Adopt b2b.next's client patterns: services, page state, feedback

Ported from the owner's b2b.next and adapted from MudBlazor to the daisyUI
components:
- LocalizableComponentBase provides CascadingState, Navigation, Toast,
  IsLoading/IsDefaultDisabled, WhenOnline/StartOnlinePolling, and after-render
  jobs that actually run.
- CascadingState starts with initialised state and polls the online status
  with a PeriodicTimer. It reports errors through ILoggingService plus a toast,
  and disposes what it holds.
- New pieces:
  - ToastService + ToastHost, the snackbar, with AddResponseError/Success/
    Warning/Exception in SUtility;
  - ErrorViewer, which shows the validation messages plus AdditionalError(s);
  - LoggingService, which writes to the console and the IndexedDB client log.
- HttpService is rebuilt and registered:
  - auth levels Get/Post/Delete, *Anon and *TotallyAnon;
  - retry with backoff;
  - classified failures (FailureCodes) instead of exceptions;
  - HTTP 410 on cancel;
  - the "default" client.
  ReadWebResult and DefaultReadFromJsonAsync read its responses.
- ClientJsonContext is source-generated, and SUtility.DefaultSerializer and
  Blazored.LocalStorage use it.
- WebResult gains a C# 14 IsInvalid extension property.

The code follows the imported rules:
- Every service and async helper takes a CancellationToken last.
- Primary constructors replace constructor-plus-fields.
- MessagesService and IStorage return Task<WebResult> / Task<List<T>>.
  MessagesService is still mock, building its results in memory; the seed
  feed and thread moved to Faker.
- Index and ExpandMessage follow the page pattern: an offline guard with
  WhenOnline, LoadData, and early returns with toasts on the results they used
  to ignore. ExpandMessage reloads on route change and shows "not found"
  instead of a null message.
- Model and state collections are [], and the fake identity defaults moved
  out of the models.
- Components:
  - no ?. chains over initialised state;
  - [Inject] instead of @inject;
  - IsDefaultDisabled on the actions;
  - autocomplete on every text input;
  - Localizer[key, args] instead of string.Format;
  - the localizer no longer leaks its inner _pLocalizer.
- Settings → General gains a language picker (English/Italiano), and
  SetDefaultCulture limits the culture to those two.

Bugs fixed along the way:
- A compose with untouched (null) content passed the empty check.
- File errors were joined with <br/> and rendered as markup.
- ClientLogs.ErrorMessage() threw on warnings.
- CoalescingStringLocalizer[key, args] showed a raw "{0}" for missing keys.
- AppStatusService exposed a call to a JS function that doesn't exist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

