ChatViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using EDaler;
using EDaler.Uris;
using NeuroAccessMaui.Resources.Languages;
using NeuroAccessMaui.Services;
using NeuroAccessMaui.Services.Notification;
using NeuroAccessMaui.Services.UI;
using NeuroAccessMaui.Services.UI.QR;
using NeuroAccessMaui.UI.Converters;
using NeuroAccessMaui.UI.Pages.Contacts.Chat.Controls;
using NeuroAccessMaui.UI.Pages.Contacts.MyContacts;
using NeuroAccessMaui.UI.Pages.Contracts.MyContracts;
using NeuroAccessMaui.UI.Pages.Contracts.ViewContract;
using NeuroAccessMaui.UI.Pages.Identity.ViewIdentity;
using NeuroAccessMaui.UI.Pages.Things.MyThings;
using NeuroAccessMaui.UI.Pages.Wallet;
using NeuroAccessMaui.UI.Pages.Wallet.MyTokens;
using NeuroAccessMaui.UI.Pages.Wallet.MyWallet.ObjectModels;
using NeuroAccessMaui.UI.Pages.Wallet.SendPayment;
using NeuroAccessMaui.UI.Pages.Wallet.TokenDetails;
using NeuroAccessMaui.UI.Popups.Xmpp.SubscribeTo;
using NeuroFeatures;
using SkiaSharp;
using System.ComponentModel;
using System.Globalization;
using System.Security.Cryptography;
using System.Text;
using System.Timers;
using System.Xml;
using Waher.Content;
using Waher.Content.Html;
using Waher.Content.Markdown;
using Waher.Content.Xml;
using Waher.Networking.XMPP;
using Waher.Networking.XMPP.Contracts;
using Waher.Networking.XMPP.HttpFileUpload;
using Waher.Persistence;
using Waher.Persistence.Filters;
 
namespace NeuroAccessMaui.UI.Pages.Contacts.Chat
{
    public partial class ChatViewModel : XmppViewModel, IChatView, ILinkableView
    {
        private readonly SortedDictionary<string, LinkedListNode<MessageRecord>> messagesByObjectId = [];
        private readonly LinkedList<MessageRecord> messages = [];
        private readonly LinkedList<MessageFrame> frames = [];
        private readonly ChatPage page;
        private readonly object synchObject = new();
        private TaskCompletionSource<bool> waitUntilBound = new();
        private IView? scrollTo;
 
        private class MessageRecord(ChatMessage Message, LinkedListNode<MessageFrame> FrameNode)
        {
            public ChatMessage Message = Message;
            public LinkedListNode<MessageFrame> FrameNode = FrameNode;
 
            public DateTime Created => this.Message.Created;
            public MessageType MessageType => this.Message.MessageType;
        }
 
        public ChatViewModel(ChatPage Page, ChatNavigationArgs? Args)
            : base()
        {
            this.page = Page;
            this.LegalId = Args?.LegalId ?? string.Empty;
            this.BareJid = Args?.BareJid ?? string.Empty;
            this.FriendlyName = Args?.FriendlyName ?? string.Empty;
            this.UniqueId = Args?.UniqueId;
 
            this.XmppUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.Xmpp));
            this.IotIdUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.IotId));
            this.IotScUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.IotSc));
            this.NeuroFeatureUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.NeuroFeature));
            this.IotDiscoUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.IotDisco));
            this.EDalerUriClicked = new Command(async Parameter => await this.ExecuteUriClicked(Parameter as string ?? "", UriScheme.EDaler));
            this.HyperlinkClicked = new Command(async Parameter => await ExecuteHyperlinkClicked(Parameter));
        }
 
        public Command XmppUriClicked { get; }
 
        public Command IotIdUriClicked { get; }
 
        public Command IotScUriClicked { get; }
 
        public Command NeuroFeatureUriClicked { get; }
 
        public Command IotDiscoUriClicked { get; }
 
        public Command EDalerUriClicked { get; }
 
        public Command HyperlinkClicked { get; }
 
        private static async Task ExecuteHyperlinkClicked(object Parameter)
        {
            if (Parameter is not string Url)
                return;
 
            await App.OpenUrlAsync(Url);
        }
 
 
        public override async Task OnInitializeAsync()
        {
            await base.OnInitializeAsync();
 
            this.scrollTo = await this.LoadMessagesAsync(false);
 
            this.waitUntilBound.TrySetResult(true);
 
            await ServiceRef.NotificationService.DeleteEvents(NotificationEventType.Contacts, this.BareJid);
 
        }
 
        public override async Task OnDisposeAsync()
        {
            await base.OnDisposeAsync();
 
            this.waitUntilBound = new TaskCompletionSource<bool>();
        }
 
        private Task Page_OnAfterAppearing(object Sender, EventArgs e)
        {
            if (this.scrollTo is Element)
            {
            //  await Task.Delay(100);  // TODO: Why is this necessary? ScrollToAsync does not scroll to end element without it...
 
