feat: implement cross-device reading progress synchronization using SignalR and remove legacy quiz generation services.

src/NexusReader.Application/Abstractions/Services/IAiGenerateQuizService.cs

@@ -1,9 +0,0 @@
-using FluentResults;
-using NexusReader.Application.Queries.Quiz;
-
-namespace NexusReader.Application.Abstractions.Services;
-
-public interface IAiGenerateQuizService
-{
-    Task<Result<QuizDto>> GenerateQuizAsync(string contextBlockId, CancellationToken cancellationToken = default);
-}

src/NexusReader.Application/Commands/Sync/UpdateReadingProgressCommand.cs

@@ -0,0 +1,6 @@
+using FluentResults;
+using MediatR;
+
+namespace NexusReader.Application.Commands.Sync;
+
+public record UpdateReadingProgressCommand(string PageId, string UserId) : IRequest<Result>;

src/NexusReader.Application/Queries/Quiz/GetQuizQuestionsQuery.cs

@@ -1,5 +0,0 @@
-using NexusReader.Application.Abstractions.Messaging;
-
-namespace NexusReader.Application.Queries.Quiz;
-
-public record GetQuizQuestionsQuery(string ContextBlockId) : IQuery<QuizDto>;

src/NexusReader.Application/Queries/Quiz/GetQuizQuestionsQueryHandler.cs

@@ -1,20 +0,0 @@
-using FluentResults;
-using NexusReader.Application.Abstractions.Messaging;
-using NexusReader.Application.Abstractions.Services;
-
-namespace NexusReader.Application.Queries.Quiz;
-
-internal sealed class GetQuizQuestionsQueryHandler : IQueryHandler<GetQuizQuestionsQuery, QuizDto>
-{
-    private readonly IAiGenerateQuizService _aiService;
-
-    public GetQuizQuestionsQueryHandler(IAiGenerateQuizService aiService)
-    {
-        _aiService = aiService;
-    }
-
-    public async Task<Result<QuizDto>> Handle(GetQuizQuestionsQuery request, CancellationToken cancellationToken)
-    {
-        return await _aiService.GenerateQuizAsync(request.ContextBlockId, cancellationToken);
-    }
-}

src/NexusReader.Domain/Entities/NexusUser.cs

@@ -36,4 +36,14 @@ public class NexusUser : IdentityUser
     /// Collection of quiz results completed by the user.
     /// </summary>
     public ICollection<QuizResult> QuizResults { get; set; } = new List<QuizResult>();
+
+    /// <summary>
+    /// ID of the last page read by the user.
+    /// </summary>
+    public string? LastReadPageId { get; set; }
+
+    /// <summary>
+    /// Timestamp of the last reading progress update.
+    /// </summary>
+    public DateTime? LastReadAt { get; set; }
 }

src/NexusReader.Infrastructure/DependencyInjection.cs

@@ -65,7 +65,6 @@ public static class DependencyInjection
         }));
 
         services.AddScoped<IKnowledgeService, KnowledgeService>();
-        services.AddTransient<IAiGenerateQuizService, FakeAiGenerateQuizService>();
         services.AddTransient<IEpubService, EpubService>();
 
         services.AddAuthorizationCore(options =>
@@ -75,6 +74,11 @@ public static class DependencyInjection
 
         services.AddScoped<IAuthorizationHandler, ProUserHandler>();
 
+        services.AddMediatR(config => 
+        {
+            config.RegisterServicesFromAssembly(typeof(DependencyInjection).Assembly);
+        });
+
         return services;
     }
 }