Pages/ExpandMessage.razor

@@ -14,29 +14,37 @@
 					@Localizer["loading"]
 				</p>
 			}
-
-			@foreach (var message in Ancestors)
+			else if (IsNotFound)
 			{
-				<Content CssContainer="ml-6 w-auto" IncludeExpand="false" Message="message"
-							 OnMessageBoost="async (m) => await OnMessageBoost(m)" OnMessageDelete="async (m) => await OnMessageDelete(m)"
-							 OnMessageFavourite="async (m) => await OnMessageFavourite(m)" OnMessageReply="async (m) => await OnMessageReply(m)"
-							 OnMessageMediaDownload="async (m) => await OnMessageMediaDownload(m)"
-							 OnUserBlock="async (u) => await OnUserBlock(u)" OnUserDirectMessage="async (u) => await OnUserDirectMessage(u)" OnUserSilence="async (u) => await OnUserSilence(u)" />
+				<p class="w-full text-center text-lg">
+					<i class="ion-ios-remove-circle-outline"></i> @Localizer["This message doesn't exist."]
+				</p>
 			}
-
-			<Content Highlighted="true" IncludeExpand="false" Message="CurrentMessage"
-							 OnMessageBoost="async (m) => await OnMessageBoost(m)" OnMessageDelete="async (m) => await OnMessageDelete(m)"
-							 OnMessageFavourite="async (m) => await OnMessageFavourite(m)" OnMessageReply="async (m) => await OnMessageReply(m)"
-							 OnMessageMediaDownload="async (m) => await OnMessageMediaDownload(m)"
-							 OnUserBlock="async (u) => await OnUserBlock(u)" OnUserDirectMessage="async (u) => await OnUserDirectMessage(u)" OnUserSilence="async (u) => await OnUserSilence(u)" />
-
-			@foreach (var message in Descendants)
+			else
 			{
-				<Content CssContainer="ml-6 w-auto" IncludeExpand="false" Message="message"
+				@foreach (var message in Ancestors)
+				{
+					<Content CssContainer="ml-6 w-auto" IncludeExpand="false" Message="message"
 							 OnMessageBoost="async (m) => await OnMessageBoost(m)" OnMessageDelete="async (m) => await OnMessageDelete(m)"
 							 OnMessageFavourite="async (m) => await OnMessageFavourite(m)" OnMessageReply="async (m) => await OnMessageReply(m)"
 							 OnMessageMediaDownload="async (m) => await OnMessageMediaDownload(m)"
 							 OnUserBlock="async (u) => await OnUserBlock(u)" OnUserDirectMessage="async (u) => await OnUserDirectMessage(u)" OnUserSilence="async (u) => await OnUserSilence(u)" />
+				}
+
+				<Content Highlighted="true" IncludeExpand="false" Message="CurrentMessage"
+						 OnMessageBoost="async (m) => await OnMessageBoost(m)" OnMessageDelete="async (m) => await OnMessageDelete(m)"
+							 OnMessageFavourite="async (m) => await OnMessageFavourite(m)" OnMessageReply="async (m) => await OnMessageReply(m)"
+							 OnMessageMediaDownload="async (m) => await OnMessageMediaDownload(m)"
+							 OnUserBlock="async (u) => await OnUserBlock(u)" OnUserDirectMessage="async (u) => await OnUserDirectMessage(u)" OnUserSilence="async (u) => await OnUserSilence(u)" />
+
+				@foreach (var message in Descendants)
+				{
+					<Content CssContainer="ml-6 w-auto" IncludeExpand="false" Message="message"
+							 OnMessageBoost="async (m) => await OnMessageBoost(m)" OnMessageDelete="async (m) => await OnMessageDelete(m)"
+							 OnMessageFavourite="async (m) => await OnMessageFavourite(m)" OnMessageReply="async (m) => await OnMessageReply(m)"
+							 OnMessageMediaDownload="async (m) => await OnMessageMediaDownload(m)"
+							 OnUserBlock="async (u) => await OnUserBlock(u)" OnUserDirectMessage="async (u) => await OnUserDirectMessage(u)" OnUserSilence="async (u) => await OnUserSilence(u)" />
+				}
 			}
 
 		</div>
@@ -45,146 +53,137 @@
 </div>
 
 @code {
-	[CascadingParameter] CascadingState CascadingState { get; set; }
-	[Inject] NavigationManager Navigation { get; set; }
 	[Inject] IStorage DbStorage { get; set; }
 	[Inject] ILocalStorageService LocalStorage { get; set; }
 	[Inject] IBlazorDownloadFileService BlazorDownloadFileService { get; set; }
 	[Inject] MessagesService MessagesService { get; set; }
 	[Parameter] public string MessageId { get; set; }
 
-	List<Message> Ancestors { get; set; } = new();
+	List<Message> Ancestors { get; set; } = [];
 	Message CurrentMessage { get; set; } = new();
-	List<Message> Descendants { get; set; } = new();
-
+	List<Message> Descendants { get; set; } = [];
+	bool IsNotFound { get; set; }
 	TimeSortingType TimeSortingType { get; set; } = TimeSortingType.Ascending;
 