            //  await this.page.ScrollView.ScrollToAsync(this.page.Bottom, ScrollToPosition.End, false);
                this.scrollTo = null;
            }
 
            return Task.CompletedTask;
        }
 
        [ObservableProperty]
        private string? uniqueId;
 
        [ObservableProperty]
        private string? bareJid;
 
        [ObservableProperty]
        private string? legalId;
 
        [ObservableProperty]
        private string? friendlyName;
 
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(SendCommand))]
        [NotifyCanExecuteChangedFor(nameof(CancelCommand))]
        private string markdownInput = string.Empty;
 
        protected override void OnPropertyChanged(PropertyChangedEventArgs e)
        {
            base.OnPropertyChanged(e);
 
            switch (e.PropertyName)
            {
                case nameof(this.MarkdownInput):
                    this.IsWriting = !string.IsNullOrEmpty(this.MarkdownInput);
                    break;
 
                case nameof(this.MessageId):
                    this.IsWriting = !string.IsNullOrEmpty(this.MessageId);
                    break;
 
                case nameof(this.IsWriting):
                    this.IsButtonExpanded = false;
                    break;
 
                case nameof(this.IsRecordingAudio):
                    // TODO: Audio
                    //
                    //this.IsRecordingPaused = audioRecorder.Value.IsPaused;
                    this.IsWriting = this.IsRecordingAudio;
 
                    //if (audioRecorderTimer is null)
                    //{
                    //  audioRecorderTimer = new System.Timers.Timer(100);
                    //  audioRecorderTimer.Elapsed += this.OnAudioRecorderTimer;
                    //  audioRecorderTimer.AutoReset = true;
                    //}
                    //
                    //audioRecorderTimer.Enabled = this.IsRecordingAudio;
 
                    this.OnPropertyChanged(nameof(RecordingTime));
                    this.CancelCommand.NotifyCanExecuteChanged();
                    break;
 
                case nameof(this.IsConnected):
                    this.SendCommand.NotifyCanExecuteChanged();
                    this.CancelCommand.NotifyCanExecuteChanged();
                    this.RecordAudioCommand.NotifyCanExecuteChanged();
                    this.TakePhotoCommand.NotifyCanExecuteChanged();
                    this.EmbedFileCommand.NotifyCanExecuteChanged();
                    this.EmbedIdCommand.NotifyCanExecuteChanged();
                    this.EmbedContractCommand.NotifyCanExecuteChanged();
                    this.EmbedMoneyCommand.NotifyCanExecuteChanged();
                    this.EmbedTokenCommand.NotifyCanExecuteChanged();
                    this.EmbedThingCommand.NotifyCanExecuteChanged();
                    break;
            }
        }
 
        [ObservableProperty]
        private string? messageId;
 
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(LoadMoreMessagesCommand))]
        private bool existsMoreMessages;
 
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(RecordAudioCommand))]
        [NotifyCanExecuteChangedFor(nameof(TakePhotoCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedFileCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedIdCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedContractCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedMoneyCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedTokenCommand))]
        [NotifyCanExecuteChangedFor(nameof(EmbedThingCommand))]
        private bool isWriting;
 
        [ObservableProperty]
        [NotifyCanExecuteChangedFor(nameof(SendCommand))]
        private bool isRecordingAudio;
 
        [ObservableProperty]
        private bool isRecordingPaused;
 
        public static string RecordingTime
        {
            get
            {
                // TODO: Audio
                //
                //double Milliseconds = audioRecorder.Value.TotalAudioTimeout.TotalMilliseconds - audioRecorder.Value.RecordingTime.TotalMilliseconds;
                //return (Milliseconds > 0) ? string.Format(CultureInfo.CurrentCulture, "{0:F0}s left", Math.Ceiling(Milliseconds / 1000.0)) : "TIMEOUT";
 
                return string.Empty;
            }
        }
 
        public async Task MessageAddedAsync(ChatMessage Message)
        {
            if(Message.ParsedXaml is null)
                    await Message.GenerateXaml(this);
 
            MainThread.BeginInvokeOnMainThread(async () =>
            {
                IView? View = await this.MessageAddedMainThread(Message, true);
 
                if (View is Element)
                {
                await Task.Delay(25);
                    double Width = this.page.ScrollView.ScrollX;
                    double Height = this.page.ScrollView.ContentSize.Height;
                    await this.page.ScrollView.ScrollToAsync(Width, Height, true);  
                }
            });
        }
 
        private async Task<IView?> MessageAddedMainThread(ChatMessage Message, bool Historic)
        {
            this.HasMessages = true;
 
            TaskCompletionSource<IView?> Result = new();
 
            try
            {
                if(Message.ParsedXaml is null)
                    await Message.GenerateXaml(this);   // Makes sure XAML is generated
 
                lock (this.synchObject)
                {
                    LinkedListNode<MessageRecord>? MessageNode = Historic ? this.messages.Last : this.messages.First;
                    LinkedListNode<MessageFrame>? FrameNode;
                    MessageFrame? Frame;
                    MessageRecord Rec;
                    IView? View;
                    // int i;
                    if (MessageNode is null)
                    {
 
                        Frame = MessageFrame.Create(Message);
                        View = Frame.AddLast(Message);
                        this.page.Messages.Add(Frame);
 
                        FrameNode = this.frames.AddLast(Frame);
 
                        Rec = new(Message, FrameNode);
                        MessageNode = this.messages.AddLast(Rec);
                    }
                    else if (Historic)
                    {
                        while (MessageNode is not null && Message.Created > MessageNode.Value.Created)
                            MessageNode = MessageNode.Next;
                        if (MessageNode is null)
                        {
                            FrameNode = this.frames.Last!;
 
                            if (FrameNode.Value.MessageType != Message.MessageType)
                            {
                                FrameNode = this.frames.AddLast(MessageFrame.Create(Message));
                                this.page.Messages.Add(FrameNode.Value);
                            }
 
                            View = FrameNode.Value.AddLast(Message);
 
                            Rec = new(Message, FrameNode);
                            MessageNode = this.messages.AddLast(Rec);
                        }
                        else
                        {
                            View = null;
                            // TODO
                        }
                    }
                    else
                    {
                        while (MessageNode is not null && Message.Created < MessageNode.Value.Created)
                            MessageNode = MessageNode.Previous;
 
