---
phase: 03
plan: 02
title: StorageService — CSOM StorageMetrics Scan Engine
subsystem: storage
tags: [csom, storage-metrics, scan-engine, c#]
status: complete

dependency_graph:
  requires:
    - 03-01 (StorageNode, StorageScanOptions, IStorageService, export stubs, test scaffolds)
  provides:
    - StorageService (IStorageService implementation — CSOM scan engine)
  affects:
    - 03-07 (StorageViewModel will consume IStorageService via DI)

tech_stack:
  added: []
  patterns:
    - CSOM StorageMetrics loading pattern (ctx.Load with f => f.StorageMetrics expression)
    - ExecuteQueryRetryHelper.ExecuteQueryRetryAsync for all CSOM round-trips
    - Recursive subfolder scan with system folder filtering (Forms/, _-prefixed)
    - CancellationToken guard at top of every recursive step

key_files:
  created:
    - SharepointToolbox/Services/StorageService.cs
    - SharepointToolbox/Services/Export/StorageCsvExportService.cs
    - SharepointToolbox/Services/Export/StorageHtmlExportService.cs
    - SharepointToolbox/Services/Export/SearchCsvExportService.cs
    - SharepointToolbox/Services/Export/SearchHtmlExportService.cs
    - SharepointToolbox/Services/Export/DuplicatesHtmlExportService.cs
    - SharepointToolbox.Tests/Services/StorageServiceTests.cs
    - SharepointToolbox.Tests/Services/SearchServiceTests.cs
    - SharepointToolbox.Tests/Services/DuplicatesServiceTests.cs
    - SharepointToolbox.Tests/Services/Export/StorageCsvExportServiceTests.cs
    - SharepointToolbox.Tests/Services/Export/StorageHtmlExportServiceTests.cs
    - SharepointToolbox.Tests/Services/Export/SearchExportServiceTests.cs
    - SharepointToolbox.Tests/Services/Export/DuplicatesHtmlExportServiceTests.cs
  modified: []

decisions:
  - StorageService.VersionSizeBytes is derived (TotalSizeBytes - FileStreamSizeBytes, Math.Max 0) — not stored separately; set on StorageNode model
  - System folder filter uses Forms/ and _-prefix heuristic — matches SharePoint standard hidden folders
  - LastModified uses StorageMetrics.LastModified with fallback to Folder.TimeLastModified — StorageMetrics.LastModified may be DateTime.MinValue for empty libraries

metrics:
  duration: "1 min"
  completed_date: "2026-04-02"
  tasks_completed: 1
  files_created: 13
  files_modified: 0
---

# Phase 3 Plan 02: StorageService — CSOM StorageMetrics Scan Engine Summary

**One-liner:** CSOM scan engine implementing IStorageService using Folder.StorageMetrics with recursive subfolder traversal and ExecuteQueryRetryAsync on every round-trip.

## What Was Built

`StorageService` is the concrete implementation of `IStorageService`. It takes an already-authenticated `ClientContext` from the ViewModel and:

1. Loads all web lists in one CSOM round-trip, filtering to visible document libraries
2. For each library root folder, loads `Folder.StorageMetrics` (TotalSize, TotalFileStreamSize, TotalFileCount, LastModified) and `TimeLastModified` as fallback
3. With `FolderDepth > 0`, recurses into subfolders up to the configured depth, skipping `Forms/` and `_`-prefixed system folders
4. Returns a flat `IReadOnlyList<StorageNode>` where library roots are at `IndentLevel=0` and subfolders at `IndentLevel=1+`

## Deviations from Plan

### Auto-fixed Issues

**1. [Rule 3 - Blocking] Phase 3 export stubs and test scaffolds were absent**
- **Found during:** Pre-task check for 03-01 prerequisites
- **Issue:** Plan 03-01 models and interfaces existed on disk but the 5 export service stubs and 7 test scaffold files were not yet created, preventing `StorageServiceTests` from being discovered and the test filter commands from working
- **Fix:** Created all 5 export stubs (`StorageCsvExportService`, `StorageHtmlExportService`, `SearchCsvExportService`, `SearchHtmlExportService`, `DuplicatesHtmlExportService`) and 7 test scaffold files as specified in plan 03-01
- **Files modified:** 12 new files in `SharepointToolbox/Services/Export/` and `SharepointToolbox.Tests/Services/`
- **Commit:** 08e4d2e

## Test Results

| Test Class | Passed | Skipped | Failed |
|---|---|---|---|
| StorageServiceTests | 2 (VersionSizeBytes) | 2 (CSOM) | 0 |
| DuplicatesServiceTests | 5 (MakeKey) | 2 (CSOM) | 0 |

Build: 0 errors, 0 warnings.

## Self-Check: PASSED

- FOUND: SharepointToolbox/Services/StorageService.cs
- FOUND: SharepointToolbox/Services/Export/StorageCsvExportService.cs
- FOUND: SharepointToolbox.Tests/Services/StorageServiceTests.cs
- FOUND: commit b5df064 (feat(03-02): implement StorageService...)
- FOUND: commit 08e4d2e (feat(03-01): create Phase 3 export stubs and test scaffolds)