DomainConfiguration.cs

using System;
using System.Collections.Generic;
using System.Diagnostics;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Security.Cryptography;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Threading.Tasks;
using Waher.Content;
using Waher.Content.Binary;
using Waher.Content.Text;
using Waher.Content.Xml;
using Waher.Events;
using Waher.Networking;
using Waher.Networking.HTTP;
using Waher.Persistence;
using Waher.Persistence.Attributes;
using Waher.Runtime.Language;
using Waher.Runtime.Settings;
using Waher.Script;
using Waher.Security;
using Waher.Security.ACME;
using Waher.Security.PKCS;
 
namespace Waher.IoTGateway.Setup
{
    public class DomainConfiguration : SystemMultiStepConfiguration
    {
        private static DomainConfiguration instance = null;
 
        private HttpResource testDomainNames = null;
        private HttpResource testDomainName = null;
        private HttpResource testCA = null;
        private HttpResource acmeChallenge = null;
        private HttpResource saveNames = null;
        private HttpResource saveDescriptions = null;
 
        private AlternativeField[] localizedNames = null;
        private AlternativeField[] localizedDescriptions = null;
        private string[] alternativeDomains = null;
        private byte[] certificate = null;
        private byte[] privateKey = null;
        private byte[] pfx = null;
        private string humanReadableName = string.Empty;
        private string humanReadableNameLanguage = string.Empty;
        private string humanReadableDescription = string.Empty;
        private string humanReadableDescriptionLanguage = string.Empty;
        private string domain = string.Empty;
        private string acmeDirectory = string.Empty;
        private string contactEMail = string.Empty;
        private string urlToS = string.Empty;
        private string password = string.Empty;
        private string openSslPath = string.Empty;
        private string dynDnsTemplate = string.Empty;
        private string checkIpScript = string.Empty;
        private string updateIpScript = string.Empty;
        private string dynDnsAccount = string.Empty;
        private string dynDnsPassword = string.Empty;
        private int dynDnsInterval = 300;
        private bool useDomainName = false;
        private bool dynamicDns = false;
        private bool useEncryption = true;
        private bool customCA = false;
        private bool acceptToS = false;
 
        private string challenge = string.Empty;
        private string token = string.Empty;
 
        public static DomainConfiguration Instance => instance;
 
        [DefaultValueStringEmpty]
        public string Domain
        {
            get => this.domain;
            set => this.domain = value;
        }
 
        [DefaultValueNull]
        public string[] AlternativeDomains
        {
            get => this.alternativeDomains;
            set => this.alternativeDomains = value;
        }
 
        [DefaultValue(false)]
        public bool UseDomainName
        {
            get => this.useDomainName;
            set
            {
                this.useDomainName = value;
                if (!this.useDomainName)
                {
                    this.domain = string.Empty;
                    this.alternativeDomains = null;
                    this.dynamicDns = false;
                    this.useEncryption = false;
                    this.customCA = false;
                }
            }
        }
 
        [DefaultValue(false)]
        public bool DynamicDns
        {
            get => this.dynamicDns;
            set => this.dynamicDns = value;
        }
 
        [DefaultValue(true)]
        public bool UseEncryption
        {
            get => this.useEncryption;
            set => this.useEncryption = value;
        }
 
        [DefaultValue(false)]
        public bool CustomCA
        {
            get => this.customCA;
            set => this.customCA = value;
        }
 
        [DefaultValueStringEmpty]
        public string AcmeDirectory
        {
            get => this.acmeDirectory;
            set => this.acmeDirectory = value;
        }
 
        [DefaultValueStringEmpty]
        public string ContactEMail
        {
            get => this.contactEMail;
            set => this.contactEMail = value;
        }
 
        [DefaultValueStringEmpty]
        public string UrlToS
        {
            get => this.urlToS;
            set => this.urlToS = value;
        }
 
        [DefaultValue(false)]
        public bool AcceptToS
        {
            get => this.acceptToS;
            set => this.acceptToS = value;
        }
 
        [DefaultValueNull]
        public byte[] Certificate
        {
            get => this.certificate;
            set => this.certificate = value;
        }
 
        [DefaultValueNull]
        public byte[] PrivateKey
        {
            get => this.privateKey;
            set => this.privateKey = value;
        }
 
        [DefaultValueNull]
        public byte[] PFX
        {
            get => this.pfx;
            set => this.pfx = value;
        }
 
        [DefaultValueStringEmpty]
        public string Password
        {
            get => this.password;
            set => this.password = value;
        }
 
        [DefaultValueStringEmpty]
        public string OpenSslPath
        {
            get => this.openSslPath;
            set => this.openSslPath = value;
        }
 
        [DefaultValueStringEmpty]
        public string DynDnsTemplate
        {
            get => this.dynDnsTemplate;
            set => this.dynDnsTemplate = value;
        }
 
        [DefaultValueStringEmpty]
        public string CheckIpScript
        {
            get => this.checkIpScript;
            set => this.checkIpScript = value;
        }
 
        [DefaultValueStringEmpty]
        public string UpdateIpScript
        {
            get => this.updateIpScript;
            set => this.updateIpScript = value;
        }
 
        [DefaultValueStringEmpty]
        public string DynDnsAccount
        {
            get => this.dynDnsAccount;
            set => this.dynDnsAccount = value;
        }
 
        [DefaultValue(300)]
        public int DynDnsInterval
        {
            get => this.dynDnsInterval;
            set => this.dynDnsInterval = value;
        }
 
        [DefaultValueStringEmpty]
        public string DynDnsPassword
        {
            get => this.dynDnsPassword;
            set => this.dynDnsPassword = value;
        }
 
        [DefaultValueStringEmpty]
        public string HumanReadableName
        {
            get => this.humanReadableName;
            set => this.humanReadableName = value;
        }
 
        [DefaultValueStringEmpty]
        public string HumanReadableNameLanguage
        {
            get => this.humanReadableNameLanguage;
            set => this.humanReadableNameLanguage = value;
        }
 
        [DefaultValueStringEmpty]
        public string HumanReadableDescription
        {
            get => this.humanReadableDescription;
            set => this.humanReadableDescription = value;
        }
 
        [DefaultValueStringEmpty]
        public string HumanReadableDescriptionLanguage
        {
            get => this.humanReadableDescriptionLanguage;
            set => this.humanReadableDescriptionLanguage = value;
        }
 
        [DefaultValueNull]
        public AlternativeField[] LocalizedNames
        {
            get => this.localizedNames;
            set => this.localizedNames = value;
        }
 