-	protected override async Task OnInitializedAsync()
+	// Parameters rather than initialization: following a link to another message reuses this page.
+	protected override async Task OnParametersSetAsync()
 	{
-		if (MessageId is { Length: 0 })
+		if (string.IsNullOrEmpty(MessageId))
 		{
-			Navigation.NavigateTo("/");
+			Navigation.NavigateTo("");
 			return;
 		}
 
-		var filters = await LocalStorage.GetItemAsync<ActionBarFilter>(nameof(ActionBarFilter));
-		if (filters == default)
-			await LocalStorage.SetItemAsync(nameof(ActionBarFilter), new ActionBarFilter());
-		else
-			TimeSortingType = filters.TimeSortingType;
+		IsLoading = true;
+		var filters = await LocalStorage.GetItemAsync<ActionBarFilter>(nameof(ActionBarFilter)) ?? new();
+		TimeSortingType = filters.TimeSortingType;
 
-		CurrentMessage = await DbStorage.GetMessage(MessageId);
-
-		Ancestors = new List<Message>
+		if (CascadingState.IsOffline)
 		{
-			new()
-			{
-				RootMessageId = default,
-				MessageId = "51C698E3-7C28-4C90-9212-48D5C81DE089",
-				User = Faker.GetRandomUser(),
-				MessageType = (MessageType)Random.Shared.Next(0, 4),
-				Title = CurrentMessage?.Title,
-				Content = "<p>esempio di messaggio <b>precedente</b> a quello espanso</p>",
-				Medias = new(),
-				CreatedAt = DateTime.UtcNow.AddMinutes(Random.Shared.Next(-5000, 0)),
-				IsFavourite = Random.Shared.Next() % 2 == 0,
-				BoostsCounter = Random.Shared.Next(0,100),
-				IsBoostedByCurrentUser = Random.Shared.Next() % 2 == 0,
-			}
-		};
+			WhenOnline(LoadData);
+			StartOnlinePolling();
+			IsLoading = false;
+			return;
+		}
 
-		Descendants = new List<Message>
-		{
-			new()
-			{
-				RootMessageId = default,
-				MessageId = "0569A1DF-46FC-4485-9F11-F8CDFB794404",
-				User = Faker.GetRandomUser(),
-				MessageType = (MessageType)Random.Shared.Next(0, 4),
-				Title = CurrentMessage?.Title,
-				Content = "<p>esempio di messaggio <b>successivo</b> a quello espanso</p>",
-				Medias = new(),
-				CreatedAt = DateTime.UtcNow.AddMinutes(Random.Shared.Next(-5000, 0)),
-				IsFavourite = Random.Shared.Next() % 2 == 0,
-				BoostsCounter = Random.Shared.Next(0,100),
-				IsBoostedByCurrentUser = Random.Shared.Next() % 2 == 0,
-			}
-		};
+		await LoadData();
 		IsLoading = false;
 	}
 
-	void OnTimeSortingChanged(TimeSortingType timeSortingType)
+	// The thread: the message from IndexedDB, the ones around it mock (Faker) until the app reads PrivaPub's context.
+	async Task LoadData()
 	{
-		TimeSortingType = timeSortingType;
+		var message = await DbStorage.GetMessage(MessageId);
+		IsNotFound = message is null;
+		if (IsNotFound)
+			return;
+
+		CurrentMessage = message;
+		(Ancestors, Descendants) = Faker.Thread(message);
 	}
 
 	async Task OnMessageReply(MessageForm messageForm)
 	{
-		var replyMessage = await MessagesService.SubmitMessage(messageForm);
-		Descendants.Add(new()
-			{
-				MessageId = Guid.NewGuid().ToString(),
-				Content = messageForm.Content?.ParseContent(messageForm.ContentType),
-				CreatedAt = DateTime.UtcNow,
-				MessageType = messageForm.MessageType,
-				Medias = messageForm.Media.Select(m => new Media
-				{
-					FileName = m.FileName,
-					AltText = m.AltText,
-					ContentType = m.ContentType,
-					Url = m.Base64Preview,
-					Blob = m.Blob
-				}).ToList(),
-				Title = messageForm.Title,
-				User = new MessageUser
-				{
-					UserId = CascadingState.User.Id,
-					UserName = CascadingState.User.UserName,
-					DisplayName = CascadingState.User.DisplayName,
-					PictureUrl = CascadingState.User.PictureUrl,
-					ProfileUrl = CascadingState.User.ProfileUrl,
-					BackgroundUrl = CascadingState.User.BackgroundUrl
-				},
-			});
+		var result = await MessagesService.SubmitMessage(messageForm, CascadingState.User);
+		if (result.IsInvalid)
+		{
+			Toast.AddResponseError(result);
+			return;
+		}
+
+		Descendants.Add(result.Data as Message);
 	}
 
