using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.WebSockets;
using System.Security.Authentication;
using System.Text;
using System.Threading.Tasks;
using IronPython.Runtime;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using MQTTnet.Adapter;
using MQTTnet.AspNetCore;
using MQTTnet.Client.Publishing;
using MQTTnet.Implementations;
using MQTTnet.Protocol;
using MQTTnet.Server.Configuration;
using MQTTnet.Server.Scripting;
using MQTTnet.Server.Status;

namespace MQTTnet.Server.Mqtt
{
    public class MqttServerService
    {
        private readonly ILogger<MqttServerService> _logger;

        private readonly MqttSettingsModel _settings;
        private readonly MqttApplicationMessageInterceptor _mqttApplicationMessageInterceptor;
        private readonly MqttServerStorage _mqttServerStorage;
        private readonly MqttClientConnectedHandler _mqttClientConnectedHandler;
        private readonly MqttClientDisconnectedHandler _mqttClientDisconnectedHandler;
        private readonly MqttClientSubscribedTopicHandler _mqttClientSubscribedTopicHandler;
        private readonly MqttClientUnsubscribedTopicHandler _mqttClientUnsubscribedTopicHandler;
        private readonly MqttServerConnectionValidator _mqttConnectionValidator;
        private readonly IMqttServer _mqttServer;
        private readonly MqttSubscriptionInterceptor _mqttSubscriptionInterceptor;
        private readonly PythonScriptHostService _pythonScriptHostService;
        private readonly MqttWebSocketServerAdapter _webSocketServerAdapter;

        public MqttServerService(
            MqttSettingsModel mqttSettings,
            CustomMqttFactory mqttFactory,
            MqttClientConnectedHandler mqttClientConnectedHandler,
            MqttClientDisconnectedHandler mqttClientDisconnectedHandler,
            MqttClientSubscribedTopicHandler mqttClientSubscribedTopicHandler,
            MqttClientUnsubscribedTopicHandler mqttClientUnsubscribedTopicHandler,
            MqttServerConnectionValidator mqttConnectionValidator,
            MqttSubscriptionInterceptor mqttSubscriptionInterceptor,
            MqttApplicationMessageInterceptor mqttApplicationMessageInterceptor,
            MqttServerStorage mqttServerStorage,
            PythonScriptHostService pythonScriptHostService,
            ILogger<MqttServerService> logger)
        {
            _settings = mqttSettings ?? throw new ArgumentNullException(nameof(mqttSettings));
            _mqttClientConnectedHandler = mqttClientConnectedHandler ?? throw new ArgumentNullException(nameof(mqttClientConnectedHandler));
            _mqttClientDisconnectedHandler = mqttClientDisconnectedHandler ?? throw new ArgumentNullException(nameof(mqttClientDisconnectedHandler));
            _mqttClientSubscribedTopicHandler = mqttClientSubscribedTopicHandler ?? throw new ArgumentNullException(nameof(mqttClientSubscribedTopicHandler));
            _mqttClientUnsubscribedTopicHandler = mqttClientUnsubscribedTopicHandler ?? throw new ArgumentNullException(nameof(mqttClientUnsubscribedTopicHandler));
            _mqttConnectionValidator = mqttConnectionValidator ?? throw new ArgumentNullException(nameof(mqttConnectionValidator));
            _mqttSubscriptionInterceptor = mqttSubscriptionInterceptor ?? throw new ArgumentNullException(nameof(mqttSubscriptionInterceptor));
            _mqttApplicationMessageInterceptor = mqttApplicationMessageInterceptor ?? throw new ArgumentNullException(nameof(mqttApplicationMessageInterceptor));
            _mqttServerStorage = mqttServerStorage ?? throw new ArgumentNullException(nameof(mqttServerStorage));
            _pythonScriptHostService = pythonScriptHostService ?? throw new ArgumentNullException(nameof(pythonScriptHostService));
            _logger = logger ?? throw new ArgumentNullException(nameof(logger));

            _webSocketServerAdapter = new MqttWebSocketServerAdapter(mqttFactory.Logger.CreateChildLogger());

            var adapters = new List<IMqttServerAdapter>
            {
                new MqttTcpServerAdapter(mqttFactory.Logger.CreateChildLogger())
                {
                    TreatSocketOpeningErrorAsWarning = true // Opening other ports than for HTTP is not allows in Azure App Services.
                },
                _webSocketServerAdapter
            };

            _mqttServer = mqttFactory.CreateMqttServer(adapters);
        }

        public void Configure()
        {
            _pythonScriptHostService.RegisterProxyObject("publish", new Action<PythonDictionary>(Publish));

            _mqttServerStorage.Configure();

            _mqttServer.ClientConnectedHandler = _mqttClientConnectedHandler;
            _mqttServer.ClientDisconnectedHandler = _mqttClientDisconnectedHandler;
            _mqttServer.ClientSubscribedTopicHandler = _mqttClientSubscribedTopicHandler;
            _mqttServer.ClientUnsubscribedTopicHandler = _mqttClientUnsubscribedTopicHandler;

            _mqttServer.StartAsync(CreateMqttServerOptions()).GetAwaiter().GetResult();