        [DefaultValueNull]
        public AlternativeField[] LocalizedDescriptions
        {
            get => this.localizedDescriptions;
            set => this.localizedDescriptions = value;
        }
 
        public bool HasToS => !string.IsNullOrEmpty(this.urlToS);
 
        public override string Resource => "/Settings/Domain.md";
 
        public override int Priority => 200;
 
        public override Task<string> Title(Language Language)
        {
            return Language.GetStringAsync(typeof(Gateway), 3, "Domain");
        }
 
        public override Task ConfigureSystem()
        {
            return Gateway.ConfigureDomain(this);
        }
 
        public override void SetStaticInstance(ISystemConfiguration Configuration)
        {
            instance = Configuration as DomainConfiguration;
        }
 
        public override Task InitSetup(HttpServer WebServer)
        {
            this.testDomainNames = WebServer.Register("/Settings/TestDomainNames", null, this.TestDomainNames, true, false, true);
            this.testDomainName = WebServer.Register("/Settings/TestDomainName", this.TestDomainName, true, false, true);
            this.testCA = WebServer.Register("/Settings/TestCA", null, this.TestCA, true, false, true);
            this.acmeChallenge = WebServer.Register("/.well-known/acme-challenge", this.AcmeChallenge, true, true, true);
            this.saveNames = WebServer.Register("/Settings/SaveNames", null, this.SaveNames, true, false, true);
            this.saveDescriptions = WebServer.Register("/Settings/SaveDescriptions", null, this.SaveDescriptions, true, false, true);
 
            return base.InitSetup(WebServer);
        }
 
        public override Task UnregisterSetup(HttpServer WebServer)
        {
            WebServer.Unregister(this.testDomainNames);
            WebServer.Unregister(this.testDomainName);
            WebServer.Unregister(this.testCA);
            WebServer.Unregister(this.acmeChallenge);
            WebServer.Unregister(this.saveNames);
            WebServer.Unregister(this.saveDescriptions);
 
            return base.UnregisterSetup(WebServer);
        }
 
        protected override string ConfigPrivilege => "Admin.Communication.Domain";
 
        private async Task TestDomainNames(HttpRequest Request, HttpResponse Response)
        {
            Gateway.AssertUserAuthenticated(Request, this.ConfigPrivilege);
 
            if (!Request.HasData)
                throw new BadRequestException();
 
            object Obj = await Request.DecodeDataAsync();
            if (!(Obj is Dictionary<string, object> Parameters))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("domainName", out Obj) || !(Obj is string DomainName) ||
                !Parameters.TryGetValue("dynamicDns", out Obj) || !(Obj is bool DynamicDns) ||
                !Parameters.TryGetValue("dynDnsTemplate", out Obj) || !(Obj is string DynDnsTemplate) ||
                !Parameters.TryGetValue("checkIpScript", out Obj) || !(Obj is string CheckIpScript) ||
                !Parameters.TryGetValue("updateIpScript", out Obj) || !(Obj is string UpdateIpScript) ||
                !Parameters.TryGetValue("dynDnsAccount", out Obj) || !(Obj is string DynDnsAccount) ||
                !Parameters.TryGetValue("dynDnsPassword", out Obj) || !(Obj is string DynDnsPassword) ||
                !Parameters.TryGetValue("dynDnsInterval", out Obj) || !(Obj is int DynDnsInterval))
            {
                throw new BadRequestException();
            }
 
            if (string.Compare(DomainName, "localhost", true) == 0)
                throw new BadRequestException("localhost is not a valid domain name.");
 
            List<string> AlternativeNames = new List<string>();
            int Index = 0;
 
            while (Parameters.TryGetValue("altDomainName" + Index.ToString(), out Obj) && Obj is string AltDomainName && !string.IsNullOrEmpty(AltDomainName))
            {
                if (string.Compare(AltDomainName, "localhost", true) == 0)
                    throw new BadRequestException("localhost is not a valid domain name.");
 
                AlternativeNames.Add(AltDomainName);
                Index++;
            }
 
            if (Parameters.TryGetValue("altDomainName", out Obj) && Obj is string AltDomainName2 && !string.IsNullOrEmpty(AltDomainName2))
            {
                if (string.Compare(AltDomainName2, "localhost", true) == 0)
                    throw new BadRequestException("localhost is not a valid domain name.");
 
                AlternativeNames.Add(AltDomainName2);
            }
 
            string TabID = Request.Header["X-TabID"];
            if (string.IsNullOrEmpty(TabID))
                throw new BadRequestException();
 
            this.dynamicDns = DynamicDns;
            this.dynDnsTemplate = DynDnsTemplate;
            this.checkIpScript = CheckIpScript;
            this.updateIpScript = UpdateIpScript;
            this.dynDnsAccount = DynDnsAccount;
            this.dynDnsPassword = DynDnsPassword;
            this.dynDnsInterval = DynDnsInterval;
            this.domain = DomainName;
            this.alternativeDomains = AlternativeNames.Count == 0 ? null : AlternativeNames.ToArray();
            this.useDomainName = true;
 
            Response.StatusCode = 200;
 
            Task _ = Task.Run(async () => await this.Test(TabID, false));
        }
 
        private Task TestDomainName(HttpRequest Request, HttpResponse Response)
        {
            Response.StatusCode = 200;
            Response.ContentType = PlainTextCodec.DefaultContentType;
            return Response.Write(this.token);
        }
 
        private async Task<bool> Test(string TabID, bool EnvironmentSetup)
        {
            try
            {
                if (!string.IsNullOrEmpty(this.domain))
                {
                    if (!await this.Test(TabID, EnvironmentSetup, this.domain))
                    {
                        if (string.IsNullOrEmpty(TabID))
                            this.LogEnvironmentError("Domain name not valid.", GATEWAY_DOMAIN_NAME, this.domain);
                        else
                            await ClientEvents.PushEvent(new string[] { TabID }, "NameNotValid", this.domain, false, "User");
                        return false;
                    }
                }
 
                if (!(this.alternativeDomains is null))
                {
                    foreach (string AltDomainName in this.alternativeDomains)
                    {
                        if (!await this.Test(TabID, EnvironmentSetup, AltDomainName))
                        {
                            if (string.IsNullOrEmpty(TabID))
                                this.LogEnvironmentError("Alternative domain name not valid.", GATEWAY_DOMAIN_ALT, AltDomainName);
                            else
                                await ClientEvents.PushEvent(new string[] { TabID }, "NameNotValid", AltDomainName, false, "User");
                            return false;
                        }
                    }
                }
 
                if (this.Step < 1)
                    this.Step = 1;
 
                this.Updated = DateTime.Now;
                await Database.Update(this);
 
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "NamesOK", string.Empty, false, "User");
 
                return true;
            }
            catch (Exception ex)
            {
                if (string.IsNullOrEmpty(TabID))
                    Log.Exception(ex);
                else
                    await ClientEvents.PushEvent(new string[] { TabID }, "ShowStatus", ex.Message, false, "User");
 
                return false;
            }
        }
 
        internal Task<bool> CheckDynamicIp()
        {
            return this.CheckDynamicIp(null, false);
        }
 
        internal Task<bool> CheckDynamicIp(bool EnvironmentSetup)
        {
            return this.CheckDynamicIp(null, EnvironmentSetup);
        }
 
        private async Task<bool> CheckDynamicIp(string TabID, bool EnvironmentSetup)
        {
            try
            {
                if (!this.useDomainName || !this.dynamicDns)
                    return true;
 
                bool Result = true;
 
                if (!await this.CheckDynamicIp(TabID, this.domain, EnvironmentSetup))
                    Result = false;
 
                foreach (string AlternativeDomain in this.alternativeDomains)
                {
                    if (!await this.CheckDynamicIp(TabID, AlternativeDomain, EnvironmentSetup))
                        Result = false;
                }
 
                return Result;
            }
            catch (Exception ex)
            {
                Log.Exception(ex);
                return false;
            }
        }
 
        internal async Task<bool> CheckDynamicIp(string TabID, string DomainName, bool EnvironmentSetup)
        {
            string Msg = await this.CheckDynamicIp(DomainName, EnvironmentSetup, async (_, Status) =>
            {
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "ShowStatus", Status, false, "User");
            });
 
            if (!string.IsNullOrEmpty(Msg))
            {
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "CertificateError", Msg, false, "User");
 
                return false;
            }
 
            return true;
        }
 
        public async Task<string> CheckDynamicIp(string DomainName, bool EnvironmentSetup, EventHandlerAsync<string> Status)
        {
            if (!this.dynamicDns)
                return null;
 
