Remove reference changes are lost

[myieye]

Resolves #30

Instead of dropping snapshots, this PR refactors the SnapshotWorker so that new snapshots triggered by deletes are handled by the same code that handles "normal" snapshots triggered by changes.

In theory we could take it even farther with something like:
private async Task UpdateEntity(Id, Action<Entity, ChangeContext, ...> updater) which would find the current entity, let the caller do there thing and then generate a new snapshot afterwards, checking whether it was deleted etc.

But, it's not quite that simple, so I didn't go for it in this PR.

Summary by CodeRabbit

• Tests

  • Expanded test coverage to validate robust handling of simultaneous updates and deletions, ensuring improved data integrity.

• Refactor

  • Streamlined internal change tracking and snapshot generation processes, enhancing overall system stability and reliability.

[coderabbitai]

Walkthrough

The pull request introduces two new test methods in the DataModelReferenceTests class to validate add/delete and update/delete behaviors in a single commit. Additionally, the ChangeContext class has been refactored to include new parameters and properties for improved internal state management, and the SnapshotWorker has been updated to use the enhanced ChangeContext for snapshot generation and deletion logic during commit processing.

Changes

Files	Change Summary
src/SIL.Harmony.Tests/…/DataModelReferenceTests.cs	Added two new test methods: one verifies that adding and deleting an entity in the same commit marks the definition as deleted, and the other verifies that an update followed by deletion correctly retains updates in the definition.
src/SIL.Harmony/…/ChangeContext.cs src/SIL.Harmony/…/SnapshotWorker.cs	Modified ChangeContext by changing its access modifier, updating its constructor to accept commitIndex and intermediateSnapshots, and adding corresponding public properties. Updated SnapshotWorker to replace direct commit usage with the new ChangeContext, including a new method for snapshot generation and updated deletion logic.

Sequence Diagram(s)

sequenceDiagram
    participant T as Test Method
    participant W as WriteNextChange
    participant CTX as ChangeContext
    participant SW as SnapshotWorker

    T->>W: Execute add/update/delete operations
    W->>CTX: Initialize ChangeContext with commitIndex & intermediateSnapshots
    CTX->>SW: Pass change context for commit processing
    SW->>SW: Generate snapshot for updated entity (GenerateSnapshotForEntity)
    SW->>CTX: Mark entity as deleted using updated ChangeContext
    T->>W: Validate entity state (reference, updated part-of-speech, and deletion timestamp)

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Assessment against linked issues

Objective	Addressed	Explanation
Ensure proper snapshot retention when entities are updated or created in the same commit (#30)	✅

Possibly related PRs

• Include snapshots from current commit when finding referencing snapshots #29: Involves changes to test methods and enhancements in reference handling via IChangeContext, which are closely related to the updated context usage and snapshot generation in this PR.

Suggested reviewers

• hahn-kev

Poem

In fields of code, I hop with glee,
New tests and snapshots, a joy to see.
Each commit a nibble on crunchy byte,
With deleted marks glowing in the night.
Hop along through loops and checks,
As I dance with changes and avoid all wrecks.
🐰 Code hops free, forever in flight!

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• 📝 Generate Docstrings

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[hahn-kev]

looks good, the slight refactoring of intermediate snapshots has made me even more uncomfortable with it than I already was... not sure what to do about that though.

[coderabbitai]

Actionable comments posted: 1

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 55f4ac3 and 4009ed7.

📒 Files selected for processing (3)

• src/SIL.Harmony.Tests/DataModelReferenceTests.cs (1 hunks)
• src/SIL.Harmony/Changes/ChangeContext.cs (1 hunks)
• src/SIL.Harmony/SnapshotWorker.cs (4 hunks)

🧰 Additional context used

🧬 Code Definitions (3)

src/SIL.Harmony.Tests/DataModelReferenceTests.cs (2)

src/SIL.Harmony.Sample/Models/Word.cs (2)

• Guid (16-25)
• Word (5-52)

src/SIL.Harmony/DataModel.cs (2)

• DataModel (14-350)
• DataModel (31-43)

src/SIL.Harmony/SnapshotWorker.cs (2)

src/SIL.Harmony/Changes/ChangeContext.cs (4)

• ChangeContext (5-29)
• ChangeContext (10-17)
• ValueTask (23-23)
• IObjectBase (28-28)

src/SIL.Harmony/Db/ObjectSnapshot.cs (2)

• ObjectSnapshot (32-80)
• ObjectSnapshot (34-48)

src/SIL.Harmony/Changes/ChangeContext.cs (4)

src/SIL.Harmony/SnapshotWorker.cs (3)

• SnapshotWorker (11-257)
• SnapshotWorker (20-29)
• SnapshotWorker (46-50)

src/SIL.Harmony/CrdtConfig.cs (2)

• CrdtConfig (12-94)
• CrdtConfig (31-37)

src/SIL.Harmony/Commit.cs (3)

• Commit (7-41)
• Commit (17-21)
• Commit (28-31)

src/SIL.Harmony/Db/ObjectSnapshot.cs (2)

• ObjectSnapshot (32-80)
• ObjectSnapshot (34-48)

⏰ Context from checks skipped due to timeout of 90000ms (3)

• GitHub Check: build
• GitHub Check: build
• GitHub Check: Analyze (csharp)

🔇 Additional comments (9)

src/SIL.Harmony.Tests/DataModelReferenceTests.cs (2)

88-104: Well-structured test for reference deletion in a single commit

This test properly validates that when a word and its definition are added and the word is immediately deleted in the same commit, the definition should still exist but be marked as deleted. This directly addresses the PR objective of ensuring reference changes aren't lost during delete operations.

---

106-128: Comprehensive test for update and delete operations in a single commit

This test effectively builds on the first test by adding complexity - it confirms that when a definition's part of speech is updated and its parent word is deleted within the same commit, both operations are properly processed. The definition retains its updated part of speech while also being marked as deleted.

src/SIL.Harmony/SnapshotWorker.cs (5)

83-83: Proper context enrichment for commit processing

The enhanced ChangeContext now receives additional parameters, allowing for better state management during commit processing.

---

101-101: Improved deletion handling and snapshot generation

By using the expanded context object and the new GenerateSnapshotForEntity method, the code now ensures that snapshots created as a result of delete operations are processed with the same logic as regular snapshots.

Also applies to: 103-104

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116-117: Updated method signature for better context preservation

Changed the MarkDeleted method to accept a ChangeContext instead of just a Commit, allowing it to access the enhanced context information. This enables consistent handling of snapshots during deletion operations.

Also applies to: 123-123

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132-133: Consistent snapshot generation and deletion handling

The consistent use of GenerateSnapshotForEntity and passing the full context to MarkDeleted ensures that recursive deletion operations maintain the same contextual awareness.

Also applies to: 137-138

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199-226: Well-encapsulated snapshot generation logic

The extraction of snapshot generation into a dedicated method greatly improves code organization and maintainability. The detailed comments explain the snapshot lifecycle well, and the logic for determining when to create root snapshots and when to preserve intermediate snapshots is clear.

The conditional saving of intermediate snapshots based on commit index parity is an interesting optimization for controlling snapshot frequency.

src/SIL.Harmony/Changes/ChangeContext.cs (2)

5-5: Appropriate access restriction for internal implementation details

Changing the class from public to internal is appropriate as it prevents external code from depending on these implementation details.

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10-17: Enhanced context construction for better state management

The constructor now accepts additional parameters to support the refactored snapshot generation logic, properly initializing the new properties.