-	async ValueTask OnMessageBoost(Message message)
+	async Task OnMessageBoost(Message message)
 	{
-		if (message.IsBoostedByCurrentUser) return;
-		var boostedMessage = await MessagesService.BoostUnboostMessage(message);
-		message.BoostsCounter += 1;
+		if (message.IsBoostedByCurrentUser)
+			return;
 
-		//Add to the home page in the background
+		var result = await MessagesService.BoostUnboostMessage(message);
+		if (result.IsInvalid)
+			Toast.AddResponseError(result);
 	}
 
-	async ValueTask OnMessageFavourite(Message message)
+	async Task OnMessageFavourite(Message message)
 	{
-		var favouriteMessage = await MessagesService.FavouriteUnfavouriteMessage(message);
-		message.IsFavourite = !message.IsFavourite;
+		var result = await MessagesService.FavouriteUnfavouriteMessage(message);
+		if (result.IsInvalid)
+			Toast.AddResponseError(result);
 	}
 
-	async ValueTask OnMessageDelete(Message message)
+	async Task OnMessageDelete(Message message)
 	{
-		var deleteResult = await MessagesService.DeleteMessage(message);
+		var result = await MessagesService.DeleteMessage(message);
+		if (result.IsInvalid)
+		{
+			Toast.AddResponseError(result);
+			return;
+		}
+
+		Toast.AddResponseSuccess(Localizer["Message deleted."]);
+		if (message == CurrentMessage)
+		{
+			Navigation.NavigateTo("");
+			return;
+		}
+
+		Ancestors.Remove(message);
+		Descendants.Remove(message);
 	}
 
-	async ValueTask OnMessageMediaDownload(Media media)
+	async Task OnMessageMediaDownload(Media media)
 	{
 		await BlazorDownloadFileService.DownloadFileAsync(media.FileName, media.Blob, media.ContentType);
 	}
 
-	async ValueTask OnUserBlock(MessageUser messageUser)
+	async Task OnUserBlock(MessageUser messageUser)
 	{
-		var blockResult = await MessagesService.BlockUserFromMessage(messageUser);
+		var result = await MessagesService.BlockUserFromMessage(messageUser);
+		if (result.IsInvalid)
+		{
+			Toast.AddResponseError(result);
+			return;
+		}
+
+		Toast.AddResponseSuccess(Localizer["{0} blocked.", messageUser.DisplayName]);
 	}
 
-	async ValueTask OnUserDirectMessage(Message message)
+	async Task OnUserDirectMessage(Message message)
 	{
-		var directMessage = await MessagesService.ReplyMessage(message, MessageType.Direct);
+		var result = await MessagesService.ReplyMessage(message, MessageType.Direct);
+		if (result.IsInvalid)
+			Toast.AddResponseError(result);
 	}
 
-	async ValueTask OnUserSilence(MessageUser messageUser)
+	async Task OnUserSilence(MessageUser messageUser)
 	{
-		var silenceResult = await MessagesService.SilenceUserFromMessage(messageUser);
+		var result = await MessagesService.SilenceUserFromMessage(messageUser);
+		if (result.IsInvalid)
+		{
+			Toast.AddResponseError(result);
+			return;
+		}
+
+		Toast.AddResponseSuccess(Localizer["{0} muted.", messageUser.DisplayName]);
 	}
-}
+}