            Expression CheckIpScript;
            Expression UpdateIpScript;
 
            try
            {
                CheckIpScript = new Expression(this.checkIpScript);
            }
            catch (Exception ex)
            {
                string Msg = "Unable to parse script checking current IP Address: " + ex.Message;
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(Msg, GATEWAY_DYNDNS_CHECK, this.checkIpScript);
 
                return Msg;
            }
 
            try
            {
                UpdateIpScript = new Expression(this.updateIpScript);
            }
            catch (Exception ex)
            {
                string Msg = "Unable to parse script updating the dynamic DNS server: " + ex.Message;
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(Msg, GATEWAY_DYNDNS_UPDATE, this.updateIpScript);
 
                return Msg;
            }
 
            await Status.Raise(this, "Checking current IP Address.");
 
            Variables Variables = HttpServer.CreateVariables();
            object Result;
 
            try
            {
                Result = await CheckIpScript.EvaluateAsync(Variables);
            }
            catch (Exception ex)
            {
                string Msg = "Unable to get current IP Address: " + ex.Message;
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(Msg, GATEWAY_DYNDNS_CHECK, this.checkIpScript);
 
                return Msg;
            }
 
            if (!(Result is string CurrentIP) || !IPAddress.TryParse(CurrentIP, out IPAddress _))
            {
                string Msg = "Unable to get current IP Address. Unexpected response.";
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(Msg, GATEWAY_DYNDNS_CHECK, this.checkIpScript);
 
                return Msg;
            }
 
            await Status.Raise(this, "Current IP Address: " + CurrentIP);
 
            string LastIP = await RuntimeSettings.GetAsync("Last.IP." + DomainName, string.Empty);
 
            if (LastIP == CurrentIP)
                await Status.Raise(this, "IP Address has not changed for " + DomainName + ".");
            else
            {
                try
                {
                    await Status.Raise(this, "Updating IP address for " + DomainName + " to " + CurrentIP + ".");
 
                    Variables["Account"] = this.dynDnsAccount;
                    Variables["Password"] = this.dynDnsPassword;
                    Variables["IP"] = CurrentIP;
                    Variables["Domain"] = DomainName;
 
                    Result = await UpdateIpScript.EvaluateAsync(Variables);
 
                    await RuntimeSettings.SetAsync("Last.IP." + DomainName, CurrentIP);
                }
                catch (Exception ex)
                {
                    string Msg = "Unable to register new dynamic IP Address: " + ex.Message;
 
                    if (EnvironmentSetup)
                        this.LogEnvironmentError(Msg, GATEWAY_DYNDNS_UPDATE, this.updateIpScript);
 
                    return Msg;
                }
            }
 
            return null;
        }
 
        private async Task<bool> Test(string TabID, bool EnvironmentSetup, string DomainName)
        {
            string Msg = await this.Test(DomainName, EnvironmentSetup, async (_, Status) =>
            {
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "ShowStatus", Status, false, "User");
            });
 
            if (!string.IsNullOrEmpty(Msg))
            {
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "CertificateError", Msg, false, "User");
 
                return false;
            }
 
            return true;
        }
 
        public async Task<string> Test(string DomainName, bool EnvironmentSetup, EventHandlerAsync<string> Status)
        {
            await Status.Raise(this, "Testing " + DomainName + "...");
 
            string Msg = await this.CheckDynamicIp(DomainName, EnvironmentSetup, Status);
            if (!string.IsNullOrEmpty(Msg))
                return Msg;
 
            this.token = Hashes.BinaryToString(Gateway.NextBytes(32));
 
            using (HttpClient HttpClient = new HttpClient()
            {
                Timeout = TimeSpan.FromMilliseconds(10000)
            })
            {
                try
                {
                    StringBuilder Url = new StringBuilder();
                    int[] HttpPorts = Gateway.GetConfigPorts("HTTP");
 
                    Url.Append("http://");
                    Url.Append(DomainName);
 
                    if (Array.IndexOf(HttpPorts, 80) < 0 && HttpPorts.Length > 0)
                    {
                        Url.Append(':');
                        Url.Append(HttpPorts[0].ToString());
                    }
 
                    Url.Append("/Settings/TestDomainName");
 
                    HttpResponseMessage Response = await HttpClient.GetAsync("http://" + DomainName + "/Settings/TestDomainName");
                    if (!Response.IsSuccessStatusCode)
                    {
                        return "Domain name does not point to this machine.";
                    }
 
                    byte[] Bin = await Response.Content.ReadAsByteArrayAsync();
                    string Token = System.Text.Encoding.ASCII.GetString(Bin);
 
                    if (Token != this.token)
                        return "Unexpected response returned. Domain name does not point to this machine.";
                }
                catch (TimeoutException)
                {
                    return "Time-out. Check that the domain name points to this machine.";
                }
                catch (Exception ex)
                {
                    return "Unable to validate domain name: " + ex.Message;
                }
            }
 
            await Status.Raise(this, "Domain name valid.");
 
            return null;
        }
 
        private async Task TestCA(HttpRequest Request, HttpResponse Response)
        {
            Gateway.AssertUserAuthenticated(Request, this.ConfigPrivilege);
 
            if (!Request.HasData)
                throw new BadRequestException();
 
            object Obj = await Request.DecodeDataAsync();
            if (!(Obj is Dictionary<string, object> Parameters))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("useEncryption", out Obj) || !(Obj is bool UseEncryption))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("customCA", out Obj) || !(Obj is bool CustomCA))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("acmeDirectory", out Obj) || !(Obj is string AcmeDirectory))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("contactEMail", out Obj) || !(Obj is string ContactEMail))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("acceptToS", out Obj) || !(Obj is bool AcceptToS))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("domainName", out Obj) || !(Obj is string DomainName) ||
                !Parameters.TryGetValue("dynamicDns", out Obj) || !(Obj is bool DynamicDns) ||
                !Parameters.TryGetValue("dynDnsTemplate", out Obj) || !(Obj is string DynDnsTemplate) ||
                !Parameters.TryGetValue("checkIpScript", out Obj) || !(Obj is string CheckIpScript) ||
                !Parameters.TryGetValue("updateIpScript", out Obj) || !(Obj is string UpdateIpScript) ||
                !Parameters.TryGetValue("dynDnsAccount", out Obj) || !(Obj is string DynDnsAccount) ||
                !Parameters.TryGetValue("dynDnsPassword", out Obj) || !(Obj is string DynDnsPassword) ||
                !Parameters.TryGetValue("dynDnsInterval", out Obj) || !(Obj is int DynDnsInterval))
                throw new BadRequestException();
 
