Files
decePubClient/CLAUDE.md
T
thepraandClaude Opus 5.5 d552baa578 Document the PrivaPub wiring
CLAUDE.md: the two APIs and their credentials, the services, where a
post is placed, the feed page and the globe, nerd stats, running
against a local PrivaPub or the pasture, and that resx keys must not
differ only by case.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw
2026-10-04 11:03:14 +02:00

377 lines
24 KiB
Markdown

# CLAUDE.md
This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
## What this is
decePubClient is a Blazor WebAssembly PWA (.NET 10). It is meant as a Pleroma-FE-like client for **PrivaPub**, the
owner's ActivityPub server, whose repo is `thepra/SocialPub`. It is deployed as a static site at
https://decepub.thepra.dev, and its API base address is `https://privapub.thepra.dev`
(`AppConfiguration:ApiBaseAddress` in `wwwroot/appsettings.json`).
It talks to PrivaPub through both of its APIs with one sign-in (see **PrivaPub wiring** below). The feed page has three
columns: navigation, the feed with a tab per kind of feed, and a 3D globe that follows the posts in view. Nerd stats sit
in tooltips wherever there is data. Development builds point at a local PrivaPub on `http://127.0.0.1:6970`
(`wwwroot/appsettings.Development.json`, never published).
`Docs/Insomnia_APIs.json` is an old API collection for a localhost backend. Don't treat it as PrivaPub's API.
## Sibling repo dependency
The project references `../SocialPub/PrivaPub.ClientModels/PrivaPub.ClientModels.csproj`, so SocialPub must be
checked out next to this repo. CI clones it there. That project supplies:
- the shared DTOs;
- `Policies` (IsAdmin, IsUser, IsModerator);
- the `FieldsNameResource` and `ErrorsResource` localization resources.
Before wiring anything to the API, read `../SocialPub/CLAUDE.md`. PrivaPub's route names (`/peasants/...`, `/mouth`,
`/anus`, ...) are deliberate. Never "correct" them. The API surface is the Mastodon client API plus PrivaPub's private
`/clientapi` and `/api/privapub/v1`.
To run against a local PrivaPub: start a mongod, run SocialPub's `PrivaPub` with the Development command in its
CLAUDE.md on `127.0.0.1:6970` (`Registrations__Mode=Open` lets `/clientapi/user/signup` create a root), then create
personas with `/clientapi/avatar/private/insert`. Federated posts come from SocialPub's pasture
(`tools/pasture/run.sh up gts akkoma`, then `tools/pasture/interop.sh gts akkoma`), whose API is `127.0.0.1:6971`.
Neither DB-IP nor PrivaPub locate private addresses, so for the globe set `RemoteInstance.Geo` in mongo and
`Statistics:Geo:Self` in PrivaPub's configuration.
## Commands
```sh
dotnet build decePubClient.csproj # what CI runs (-c Release) on every push to master and on PRs
dotnet run # dev server: https://localhost:7046 / http://localhost:5046
dotnet publish decePubClient.csproj -c Release -o publish # static site lands in publish/wwwroot
```
`global.json` pins SDK 10.0.100 with `rollForward: latestFeature`. There are no tests and no linter.
## CSS: Tailwind 4 + daisyUI 5, vendored, offline
`Styles/app.css` is compiled into `wwwroot/css/app.css` by the Tailwind CSS standalone binary with the daisyUI
plugin. `app.css` is gitignored and regenerated on every build.
**Nothing in the build or the CI may download from github.com.** Tools live in the repo, and the CSS build runs
without network access. NuGet restore still uses nuget.org.
- `tools/tailwind/` holds the pinned tools:
- Tailwind 4.3.3 as `tailwindcss-linux-x64.xz`;
- daisyUI 5.7.47 (`daisyui.mjs`, `daisyui-theme.mjs`);
- daisyUI's component reference, `daisyui-llms.txt`.
- `.gitattributes` keeps these files byte-exact.
- `tools/tailwind.sh prepare` checks them against the sha256 values pinned in the script, and unpacks the binary into
the gitignored `.tools/tailwind/`. It needs `xz`.
- Only linux-x64 is vendored.
- The script's header explains how to upgrade or add a platform.
