---
phase: 01-foundation
plan: 03
subsystem: persistence
tags: [dotnet10, csharp, system-text-json, semaphoreslim, write-then-replace, unit-tests, xunit]

# Dependency graph
requires:
  - 01-01 (solution scaffold, test project)
  - 01-02 (TenantProfile model)
provides:
  - ProfileRepository: file I/O for profiles JSON with SemaphoreSlim write lock and write-then-replace
  - ProfileService: CRUD (GetProfiles/AddProfile/RenameProfile/DeleteProfile) with input validation
  - SettingsRepository: file I/O for settings JSON with same write-then-replace safety pattern
  - SettingsService: GetSettings/SetLanguage/SetDataFolder with supported-language validation
  - AppSettings model: DataFolder + Lang with camelCase JSON compatibility
affects:
  - 01-04 (MsalClientFactory may use ProfileService for tenant list)
  - 01-05 (TranslationSource uses SettingsService for lang)
  - 01-06 (FeatureViewModelBase may use ProfileService/SettingsService)
  - all feature plans (profile and settings are the core data contracts)

# Tech tracking
tech-stack:
  added: []
  patterns:
    - Write-then-replace: write to .tmp, validate JSON round-trip via JsonDocument.Parse, then File.Move(overwrite:true)
    - SemaphoreSlim(1,1) for async exclusive write access on per-repository basis
    - System.Text.Json with PropertyNamingPolicy.CamelCase for schema-compatible serialization
    - PropertyNameCaseInsensitive=true for deserialization to handle both old and new JSON
    - TDD with IDisposable temp file pattern for isolated unit tests

key-files:
  created:
    - SharepointToolbox/Core/Models/AppSettings.cs
    - SharepointToolbox/Infrastructure/Persistence/ProfileRepository.cs
    - SharepointToolbox/Infrastructure/Persistence/SettingsRepository.cs
    - SharepointToolbox/Services/ProfileService.cs
    - SharepointToolbox/Services/SettingsService.cs
    - SharepointToolbox.Tests/Services/ProfileServiceTests.cs
    - SharepointToolbox.Tests/Services/SettingsServiceTests.cs
  modified: []

key-decisions:
  - "Explicit System.IO using required in WPF project — WPF temp build project does not include System.IO in implicit usings; all file I/O classes need explicit namespace import"
  - "SettingsService validates only 'en' and 'fr' — matches app's supported locales; throws ArgumentException for any other code"
  - "LoadAsync on corrupt JSON throws InvalidDataException (not silent empty) — explicit failure is safer than silently discarding user data"

patterns-established:
  - "Write-then-replace: all file persistence uses .tmp write + JsonDocument.Parse validation + File.Move(overwrite:true) to protect against crash-corruption"
  - "IDisposable test pattern: unit tests use Path.GetTempFileName() + Dispose() for clean isolated file I/O tests"

requirements-completed:
  - FOUND-02
  - FOUND-10
  - FOUND-12

# Metrics
duration: 8min
completed: 2026-04-02
---

# Phase 1 Plan 03: Persistence Layer Summary

**ProfileRepository + SettingsRepository with write-then-replace safety, ProfileService + SettingsService with validation, 18 unit tests covering round-trips, corrupt-file recovery, concurrency, and JSON schema compatibility**

## Performance

- **Duration:** 8 min
- **Started:** 2026-04-02T10:09:13Z
- **Completed:** 2026-04-02T10:17:00Z
- **Tasks:** 2
- **Files modified:** 7

## Accomplishments

- ProfileRepository and SettingsRepository both implement write-then-replace (tmp file → JSON validation → File.Move) with SemaphoreSlim(1,1) preventing concurrent write corruption
- JSON serialization uses camelCase (PropertyNamingPolicy.CamelCase) — preserves existing user data field names: `profiles`, `name`, `tenantUrl`, `clientId`, `dataFolder`, `lang`
- ProfileService provides full CRUD with input validation (Name not empty, TenantUrl valid absolute URL, ClientId not empty)
- SettingsService validates language codes against supported set (en/fr only), allows empty dataFolder
- All 18 unit tests pass (10 ProfileServiceTests + 8 SettingsServiceTests); no skips

## Task Commits

Each task was committed atomically:

1. **Task 1: ProfileRepository and ProfileService with write-then-replace** - `769196d` (feat)
2. **Task 2: SettingsRepository and SettingsService** - `ac3fa5c` (feat)

**Plan metadata:** (docs commit follows)

## Files Created/Modified

- `SharepointToolbox/Core/Models/AppSettings.cs` - AppSettings model; DataFolder + Lang with camelCase JSON
- `SharepointToolbox/Infrastructure/Persistence/ProfileRepository.cs` - File I/O; SemaphoreSlim; write-then-replace; camelCase
- `SharepointToolbox/Infrastructure/Persistence/SettingsRepository.cs` - Same pattern as ProfileRepository for settings
- `SharepointToolbox/Services/ProfileService.cs` - CRUD on profiles; validates Name/TenantUrl/ClientId; throws KeyNotFoundException
- `SharepointToolbox/Services/SettingsService.cs` - Get/SetLanguage/SetDataFolder; validates language codes
- `SharepointToolbox.Tests/Services/ProfileServiceTests.cs` - 10 tests: round-trip, missing file, corrupt JSON, concurrency, schema keys
- `SharepointToolbox.Tests/Services/SettingsServiceTests.cs` - 8 tests: defaults, round-trip, JSON keys, tmp file, language/folder persistence

## Decisions Made

- Explicit `using System.IO;` required in WPF main project — the WPF temp build project does not include `System.IO` in its implicit usings, unlike the standard non-WPF SDK. All repositories need explicit namespace imports.
- `SettingsService.SetLanguageAsync` validates only "en" and "fr" using a case-insensitive `HashSet<string>`. Other codes throw `ArgumentException` immediately.
- `LoadAsync` on corrupt JSON throws `InvalidDataException` (not silent empty list/default) — this is an explicit safety decision: silently discarding corrupt data could mask accidental overwrites.

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] Added explicit System.IO using to WPF project files**
- **Found during:** Task 1 (dotnet test — first GREEN attempt)
- **Issue:** WPF temporary build project does not include `System.IO` in its implicit usings. `File`, `Path`, `Directory`, `IOException`, `InvalidDataException` all unresolved in the main project and test project.
- **Fix:** Added `using System.IO;` at the top of ProfileRepository.cs, SettingsRepository.cs, ProfileServiceTests.cs, and SettingsServiceTests.cs
- **Files modified:** All 4 implementation and test files
- **Verification:** Build succeeded with 0 errors, 18/18 tests pass
- **Committed in:** 769196d and ac3fa5c (inline with respective task commits)

---

**Total deviations:** 1 auto-fixed (Rule 3 — blocking build issue)
**Impact on plan:** One-line fix per file, no logic changes, no scope creep.

## Issues Encountered

None beyond the auto-fixed deviation above.

## User Setup Required

None - no external service configuration required.

## Next Phase Readiness

- ProfileService and SettingsService ready for injection in plan 01-04 (MsalClientFactory may need tenant list from ProfileService)
- SettingsService.SetLanguageAsync ready for TranslationSource in plan 01-05
- Both services follow the same constructor injection pattern — ready for DI container registration in plan 01-06 or 01-07
- JSON schema contracts locked: field names are tested and verified camelCase

---
*Phase: 01-foundation*
*Completed: 2026-04-02*