            List<string> AlternativeNames = new List<string>();
            int Index = 0;
 
            while (Parameters.TryGetValue("altDomainName" + Index.ToString(), out Obj) && Obj is string AltDomainName && !string.IsNullOrEmpty(AltDomainName))
            {
                AlternativeNames.Add(AltDomainName);
                Index++;
            }
 
            if (Parameters.TryGetValue("altDomainName", out Obj) && Obj is string AltDomainName2 && !string.IsNullOrEmpty(AltDomainName2))
                AlternativeNames.Add(AltDomainName2);
 
            string TabID = Request.Header["X-TabID"];
            if (string.IsNullOrEmpty(TabID))
                throw new BadRequestException();
 
            this.dynamicDns = DynamicDns;
            this.dynDnsTemplate = DynDnsTemplate;
            this.checkIpScript = CheckIpScript;
            this.updateIpScript = UpdateIpScript;
            this.dynDnsAccount = DynDnsAccount;
            this.dynDnsPassword = DynDnsPassword;
            this.dynDnsInterval = DynDnsInterval;
            this.domain = DomainName;
            this.alternativeDomains = AlternativeNames.Count == 0 ? null : AlternativeNames.ToArray();
            this.useDomainName = true;
            this.useEncryption = UseEncryption;
            this.customCA = CustomCA;
            this.acmeDirectory = AcmeDirectory;
            this.contactEMail = ContactEMail;
            this.acceptToS = AcceptToS;
 
            Response.StatusCode = 200;
 
            if (!this.inProgress)
            {
                this.inProgress = true;
                Task _ = Task.Run(async () =>
                {
                    try
                    {
                        await this.CreateCertificate(TabID, false);
                    }
                    catch (Exception ex)
                    {
                        Log.Exception(ex);
                    }
                });
            }
        }
 
        private bool inProgress = false;
 
        public async Task<string> AddDomain(string Name, EventHandlerAsync<string> Status)
        {
            if (this.IsDomainRegistered(Name))
                return "Domain already registered.";
 
            string Msg = await this.Test(Name, false, Status);
            if (!string.IsNullOrEmpty(Msg))
                return Msg;
 
            string DomainBak = this.domain;
            bool UseDomainBak = this.useDomainName;
            string[] AlternativeBak = this.alternativeDomains;
 
            if (string.IsNullOrEmpty(this.domain))
            {
                this.domain = Name;
                this.useDomainName = true;
            }
            else if (this.alternativeDomains is null)
                this.alternativeDomains = new string[] { Name };
            else
            {
                int c = this.alternativeDomains.Length;
                string[] NewArray = new string[c + 1];
                this.alternativeDomains.CopyTo(NewArray, 0);
                NewArray[c] = Name;
                this.alternativeDomains = NewArray;
            }
 
            Msg = await this.CreateCertificate(false, Status, (_, __) => Task.CompletedTask);
            if (!string.IsNullOrEmpty(Msg))
            {
                this.domain = DomainBak;
                this.useDomainName = UseDomainBak;
                this.alternativeDomains = AlternativeBak;
 
                return Msg;
            }
 
            this.Updated = DateTime.Now;
            await Database.Update(this);
 
            return null;
        }
 
        public async Task<string> RemoveDomain(string Name, EventHandlerAsync<string> Status)
        {
            if (!this.IsDomainRegistered(Name))
                return "Domain not registered.";
 
            string DomainBak = this.domain;
            bool UseDomainBak = this.useDomainName;
            string[] AlternativeBak = this.alternativeDomains;
            string[] NewArray;
 
            if (string.Compare(this.domain, Name, true) == 0)
            {
                if ((this.alternativeDomains?.Length ?? 0) == 0)
                {
                    this.domain = string.Empty;
                    this.useDomainName = false;
                }
                else
                {
                    this.domain = this.alternativeDomains[0];
 
                    int c = this.alternativeDomains.Length;
 
                    if (c == 1)
                        this.alternativeDomains = null;
                    else
                    {
                        NewArray = new string[c - 1];
                        Array.Copy(this.alternativeDomains, 1, NewArray, 0, c - 1);
                        this.alternativeDomains = NewArray;
                    }
                }
            }
            else if (!(this.alternativeDomains is null))
            {
                int c = this.alternativeDomains.Length;
                if (c == 1)
                    this.alternativeDomains = null;
                else
                {
                    int i = Array.IndexOf(this.alternativeDomains, Name);
 
                    NewArray = new string[c - 1];
 
                    if (i > 0)
                        Array.Copy(this.alternativeDomains, 0, NewArray, 0, i);
 
                    if (i < c - 1)
                        Array.Copy(this.alternativeDomains, i + 1, NewArray, i, c - i - 1);
 
                    this.alternativeDomains = NewArray;
                }
            }
 
            if (this.useDomainName)
            {
                string Msg = await this.CreateCertificate(false, Status, (_, __) => Task.CompletedTask);
                if (!string.IsNullOrEmpty(Msg))
                {
                    this.domain = DomainBak;
                    this.useDomainName = UseDomainBak;
                    this.alternativeDomains = AlternativeBak;
 
                    return Msg;
                }
            }
 
            this.Updated = DateTime.Now;
            await Database.Update(this);
 
            return null;
        }
 
        public bool IsDomainRegistered(string Name)
        {
            if (string.Compare(Name, this.domain, true) == 0)
                return true;
 
            if (this.alternativeDomains is null)
                return false;
 
            foreach (string Alternative in this.alternativeDomains)
            {
                if (string.Compare(Name, Alternative, true) == 0)
                    return true;
            }
 
            return false;
        }
 
        internal Task<bool> CreateCertificate()
        {
            return this.CreateCertificate(null, false);
        }
 
        private async Task<bool> CreateCertificate(string TabID, bool EnvironmentSetup)
        {
            try
            {
                string Msg = await this.CreateCertificate(EnvironmentSetup,
                    async (_, Status) =>
                    {
                        if (!string.IsNullOrEmpty(TabID))
                            await ClientEvents.PushEvent(new string[] { TabID }, "ShowStatus", Status, false, "User");
                    },
                    async (_, URL) =>
                    {
                        if (!string.IsNullOrEmpty(TabID))
                            await ClientEvents.PushEvent(new string[] { TabID }, "TermsOfService", URL, false, "User");
                    });
 
                if (string.IsNullOrEmpty(Msg))
                {
                    if (!string.IsNullOrEmpty(TabID))
                        await ClientEvents.PushEvent(new string[] { TabID }, "CertificateOk", string.Empty, false, "User");
 
                    return true;
                }
                else
                {
                    if (!string.IsNullOrEmpty(TabID))
                        await ClientEvents.PushEvent(new string[] { TabID }, "CertificateError", Msg, false, "User");
 
                    return false;
                }
            }
            catch (Exception ex)
            {
                if (!string.IsNullOrEmpty(TabID))
                    await ClientEvents.PushEvent(new string[] { TabID }, "CertificateError", ex.Message, false, "User");
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(ex.Message, GATEWAY_ENCRYPTION, this.useEncryption);
 
                return false;
            }
        }
 
        internal async Task<string> CreateCertificate(bool EnvironmentSetup, EventHandlerAsync<string> Status,
            EventHandlerAsync<string> TermsOfService)
        {
            try
            {
                string URL = this.customCA ? this.acmeDirectory : "https://acme-v02.api.letsencrypt.org/directory";
                RSAParameters Parameters;
                CspParameters CspParams = new CspParameters()
                {
                    Flags = CspProviderFlags.UseMachineKeyStore,
                    KeyContainerName = "IoTGateway:" + URL
                };
 
                try
                {
                    bool Ok;
 
                    using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(4096, CspParams))
                    {
                        Parameters = RSA.ExportParameters(true);
 