- The `TailwindCompile` target in the csproj runs it, so `dotnet build` / `publish` are enough, in CI as well. Debug
builds use `--optimize`, Release builds `--minify`. Pass `-p:SkipTailwind=true` to skip it.
- `IncludeTailwindOutput` adds the generated file to `Content` before static web assets are resolved. Without that, a
clean-clone publish would ship `app.css` without its `.gz`/`.br` copies and outside `service-worker-assets.js`.
The deploy workflow checks for `css/app.css.gz`.
- `bash tools/tailwind.sh watch` rebuilds the CSS live next to `dotnet watch`.
- Tailwind scans every file `.gitignore` doesn't exclude (minus `tools/`, `wwwroot/vendor/`, `Docs/`), and only
generates the classes it finds written out **whole**. Never build a class name by concatenation or interpolation (`"btn-" + size`, `$"btn-{size}"`). Write
every variant as a literal, e.g. in a switch arm.
Ionicons 4.5 (`wwwroot/vendor/ionicons.min.css`, `<i class="ion-md-...">`) is loaded as its own stylesheet.
## Theme and neumorphism
- `Styles/theme.css` holds two daisyUI themes, `neo-light` (default) and `neo-dark` (`prefersdark`). Every colour
is an `hsl()` of `--neo-hue-light` / `--neo-hue-dark` / `--neo-chroma` (0 for the grey themes).
- `wwwroot/js/theme.js` sets those variables and `data-theme` on `<html>` from `PageSettings`. It runs in `<head>`
from localStorage, so there is no flash before Blazor boots. After that, CascadingState calls it through
`AppStatusService.ApplyTheme` whenever the settings change. With `PreferSystemTheming` it leaves `data-theme` off,
and the OS decides.
- Change the theme flags through `PageSettings.SetDarkMode` / `SetGray` / `SetHue` and
`CascadingState.UpdatePageSettings`, which keep the flags consistent:
- choosing light or dark leaves system theming;
- picking a hue leaves grey.
- `AppStatusService.IsDarkTheme()` tells which variant is showing.
- Settings → General edits every theme setting. NavMenu's toggle and slider are shortcuts to the dark and hue ones.
- `Styles/neo.css` holds the neumorphic layer:
- `neo-raised` / `neo-inset` / `neo-flat`, with sizes `neo-2xs` / `neo-xs` / `neo-sm` / `neo-md` (these replace the
old `neomorph is-nxsmall` classes);
- `neo-gradient(-pressed)` and `neo-hue-track`;
- `@utility <daisy-component>` overrides that give btn, input, select, card, … the neo look. daisyUI puts its rules
in sublayers of `utilities`, so these overrides beat **every** daisyUI rule. Each override must exclude the
daisyUI variants it shouldn't touch, e.g. `:not(:where(.btn-ghost, .btn-link, ...))`, and call sites drop a neo
shadow with `shadow-none!`.
- Never write `@utility collapse`. It brings back Tailwind's own `collapse` utility (`visibility: collapse`), and
every collapse disappears.
## daisyUI Blazor components (`Components/Daisy/`)
Every daisyUI component has a `D`-prefixed wrapper (`DButton`, `DModal`, `DDropdown`, `DInput`, ...), grouped by
daisyUI's categories into folders whose namespaces are imported in `_Imports.razor`. `/styleguide` (not linked) renders
all of them in every theme. When you add or change one:
- Map each enum to its classes in a switch with whole literal class names.
- Value-holding fields derive from `DInputBase<TValue>`, Blazor's `InputBase`, so `@bind-Value` and EditForm
validation work. Everything else derives from `DComponentBase` (`Class`, pass-through attributes, `Cx(...)`).
- Open/active state lives in C# (`@bind-IsOpen`, `@bind-Active`) and is rendered with daisyUI's `*-open` modifier
classes. No JS interop.
- What daisyUI does with scripts has a script-free equivalent here: `DCheckbox.Indeterminate` renders
`aria-checked="mixed"`, and `DCarousel`'s navigation links to the slides' ids, which Blazor scrolls to.
- `DCalendar` is the one exception: it wraps the vendored Cally web component (`wwwroot/vendor/cally.js`).
- Images and links in `/styleguide` stay local (`wwwroot/imgs/styleguide/`).
- Don't name a parameter after an HTML attribute (`Title`, `Style`, `Id`, `Label`, ...). Blazor matches attributes
to parameters without regard to case, so the parameter would swallow the attribute.