                        if (MessageNode is null)
                        {
                            FrameNode = this.frames.First!;
 
                            if (FrameNode.Value.MessageType != Message.MessageType)
                            {
                                FrameNode = this.frames.AddFirst(MessageFrame.Create(Message));
                                this.page.Messages.Insert(0, FrameNode.Value);
                            }
 
                            View = FrameNode.Value.AddFirst(Message);
 
                            Rec = new(Message, FrameNode);
                            MessageNode = this.messages.AddFirst(Rec);
                        }
                        else
                        {
                            View = null;
                            // TODO
                        }
                    }
 
                    Result.TrySetResult(View);
 
                    {
 
 
                        //else if (MessageNode.Value.ParsedXaml is IView PrevMessageXaml &&
                        //  (i = this.page.Messages.IndexOf(PrevMessageXaml)) >= 0)
                        //{
                        //  if (MessageNode.Value.ObjectId == Message.ObjectId)
                        //  {
                        //      this.page.Messages.RemoveAt(i);
                        //      this.page.Messages.Insert(i, MessageXaml);
                        //
                        //      MessageNode.Value = Message;
                        //  }
                        //  else
                        //  {
                        //      this.page.Messages.Insert(i + 1, MessageXaml);
                        //      MessageNode = this.messages.AddAfter(MessageNode, Message);
                        //  }
                        //}
                        //else
                        //{
                        //  MessageNode = this.messages.AddLast(Message);
                        //  this.page.Messages.Children.Add(MessageXaml);
                        //}
                    }
 
                    this.messagesByObjectId[Message.ObjectId ?? string.Empty] = MessageNode;
                }
            }
            catch (Exception Ex)
            {
                Result.TrySetException(Ex);
            }
 
            return await Result.Task;
        }
 
        public async Task MessageUpdatedAsync(ChatMessage Message)
        {
            try
            {
                await Message.GenerateXaml(this);
            }
            catch (Exception Ex)
            {
                ServiceRef.LogService.LogException(Ex);
                return;
            }
 
            if (Message.ParsedXaml is not IView MessageXaml || string.IsNullOrEmpty(Message.ObjectId))
                return;
 
            MainThread.BeginInvokeOnMainThread(() =>
            {
                try
                {
                    lock (this.synchObject)
                    {
                        int Index;
 
                        if (this.messagesByObjectId.TryGetValue(Message.ObjectId, out LinkedListNode<MessageRecord>? Node) &&
                            Node.Value.Message.ParsedXaml is IView PrevMessageXaml &&
                            PrevMessageXaml.Parent is VerticalStackLayout Parent &&
                            (Index = Parent.IndexOf(PrevMessageXaml)) >= 0)
                        {
                            Parent.RemoveAt(Index);
                            Parent.Insert(Index, MessageXaml);
 
                            Node.Value.Message = Message;
 
                            // TODO: Update XAML
                        }
                    }
                }
                catch (Exception Ex)
                {
                    ServiceRef.LogService.LogException(Ex);
                }
            });
        }
 
        private async Task<IView?> LoadMessagesAsync(bool LoadMore = true)
        {
            IEnumerable<ChatMessage>? Messages = null;
            int C = Constants.BatchSizes.MessageBatchSize;
            DateTime LastTime;
            ChatMessage[] A;
 
            try
            {
                this.ExistsMoreMessages = false;
 
                lock (this.synchObject)
                {
                    LastTime = LoadMore && this.messages.First is not null ? this.messages.First.Value.Created : DateTime.MaxValue;
                }
 
                Messages = await Database.Find<ChatMessage>(0, Constants.BatchSizes.MessageBatchSize, new FilterAnd(
                    new FilterFieldEqualTo("RemoteBareJid", this.BareJid),
                    new FilterFieldLesserThan("Created", LastTime)), "-Created");
 
                A = [.. Messages];
                C -= A.Length;
 
                if (!LoadMore)
                    Array.Reverse(A);
            }
            catch (Exception Ex)
            {
                ServiceRef.LogService.LogException(Ex);
                this.ExistsMoreMessages = false;
                return null;
            }
 
            TaskCompletionSource<IView?> Result = new();
 
            MainThread.BeginInvokeOnMainThread(async () =>
            {
                try
                {
                    IView? Last = null;
 
                    foreach (ChatMessage Message in A)
                        Last = await this.MessageAddedMainThread(Message, true);
 
                    this.ExistsMoreMessages = C <= 0;
 
                    Result.TrySetResult(Last);
                }
                catch (Exception Ex)
                {
                    Result.TrySetException(Ex);
                }
            });
 
            return await Result.Task;
        }
 
        [ObservableProperty]
        private bool hasMessages = false;
 
        [ObservableProperty]
        private bool isButtonExpanded;
 