            _logger.LogInformation("MQTT server started.");
        }

        public Task RunWebSocketConnectionAsync(WebSocket webSocket, HttpContext httpContext)
        {
            return _webSocketServerAdapter.RunWebSocketConnectionAsync(webSocket, httpContext);
        }

        public Task<IList<IMqttClientStatus>> GetClientStatusAsync()
        {
            return _mqttServer.GetClientStatusAsync();
        }

        public Task<IList<IMqttSessionStatus>> GetSessionStatusAsync()
        {
            return _mqttServer.GetSessionStatusAsync();
        }

        public Task ClearRetainedApplicationMessagesAsync()
        {
            return _mqttServer.ClearRetainedApplicationMessagesAsync();
        }

        public Task<IList<MqttApplicationMessage>> GetRetainedApplicationMessagesAsync()
        {
            return _mqttServer.GetRetainedApplicationMessagesAsync();
        }

        public Task<MqttClientPublishResult> PublishAsync(MqttApplicationMessage applicationMessage)
        {
            if (applicationMessage == null) throw new ArgumentNullException(nameof(applicationMessage));

            return _mqttServer.PublishAsync(applicationMessage);
        }

        private void Publish(PythonDictionary parameters)
        {
            try
            {
                var applicationMessageBuilder = new MqttApplicationMessageBuilder()
                    .WithTopic((string)parameters.get("topic", null))
                    .WithRetainFlag((bool)parameters.get("retain", false))
                    .WithQualityOfServiceLevel((MqttQualityOfServiceLevel)(int)parameters.get("qos", 0));

                var payload = parameters.get("payload", null);
                byte[] binaryPayload;

                if (payload == null)
                {
                    binaryPayload = new byte[0];
                }
                else if (payload is string stringPayload)
                {
                    binaryPayload = Encoding.UTF8.GetBytes(stringPayload);
                }
                else if (payload is ByteArray byteArray)
                {
                    binaryPayload = byteArray.ToArray();
                }
                else if (payload is IEnumerable<int> intArray)
                {
                    binaryPayload = intArray.Select(Convert.ToByte).ToArray();
                }
                else
                {
                    throw new NotSupportedException("Payload type not supported.");
                }

                applicationMessageBuilder = applicationMessageBuilder
                    .WithPayload(binaryPayload);

                var applicationMessage = applicationMessageBuilder.Build();

                _mqttServer.PublishAsync(applicationMessage).GetAwaiter().GetResult();
            }
            catch (Exception exception)
            {
                _logger.LogError(exception, "Error while publishing application message from server.");
            }
        }

        private IMqttServerOptions CreateMqttServerOptions()
        {
            var options = new MqttServerOptionsBuilder()
                .WithMaxPendingMessagesPerClient(_settings.MaxPendingMessagesPerClient)
                .WithDefaultCommunicationTimeout(TimeSpan.FromSeconds(_settings.CommunicationTimeout))
                .WithConnectionValidator(_mqttConnectionValidator)
                .WithApplicationMessageInterceptor(_mqttApplicationMessageInterceptor)
                .WithSubscriptionInterceptor(_mqttSubscriptionInterceptor)
                .WithStorage(_mqttServerStorage);

            // Configure unencrypted connections
            if (_settings.TcpEndPoint.Enabled)
            {
                options.WithDefaultEndpoint();

                if (_settings.TcpEndPoint.TryReadIPv4(out var address4))
                {
                    options.WithDefaultEndpointBoundIPAddress(address4);
                }

                if (_settings.TcpEndPoint.TryReadIPv6(out var address6))
                {
                    options.WithDefaultEndpointBoundIPV6Address(address6);
                }

                if (_settings.TcpEndPoint.Port > 0)
                {
                    options.WithDefaultEndpointPort(_settings.TcpEndPoint.Port);
                }
            }
            else
            {
                options.WithoutDefaultEndpoint();
            }

            // Configure encrypted connections
            if (_settings.EncryptedTcpEndPoint.Enabled)
            {
                options
                    .WithEncryptedEndpoint()
                    .WithEncryptionSslProtocol(SslProtocols.Tls12);
                
                if (!string.IsNullOrEmpty(_settings.EncryptedTcpEndPoint?.Certificate?.Path))
                {
                    IMqttServerCertificateCredentials certificateCredentials = null;

                    if (!string.IsNullOrEmpty(_settings.EncryptedTcpEndPoint?.Certificate?.Password))
                    {
                        certificateCredentials = new MqttServerCertificateCredentials
                        {
                            Password = _settings.EncryptedTcpEndPoint.Certificate.Password
                        };
                    }

                    options.WithEncryptionCertificate(_settings.EncryptedTcpEndPoint.Certificate.ReadCertificate(), certificateCredentials);
                }
                
                if (_settings.EncryptedTcpEndPoint.TryReadIPv4(out var address4))
                {
                    options.WithEncryptedEndpointBoundIPAddress(address4);
                }

                if (_settings.EncryptedTcpEndPoint.TryReadIPv6(out var address6))
                {
                    options.WithEncryptedEndpointBoundIPV6Address(address6);
                }

                if (_settings.EncryptedTcpEndPoint.Port > 0)
                {
                    options.WithEncryptedEndpointPort(_settings.EncryptedTcpEndPoint.Port);
                }
            }
            else
            {
                options.WithoutEncryptedEndpoint();
            }

            if (_settings.ConnectionBacklog > 0)
            {
                options.WithConnectionBacklog(_settings.ConnectionBacklog);
            }

            if (_settings.EnablePersistentSessions)
            {
                options.WithPersistentSessions();
            }

            return options.Build();
        }
    }
}