- Components don't use `Localizer` or `CascadingState`; their user-visible strings are parameters.
## Architecture
**Startup (`Program.cs`).**
- DI registration happens here.
- The named `HttpClient` "default" uses `ApiBaseAddress` as its base address. It falls back to the host's base
address when that setting is empty.
- `SetDefaultCulture()` (`Extensions/ExtensionMethods.cs`) runs before the app starts. It picks the culture from the
saved `PublicCacheData`, or on a first visit from the browser language.
- Only English (`en-GB`) and Italian (`it-IT`) have resources; any other language gets English.
- Settings → General changes the language, saves it, and reloads the app.
**`LayerComponents/CascadingState.razor`** wraps the router in `App.razor`. It is the app-wide state object. It handles:
- `PublicCacheData` (page settings: theme colours, dark/light/system theming, language), persisted in localStorage;
- the theme, applied through `AppStatusService.ApplyTheme` (`wwwroot/js/theme.js`);
- `IsOnline` / `IsOffline`, polled every 10 seconds;
- the session: `IsSignedIn`, `Personas` (the root's), `PersonaId` and `Persona` (its Mastodon `Account`), with
`LoadSession`, `SwitchPersona` and `SignOut`. A persona change re-renders every subscriber; pages compare
`PersonaId` and reload what belongs to the persona. The JWT is renewed hourly when needed;
- `ProcessError` / `ProcessWarning`, which log through `ILoggingService` and show a toast;
- `LogFromJs`, which JS calls back into through a `DotNetObjectReference`.
**Components and pages** inherit `LocalizableComponentBase`, the equivalent of b2b.next's `WidmannComponentBase`. It
supplies:
- `CascadingState`, `Localizer`, `Navigation` and `Toast`;
- `IsLoading`, which starts true, and `IsDefaultDisabled`;
- `AfterRenderAsyncJobs`, run once after the next render;
- `WhenOnline` / `StartOnlinePolling`.
`PagesBase` is an empty subclass of it that nothing uses. Never redeclare the base's members in a component.
**UI feedback.**
- `Services/ToastService.cs` is the snackbar: the SUtility extensions `AddResponseError(WebResult)` (silent on
410/cancelled; connectivity failures show as warnings), `AddResponseError(string)`, `AddResponseSuccess` (closes
after 5 s), `AddWarning` and `AddException`. `Components/ToastHost.razor`, placed in `MainLayout`, shows the
messages.
- `Components/ErrorViewer.razor` shows in-page errors: the cascading `EditContext`'s validation messages,
`AdditionalError` and `AdditionalErrors`.
**HTTP (`Services/IHttpService.cs`).**
- Routes are constants in `Models/APIs.cs` (b2b.next naming: `GET_`/`POST_`/`DELETE_`, `_M_` for routes built from
parameters), relative to `ApiBaseAddress`.
- The route picks the credentials: `clientapi/` sends the root's JWT, `api/` the current persona's Mastodon token
(exchanged when missing, exchanged once more and retried when PrivaPub refuses it), `oauth/` nothing.
- It also picks the JSON: `SUtility.MastodonSerializer` (snake_case, `MastodonJsonContext`) for `api/` and `oauth/`,
`SUtility.DefaultSerializer` (camelCase, enums by name like PrivaPub, `ClientJsonContext`) for `clientapi/`. A payload
can be an object (JSON), name/value pairs (a form) or a `Func<HttpContent>` (multipart), built once per attempt.
- Auth levels: `Get` / `Post` / `Delete` need credentials and end the session when PrivaPub refuses them; `GetAnon` /
`PostAnon` add them when there are some; `*TotallyAnon` send none (the login must not carry a JWT: PrivaPub
redirects it).
- `retryOnError` backoff: 1, 2, 4, 8, 16, 29 s, then 60 s, for at most 10 minutes.
- Failures never throw. They come back as responses carrying an invalid `WebResult`, with an `ErrorCode` from
`Models/FailureCodes.cs`; a cancelled request comes back as HTTP 410.
- Read failures with `ReadWebResult` (it understands `WebResult`, validation ProblemDetails and Mastodon's
`{"error": ...}`) and bodies with `DefaultReadFromJsonAsync` / `MastodonReadFromJsonAsync`; a body that doesn't fit
comes back as the default and is written to the browser console. `PageCursors()` reads `max_id`/`min_id` from `Link`.