        [RelayCommand]
        private void ExpandButtons()
        {
            this.IsButtonExpanded = !this.IsButtonExpanded;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteLoadMoreMessages))]
        private Task<IView?> LoadMoreMessages()
        {
            return this.LoadMessagesAsync(true);
        }
 
        private bool CanExecuteLoadMoreMessages()
        {
            return this.ExistsMoreMessages && this.page.Messages.Count > 0;
        }
 
        private bool CanExecuteSendMessage()
        {
            return this.IsConnected && (!string.IsNullOrEmpty(this.MarkdownInput) || this.IsRecordingAudio);
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteSendMessage))]
        private async Task Send()
        {
            if (this.IsRecordingAudio)
            {
                // TODO: Audio
                //
                // try
                // {
                //  await audioRecorder.Value.StopRecording();
                //  string audioPath = await this.audioRecorderTask!;
                // 
                //  if (audioPath is not null)
                //      await this.EmbedMedia(audioPath, true);
                // }
                // catch (Exception ex)
                // {
                //  ServiceRef.LogService.LogException(ex);
                // }
                // finally
                // {
                //  this.IsRecordingAudio = false;
                // }
            }
            else
            {
                await this.ExecuteSendMessage(this.MessageId, this.MarkdownInput);
                await this.Cancel();
            }
        }
 
        private Task ExecuteSendMessage(string? ReplaceObjectId, string MarkdownInput)
        {
            return ExecuteSendMessage(ReplaceObjectId, MarkdownInput, this.BareJid!, this);
        }
 
        public static Task ExecuteSendMessage(string? ReplaceObjectId, string MarkdownInput, string BareJid)
        {
            return ExecuteSendMessage(ReplaceObjectId, MarkdownInput, BareJid, null);
        }
 
        public static async Task ExecuteSendMessage(string? ReplaceObjectId, string MarkdownInput, string BareJid, ChatViewModel? ChatViewModel)
        {
            try
            {
                if (string.IsNullOrEmpty(MarkdownInput))
                    return;
 
                MarkdownSettings Settings = new()
                {
                    AllowScriptTag = false,
                    EmbedEmojis = false,    // TODO: Emojis
                    AudioAutoplay = false,
                    AudioControls = false,
                    ParseMetaData = false,
                    VideoAutoplay = false,
                    VideoControls = false
                };
 
                MarkdownDocument Doc = await MarkdownDocument.CreateAsync(MarkdownInput, Settings);
 
                ChatMessage Message = new()
                {
                    Created = DateTime.UtcNow,
                    RemoteBareJid = BareJid,
                    RemoteObjectId = string.Empty,
 
                    MessageType = MessageType.Sent,
                    Html = HtmlDocument.GetBody(await Doc.GenerateHTML()),
                    PlainText = (await Doc.GeneratePlainText()).Trim(),
                    Markdown = MarkdownInput
                };
 
                StringBuilder Xml = new();
 
                Xml.Append("<content xmlns=\"urn:xmpp:content\" type=\"text/markdown\">");
                Xml.Append(XML.Encode(MarkdownInput));
                Xml.Append("</content><html xmlns='http://jabber.org/protocol/xhtml-im'><body xmlns='http://www.w3.org/1999/xhtml'>");
 
                HtmlDocument HtmlDoc = new("<root>" + Message.Html + "</root>");
 
                foreach (HtmlNode N in (HtmlDoc.Body ?? HtmlDoc.Root).Children)
                    N.Export(Xml);
 
                Xml.Append("</body></html>");
 
                if (!string.IsNullOrEmpty(ReplaceObjectId))
                {
                    Xml.Append("<replace id='");
                    Xml.Append(ReplaceObjectId);
                    Xml.Append("' xmlns='urn:xmpp:message-correct:0'/>");
                }
 
                if (string.IsNullOrEmpty(ReplaceObjectId))
                {
                    await Database.Insert(Message);
 
                    if (ChatViewModel is not null)
                        await ChatViewModel.MessageAddedAsync(Message);
                }
                else
                {
                    ChatMessage Old = await Database.TryLoadObject<ChatMessage>(ReplaceObjectId);
 
                    if (Old is null)
                    {
                        ReplaceObjectId = null;
                        await Database.Insert(Message);
 
                        if (ChatViewModel is not null)
                            await ChatViewModel.MessageAddedAsync(Message);
                    }
                    else
                    {
                        Old.Updated = Message.Created;
                        Old.Html = Message.Html;
                        Old.PlainText = Message.PlainText;
                        Old.Markdown = Message.Markdown;
 
                        await Database.Update(Old);
 
                        Message = Old;
 
                        if (ChatViewModel is not null)
                            await ChatViewModel.MessageUpdatedAsync(Message);
                    }
                }
                ServiceRef.XmppService.SendMessage(QoSLevel.Unacknowledged, Waher.Networking.XMPP.MessageType.Chat, Message.ObjectId ?? string.Empty,
                    BareJid, Xml.ToString(), Message.PlainText, string.Empty, string.Empty, string.Empty, string.Empty, null, null);
            }
            catch (Exception Ex)
            {
                await ServiceRef.UiService.DisplayException(Ex);
            }
        }
 
        [RelayCommand(CanExecute = nameof(CanExecutePauseResume))]
        private Task PauseResume()
        {
            // TODO: Audio
            //
            // if (audioRecorder.Value.IsPaused)
            //  await audioRecorder.Value.Resume();
            // else
            //  await audioRecorder.Value.Pause();
            // 
            // this.IsRecordingPaused = audioRecorder.Value.IsPaused;
 
            return Task.CompletedTask;
        }
 
        private static bool CanExecutePauseResume()
        {
            // TODO: Audio
            //
            // return this.IsRecordingAudio && audioRecorder.Value.IsRecording;
            return false;
        }
 
        private bool CanExecuteCancelMessage()
        {
            return this.IsConnected && (!string.IsNullOrEmpty(this.MarkdownInput) || this.IsRecordingAudio);
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteCancelMessage))]
        private Task Cancel()
        {
            if (this.IsRecordingAudio)
            {
                // TODO: Audio
                //
                // try
                // {
                //  return audioRecorder.Value.StopRecording();
                // }
                // catch (Exception ex)
                // {
                //  ServiceRef.LogService.LogException(ex);
                // }
                // finally
                // {
                //  this.IsRecordingAudio = false;
                // }
            }
            else
            {
                this.MarkdownInput = string.Empty;
                this.MessageId = string.Empty;
            }
 
