---
phase: 10-branding-data-foundation
plan: 01
subsystem: branding
tags: [logo, base64, json-persistence, wpf-imaging, magic-bytes, compression]

requires: []

provides:
  - LogoData record (Base64 + MimeType init properties) — shared model for all logo storage
  - BrandingSettings class with nullable MspLogo — MSP-level branding persistence model
  - TenantProfile.ClientLogo property — per-tenant client logo (additive, no breaking changes)
  - BrandingRepository — JSON persistence with write-then-replace safety using SemaphoreSlim
  - IBrandingService / BrandingService — magic byte validation, auto-compression, MSP logo CRUD

affects:
  - 10-02 (branding UI ViewModel will consume IBrandingService)
  - 11-report-branding (HTML export will use LogoData from BrandingSettings and TenantProfile)
  - Phase 13-14 (TenantProfile extended — profile serialization must stay compatible)

tech-stack:
  added: []
  patterns:
    - BrandingRepository mirrors SettingsRepository exactly (SemaphoreSlim write-then-replace, JsonDocument validation)
    - LogoData as non-positional record with init properties (avoids System.Text.Json positional constructor pitfall)
    - BrandingService uses WPF PresentationCore (BitmapDecoder/TransformedBitmap/BitmapEncoder) for compression — no new NuGet package required
    - Magic byte detection (4 bytes PNG, 3 bytes JPEG) before extension check — format is determined by content, not filename

key-files:
  created:
    - SharepointToolbox/Core/Models/LogoData.cs
    - SharepointToolbox/Core/Models/BrandingSettings.cs
    - SharepointToolbox/Infrastructure/Persistence/BrandingRepository.cs
    - SharepointToolbox/Services/IBrandingService.cs
    - SharepointToolbox/Services/BrandingService.cs
    - SharepointToolbox.Tests/Services/BrandingRepositoryTests.cs
    - SharepointToolbox.Tests/Services/BrandingServiceTests.cs
  modified:
    - SharepointToolbox/Core/Models/TenantProfile.cs

key-decisions:
  - "Used WPF PresentationCore (BitmapDecoder/TransformedBitmap/JpegBitmapEncoder) for image compression instead of System.Drawing.Bitmap — System.Drawing.Common is not available without a new NuGet package on .NET 10, but WPF PresentationCore is already in the stack (net10.0-windows + UseWPF=true)"
  - "LogoData is a non-positional record (init properties, not constructor parameters) — prevents System.Text.Json deserialization failure on records with positional constructors"
  - "BrandingService.ImportLogoAsync is pure (no persistence) — caller decides where to store the LogoData; ViewModel in Phase 11 will call SaveMspLogoAsync or equivalent client logo save"

patterns-established:
  - "Repository pattern: BrandingRepository is structural clone of SettingsRepository — same SemaphoreSlim(1,1) write lock, write-tmp-then-validate-then-move safety protocol"
  - "Magic byte validation: PNG checked with 4 bytes (0x89 0x50 0x4E 0x47), JPEG with 3 bytes (0xFF 0xD8 0xFF) — content-based not extension-based"
  - "Compression two-pass: 300x300 quality 75 first, 200x200 quality 50 if still over limit"
  - "Test pattern: IDisposable + Path.GetTempFileName() + Dispose cleanup of .tmp files — matches existing SettingsServiceTests"

requirements-completed:
  - BRAND-01
  - BRAND-03
  - BRAND-06

duration: 4min
completed: 2026-04-08
---

# Phase 10 Plan 01: Branding Data Foundation Summary

**LogoData record + BrandingRepository (write-then-replace JSON) + BrandingService with PNG/JPEG magic byte validation and WPF-based auto-compression to 512 KB limit**

## Performance

- **Duration:** ~4 min
- **Started:** 2026-04-08T00:28:31Z
- **Completed:** 2026-04-08T00:32:26Z
- **Tasks:** 2
- **Files modified:** 8 (7 created, 1 modified)