- Every request PrivaPub answers is recorded in `RequestStats` (method, route template, status, duration, size, rate
limit headers; never a body or a token), for the nerd stats.
- PrivaPub's `WebResult` gets `IsInvalid` from `Extensions/WebResultExtensions.cs`, a C# 14 extension property.
**PrivaPub wiring.**
- **One sign-in** (`Services/AuthService.cs`, `Pages/Login.razor`): the root signs in on `/clientapi/user/login`, then
each persona the client uses gets its own Mastodon token in exchange for the JWT (PrivaPub's `PersonaExchange`,
RFC 8693 on `/oauth/token`, first-party client id `AppConfiguration:ClientId`). `AuthData` keeps the JWT and the
persona tokens; logout revokes every persona token, then forgets the session and IndexedDB.
- **Services** (`Services/`): `TimelineService` (every feed as `FeedPage`s of `FeedPost`s, paged by `max_id`/`min_id`;
circles are read as ids from `/clientapi` and hydrated through `/api/v1/statuses?id[]=`; located posts come from
`/clientapi/post/nearby` and have no Mastodon actions), `StatusService` (publish, favourite, boost, bookmark, delete,
threads, mute, block; located and group posts go through `/clientapi/post/insert`), `MediaService` (uploads),
`GroupService`, `InstanceService` and `ProvenanceService`.
- **Mastodon DTOs** are client-side, in `Models/Mastodon/` (snake_case). `/clientapi` DTOs come from
`PrivaPub.ClientModels`.
- **Where a post is** (`InstanceService.Locate`, `Models/FeedPost.cs`): its own place (Pixelfed's, `privapub.place`),
its event's venue, the reader for a located post, its author's server (PrivaPub's public projection: 0.1° for servers
with at least 10 users, else the country, drawn at `Helpers/CountryPoints.cs`), or nowhere (a CDN-fronted server).
Server descriptions are cached a day in localStorage (`ServerInfos`). PrivaPub's own host is the signed-in persona's
account host, since the API may be reached under another name.
- **The feed page** (`Pages/Index.razor`): `FeedTabs`, `Content` (the card, which does its own actions), `Composer`,
`GlobePanel`. Older pages load as the end comes near (`wwwroot/js/feed.js`); newer ones are polled every 45 s while
the page is visible (PrivaPub has no streaming) and wait behind a "new" button.
- **The globe** (`wwwroot/js/globe.js`, an ES module imported by `GlobePanel`) runs on globe.gl, vendored in
`wwwroot/vendor/globe/` with its textures (`SOURCES.md` has versions, licences and hashes; the service worker never
precaches it). It looks at the spherical mean of the located posts in view, pulses and draws an arc to a hovered
post, follows the theme (day/night texture), honours `prefers-reduced-motion` and pauses while hidden. The posts'
places reach it in one call per feed change; cards are matched by `data-post-id`.
- **Nerd stats** (`Components/Nerd/NerdTip.razor`, rows from `NerdRow`): a post's ids, times and provenance (read on
hover), its author and server, its place, media and counts; the feed's paging and last request; the globe's camera,
points and frame rate.
**Localization (`Services/CoalescingStringLocalizer.cs`).**
- Lookup order: this repo's `Resources/AllStrings.resx` (+ `.it.resx`), then `FieldsNameResource`, then
`ErrorsResource`.
- A missing key renders as the key itself, formatted with its arguments, so a typo fails silently.
- The class lives in namespace `collAnon.Client.Services`, a leftover from another project.
- `Resources/ErrorMessages.resx` is read by `[Required]` / `[StringLength]` through `ErrorMessageResourceType`. A new key
needs its `public static string` property in `ErrorMessages.Designer.cs` too, or validation throws at runtime.
**Client storage** comes in two layers:
- **localStorage** (Blazored.LocalStorage, camelCase JSON) holds `AuthData`, `PublicCacheData`, `FeedFilter` and the
server cache `ServerInfos`, keyed by `nameof(Type)`.
- **IndexedDB** (DnetIndexedDb, database `data`) is reached through `IStorage`. Its schema is declared in
`GenericExtensions.AddIndexedDb()`, and you must bump `WithVersion` when you change it.