            return Task.CompletedTask;
        }
 
        // TODO: Audio
        // 
        // private static System.Timers.Timer audioRecorderTimer;
        // 
        // private static readonly Lazy<AudioRecorderService> audioRecorder = new(() =>
        // {
        //  return new AudioRecorderService()
        //  {
        //      StopRecordingOnSilence = false,
        //      StopRecordingAfterTimeout = true,
        //      TotalAudioTimeout = TimeSpan.FromSeconds(60)
        //  };
        // }, LazyThreadSafetyMode.PublicationOnly);
        //
        //private readonly Task<string>? audioRecorderTask = null;
 
        private bool CanExecuteRecordAudio()
        {
            return this.IsConnected && !this.IsWriting && ServiceRef.XmppService.FileUploadIsSupported;
        }
 
        private void OnAudioRecorderTimer(object? source, ElapsedEventArgs e)
        {
            this.OnPropertyChanged(nameof(RecordingTime));
 
            // TODO: Audio
            //
            // this.IsRecordingPaused = audioRecorder.Value.IsPaused;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteRecordAudio))]
        private async Task RecordAudio()
        {
            if (!ServiceRef.XmppService.FileUploadIsSupported)
            {
                await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.TakePhoto)],
                    ServiceRef.Localizer[nameof(AppResources.ServerDoesNotSupportFileUpload)]);
                return;
            }
 
            try
            {
                PermissionStatus Status = await Permissions.RequestAsync<Permissions.Microphone>();
 
                if (Status == PermissionStatus.Granted)
                {
                    // TODO: Audio
                    //
                    // this.audioRecorderTask = await audioRecorder.Value.StartRecording();
                    // this.IsRecordingAudio = true;
                }
            }
            catch (Exception Ex)
            {
                ServiceRef.LogService.LogException(Ex);
            }
        }
 
        private bool CanExecuteTakePhoto()
        {
            return this.IsConnected && !this.IsWriting && ServiceRef.XmppService.FileUploadIsSupported;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteTakePhoto))]
        private async Task TakePhoto()
        {
            if (!ServiceRef.XmppService.FileUploadIsSupported)
            {
                await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.TakePhoto)],
                    ServiceRef.Localizer[nameof(AppResources.ServerDoesNotSupportFileUpload)]);
                return;
            }
 
            bool Permitted = await ServiceRef.PermissionService.CheckCameraPermissionAsync();
            if (!Permitted)
                return;
 
            if (DeviceInfo.Platform == DevicePlatform.iOS)
            {
                FileResult? CapturedPhoto;
 
                try
                {
                    CapturedPhoto = await MediaPicker.Default.CapturePhotoAsync(new MediaPickerOptions()
                    {
                        Title = ServiceRef.Localizer[nameof(AppResources.TakePhotoToShare)]
                    });
                }
                catch (Exception Ex)
                {
                    await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.TakePhoto)],
                        ServiceRef.Localizer[nameof(AppResources.TakingAPhotoIsNotSupported)] + ": " + Ex.Message);
                    return;
                }
 
                if (CapturedPhoto is not null)
                {
                    try
                    {
                        await this.EmbedMedia(CapturedPhoto.FullPath, true);
                    }
                    catch (Exception Ex)
                    {
                        await ServiceRef.UiService.DisplayException(Ex);
                    }
                }
            }
            else
            {
                FileResult? CapturedPhoto;
 
                try
                {
                    CapturedPhoto = await MediaPicker.CapturePhotoAsync();
                    if (CapturedPhoto is null)
                        return;
                }
                catch (Exception Ex)
                {
                    await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.TakePhoto)],
                        ServiceRef.Localizer[nameof(AppResources.TakingAPhotoIsNotSupported)] + ": " + Ex.Message);
                    return;
                }
 
                if (CapturedPhoto is not null)
                {
                    try
                    {
                        await this.EmbedMedia(CapturedPhoto.FullPath, true);
                    }
                    catch (Exception Ex)
                    {
                        await ServiceRef.UiService.DisplayException(Ex);
                    }
                }
            }
        }
 
        private async Task EmbedMedia(string FilePath, bool DeleteFile)
        {
            try
            {
                byte[] Bin = File.ReadAllBytes(FilePath);
                if (!InternetContent.TryGetContentType(Path.GetExtension(FilePath), out string ContentType))
                    ContentType = "application/octet-stream";
 
                if (Bin.Length > ServiceRef.TagProfile.HttpFileUploadMaxSize)
                {
                    await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                        ServiceRef.Localizer[nameof(AppResources.PhotoIsTooLarge)]);
                    return;
                }
 
                // Taking or picking photos switches to another app, so ID app has to reconnect again after.
                if (!await ServiceRef.XmppService.WaitForConnectedState(Constants.Timeouts.XmppConnect))
                {
                    await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.ErrorTitle)],
                        ServiceRef.Localizer[nameof(AppResources.UnableToConnectTo), ServiceRef.TagProfile.Domain ?? string.Empty]);
                    return;
                }
 
                string FileName = Path.GetFileName(FilePath);
 
                // Encrypting image
 
                using RandomNumberGenerator Rnd = RandomNumberGenerator.Create();
                byte[] Key = new byte[16];
                byte[] IV = new byte[16];
 
                Rnd.GetBytes(Key);
                Rnd.GetBytes(IV);
 
                Aes Aes = Aes.Create();
                Aes.BlockSize = 128;
                Aes.KeySize = 256;
                Aes.Mode = CipherMode.CBC;
                Aes.Padding = PaddingMode.PKCS7;
 
                using ICryptoTransform Transform = Aes.CreateEncryptor(Key, IV);
                Bin = Transform.TransformFinalBlock(Bin, 0, Bin.Length);
 
                // Preparing File upload service that content uploaded next is encrypted, and can be stored in encrypted storage.
 
