Track and restore latest URL

[myieye]

Resolves #2210

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR implements server-side JSON file-backed preferences storage and integrates URL persistence across the application. It adds a new JsonFilePreferencesService, introduces preference key enumeration, updates app startup to restore last URLs, creates reactive storage utilities for frontend persistence, and replaces localStorage-based preferences with service-backed storage.

Changes

Cohort / File(s)	Summary
Backend Preferences Service Implementation backend/FwLite/FwLiteShared/Services/JsonFilePreferencesService.cs, backend/FwLite/FwLiteShared/Services/PreferenceKey.cs	New JSON file-backed preferences service with thread-safe in-memory caching, atomic save operations, and corresponding PreferenceKey enum with AppLastUrl member.
Backend Integration & Service Registration backend/FwLite/FwLiteMaui/App.xaml.cs, backend/FwLite/FwLiteWeb/FwLiteWebKernel.cs, backend/FwLite/FwLiteWeb/Program.cs, backend/FwLite/FwLiteShared/TypeGen/ReinforcedFwLiteTypingConfig.cs	Injects IPreferencesService into App constructor to restore last URL on startup; registers JsonFilePreferencesService in DI container; updates browser launch logic to use saved URL; exports PreferenceKey enum to TypeScript.
Frontend Storage & State Management Utilities frontend/viewer/src/lib/utils/storage-prop.svelte.ts, frontend/viewer/src/lib/utils/app-storage.svelte.ts, frontend/viewer/src/lib/utils/project-storage.svelte.ts	Introduces StorageProp class for reactive async-persisted storage values; adds app-storage singleton for tracking last URL; refactors project-storage to use new project-scoped StorageProp pattern instead of localStorage.
Frontend Route Tracking & Service API frontend/viewer/src/lib/services/service-provider.ts, frontend/viewer/src/AppRoutes.svelte	Changes tryUsePreferencesService to usePreferencesService (non-undefined return); adds runtime URL tracking via debounced pushState/replaceState/popstate handlers to persist current pathname+query+hash.
Generated TypeScript Types frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/PreferenceKey.ts, frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/index.ts	Generates TypeScript enum PreferenceKey with AppLastUrl member; adds re-export in Services index.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• Handles IPreferencesService wiring and TS type generation shared with MAUI/localStorage implementations (#2158)
• Refactors project-scoped storage architecture to use reactive StorageProp pattern for task selection persistence (#2142)
• Modifies frontend routing/URL initialization logic for persistent state restoration across sessions (#2018)

Suggested labels

🟨Medium

Suggested reviewers

• rmunn
• imnasnainaec

Poem

🐰 A rabbit's delight in persistent paths!
URLs remembered, no second lapse,
JSON files hold preferences dear,
Reactive storage keeps configs near,
Click, save, reload—same place reappears! 📍✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 7.14% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The PR fully meets issue #2189 objectives: introduces JsonFilePreferencesService backend implementation [App.xaml.cs, JsonFilePreferencesService.cs, FwLiteWebKernel.cs], enables server-side preference persistence with shared PreferenceKey enum [PreferenceKey.cs, ReinforcedFwLiteTypingConfig.cs], integrates URL restoration logic across backend and frontend [Program.cs, AppRoutes.svelte, app-storage.svelte.ts], and replaces localStorage with backend-backed approach [storage-prop.svelte.ts, project-storage.svelte.ts].
Out of Scope Changes check	✅ Passed	All changes are within scope of issue #2189: JSON-file preferences backend for Linux, preference key infrastructure, URL persistence and restoration across restarts, and shared type definitions between C# and TypeScript.
Title check	✅ Passed	The title 'Track and restore latest URL' accurately summarizes the main change: implementing URL tracking and restoration functionality across app restarts, which is the core objective of the PR.
Description check	✅ Passed	The pull request description 'Resolves #2210' is directly related to the changeset, which implements JSON-file-backed preferences for user URL restoration.

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✨ Finishing Touches

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• 📝 Generate docstrings (commit on current branch)

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch claude/track-url-session-restore-9Wd2q

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• Generate coding plan

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[github-actions]

UI unit Tests

  1 files  ±0   54 suites  ±0   28s ⏱️ +4s
140 tests ±0  140 ✅ ±0  0 💤 ±0  0 ❌ ±0 
207 runs  ±0  207 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit bc56c5f. ± Comparison against base commit 626dc12.

♻️ This comment has been updated with latest results.