src/NexusReader.Infrastructure/Handlers/UpdateReadingProgressCommandHandler.cs

@@ -0,0 +1,46 @@
+using FluentResults;
+using MediatR;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.EntityFrameworkCore;
+using NexusReader.Application.Commands.Sync;
+using NexusReader.Domain.Entities;
+using NexusReader.Infrastructure.Persistence;
+using NexusReader.Infrastructure.RealTime;
+
+namespace NexusReader.Infrastructure.Handlers;
+
+public class UpdateReadingProgressCommandHandler : IRequestHandler<UpdateReadingProgressCommand, Result>
+{
+    private readonly AppDbContext _context;
+    private readonly IHubContext<SyncHub> _hubContext;
+
+    public UpdateReadingProgressCommandHandler(
+        AppDbContext context, 
+        IHubContext<SyncHub> hubContext)
+    {
+        _context = context;
+        _hubContext = hubContext;
+    }
+
+    public async Task<Result> Handle(UpdateReadingProgressCommand request, CancellationToken cancellationToken)
+    {
+        var user = await _context.Users.FirstOrDefaultAsync(u => u.Id == request.UserId, cancellationToken);
+        if (user == null)
+        {
+            return Result.Fail("User not found.");
+        }
+
+        var now = DateTime.UtcNow;
+        user.LastReadPageId = request.PageId;
+        user.LastReadAt = now;
+
+        await _context.SaveChangesAsync(cancellationToken);
+
+        // Broadcast to other devices
+        await _hubContext.Clients
+            .Group($"User_{request.UserId}")
+            .SendAsync("ProgressUpdated", request.PageId, now, cancellationToken);
+
+        return Result.Ok();
+    }
+}

src/NexusReader.Infrastructure/NexusReader.Infrastructure.csproj

@@ -1,9 +1,13 @@
-<Project Sdk="Microsoft.NET.Sdk">
-
-  <ItemGroup>
-    <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
-  </ItemGroup>
-
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <ItemGroup>
+    <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+
   <ItemGroup>
     <PackageReference Include="GeminiDotnet.Extensions.AI" Version="0.23.0" />
     <PackageReference Include="Microsoft.AspNetCore.Authorization" Version="10.0.7" />

src/NexusReader.Infrastructure/Persistence/AppDbContext.cs

@@ -16,6 +16,12 @@ public class AppDbContext : IdentityDbContext<NexusUser>
 
     protected override void OnModelCreating(ModelBuilder modelBuilder)
     {
+        modelBuilder.Entity<NexusUser>(entity =>
+        {
+            entity.Property(u => u.LastReadPageId).HasMaxLength(255);
+            entity.Property(u => u.LastReadAt).IsRequired(false);
+        });
+
         base.OnModelCreating(modelBuilder);
 
         modelBuilder.Entity<SemanticKnowledgeCache>(entity =>

src/NexusReader.Infrastructure/RealTime/SyncHub.cs

@@ -0,0 +1,46 @@
+using MediatR;
+using Microsoft.AspNetCore.SignalR;
+using Microsoft.AspNetCore.Authorization;
+using NexusReader.Application.Commands.Sync;
+
+namespace NexusReader.Infrastructure.RealTime;
+
+[Authorize]
+public class SyncHub : Hub
+{
+    private readonly IMediator _mediator;
+
+    public SyncHub(IMediator mediator)
+    {
+        _mediator = mediator;
+    }
+
+    public async Task UpdateProgress(string pageId)
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await _mediator.Send(new UpdateReadingProgressCommand(pageId, userId));
+        }
+    }
+
+    public override async Task OnConnectedAsync()
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await Groups.AddToGroupAsync(Context.ConnectionId, $"User_{userId}");
+        }
+        await base.OnConnectedAsync();
+    }
+
+    public override async Task OnDisconnectedAsync(Exception? exception)
+    {
+        var userId = Context.UserIdentifier;
+        if (!string.IsNullOrEmpty(userId))
+        {
+            await Groups.RemoveFromGroupAsync(Context.ConnectionId, $"User_{userId}");
+        }
+        await base.OnDisconnectedAsync(exception);
+    }
+}

