>
        /// <param name="password"></param>
        public async void Connect(string ip, int port, string clientId, string username, string password)
        {
            try
            {
                MqttClientOptions options = new MqttClientOptionsBuilder()
                .WithTcpServer(ip, port)
                .WithClientId(clientId)
                .WithCredentials(username, password)
                .WithTls(o =>   //开启ssl
                {
                    o.CertificateValidationHandler = _ => true;

                    o.SslProtocol = SslProtocols.Tls12;
                }).Build();
                client = new MqttFactory().CreateMqttClient();

                client.ApplicationMessageReceivedAsync += MqttClient_ApplicationMessageReceived;

                MqttClientConnectResult result = await client.ConnectAsync(options);

                if (result != null)
                {
                    if (result.ResultCode == MQTTnet.Client.MqttClientConnectResultCode.Success)
                    {
                        PrintMessageReceivedEvent?.Invoke($"连接服务器成功{ip}:{port}");
                    }
                    else
                    {
                        PrintMessageReceivedEvent?.Invoke($"连接服务器失败");
                    }
                }
            }
            catch (Exception ex)
            {
                PrintMessageReceivedEvent?.Invoke($"连接服务器异常：{ex.Message}");
            }
        }

        /// <summary>
        /// 断开链接
        /// </summary>
        public void DisConnect()
        {
            client.DisconnectAsync();
            PrintMessageReceivedEvent?.Invoke($"断开连接");
        }

        /// <summary>
        /// 订阅主题
        /// </summary>
        /// <param name="topic"></param>
        public async void SubscriptionAsync(string topic)
        {
            try
            {
                var mqttFactory = new MqttFactory();
                var mqttSubscribeOptions = mqttFactory.CreateSubscribeOptionsBuilder()
                    .WithTopicFilter(
                        f =>
                        {
                            f.WithTopic(topic);
                        })
                    .Build();

                MqttClientSubscribeResult result = await client.SubscribeAsync(mqttSubscribeOptions, CancellationToken.None);

                PrintMessageReceivedEvent?.Invoke($"订阅主题:{topic}");
            }
            catch (Exception ex)
            {
                PrintMessageReceivedEvent?.Invoke($"订阅主题异常:{ex.Message}");
            }
        }

        /// <summary>
        /// 取消订阅
        /// </summary>
        /// <param name="topic"></param>
        public void Unsubscribe(string topic)
        {
            client.UnsubscribeAsync(topic);
            PrintMessageReceivedEvent?.Invoke($"取消订阅，主题：{topic}");
        }

        /// <summary>
        /// 推送消息
        /// </summary>
        /// <param name="topic"></param>
        /// <param name="message"></param>
        public void Publish(string topic, string message)
        {
            try
            {
                var msg = new MqttApplicationMessageBuilder().WithTopic(topic).WithPayload(message)
                .Build();
                client.PublishAsync(msg, CancellationToken.None);
                PrintMessageReceivedEvent?.Invoke($"向服务端推送成功，主题：{topic}；内容：{message}");
            }
            catch (Exception ex)
            {
                PrintMessageReceivedEvent?.Invoke($"向服务端推送消息异常：{ex.Message}");
            }
        }

        private async Task MqttClient_ApplicationMessageReceived(MqttApplicationMessageReceivedEventArgs eventArgs)
        {
            var info = $"接收到主题：{eventArgs.ApplicationMessage.Topic}的消息，内容：{Encoding.UTF8.GetString(eventArgs.ApplicationMessage.Payload)}";
            PrintMessageReceivedEvent?.Invoke(info);
        }


    }
}