Navigation

Navigation is view-model-first. A route is a string key that maps to a view model type. Navigating resolves the view model from DI, and Avalonia finds the matching view by naming convention. Views never navigate to other views directly.

The flow

1. Something calls INavigationService.NavigateTo(route, parameter). Usually the sidebar, sometimes a feature view model (for example, the deck list navigating to flashcard-deck).
2. NavigationService (Mnemo.UI/Services/NavigationService.cs) looks the route up in its registry and resolves the view model type from the service provider. Route view models are transient, so each navigation gets a fresh instance.
3. If the view model implements INavigationAware, OnNavigatedTo(parameter) runs. This is how detail pages receive their subject, for example which deck to show.
4. The previous view model is disposed if it implements IDisposable, CurrentViewModel changes, and the Navigated event fires.
5. MainWindow.axaml binds a ContentControl to Navigation.CurrentViewModel. The global ViewLocator (Mnemo.UI/ViewLocator.cs) maps the view model type to a view by replacing ViewModels with Views and ViewModel with View in the type name, then instantiates it.

The convention in step 5 is the one hard requirement: a view model in ...ViewModels.FooViewModel must have a view at ...Views.FooView, or the workspace shows nothing.

Route registration

Modules register routes during bootstrap:

registry.RegisterRoute("flashcard-deck", typeof(FlashcardDeckDetailViewModel));

Route keys are referenced from sidebar items, search results (SearchNavigationTarget), and AI tools (navigate_to), so treat them as a public, stable surface.

AI gating

NavigationService watches the AI.EnableAssistant setting. The routes chat, path, and path-detail redirect to overview while the assistant is disabled. Turning the assistant off while on one of those routes resets the stack and navigates home. If you add an AI-only route, this is where the gate lives.

Known limitation: the back stack

The history stack is push-only. CanGoBack is exposed, but there is no GoBack(); nothing ever pops except the AI-disable reset. Breadcrumb navigation pushes a new entry rather than truncating the trail. Treat the back stack as unfinished; do not build features that depend on it.

Side effects

NavigationStatisticsTracker subscribes to Navigated and records dwell time per route into the statistics store. The keybind system also follows navigation: IKeyMap.SetActiveRoute switches which local keybind namespace is active.

Where the code lives

Concern	Path
Contracts	Mnemo.Core/Services/INavigationService.cs, INavigationRegistry.cs, INavigationAware.cs
Implementation	Mnemo.UI/Services/NavigationService.cs
View resolution	Mnemo.UI/ViewLocator.cs, registered in Mnemo.UI/App.axaml
Host control	Mnemo.UI/Views/MainWindow.axaml
Dwell tracking	Mnemo.UI/Services/NavigationStatisticsTracker.cs