src/NexusReader.Infrastructure/Services/FakeAiGenerateQuizService.cs

@@ -1,23 +0,0 @@
-using FluentResults;
-using NexusReader.Application.Abstractions.Services;
-using NexusReader.Application.Queries.Quiz;
-
-namespace NexusReader.Infrastructure.Services;
-
-public sealed class FakeAiGenerateQuizService : IAiGenerateQuizService
-{
-    public async Task<Result<QuizDto>> GenerateQuizAsync(string contextBlockId, CancellationToken cancellationToken = default)
-    {
-        // 2000ms delay to highlight Skeleton loader visually
-        await Task.Delay(2000, cancellationToken);
-
-        var fakeQuiz = new List<QuizQuestionDto>
-        {
-            new("Co było głównym centrum włoskiego Renesansu?", new List<string> { "Wenecja", "Rzym", "Florencja", "Mediolan" }, 2),
-            new("Kto stanowił wpływowy ród mecenasów sztuki?", new List<string> { "Habsburgowie", "Medyceusze", "Borgiowie", "Sforzowie" }, 1),
-            new("Jaką koncepcją filozoficzną charakteryzował się renesans?", new List<string> { "Teocentryzmem", "Nihilizmem", "Humanizmem", "Egzystencjalizmem" }, 2)
-        };
-
-        return Result.Ok(new QuizDto(fakeQuiz));
-    }
-}

src/NexusReader.Maui/MauiProgram.cs

@@ -2,6 +2,8 @@ using Microsoft.Extensions.Logging;
 using NexusReader.Application.Abstractions.Services;
 using NexusReader.Infrastructure.Mobile.Services;
 using NexusReader.UI.Shared.Services;
+using NexusReader.Application;
+using MediatR;
 
 namespace NexusReader.Maui;
 
@@ -39,6 +41,14 @@ public static class MauiProgram
 			builder.Services.AddScoped<IThemeService, ThemeService>();
 			builder.Services.AddScoped<IFocusModeService, FocusModeService>();
 			builder.Services.AddScoped<IQuizStateService, QuizStateService>();
+			builder.Services.AddScoped<IReaderNavigationService, ReaderNavigationService>();
+			builder.Services.AddScoped<IKnowledgeGraphService, KnowledgeGraphService>();
+			builder.Services.AddScoped<IReaderInteractionService, ReaderInteractionService>();
+			builder.Services.AddScoped<KnowledgeCoordinator>();
+			builder.Services.AddScoped<ISyncService, SyncService>();
+			builder.Services.AddScoped<IIdentityService, IdentityService>();
+			
+			builder.Services.AddApplication();
 
 			return builder.Build();
 		}

src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor

@@ -10,6 +10,7 @@
 @inject IReaderNavigationService NavigationService
 @inject KnowledgeCoordinator Coordinator
 @inject IReaderInteractionService InteractionService
+@inject ISyncService SyncService
 
 <div class="reader-canvas @(ThemeService.IsLightMode ? "theme-light" : "theme-dark")">
     @if (ViewModel == null)
@@ -77,6 +78,11 @@
 
     protected override async Task OnAfterRenderAsync(bool firstRender)
     {
+        if (firstRender)
+        {
+            await SyncService.InitializeAsync();
+        }
+
         if (ViewModel != null && !_isJsInitialized)
         {
             _isJsInitialized = true;
@@ -109,6 +115,23 @@
     public void HandleBlockReached(string blockId, string content)
     {
         Coordinator.OnBlockReached(blockId, content);
+        
+        // Debounce sync update (simple version: every 5 seconds or on a timer)
+        _ = SyncService.UpdateProgressAsync(blockId);
+    }
+
+    private void HandleSyncProgressReceived(string blockId, DateTime timestamp)
+    {
+        // For now, let's just scroll to the node if it's in the current view, 
+        // or just log it. Usually, we should prompt the user.
+        Console.WriteLine($"[Sync] Received progress from another device: {blockId} at {timestamp}");
+        
+        // Simple auto-scroll if it's newer than what we have (we don't track our own timestamp yet, 
+        // but we can assume incoming syncs are from other active devices)
+        _ = InvokeAsync(async () => {
+             await ScrollToNodeAsync(blockId);
+             StateHasChanged();
+        });
     }
 