[github-actions]

C# Unit Tests

165 tests  +3   165 ✅ +3   18s ⏱️ -1s
 23 suites ±0     0 💤 ±0 
  1 files   ±0     0 ❌ ±0 

Results for commit bc56c5f. ± Comparison against base commit 626dc12.

♻️ This comment has been updated with latest results.

[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (1)

frontend/viewer/src/AppRoutes.svelte (1)

25-28: Avoid magic number for debounce delay.

200 should be a named constant so this behavior is easier to tune and reason about.

💡 Suggested tweak

+  const URL_SAVE_DEBOUNCE_MS = 200;
   onMount(() => {
     let timeout: ReturnType<typeof setTimeout>;
     const saveUrl = () => {
       clearTimeout(timeout);
       timeout = setTimeout(() => {
         const { pathname, search, hash } = document.location;
         void appStorage.lastUrl.set(pathname + search + hash);
-      }, 200);
+      }, URL_SAVE_DEBOUNCE_MS);
     };

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@frontend/viewer/src/AppRoutes.svelte` around lines 25 - 28, Replace the magic
number 200 with a named constant (e.g., URL_SAVE_DEBOUNCE_MS) declared in module
scope of AppRoutes.svelte and use that constant when creating the timeout;
update the timeout logic that references the variable timeout and the call to
appStorage.lastUrl.set(pathname + search + hash) to use the new constant so the
debounce delay is easy to find and tune.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@backend/FwLite/FwLiteShared/Services/JsonFilePreferencesService.cs`:
- Around line 76-90: Save() currently catches and logs all exceptions, causing
Set()/Remove() to appear successful even when disk writes fail; change Save() to
surface failures instead of swallowing them by either rethrowing the caught
exception after logging (throw;) or returning a failure result that callers must
check, and update Set() and Remove() to propagate that failure (i.e., throw on
Save failure or return/propagate a false result) so callers get an exception or
error when File.WriteAllText/File.Move fails; reference Save(), Set(), Remove(),
_logger and _filePath when making the change.

In `@frontend/viewer/src/lib/utils/storage-prop.svelte.ts`:
- Line 27: The constructor currently calls void this.load() and other spots
(lines ~48-54) fire-and-forget the async load which can leave this.loading true
and produce unhandled rejections if backend.get() rejects; update the code so
the load() promise is observed and errors are handled: either add a .catch(...)
to the void this.load() call(s) in the constructor and at the other
fire-and-forget sites to log/handle the error, and/or modify the load() method
(the function named load that calls backend.get()) to wrap its await in
try/catch and a finally that always sets this.loading = false; ensure references
to backend.get() remain and use the class method names (constructor, load) so
the loading flag cannot remain true and no unhandled rejection escapes.

---

Nitpick comments:
In `@frontend/viewer/src/AppRoutes.svelte`:
- Around line 25-28: Replace the magic number 200 with a named constant (e.g.,
URL_SAVE_DEBOUNCE_MS) declared in module scope of AppRoutes.svelte and use that
constant when creating the timeout; update the timeout logic that references the
variable timeout and the call to appStorage.lastUrl.set(pathname + search +
hash) to use the new constant so the debounce delay is easy to find and tune.

---

ℹ️ Review info

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between dc02e1c and ab65466.

📒 Files selected for processing (13)

• backend/FwLite/FwLiteMaui/App.xaml.cs
• backend/FwLite/FwLiteShared/Services/JsonFilePreferencesService.cs
• backend/FwLite/FwLiteShared/Services/PreferenceKey.cs
• backend/FwLite/FwLiteShared/TypeGen/ReinforcedFwLiteTypingConfig.cs
• backend/FwLite/FwLiteWeb/FwLiteWebKernel.cs
• backend/FwLite/FwLiteWeb/Program.cs
• frontend/viewer/src/AppRoutes.svelte
• frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/PreferenceKey.ts
• frontend/viewer/src/lib/dotnet-types/generated-types/FwLiteShared/Services/index.ts
• frontend/viewer/src/lib/services/service-provider.ts
• frontend/viewer/src/lib/utils/app-storage.svelte.ts
• frontend/viewer/src/lib/utils/project-storage.svelte.ts
• frontend/viewer/src/lib/utils/storage-prop.svelte.ts

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Build	Status	Details	Updated (UTC)
default (Inspect)	✅ No changes detected	-	Mar 12, 2026, 10:23 AM