- The schema is at version 3: the `ClientLogs` store that `IStorage.AddLog` writes (version 2 added it; version 3 left
the mock feed's `Message` store out).
**Auth.** `TokenAuthStateProvider` holds `AuthData` (localStorage, cached in memory) and builds the auth state from
it: the root's name, its policies as claims, and the current persona. Pages that need a session carry
`[Authorize]`; `RedirectToLogin` sends the reader to `/login?returnUrl=…`.
**JS interop.**
- `wwwroot/main.js` defines `window.*` helpers. `Services/AppStatusService.cs` calls them, mostly through the
synchronous `IJSInProcessRuntime`.
- Each helper reports its errors back through `window.logFromJs`.
- The other scripts (IndexedDB, HeadElement, rxjs) are loaded by `<script>` tags in `wwwroot/index.html`; the feed's
modules (`js/feed.js`, `js/globe.js`) are imported on demand through `IJSObjectReference`.
**PWA.** Published builds use `wwwroot/service-worker.published.js`, and `service-worker.js` is the dev version.
## Development rules
These rules are adapted from the owner's b2b.next project. They are enforced by review: the build doesn't check them,
so follow them in every change.
| Area | Rule |
|---|---|
| All | `var` everywhere; uninitialised locals are `var x = default(T);` |
| All | Primary constructors for DI (`class Foo(IBar bar)`), not constructor + fields |
| All | Every async method takes a `CancellationToken` as its last parameter |
| All | Early return on error: guard, handle, `return`; never if/else for success vs failure |
| Models / state | Lists and arrays `= []`, never null; no `= string.Empty` / `""` defaults; explicit enum defaults |
| Components | No `@{ }` blocks in markup: locals become `@code` members |
| Components | `[Inject]` in `@code`, never `@inject` |
| Components | Disable controls with `IsDefaultDisabled` (plus local conditions), never bare offline state |
| Components | Every text/number input declares `autocomplete` |
| Services | `Task<WebResult>` for mutations, `Task<List<T>>` (`[]` on error) for lists, `Task<T>` with a default for values |
| Localization | Every user-facing string through `Localizer`, its key in **both** `AllStrings.resx` and `AllStrings.it.resx` |
**CancellationToken.** It goes on every async method in services, `CascadingState` and helpers, defaulting to
`default`; pass it on to what you call. Exempt: Blazor lifecycle overrides, `[JSInvokable]` methods, framework overrides
(`GetAuthenticationStateAsync`), and private UI handlers bound from markup.
**State initialisation.** Initialise page and component state (`= new()`, `= []`) and bind it directly. No passthrough
getters and no `?.` chains over state that can't be null:
```csharp
List<FeedPost> posts = []; // DO
@posts.Count // DO
@(posts?.Count ?? 0) // DON'T
```
`= ""` is allowed only as a documented exception, with the reason in a comment (e.g. a decorative image's `Alt`).
**Pages that load data.** Pages fetch in `LoadData` and keep lifecycle concerns in the lifecycle method:
```csharp
protected override async Task OnInitializedAsync()
{
if (CascadingState.IsOffline)
{
WhenOnline(LoadData);
StartOnlinePolling();
IsLoading = false;
return;
}
await LoadData();
IsLoading = false;
}
```
- Reuse the base `IsLoading`; don't add per-section loading flags.
- A component that binds `IsDefaultDisabled` must set `IsLoading = false` once it is ready, even if it loads nothing;
otherwise its controls stay disabled.
- Never wrap a service call in try/catch. Services already catch and log, and return an invalid `WebResult`. Branch on
`result.IsInvalid` instead:
```csharp
var result = await StatusService.Delete(Status.Id);
if (result.IsInvalid)
{
Toast.AddResponseError(result);
return;
}
Toast.AddResponseSuccess(Localizer["Message deleted."]);
await OnDeleted.InvokeAsync(Post);
```
**Client services** follow b2b.next's two patterns (see its `StoreService`):
- Create `var result = new WebResult();`, call `httpService` inside a try/catch, and on a non-success status
`result = await response.Content.ReadWebResult(response.StatusCode, localizer, ct)`. Log with `ILoggingService`.
- Return `result` (mutations) or `[]` (lists), and set `result.Data` on success.