     [JSInvokable]
@@ -196,5 +219,6 @@
         InteractionService.OnScrollToBlockRequested -= HandleScrollRequested;
         InteractionService.OnHighlightBlockRequested -= HandleHighlightRequested;
         InteractionService.OnTextSelected -= HandleTextSelected;
+        SyncService.OnProgressReceived -= HandleSyncProgressReceived;
     }
 }

src/NexusReader.UI.Shared/NexusReader.UI.Shared.csproj

@@ -13,6 +13,7 @@
     <PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="10.0.7" />
     <PackageReference Include="MediatR" Version="12.1.1" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="10.0.7" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="10.0.7" />
   </ItemGroup>
 
   <ItemGroup>

src/NexusReader.UI.Shared/Services/ISyncService.cs

@@ -0,0 +1,11 @@
+using FluentResults;
+
+namespace NexusReader.UI.Shared.Services;
+
+public interface ISyncService
+{
+    Task<Result> InitializeAsync();
+    Task<Result> UpdateProgressAsync(string pageId);
+    event Action<string, DateTime> OnProgressReceived;
+    Task DisposeAsync();
+}

src/NexusReader.UI.Shared/Services/SyncService.cs

@@ -0,0 +1,112 @@
+using FluentResults;
+using Microsoft.AspNetCore.SignalR.Client;
+using NexusReader.Application.Abstractions.Services;
+using System.Net.Http;
+
+namespace NexusReader.UI.Shared.Services;
+
+public class SyncService : ISyncService, IAsyncDisposable
+{
+    private readonly HttpClient _httpClient;
+    private readonly INativeStorageService _storageService;
+    private readonly IPlatformService _platformService;
+    private HubConnection? _hubConnection;
+    private bool _isInitialized;
+    private CancellationTokenSource? _debounceCts;
+
+    public event Action<string, DateTime>? OnProgressReceived;
+
+    public SyncService(
+        HttpClient httpClient,
+        INativeStorageService storageService,
+        IPlatformService platformService)
+    {
+        _httpClient = httpClient;
+        _storageService = storageService;
+        _platformService = platformService;
+    }
+
+    public async Task<Result> InitializeAsync()
+    {
+        if (_isInitialized) return Result.Ok();
+
+        var tokenResult = await _storageService.GetSecureString("nexus_auth_token");
+        if (tokenResult.IsFailed) return Result.Fail("Not authenticated");
+
+        var baseUrl = _httpClient.BaseAddress?.ToString() ?? "http://localhost:5000/";
+        var hubUrl = new Uri(new Uri(baseUrl), "synchub").ToString();
+
+        _hubConnection = new HubConnectionBuilder()
+            .WithUrl(hubUrl, options =>
+            {
+                options.AccessTokenProvider = () => Task.FromResult<string?>(tokenResult.Value);
+            })
+            .WithAutomaticReconnect()
+            .Build();
+
+        _hubConnection.On<string, DateTime>("ProgressUpdated", (pageId, timestamp) =>
+        {
+            OnProgressReceived?.Invoke(pageId, timestamp);
+        });
+
+        try
+        {
+            await _hubConnection.StartAsync();
+            _isInitialized = true;
+            return Result.Ok();
+        }
+        catch (Exception ex)
+        {
+            return Result.Fail(ex.Message);
+        }
+    }
+
+    private string? _lastSentPageId;
+
+    public async Task<Result> UpdateProgressAsync(string pageId)
+    {
+        if (pageId == _lastSentPageId) return Result.Ok();
+        
+        // Proper trailing-edge debounce
+        _debounceCts?.Cancel();
+        _debounceCts = new CancellationTokenSource();
+        var token = _debounceCts.Token;
+
+        _ = Task.Run(async () =>
+        {
+            try
+            {
+                await Task.Delay(2000, token);
+                
+                if (!_isInitialized) await InitializeAsync();
+                
+                if (_hubConnection?.State == HubConnectionState.Connected)
+                {
+                    await _hubConnection.SendAsync("UpdateProgress", pageId, token);
+                    _lastSentPageId = pageId;
+                }
+            }
+            catch (TaskCanceledException) { /* Ignored, user kept scrolling */ }
+            catch (Exception ex)
+            {
+                Console.WriteLine($"[SyncService] Error sending progress: {ex.Message}");
+            }
+        }, token);
+
+        return Result.Ok();
+    }
+
+    public async Task DisposeAsync()
+    {
+        _debounceCts?.Cancel();
+        if (_hubConnection != null)
+        {
+            await _hubConnection.DisposeAsync();
+        }
+    }
+
+    async ValueTask IAsyncDisposable.DisposeAsync()
+    {
+        await DisposeAsync();
+    }
+}