                StringBuilder Xml = new();
 
                Xml.Append("<prepare xmlns='http://waher.se/Schema/EncryptedStorage.xsd' filename='");
                Xml.Append(XML.Encode(FileName));
                Xml.Append("' size='");
                Xml.Append(Bin.Length.ToString(CultureInfo.InvariantCulture));
                Xml.Append("' content-type='application/octet-stream'/>");
 
                await ServiceRef.XmppService.IqSetAsync(ServiceRef.TagProfile.HttpFileUploadJid!, Xml.ToString());
                // Empty response expected. Errors cause an exception to be raised.
 
                // Requesting upload slot
 
                HttpFileUploadEventArgs Slot = await ServiceRef.XmppService.RequestUploadSlotAsync(
                    FileName, "application/octet-stream", Bin.Length);
 
                if (!Slot.Ok)
                    throw Slot.StanzaError ?? new Exception(Slot.ErrorText);
 
                // Uploading encrypted image
 
                await Slot.PUT(Bin, "application/octet-stream", (int)Constants.Timeouts.UploadFile.TotalMilliseconds);
 
                // Generating Markdown message to send to recipient
 
                StringBuilder Markdown = new();
 
                Markdown.Append("![");
                Markdown.Append(MarkdownDocument.Encode(FileName));
                Markdown.Append("](");
                Markdown.Append(Constants.UriSchemes.Aes256);
                Markdown.Append(':');
                Markdown.Append(Convert.ToBase64String(Key));
                Markdown.Append(':');
                Markdown.Append(Convert.ToBase64String(IV));
                Markdown.Append(':');
                Markdown.Append(ContentType);
                Markdown.Append(':');
                Markdown.Append(Slot.GetUrl);
 
                SKImageInfo ImageInfo = SKBitmap.DecodeBounds(Bin);
                if (!ImageInfo.IsEmpty)
                {
                    Markdown.Append(' ');
                    Markdown.Append(ImageInfo.Width.ToString(CultureInfo.InvariantCulture));
                    Markdown.Append(' ');
                    Markdown.Append(ImageInfo.Height.ToString(CultureInfo.InvariantCulture));
                }
 
                Markdown.Append(')');
 
                await this.ExecuteSendMessage(string.Empty, Markdown.ToString());
 
                // TODO: End-to-End encryption, or using Elliptic Curves of recipient together with sender to deduce shared secret.
 
                if (DeleteFile)
                    File.Delete(FilePath);
            }
            catch (Exception Ex)
            {
                await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.ErrorTitle)], Ex.Message);
                ServiceRef.LogService.LogException(Ex);
                return;
            }
        }
 
        private bool CanExecuteEmbedFile()
        {
            return this.IsConnected && !this.IsWriting && ServiceRef.XmppService.FileUploadIsSupported;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedFile))]
        private async Task EmbedFile()
        {
            if (!ServiceRef.XmppService.FileUploadIsSupported)
            {
                await ServiceRef.UiService.DisplayAlert(ServiceRef.Localizer[nameof(AppResources.PickPhoto)], ServiceRef.Localizer[nameof(AppResources.SelectingAPhotoIsNotSupported)]);
                return;
            }
 
            FileResult? PickedPhoto = await MediaPicker.PickPhotoAsync();
 
            if (PickedPhoto is not null)
                await this.EmbedMedia(PickedPhoto.FullPath, false);
        }
 
        private bool CanExecuteEmbedId()
        {
            return this.IsConnected && !this.IsWriting;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedId))]
        private async Task EmbedId()
        {
            TaskCompletionSource<ContactInfoModel?> SelectedContact = new();
            ContactListNavigationArgs Args = new(ServiceRef.Localizer[nameof(AppResources.SelectContactToPay)], SelectedContact)
            {
                CanScanQrCode = true
            };
 
            await ServiceRef.NavigationService.GoToAsync(nameof(MyContactsPage), Args, BackMethod.Pop);
 
            ContactInfoModel? Contact = await SelectedContact.Task;
            if (Contact is null)
                return;
 
            await this.waitUntilBound.Task;     // Wait until view is bound again.
 
            if (Contact.LegalIdentity is not null)
            {
                StringBuilder Markdown = new();
 
                Markdown.Append("```");
                Markdown.AppendLine(Constants.UriSchemes.IotId);
 
                Contact.LegalIdentity.Serialize(Markdown, true, true, true, true, true, true, true);
 
                Markdown.AppendLine();
                Markdown.AppendLine("```");
 
                await this.ExecuteSendMessage(string.Empty, Markdown.ToString());
                return;
            }
 
            if (!string.IsNullOrEmpty(Contact.LegalId))
            {
                await this.ExecuteSendMessage(string.Empty, "![" + MarkdownDocument.Encode(Contact.FriendlyName) + "](" + ContractsClient.LegalIdUriString(Contact.LegalId) + ")");
                return;
            }
 
            if (!string.IsNullOrEmpty(Contact.BareJid))
            {
                await this.ExecuteSendMessage(string.Empty, "![" + MarkdownDocument.Encode(Contact.FriendlyName) + "](xmpp:" + Contact.BareJid + "?subscribe)");
                return;
            }
        }
 
        private bool CanExecuteEmbedContract()
        {
            return this.IsConnected && !this.IsWriting;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedContract))]
        private async Task EmbedContract()
        {
            TaskCompletionSource<Contract?> SelectedContract = new();
            MyContractsNavigationArgs Args = new(ContractsListMode.Contracts, SelectedContract);
 
            await ServiceRef.NavigationService.GoToAsync(nameof(MyContractsPage), Args, BackMethod.Pop);
 
            Contract? Contract = await SelectedContract.Task;
            if (Contract is null)
                return;
 
            await this.waitUntilBound.Task;     // Wait until view is bound again.
 