                        if (RSA.KeySize < 4096)
                        {
                            RSA.PersistKeyInCsp = false;
                            RSA.Clear();
                            Ok = false;
                        }
                        else
                            Ok = true;
                    }
 
                    if (!Ok)
                    {
                        using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(4096, CspParams))
                        {
                            Parameters = RSA.ExportParameters(true);
                        }
                    }
                }
                catch (CryptographicException ex)
                {
                    throw new CryptographicException("Unable to get access to cryptographic key for \"IoTGateway:" + URL +
                        "\". Was the database created using another user?", ex);
                }
 
                using (AcmeClient Client = new AcmeClient(new Uri(URL), Parameters))
                {
                    await Status.Raise(this, "Connecting to directory.");
 
                    AcmeDirectory AcmeDirectory = await Client.GetDirectory();
 
                    if (AcmeDirectory.ExternalAccountRequired)
                        await Status.Raise(this, "An external account is required.");
 
                    if (!(AcmeDirectory.TermsOfService is null))
                    {
                        URL = AcmeDirectory.TermsOfService.ToString();
                        await Status.Raise(this, "Terms of service available on: " + URL);
                        await TermsOfService.Raise(this, URL);
 
                        this.urlToS = URL;
 
                        if (!this.acceptToS)
                        {
                            string Msg = "You need to accept the terms of service.";
 
                            if (EnvironmentSetup)
                                this.LogEnvironmentError(Msg, GATEWAY_ACME_ACCEPT_TOS, this.acceptToS);
 
                            return Msg;
                        }
                    }
 
                    if (!(AcmeDirectory.Website is null))
                        await Status.Raise(this, "Web site available on: " + AcmeDirectory.Website.ToString());
 
                    await Status.Raise(this, "Getting account.");
 
                    List<string> Names = new List<string>();
 
                    if (!string.IsNullOrEmpty(this.domain))
                        Names.Add(this.domain);
 
                    if (!(this.alternativeDomains is null))
                    {
                        foreach (string Name in this.alternativeDomains)
                        {
                            if (!Names.Contains(Name))
                                Names.Add(Name);
                        }
                    }
                    string[] DomainNames = Names.ToArray();
 
                    AcmeAccount Account;
 
                    try
                    {
                        Account = await Client.GetAccount();
 
                        await Status.Raise(this, "Account found.");
                        await Status.Raise(this, "Created: " + Account.CreatedAt.ToString());
                        await Status.Raise(this, "Initial IP: " + Account.InitialIp);
                        await Status.Raise(this, "Status: " + Account.Status.ToString());
 
                        if (string.IsNullOrEmpty(this.contactEMail))
                        {
                            if (!(Account.Contact is null) && Account.Contact.Length != 0)
                            {
                                await Status.Raise(this, "Updating contact URIs in account.");
                                Account = await Account.Update(new string[0]);
                                await Status.Raise(this, "Account updated.");
                            }
                        }
                        else
                        {
                            if (Account.Contact is null || Account.Contact.Length != 1 || Account.Contact[0] != "mailto:" + this.contactEMail)
                            {
                                await Status.Raise(this, "Updating contact URIs in account.");
                                Account = await Account.Update(new string[] { "mailto:" + this.contactEMail });
                                await Status.Raise(this, "Account updated.");
                            }
                        }
                    }
                    catch (AcmeAccountDoesNotExistException)
                    {
                        await Status.Raise(this, "Account not found.");
                        await Status.Raise(this, "Creating account.");
 
                        Account = await Client.CreateAccount(string.IsNullOrEmpty(this.contactEMail) ? new string[0] : new string[] { "mailto:" + this.contactEMail },
                            this.acceptToS);
 
                        await Status.Raise(this, "Account created.");
                        await Status.Raise(this, "Status: " + Account.Status.ToString());
                    }
 
                    await Status.Raise(this, "Generating new key.");
                    await Account.NewKey();
 
                    using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(4096, CspParams))
                    {
                        RSA.ImportParameters(Client.ExportAccountKey(true));
                    }
 
                    await Status.Raise(this, "New key generated.");
 
                    await Status.Raise(this, "Creating order.");
                    AcmeOrder Order;
 
                    try
                    {
                        Order = await Account.OrderCertificate(DomainNames, null, null);
                    }
                    catch (AcmeMalformedException)  // Not sure why this is necessary. Perhaps because it takes time to propagate the keys correctly on the remote end?
                    {
                        await Task.Delay(5000);
                        await Status.Raise(this, "Retrying.");
                        Order = await Account.OrderCertificate(DomainNames, null, null);
                    }
 
                    await Status.Raise(this, "Order created.");
 
                    AcmeAuthorization[] Authorizations;
 
                    await Status.Raise(this, "Getting authorizations.");
                    try
                    {
                        Authorizations = await Order.GetAuthorizations();
                    }
                    catch (AcmeMalformedException)  // Not sure why this is necessary. Perhaps because it takes time to propagate the keys correctly on the remote end?
                    {
                        await Task.Delay(5000);
                        await Status.Raise(this, "Retrying.");
                        Authorizations = await Order.GetAuthorizations();
                    }
 
                    foreach (AcmeAuthorization Authorization in Authorizations)
                    {
                        await Status.Raise(this, "Processing authorization for " + Authorization.Value);
 
                        AcmeChallenge Challenge;
                        bool Acknowledged = false;
                        int Index = 1;
                        int NrChallenges = Authorization.Challenges.Length;
 
                        for (Index = 1; Index <= NrChallenges; Index++)
                        {
                            Challenge = Authorization.Challenges[Index - 1];
 
                            if (Challenge is AcmeHttpChallenge HttpChallenge)
                            {
                                this.challenge = "/" + HttpChallenge.Token;
                                this.token = HttpChallenge.KeyAuthorization;
 
                                await Status.Raise(this, "Acknowleding challenge.");
 
                                string Msg = await this.CheckDynamicIp(Authorization.Value, EnvironmentSetup, Status);
                                if (string.IsNullOrEmpty(Msg))
                                {
                                    Challenge = await HttpChallenge.AcknowledgeChallenge();
                                    await Status.Raise(this, "Challenge acknowledged: " + Challenge.Status.ToString());
 
                                    Acknowledged = true;
                                }
                                else
                                    return Msg;
                            }
                        }
 
                        if (!Acknowledged)
                        {
                            string Msg = "No automated method found to respond to any of the authorization challenges.";
 
                            if (EnvironmentSetup)
                                this.LogEnvironmentError(Msg, GATEWAY_ENCRYPTION, this.useEncryption);
 
                            return Msg;
                        }
 
                        AcmeAuthorization Authorization2 = Authorization;
 
                        do
                        {
                            await Status.Raise(this, "Waiting to poll authorization status.");
                            await Task.Delay(5000);
 