src/NexusReader.Web.Client/NexusReader.Web.Client.csproj

@@ -16,7 +16,6 @@
 
   <ItemGroup>
     <ProjectReference Include="..\NexusReader.Application\NexusReader.Application.csproj" />
-    <ProjectReference Include="..\NexusReader.Infrastructure\NexusReader.Infrastructure.csproj" />
     <ProjectReference Include="..\NexusReader.UI.Shared\NexusReader.UI.Shared.csproj" />
   </ItemGroup>
 

src/NexusReader.Web.Client/Program.cs

@@ -4,8 +4,7 @@ using NexusReader.Application.Abstractions.Services;
 using NexusReader.Web.Client.Services;
 using NexusReader.UI.Shared.Services;
 using NexusReader.Application;
-using NexusReader.Infrastructure;
-using NexusReader.Infrastructure.Services;
+
 
 var builder = WebAssemblyHostBuilder.CreateDefault(args);
 
@@ -19,6 +18,7 @@ builder.Services.AddScoped<IReaderNavigationService, ReaderNavigationService>();
 builder.Services.AddScoped<IKnowledgeGraphService, KnowledgeGraphService>();
 builder.Services.AddScoped<IReaderInteractionService, ReaderInteractionService>();
 builder.Services.AddScoped<KnowledgeCoordinator>();
+builder.Services.AddScoped<ISyncService, SyncService>();
 
 // Identity & Auth Services
 builder.Services.AddOptions();
@@ -34,6 +34,5 @@ builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.
 
 builder.Services.AddApplication();
 builder.Services.AddScoped<IEpubService, WasmEpubService>();
-builder.Services.AddTransient<IAiGenerateQuizService, FakeAiGenerateQuizService>();
 
 await builder.Build().RunAsync();

src/NexusReader.Web.New/Program.cs

@@ -31,6 +31,8 @@ builder.Services.AddServerSideBlazor()
     {
         options.DetailedErrors = true;
     });
+builder.Services.AddSignalR();
+builder.Services.AddHttpContextAccessor();
 
 builder.Services.AddScoped<IPlatformService, WebPlatformService>();
 builder.Services.AddScoped<INativeStorageService, NexusReader.UI.Shared.Services.WebStorageService>();
@@ -41,6 +43,7 @@ builder.Services.AddScoped<IReaderNavigationService, ReaderNavigationService>();
 builder.Services.AddScoped<IKnowledgeGraphService, KnowledgeGraphService>();
 builder.Services.AddScoped<IReaderInteractionService, ReaderInteractionService>();
 builder.Services.AddScoped<KnowledgeCoordinator>();
+builder.Services.AddScoped<ISyncService, SyncService>();
 
 builder.Services.AddHttpClient("NexusAPI", client => 
 {
@@ -181,6 +184,7 @@ app.UseAntiforgery();
 app.UseAuthentication();
 app.UseAuthorization();
 app.MapStaticAssets();
+app.MapHub<NexusReader.Infrastructure.RealTime.SyncHub>("/synchub");
 
 // API endpoint for WASM client to fetch EPUB content
 app.MapGet("/api/epub/{index}", async (int index, IEpubService epubService) =>