            StringBuilder Markdown = new();
 
            Markdown.Append("```");
            Markdown.AppendLine(Constants.UriSchemes.IotSc);
 
            Contract.Serialize(Markdown, true, true, true, true, true, true, true);
 
            Markdown.AppendLine();
            Markdown.AppendLine("```");
 
            await this.ExecuteSendMessage(string.Empty, Markdown.ToString());
        }
 
        private bool CanExecuteEmbedMoney()
        {
            return this.IsConnected && !this.IsWriting;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedMoney))]
        private async Task EmbedMoney()
        {
            StringBuilder Sb = new();
 
            Sb.Append("edaler:");
 
            if (!string.IsNullOrEmpty(this.LegalId))
            {
                Sb.Append("ti=");
                Sb.Append(this.LegalId);
            }
            else if (!string.IsNullOrEmpty(this.BareJid))
            {
                Sb.Append("t=");
                Sb.Append(this.BareJid);
            }
            else
                return;
 
            Balance CurrentBalance = await ServiceRef.XmppService.GetEDalerBalance();
 
            Sb.Append(";cu=");
            Sb.Append(CurrentBalance.Currency);
 
            if (!EDalerUri.TryParse(Sb.ToString(), out EDalerUri Parsed))
                return;
 
            TaskCompletionSource<string?> UriToSend = new();
            EDalerUriNavigationArgs Args = new(Parsed, this.FriendlyName ?? string.Empty, UriToSend);
 
            await ServiceRef.NavigationService.GoToAsync(nameof(SendPaymentPage), Args, BackMethod.Pop);
 
            string? Uri = await UriToSend.Task;
            if (string.IsNullOrEmpty(Uri) || !EDalerUri.TryParse(Uri, out Parsed))
                return;
 
            await this.waitUntilBound.Task;     // Wait until view is bound again.
 
            Sb.Clear();
            Sb.Append(MoneyToString.ToString(Parsed.Amount));
 
            if (Parsed.AmountExtra.HasValue)
            {
                Sb.Append(" (+");
                Sb.Append(MoneyToString.ToString(Parsed.AmountExtra.Value));
                Sb.Append(')');
            }
 
            Sb.Append(' ');
            Sb.Append(Parsed.Currency);
 
            await this.ExecuteSendMessage(string.Empty, "![" + Sb.ToString() + "](" + Uri + ")");
        }
 
        private bool CanExecuteEmbedToken()
        {
            return this.IsConnected && !this.IsWriting;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedToken))]
        private async Task EmbedToken()
        {
            MyTokensNavigationArgs Args = new();
 
            await ServiceRef.NavigationService.GoToAsync(nameof(MyTokensPage), Args, BackMethod.Pop);
 
            TokenItem? Selected = await Args.TokenItemProvider.Task;
 
            if (Selected is null)
                return;
 
            StringBuilder Markdown = new();
 
            Markdown.AppendLine("```nfeat");
 
            Selected.Token.Serialize(Markdown);
 
            Markdown.AppendLine();
            Markdown.AppendLine("```");
 
            await this.ExecuteSendMessage(string.Empty, Markdown.ToString());
        }
 
        private bool CanExecuteEmbedThing()
        {
            return this.IsConnected && !this.IsWriting;
        }
 
        [RelayCommand(CanExecute = nameof(CanExecuteEmbedThing))]
        private async Task EmbedThing()
        {
            TaskCompletionSource<ContactInfoModel?> ThingToShare = new();
            MyThingsNavigationArgs Args = new(ThingToShare);
 
            await ServiceRef.NavigationService.GoToAsync(nameof(MyThingsPage), Args, BackMethod.Pop);
 
            ContactInfoModel? Thing = await ThingToShare.Task;
            if (Thing is null)
                return;
 
            await this.waitUntilBound.Task;     // Wait until view is bound again.
 
            StringBuilder Sb = new();
 
            Sb.Append("![");
            Sb.Append(MarkdownDocument.Encode(Thing.FriendlyName));
            Sb.Append("](iotdisco:JID=");
            Sb.Append(Thing.BareJid);
 
            if (!string.IsNullOrEmpty(Thing.SourceId))
            {
                Sb.Append(";SID=");
                Sb.Append(Thing.SourceId);
            }
 
            if (!string.IsNullOrEmpty(Thing.Partition))
            {
                Sb.Append(";PT=");
                Sb.Append(Thing.Partition);
            }
 
            if (!string.IsNullOrEmpty(Thing.NodeId))
            {
                Sb.Append(";NID=");
                Sb.Append(Thing.NodeId);
            }
 
            Sb.Append(')');
 
            await this.ExecuteSendMessage(string.Empty, Sb.ToString());
        }
 
        [RelayCommand]
        private Task MessageSelected(object Parameter)
        {
            if (Parameter is ChatMessage Message)
            {
                // TODO: Audio
                //
                // if (Message.ParsedXaml is View View)
                // {
                //  AudioPlayerControl AudioPlayer = View.Descendants().OfType<AudioPlayerControl>().FirstOrDefault();
                //  if (AudioPlayer is not null)
                //  {
                //      return Task.CompletedTask;
                //  }
                // }
 
                switch (Message.MessageType)
                {
 
                    case MessageType.Sent:
                        this.MessageId = Message.ObjectId;
                        this.MarkdownInput = Message.Markdown;
                        break;
 
 
                    case MessageType.Received:
                        string S = Message.Markdown;
                        if (string.IsNullOrEmpty(S))
                            S = MarkdownDocument.Encode(Message.PlainText);
 