                            await Status.Raise(this, "Polling authorization.");
                            Authorization2 = await Authorization2.Poll();
 
                            await Status.Raise(this, "Authorization polled: " + Authorization2.Status.ToString());
                        }
                        while (Authorization2.Status == AcmeAuthorizationStatus.pending);
 
                        if (Authorization2.Status != AcmeAuthorizationStatus.valid)
                        {
                            switch (Authorization2.Status)
                            {
                                case AcmeAuthorizationStatus.deactivated:
                                    throw new Exception("Authorization deactivated.");
 
                                case AcmeAuthorizationStatus.expired:
                                    throw new Exception("Authorization expired.");
 
                                case AcmeAuthorizationStatus.invalid:
                                    throw new Exception("Authorization invalid.");
 
                                case AcmeAuthorizationStatus.revoked:
                                    throw new Exception("Authorization revoked.");
 
                                default:
                                    throw new Exception("Authorization not validated.");
                            }
                        }
                    }
 
                    using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider(4096))   // TODO: Make configurable
                    {
                        await Status.Raise(this, "Finalizing order.");
 
                        SignatureAlgorithm SignAlg = new RsaSha256(RSA);
 
                        Order = await Order.FinalizeOrder(new CertificateRequest(SignAlg)
                        {
                            CommonName = this.domain,
                            SubjectAlternativeNames = DomainNames,
                            EMailAddress = this.contactEMail
                        });
 
                        await Status.Raise(this, "Order finalized: " + Order.Status.ToString());
 
                        if (Order.Status != AcmeOrderStatus.valid)
                        {
                            switch (Order.Status)
                            {
                                case AcmeOrderStatus.invalid:
                                    throw new Exception("Order invalid.");
 
                                default:
                                    throw new Exception("Unable to validate order.");
                            }
                        }
 
                        if (Order.Certificate is null)
                            throw new Exception("No certificate URI provided.");
 
                        await Status.Raise(this, "Downloading certificate.");
 
                        X509Certificate2[] Certificates = await Order.DownloadCertificate();
                        X509Certificate2 Certificate = Certificates[0];
 
                        await Status.Raise(this, "Exporting certificate.");
 
                        this.certificate = Certificate.Export(X509ContentType.Cert);
                        this.privateKey = RSA.ExportCspBlob(true);
                        this.pfx = null;
                        this.password = string.Empty;
 
                        await Status.Raise(this, "Adding private key.");
 
                        try
                        {
                            Certificate.PrivateKey = RSA;
                        }
                        catch (PlatformNotSupportedException)
                        {
                            await Status.Raise(this, "Platform does not support adding of private key.");
                            await Status.Raise(this, "Searching for OpenSSL on machine.");
 
                            string[] Files;
                            string Password = Hashes.BinaryToString(Gateway.NextBytes(32));
                            string CertFileName = null;
                            string CertFileName2 = null;
                            string KeyFileName = null;
 
                            if (string.IsNullOrEmpty(this.openSslPath) || !File.Exists(this.openSslPath))
                            {
                                string[] Folders = Gateway.GetFolders(new Environment.SpecialFolder[]
                                    {
                                        Environment.SpecialFolder.ProgramFiles,
                                        Environment.SpecialFolder.ProgramFilesX86
                                    },
                                    Path.DirectorySeparatorChar + "OpenSSL-Win32",
                                    Path.DirectorySeparatorChar + "OpenSSL-Win64");
 
                                Files = Gateway.FindFiles(Folders, "openssl.exe", 2, int.MaxValue);
                            }
                            else
                                Files = new string[] { this.openSslPath };
 
                            try
                            {
                                if (Files.Length == 0)
                                {
                                    string Msg = "Unable to join certificate with private key. Try installing <a target=\"_blank\" href=\"https://wiki.openssl.org/index.php/Binaries\">OpenSSL</a> and try again.";
 
                                    if (EnvironmentSetup)
                                        this.LogEnvironmentError(Msg, GATEWAY_ENCRYPTION, this.useEncryption);
 
                                    return Msg;
                                }
                                else
                                {
                                    foreach (string OpenSslFile in Files)
                                    {
                                        if (CertFileName is null)
                                        {
                                            await Status.Raise(this, "Generating temporary certificate file.");
 
                                            StringBuilder PemOutput = new StringBuilder();
                                            byte[] Bin = Certificate.Export(X509ContentType.Cert);
 
                                            PemOutput.AppendLine("-----BEGIN CERTIFICATE-----");
                                            PemOutput.AppendLine(Convert.ToBase64String(Bin, Base64FormattingOptions.InsertLineBreaks));
                                            PemOutput.AppendLine("-----END CERTIFICATE-----");
 
                                            CertFileName = Path.Combine(Gateway.AppDataFolder, "Certificate.pem");
                                            await Resources.WriteAllTextAsync(CertFileName, PemOutput.ToString(), System.Text.Encoding.ASCII);
 
                                            await Status.Raise(this, "Generating temporary key file.");
 
                                            DerEncoder KeyOutput = new DerEncoder();
                                            SignAlg.ExportPrivateKey(KeyOutput);
 
                                            PemOutput.Clear();
                                            PemOutput.AppendLine("-----BEGIN RSA PRIVATE KEY-----");
                                            PemOutput.AppendLine(Convert.ToBase64String(KeyOutput.ToArray(), Base64FormattingOptions.InsertLineBreaks));
                                            PemOutput.AppendLine("-----END RSA PRIVATE KEY-----");
 
                                            KeyFileName = Path.Combine(Gateway.AppDataFolder, "Certificate.key");
 
                                            await Resources.WriteAllTextAsync(KeyFileName, PemOutput.ToString(), System.Text.Encoding.ASCII);
                                        }
 
                                        await Status.Raise(this, "Converting to PFX using " + OpenSslFile);
 
                                        Process P = new Process()
                                        {
                                            StartInfo = new ProcessStartInfo()
                                            {
                                                FileName = OpenSslFile,
                                                Arguments = "pkcs12 -nodes -export -out Certificate.pfx -inkey Certificate.key -in Certificate.pem -password pass:" + Password,
                                                UseShellExecute = false,
                                                RedirectStandardError = true,
                                                RedirectStandardOutput = true,
                                                WorkingDirectory = Gateway.AppDataFolder,
                                                CreateNoWindow = true,
                                                WindowStyle = ProcessWindowStyle.Hidden
                                            }
                                        };
 
                                        P.Start();
 
                                        if (!P.WaitForExit(60000) || P.ExitCode != 0)
                                        {
                                            if (!P.StandardOutput.EndOfStream)
                                                await Status.Raise(this, "Output: " + P.StandardOutput.ReadToEnd());
 
                                            if (!P.StandardError.EndOfStream)
                                                await Status.Raise(this, "Error: " + P.StandardError.ReadToEnd());
 
                                            continue;
                                        }
 
                                        await Status.Raise(this, "Loading PFX.");
 
                                        CertFileName2 = Path.Combine(Gateway.AppDataFolder, "Certificate.pfx");
                                        this.pfx = await Resources.ReadAllBytesAsync(CertFileName2);
                                        this.password = Password;
                                        this.openSslPath = OpenSslFile;
 
                                        await Status.Raise(this, "PFX successfully generated using OpenSSL.");
                                        break;
                                    }
 