- POST bodies are JSON payloads for `/clientapi` and the Mastodon API (snake_case DTOs), forms for `/oauth`.
**In-page errors.** `ErrorViewer` takes `AdditionalError` for one message and `AdditionalErrors` for a list. Never
join a list into one string with `<br/>` or `\n`.
**Autocomplete values:**
- `autocomplete="off"` for search, filter and free text;
- `new-password` when setting a password;
- `one-time-code` for OTP (DOtp sets it);
- `username` and `current-password` on the login form, so password managers fill it;
- inside `Components/Daisy`, attributes pass through from the caller.
**Localization:**
- Keys are English source strings. Grep both resx files for an existing key before adding one; match keys exactly.
- Never add a key that differs from an existing one only by case ("users" next to "Users"): resource lookups collide
on them and one of the two silently shows the other's text. Reuse the existing key.
- Use `Localizer[key, args]`, never `string.Format(Localizer[key], …)`. Don't write `.Value`.
- Enum members shown through `Localizer[value.ToString()]` are keys too: when you add a member, add its key.
- Language names in the language picker stay in their own language.
**Formatting.** Date formats come from `SUtility.dateTimeFormat` / `timeFormat` / `dateTimeFormatExt`. Relative times
and sizes come from `GetPassedTime` / `GetFileSize` (`Extensions/GenericExtensions.cs`). No inline format strings for
display.
**JSON.** Register every `/clientapi` or localStorage type in `ClientJsonContext.cs` (camelCase: `theme.js` reads
`pageSettings` straight from localStorage), every Mastodon API type in `MastodonJsonContext.cs` (snake_case).
**Wiring a feature to PrivaPub:**
1. For `/clientapi`, add the request/response DTOs to `PrivaPub.ClientModels` in the SocialPub repo: `View*` for
responses, `*Request` for requests, `*Form` for forms with validation. Lists `= []`, no string defaults. For the
Mastodon API, add the shape to `Models/Mastodon/`.
2. Register them in `ClientJsonContext` or `MastodonJsonContext`, and the route in `Models/APIs.cs`.
3. Add a client service method that calls `IHttpService` against the server's route, following the patterns above.
4. Wire the page with early returns, toasts and/or an `ErrorViewer`.
**Not adopted from b2b.next, on purpose:**
- **The `tw:` Tailwind prefix.** b2b.next needs it next to MudBlazor's CSS; here daisyUI is the only component CSS.
- **Server-only rules:** no 5XX responses, the controller pattern, `IOptionsMonitor`, data access and caching.
- **b2b.next-specific features:** Excel import/export, password policy, legacy porting rules, the `{culture}` route
placeholder (PrivaPub's routes are absolute `/clientapi/...`), and the release/API-status worker.
- **Mandatory `/// <summary>` on every `[Parameter]`.** Document only what isn't obvious from the name.
## Deployment
Both workflows check the repo out with a plain `git fetch` from this Gitea, not `actions/checkout`, because the runner
would download that action from github.com. Never add a `uses:` step.
`.gitea/workflows/deploy.yml` runs on a `v*` tag or a manual dispatch, on a self-hosted runner that is also the web
host. The steps:
1. Publish the site.
2. Write `build.json` (commit, ref, time).
3. Snapshot the live directory to `/var/backups/decepub.thepra.dev`.
4. `rsync --delete` into `/var/www/decepub.thepra.dev`.
5. Check that `build.json` serves the new commit and that a deep client route returns 200 (the SPA fallback). Otherwise,
roll back to the snapshot.
The nginx vhost and headers are in `deploy/nginx/` (it sends `X-Robots-Tag: noindex, nofollow`), and
`deploy/max/setup.sh` is the one-time root setup on the server. If you add a file that must never be cached, add it to the `expires -1` locations in the vhost.
## Conventions
- Indent with tabs.
- `Nullable` is disabled and `ImplicitUsings` is enabled.
- Global Razor usings are in `_Imports.razor`.
- Styling uses the D components, Tailwind utilities and the `neo-*` utilities. Use `gap-*` rather than `space-x/y-*`
on flex containers; the feeds use `flex-col-reverse`, which `space-*` gets wrong.
- `SUtility.IfTrueThen(cond, "class")` is the helper for conditional classes.