[WordService] Refactor RestoreFrontierWords

[imnasnainaec]

This change is 

Summary by CodeRabbit

• New Features

  • Batch retrieval of multiple words for faster, more efficient fetching.
  • Single-word fetches now respect project scoping.

• Bug Fixes

  • Improved word restoration: handles empty input, deduplicates IDs, validates existence and non-deleted status in batch, and performs all-or-nothing restores to prevent partial or invalid restorations.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

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📝 Walkthrough

Walkthrough

Added a bulk GetWords method to the repository interface, implementation, and mock; and refactored RestoreFrontierWords to deduplicate IDs, perform batch validation/fetch via the new GetWords, and add all valid words to the Frontier in one all‑or‑nothing operation.

Changes

Cohort / File(s)	Summary
Repository Interface & Impl Backend/Interfaces/IWordRepository.cs, Backend/Repositories/WordRepository.cs	Added GetWords(string projectId, List<string> wordIds) to the interface and implementation; implementation opens an OTEL activity and returns project-scoped results as List<Word>.
Repository Mock Backend.Tests/Mocks/WordRepositoryMock.cs	Added GetWords(string projectId, List<string> wordIds) to the mock; updated GetWord(string projectId, string wordId) to filter by both ProjectId and Id and return cloned Word instances.
Service Logic Backend/Services/WordService.cs	Refactored RestoreFrontierWords to short-circuit on empty input, deduplicate IDs, batch-check frontier membership, fetch words via GetWords, validate existence/non-deleted in bulk, and perform a single batch addition to the Frontier (all-or-nothing).

Sequence Diagram(s)

sequenceDiagram
    participant Client as Client
    participant Service as WordService
    participant Repo as WordRepository
    participant Store as DataStore

    Client->>Service: RestoreFrontierWords(projectId, wordIds)
    Service->>Service: Deduplicate IDs & early return if empty
    Service->>Repo: GetWords(projectId, dedupedWordIds)
    Repo->>Store: Query words filtered by project + ids
    Store-->>Repo: Return matching Word records
    Repo-->>Service: Return List<Word>
    Service->>Service: Validate existence, non-deleted, not-in-frontier
    alt All valid
        Service->>Store: Add words to Frontier (batch)
        Store-->>Service: Acknowledge
        Service-->>Client: Success (true)
    else Any invalid
        Service-->>Client: Failure (false)
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~22 minutes

Possibly related PRs

• Allow getting a word from the Frontier #4148 — modifies repository word-retrieval APIs and adds bulk fetch semantics related to GetWords and frontier operations.

Suggested labels

refactor

Suggested reviewers

• jasonleenaylor

Poem

🐰 I hopped through lists and gathered each one,
Dedupe and fetch — a tidy batch is done.
No deleted leaves be carried on the run,
The Frontier fills in a single sunlit hop. 🥕

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 43.75% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title '[WordService] Refactor RestoreFrontierWords' clearly and specifically identifies the main change: refactoring the RestoreFrontierWords method in WordService with supporting changes to interfaces and implementations.

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✨ Finishing Touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch word-service-restore-frontier-words

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[codecov]

Codecov Report

❌ Patch coverage is 71.42857% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.08%. Comparing base (e85c895) to head (97711ee).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
Backend/Services/WordService.cs	71.42%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master    #4161       +/-   ##
===========================================
+ Coverage   74.79%   86.08%   +11.28%     
===========================================
  Files         302       56      -246     
  Lines       11081     4842     -6239     
  Branches     1393      603      -790     
===========================================
- Hits         8288     4168     -4120     
+ Misses       2390      528     -1862     
+ Partials      403      146      -257     

Flag	Coverage Δ
backend	86.08% <71.42%> (-0.09%)	⬇️
frontend	?

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[jasonleenaylor]

@jasonleenaylor reviewed 4 files and all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on imnasnainaec).