                                    if (this.pfx is null)
                                    {
                                        this.openSslPath = string.Empty;
 
                                        string Msg = "Unable to convert to PFX using OpenSSL.";
 
                                        if (EnvironmentSetup)
                                            this.LogEnvironmentError(Msg, GATEWAY_ENCRYPTION, this.useEncryption);
 
                                        return Msg;
                                    }
                                }
                            }
                            finally
                            {
                                if (!(CertFileName is null) && File.Exists(CertFileName))
                                {
                                    await Status.Raise(this, "Deleting temporary certificate file.");
                                    File.Delete(CertFileName);
                                }
 
                                if (!(KeyFileName is null) && File.Exists(KeyFileName))
                                {
                                    await Status.Raise(this, "Deleting temporary key file.");
                                    File.Delete(KeyFileName);
                                }
 
                                if (!(CertFileName2 is null) && File.Exists(CertFileName2))
                                {
                                    await Status.Raise(this, "Deleting temporary pfx file.");
                                    File.Delete(CertFileName2);
                                }
                            }
                        }
 
 
                        if (this.Step < 2)
                            this.Step = 2;
 
                        this.Updated = DateTime.Now;
                        await Database.Update(this);
 
                        await Gateway.UpdateCertificate(this);
 
                        return null;
                    }
                }
            }
            catch (Exception ex)
            {
                Log.Exception(ex);
 
                string Msg = "Unable to create certificate: " + XML.HtmlValueEncode(ex.Message);
 
                if (EnvironmentSetup)
                    this.LogEnvironmentError(Msg, GATEWAY_ENCRYPTION, this.useEncryption);
 
                return Msg;
            }
            finally
            {
                this.inProgress = false;
            }
        }
 
        private Task AcmeChallenge(HttpRequest Request, HttpResponse Response)
        {
            if (Request.SubPath != this.challenge)
                throw new NotFoundException("ACME Challenge not found.");
 
            Response.StatusCode = 200;
            Response.ContentType = BinaryCodec.DefaultContentType;
            return Response.Write(System.Text.Encoding.ASCII.GetBytes(this.token));
        }
 
        private async Task SaveNames(HttpRequest Request, HttpResponse Response)
        {
            Gateway.AssertUserAuthenticated(Request, this.ConfigPrivilege);
 
            if (!Request.HasData)
                throw new BadRequestException();
 
            object Obj = await Request.DecodeDataAsync();
            if (!(Obj is Dictionary<string, object> Parameters))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("humanReadableName", out Obj) ||
                !(Obj is string HumanReadableName) ||
                !Parameters.TryGetValue("humanReadableNameLanguage", out Obj) ||
                !(Obj is string HumanReadableNameLanguage))
            {
                throw new BadRequestException();
            }
 
            List<AlternativeField> LocalizedNames = new List<AlternativeField>();
            int Index = 1;
 
            while (Parameters.TryGetValue("nameLanguage" + Index.ToString(), out Obj) &&
                Obj is string NameLanguage &&
                Parameters.TryGetValue("nameLocalized" + Index.ToString(), out Obj) &&
                Obj is string NameLocalized)
            {
                if (string.IsNullOrEmpty(NameLanguage))
                    throw new BadRequestException("Language cannot be empty.");
 
                if (string.IsNullOrEmpty(NameLocalized))
                    throw new BadRequestException("Localized name cannot be empty.");
 
                LocalizedNames.Add(new AlternativeField(NameLanguage, NameLocalized));
                Index++;
            }
 
            this.HumanReadableName = HumanReadableName;
            this.HumanReadableNameLanguage = HumanReadableNameLanguage;
            this.LocalizedNames = LocalizedNames.ToArray();
 
            this.Updated = DateTime.Now;
            await Database.Update(this);
        }
 
        private async Task SaveDescriptions(HttpRequest Request, HttpResponse Response)
        {
            Gateway.AssertUserAuthenticated(Request, this.ConfigPrivilege);
 
            if (!Request.HasData)
                throw new BadRequestException();
 
            object Obj = await Request.DecodeDataAsync();
            if (!(Obj is Dictionary<string, object> Parameters))
                throw new BadRequestException();
 
            if (!Parameters.TryGetValue("humanReadableDescription", out Obj) ||
                !(Obj is string HumanReadableDescription) ||
                !Parameters.TryGetValue("humanReadableDescriptionLanguage", out Obj) ||
                !(Obj is string HumanReadableDescriptionLanguage))
            {
                throw new BadRequestException();
            }
 
            List<AlternativeField> LocalizedDescriptions = new List<AlternativeField>();
            int Index = 1;
 
            while (Parameters.TryGetValue("descriptionLanguage" + Index.ToString(), out Obj) &&
                Obj is string DescriptionLanguage &&
                Parameters.TryGetValue("descriptionLocalized" + Index.ToString(), out Obj) &&
                Obj is string DescriptionLocalized)
            {
                if (string.IsNullOrEmpty(DescriptionLanguage))
                    throw new BadRequestException("Language cannot be empty.");
 
                if (string.IsNullOrEmpty(DescriptionLocalized))
                    throw new BadRequestException("Localized description cannot be empty.");
 
                LocalizedDescriptions.Add(new AlternativeField(DescriptionLanguage, DescriptionLocalized));
                Index++;
            }
 
            this.HumanReadableDescription = HumanReadableDescription;
            this.HumanReadableDescriptionLanguage = HumanReadableDescriptionLanguage;
            this.LocalizedDescriptions = LocalizedDescriptions.ToArray();
 
            this.Updated = DateTime.Now;
            await Database.Update(this);
        }
 
        public override Task<bool> SimplifiedConfiguration()
        {
            return Task.FromResult(true);
        }
 
        public const string GATEWAY_DOMAIN_USE = nameof(GATEWAY_DOMAIN_USE);
 
        public const string GATEWAY_DOMAIN_NAME = nameof(GATEWAY_DOMAIN_NAME);
 
        // If a Domain Name is configured(<see cref="GATEWAY_DOMAIN"/> variable), the following variables define its operation:
 
        public const string GATEWAY_DOMAIN_ALT = nameof(GATEWAY_DOMAIN_ALT);
 
        public const string GATEWAY_DYNDNS = nameof(GATEWAY_DYNDNS);
 
        public const string GATEWAY_ENCRYPTION = nameof(GATEWAY_ENCRYPTION);
 
        public const string GATEWAY_CA_CUSTOM = nameof(GATEWAY_CA_CUSTOM);
 
        public const string GATEWAY_ACME_EMAIL = nameof(GATEWAY_ACME_EMAIL);
 
        public const string GATEWAY_ACME_ACCEPT_TOS = nameof(GATEWAY_ACME_ACCEPT_TOS);
 
        public const string GATEWAY_HR_NAME = nameof(GATEWAY_HR_NAME);
 
        public const string GATEWAY_HR_NAME_LANG = nameof(GATEWAY_HR_NAME_LANG);
 
        public const string GATEWAY_HR_DESC = nameof(GATEWAY_HR_DESC);
 
        public const string GATEWAY_HR_DESC_LANG = nameof(GATEWAY_HR_DESC_LANG);
 
        public const string GATEWAY_HR_NAME_LOC = nameof(GATEWAY_HR_NAME_LOC);
 
        public const string GATEWAY_HR_NAME_ = nameof(GATEWAY_HR_NAME_);
 
        public const string GATEWAY_HR_DESC_LOC = nameof(GATEWAY_HR_DESC_LOC);
 
        public const string GATEWAY_HR_DESC_ = nameof(GATEWAY_HR_DESC_);
 