## Accomplishments
- LogoData record, BrandingSettings model, and TenantProfile.ClientLogo property established as the shared data models for all logo storage across v2.2
- BrandingRepository persists BrandingSettings to branding.json with write-then-replace safety (SemaphoreSlim + tmp file + JsonDocument validation before move)
- BrandingService validates PNG/JPEG via magic bytes, rejects all other formats with descriptive error message mentioning PNG and JPG, auto-compresses files over 512 KB using WPF imaging in two passes

## Task Commits

Each task was committed atomically:

1. **Task 1: Create logo models, BrandingRepository, and repository tests** - `2280f12` (feat)
2. **Task 2: Create BrandingService with validation, compression, and tests** - `1303866` (feat)

## Files Created/Modified
- `SharepointToolbox/Core/Models/LogoData.cs` - Non-positional record with Base64 and MimeType init properties
- `SharepointToolbox/Core/Models/BrandingSettings.cs` - MSP logo wrapper with nullable MspLogo property
- `SharepointToolbox/Core/Models/TenantProfile.cs` - Extended with nullable ClientLogo property (additive only)
- `SharepointToolbox/Infrastructure/Persistence/BrandingRepository.cs` - JSON persistence mirroring SettingsRepository pattern
- `SharepointToolbox/Services/IBrandingService.cs` - Interface with ImportLogoAsync, Save/Clear/GetMspLogoAsync
- `SharepointToolbox/Services/BrandingService.cs` - Magic byte validation, WPF-based compression, MSP logo CRUD
- `SharepointToolbox.Tests/Services/BrandingRepositoryTests.cs` - 5 tests: defaults, round-trip, dir creation, TenantProfile serialization
- `SharepointToolbox.Tests/Services/BrandingServiceTests.cs` - 9 tests: PNG/JPEG acceptance, BMP rejection, empty file, no-compression, compression, CRUD

## Decisions Made
- Used WPF PresentationCore imaging (BitmapDecoder, TransformedBitmap, JpegBitmapEncoder) for compression — `System.Drawing.Common` is not available without a new NuGet package on .NET 10 and is not in the existing stack
- `ImportLogoAsync` is kept pure (no persistence side-effects) — caller decides where to store the returned `LogoData`, enabling reuse for both MSP logo and per-tenant client logo paths

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 1 - Bug] Used WPF PresentationCore instead of System.Drawing.Bitmap for compression**
- **Found during:** Task 2 (BrandingService implementation)
- **Issue:** Plan specified `System.Drawing.Bitmap` and `ImageCodecInfo`, but `System.Drawing.Common` is not in the project's package list and is not available on .NET 10 without an explicit NuGet package reference. Adding it would violate the v2.2 constraint ("No new NuGet packages")
- **Fix:** Implemented compression using `System.Windows.Media.Imaging` classes (BitmapDecoder, TransformedBitmap, JpegBitmapEncoder, PngBitmapEncoder) — fully available via WPF PresentationCore which is already in the stack
- **Files modified:** SharepointToolbox/Services/BrandingService.cs
- **Verification:** All 9 BrandingServiceTests pass including the compression test (400x400 random-pixel PNG over 512 KB compressed to under 512 KB)
- **Committed in:** 1303866 (Task 2 commit)

---

**Total deviations:** 1 auto-fixed (Rule 1 — implementation approach)
**Impact on plan:** No scope change. Compression behavior is identical: proportional resize to 300x300 at quality 75, then 200x200 at quality 50 if still over limit. WPF APIs provide the same capability without a new dependency.

## Issues Encountered
None — build and all tests passed first time after implementation.

## User Setup Required
None - no external service configuration required.

## Next Phase Readiness
- All logo storage models and infrastructure are ready for Phase 10 Plan 02 (branding UI ViewModel)
- BrandingService.ImportLogoAsync is the entry point for logo import flows in Phase 11
- TenantProfile.ClientLogo is ready; ProfileRepository requires no code changes (System.Text.Json handles the new nullable property automatically)
- 14 total Branding tests passing; 10 ProfileService tests confirm no regression from TenantProfile extension

---
*Phase: 10-branding-data-foundation*
*Completed: 2026-04-08*