                        string[] Rows = S.Replace("\r\n", "\n").Replace("\r", "\n").Split('\n');
 
                        StringBuilder Quote = new();
 
                        foreach (string Row in Rows)
                        {
                            Quote.Append("> ");
                            Quote.AppendLine(Row);
                        }
 
                        Quote.AppendLine();
 
                        this.MessageId = string.Empty;
                        this.MarkdownInput = Quote.ToString();
                        break;
                }
            }
 
            return Task.CompletedTask;
        }
 
        public async Task ExecuteUriClicked(string Uri, UriScheme Scheme)
        {
            try
            {
                if (Scheme == UriScheme.Xmpp)
                    await ProcessXmppUri(Uri);
                else
                {
                    int I = Uri.IndexOf(':');
                    if (I < 0)
                        return;
 
                    string S = Uri[(I + 1)..].Trim();
                    if (S.StartsWith('<') && S.EndsWith('>'))  // XML
                    {
                        XmlDocument Doc = new()
                        {
                            PreserveWhitespace = true
                        };
                        Doc.LoadXml(S);
 
                        switch (Scheme)
                        {
                            case UriScheme.IotId:
                                LegalIdentity Id = LegalIdentity.Parse(Doc.DocumentElement);
                                ViewIdentityNavigationArgs ViewIdentityArgs = new(Id);
 
                                await ServiceRef.NavigationService.GoToAsync(nameof(ViewIdentityPage), ViewIdentityArgs, BackMethod.Pop);
                                break;
 
                            case UriScheme.IotSc:
                                ParsedContract ParsedContract = await Contract.Parse(Doc.DocumentElement, ServiceRef.XmppService.ContractsClient, true);
                                ViewContractNavigationArgs ViewContractArgs = new(ParsedContract.Contract, false);
 
                                await ServiceRef.NavigationService.GoToAsync(nameof(ViewContractPage), ViewContractArgs, BackMethod.Pop);
                                break;
 
                            case UriScheme.NeuroFeature:
                                Token? ParsedToken = await Token.TryParse(Doc.DocumentElement);
                                if (ParsedToken is null)
                                    throw new Exception(ServiceRef.Localizer[nameof(AppResources.InvalidNeuroFeatureToken)]);
 
                                if (!ServiceRef.NotificationService.TryGetNotificationEvents(NotificationEventType.Wallet, ParsedToken.TokenId, out NotificationEvent[]? Events))
                                    Events = [];
 
                                TokenDetailsNavigationArgs Args = new(new TokenItem(ParsedToken, Events));
 
                                await ServiceRef.NavigationService.GoToAsync(nameof(TokenDetailsPage), Args, BackMethod.Pop);
                                break;
 
                            default:
                                return;
                        }
                    }
                    else
                        await QrCode.OpenUrl(Uri);
                }
            }
            catch (Exception Ex)
            {
                await ServiceRef.UiService.DisplayException(Ex);
            }
        }
 
        public static async Task<bool> ProcessXmppUri(string Uri)
        {
            int I = Uri.IndexOf(':');
            if (I < 0)
                return false;
 
            string Jid = Uri[(I + 1)..].TrimStart();
            string Command;
 
            I = Jid.IndexOf('?');
            if (I < 0)
                Command = "subscribe";
            else
            {
                Command = Jid[(I + 1)..].TrimStart();
                Jid = Jid[..I].TrimEnd();
            }
 
            Jid = System.Web.HttpUtility.UrlDecode(Jid);
            Jid = XmppClient.GetBareJID(Jid);
 
            switch (Command.ToLower(CultureInfo.InvariantCulture))
            {
                case "subscribe":
                    SubscribeToViewModel SubscribeToViewModel = new(Jid);
                    SubscribeToPopup SubscribeToPopup = new(SubscribeToViewModel);
 
                    await ServiceRef.PopupService.PushAsync(SubscribeToPopup);
                    bool? SubscribeTo = await SubscribeToViewModel.Result;
 
                    if (SubscribeTo.HasValue && SubscribeTo.Value)
                    {
                        string IdXml;
 
                        if (ServiceRef.TagProfile.LegalIdentity is null)
                            IdXml = string.Empty;
                        else
                        {
                            StringBuilder Xml = new();
                            ServiceRef.TagProfile.LegalIdentity.Serialize(Xml, true, true, true, true, true, true, true);
                            IdXml = Xml.ToString();
                        }
 
                        ServiceRef.XmppService.RequestPresenceSubscription(Jid, IdXml);
                    }
                    return true;
 
                case "unsubscribe":
                    // TODO
                    return false;
 
                case "remove":
                    ServiceRef.XmppService.GetRosterItem(Jid);
                    // TODO
                    return false;
 
                default:
                    return false;
            }
        }
 
        #region ILinkableView
 
        public bool IsLinkable => true;
 
        public bool EncodeAppLinks => true;
 
        public string Link => Constants.UriSchemes.Xmpp + ":" + this.BareJid;
 
        public Task<string> Title => Task.FromResult<string>(this.FriendlyName ?? string.Empty);
 
        public bool HasMedia => false;
 
        public byte[]? Media => null;
 
        public string? MediaContentType => null;
 
        #endregion
 
    }
}