        // If Dynamic DNS is configured (<see cref="GATEWAY_DYNDNS"/> variable), the following variables define its operation:
 
        public const string GATEWAY_DYNDNS_TEMPLATE = nameof(GATEWAY_DYNDNS_TEMPLATE);
 
        public const string GATEWAY_DYNDNS_CHECK = nameof(GATEWAY_DYNDNS_CHECK);
 
        public const string GATEWAY_DYNDNS_UPDATE = nameof(GATEWAY_DYNDNS_UPDATE);
 
        public const string GATEWAY_DYNDNS_ACCOUNT = nameof(GATEWAY_DYNDNS_ACCOUNT);
 
        public const string GATEWAY_DYNDNS_PASSWORD = nameof(GATEWAY_DYNDNS_PASSWORD);
 
        public const string GATEWAY_DYNDNS_INTERVAL = nameof(GATEWAY_DYNDNS_INTERVAL);
 
        // If a Custom Certificate Authority is configured(<see cref="GATEWAY_CA_CUSTOM"/> variable), the following variables define its operation:
 
        public const string GATEWAY_ACME_DIRECTORY = nameof(GATEWAY_ACME_DIRECTORY);
 
        public override async Task<bool> EnvironmentConfiguration()
        {
            if (!this.TryGetEnvironmentVariable(GATEWAY_DOMAIN_USE, false, out this.useDomainName))
                return false;
 
            if (!this.useDomainName)
            {
                this.Domain = string.Empty;
                this.DynamicDns = false;
                this.UseEncryption = false;
                this.CustomCA = false;
                this.ContactEMail = string.Empty;
                this.AcceptToS = false;
            }
            else
            {
                if (!this.TryGetEnvironmentVariable(GATEWAY_DOMAIN_NAME, true, out string Value))
                    return true;
 
                if (string.Compare(Value, "localhost", true) == 0)
                {
                    this.LogEnvironmentError("localhost is not a valid domain name.", GATEWAY_DOMAIN_NAME, Value);
                    return false;
                }
 
                this.Domain = Value;
 
                Value = Environment.GetEnvironmentVariable(GATEWAY_DOMAIN_ALT);
                if (string.IsNullOrEmpty(Value))
                    this.AlternativeDomains = null;
                else
                {
                    string[] Parts = Value.Split(',');
 
                    foreach (string Part in Parts)
                    {
                        if (string.Compare(Part, "localhost", true) == 0)
                        {
                            this.LogEnvironmentError("localhost is not a valid alternative domain name.", GATEWAY_DOMAIN_ALT, Value);
                            return false;
                        }
                    }
 
                    this.AlternativeDomains = Parts;
                }
 
                if (!this.TryGetEnvironmentVariable(GATEWAY_DYNDNS, out this.dynamicDns, false))
                    return false;
 
                if (this.dynamicDns)
                {
                    if (!this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_TEMPLATE, true, out Value))
                        return false;
 
                    this.DynDnsTemplate = Value;
 
                    if (!this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_CHECK, true, out Value))
                        return false;
 
                    this.CheckIpScript = Value;
 
                    if (!this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_UPDATE, true, out Value))
                        return false;
 
                    this.UpdateIpScript = Value;
 
                    this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_ACCOUNT, false, out this.dynDnsAccount);
                    this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_PASSWORD, false, out this.dynDnsPassword);
 
                    if (!this.TryGetEnvironmentVariable(GATEWAY_DYNDNS_UPDATE, 60, 86400, true, ref this.dynDnsInterval))
                        return false;
                }
 
                if (!this.TryGetEnvironmentVariable(GATEWAY_ENCRYPTION, true, out this.useEncryption))
                    return false;
 
                if (this.useEncryption)
                {
                    if (!this.TryGetEnvironmentVariable(GATEWAY_CA_CUSTOM, out this.customCA, false))
                        return false;
 
                    if (this.customCA)
                    {
                        if (!this.TryGetEnvironmentVariable(GATEWAY_ACME_DIRECTORY, true, out this.acmeDirectory))
                            return false;
                    }
 
                    if (!this.TryGetEnvironmentVariable(GATEWAY_ACME_EMAIL, true, out this.contactEMail))
                        return false;
 
                    if (!this.TryGetEnvironmentVariable(GATEWAY_ACME_ACCEPT_TOS, true, out this.acceptToS))
                        return false;
                }
            }
 
            AlternativeField LocalizedString = this.GetLocalizedEnvironmentVariable(GATEWAY_HR_NAME, GATEWAY_HR_NAME_LANG);
            if (LocalizedString is null)
                return false;
 
            this.HumanReadableName = LocalizedString.Value;
            this.HumanReadableNameLanguage = LocalizedString.Key;
 
            LocalizedString = this.GetLocalizedEnvironmentVariable(GATEWAY_HR_DESC, GATEWAY_HR_DESC_LANG);
            if (LocalizedString is null)
                return false;
 
            this.HumanReadableDescription = LocalizedString.Value;
            this.HumanReadableDescriptionLanguage = LocalizedString.Key;
 
            this.localizedNames = this.GetLocalizedEnvironmentVariables(GATEWAY_HR_NAME_LOC, GATEWAY_HR_NAME_);
            if (this.localizedNames is null)
                return false;
 
            this.localizedDescriptions = this.GetLocalizedEnvironmentVariables(GATEWAY_HR_DESC_LOC, GATEWAY_HR_DESC_);
            if (this.localizedDescriptions is null)
                return false;
 
            if (!await this.Test(null, true))                                                           // Tests domain names.
                return false;
 
            if (this.dynamicDns && !await this.CheckDynamicIp(true))                                    // Tests dynamic DNS settings.
                return false;
 
            if (this.useEncryption && this.useDomainName && !await this.CreateCertificate(null, true))  // Creates certificate.
                return false;
 
            return true;
        }
 
        private AlternativeField GetLocalizedEnvironmentVariable(string VariableName, string LanguageVariableName)
        {
            if (!this.TryGetEnvironmentVariable(VariableName, true, out string Value) ||
                !this.TryGetEnvironmentVariable(LanguageVariableName, true, out string Language))
            {
                return null;
            }
 
            return new AlternativeField(Value, Language);
        }
 
        private AlternativeField[] GetLocalizedEnvironmentVariables(string CollectionVariableName, string VariableName)
        {
            List<AlternativeField> Result = new List<AlternativeField>();
 
            string Value = Environment.GetEnvironmentVariable(CollectionVariableName);
            if (!string.IsNullOrEmpty(Value))
            {
                string[] Languages = Value.Split(',');
                string Name;
 
                foreach (string Language in Languages)
                {
                    Name = VariableName + Language;
 
                    if (!this.TryGetEnvironmentVariable(Name, true, out Value))
                        return null;
 
                    Result.Add(new AlternativeField(Language, Value));
                }
            }
 
            return Result.ToArray();
        }
 
    }
}