QrXmppViewModel.cs

using CommunityToolkit.Mvvm.ComponentModel;
using CommunityToolkit.Mvvm.Input;
using NeuroAccessMaui.Services;
using NeuroAccessMaui.UI.Popups.QR;
using Waher.Content.Html.Elements;
using System; // For StringComparison
using System.IO; // For MemoryStream
using Microsoft.Maui.Storage; // For FileSystem paths
 
namespace NeuroAccessMaui.UI.Pages
{
    public abstract partial class QrXmppViewModel : XmppViewModel, ILinkableView
    {
        private readonly object qrSync = new();
 
        protected QrXmppViewModel()
            : base()
        {
        }
 
 
        private string? qrTempFilePath;
 
        public void GenerateQrCode(string Uri)
        {
            lock (this.qrSync)
            {
                // Idempotency: Avoid regenerating the same QR multiple times (mitigates race conditions during animations)
                if (this.QrCode is not null && string.Equals(this.QrCodeUri, Uri, StringComparison.Ordinal))
                {
                    ServiceRef.LogService.LogDebug($"GenerateQrCode skipped (same URI): {Uri}");
                    return;
                }
 
                if (this.QrCodeWidth == 0 || this.QrCodeHeight == 0)
                {
                    this.QrCodeWidth = Constants.QrCode.DefaultImageWidth;
                    this.QrCodeHeight = Constants.QrCode.DefaultImageHeight;
                }
 
                if (this.QrResolutionScale == 0)
                    this.QrResolutionScale = Constants.QrCode.DefaultResolutionScale;
 
                ServiceRef.LogService.LogDebug($"GenerateQrCode start: {Uri} ({this.QrCodeWidth}x{this.QrCodeHeight} scale={this.QrResolutionScale})");
                byte[] Bin = Services.UI.QR.QrCode.GeneratePng(Uri, this.QrCodeWidth * this.QrResolutionScale, this.QrCodeHeight * this.QrResolutionScale);
                this.QrCodeBin = Bin;
 
                try
                {
                    // Persist to a temporary file to avoid premature bitmap recycling when view hierarchies animate.
                    string CacheDir = FileSystem.CacheDirectory;
                    string FileName = $"qr_{Guid.NewGuid():N}.png";
                    string FullPath = Path.Combine(CacheDir, FileName);
                    File.WriteAllBytes(FullPath, Bin);
                    this.qrTempFilePath = FullPath;
                    this.QrCode = ImageSource.FromFile(FullPath);
                }
                catch (Exception Ex)
                {
                    ServiceRef.LogService.LogException(Ex);
                    // Fallback to in-memory stream method if file write fails
                    this.QrCode = ImageSource.FromStream(() => new MemoryStream(Bin));
                }
 
                this.QrCodeContentType = Constants.MimeTypes.Png;
                this.QrCodeUri = Uri;
                this.HasQrCode = true;
                ServiceRef.LogService.LogDebug($"GenerateQrCode done: {Uri} (bytes={Bin.Length})");
            }
        }
 
        public void RemoveQrCode()
        {
            lock (this.qrSync)
            {
                this.QrCode = null;
                this.QrCodeBin = null;
                this.QrCodeContentType = null;
                this.QrCodeUri = null;
                this.HasQrCode = false;
                if (!string.IsNullOrEmpty(this.qrTempFilePath))
                {
                    try
                    {
                        if (File.Exists(this.qrTempFilePath))
                            File.Delete(this.qrTempFilePath);
                    }
                    catch (Exception Ex)
                    {
                        ServiceRef.LogService.LogException(Ex);
                    }
                    finally
                    {
                        this.qrTempFilePath = null;
                    }
                }
            }
        }
 
        [RelayCommand]
        public async Task OpenQrPopup(string? Title)
        {
            if (this.QrCodeBin is null) return;
 
            ShowQRPopup QrPopup;
 
            if (!string.IsNullOrEmpty(Title))
                QrPopup = new(this.QrCodeBin, this.QrCodeUri, Title);
            else
                QrPopup = new(this.QrCodeBin, this.QrCodeUri);
 
            await ServiceRef.PopupService.PushAsync(QrPopup);
        }
 
        #region Properties
 
        [ObservableProperty]
        private ImageSource? qrCode;
 
        [ObservableProperty]
        private bool hasQrCode;
 
        [ObservableProperty]
        private string? qrCodeUri;
 
        [ObservableProperty]
        private int qrCodeWidth;
 
        [ObservableProperty]
        private int qrCodeHeight;
 
        [ObservableProperty]
        private int qrResolutionScale;
 
        [ObservableProperty]
        private byte[]? qrCodeBin;
 
        [ObservableProperty]
        private string? qrCodeContentType;
 
 
 
        #endregion
 
        #region ILinkableView
 
        public virtual bool IsLinkable => this.HasQrCode;
 
        public virtual bool EncodeAppLinks => true;
 
        public virtual string? Link => this.QrCodeUri;
 
        public abstract Task<string> Title { get; }
 
        public virtual bool HasMedia => this.HasQrCode;
 
        public virtual byte[]? Media => this.QrCodeBin;
 
        public virtual string? MediaContentType => this.QrCodeContentType;
 
        #endregion
    }
}