Extract shared diff spatial types

[benvinegar]

Summary

• extract reusable VerticalBounds and SectionGeometry types into src/ui/lib/diffSpatial.ts
• update planned review row geometry and diff section geometry to share the same spatial model
• keep the existing hunk-specific metadata layered on top of the shared bounds types

Testing

• bun run typecheck
• bun test test/diff-section-geometry.test.ts test/ui-lib.test.ts

This PR description was generated by Pi using OpenAI o3

[greptile-apps]

Greptile Summary

This PR extracts the shared spatial primitive types VerticalBounds and SectionGeometry<THunkBounds> from the two geometry modules into a new src/ui/lib/diffSpatial.ts file, then threads them through PlannedHunkBounds, PlannedSectionGeometry, DiffSectionRowBounds, and DiffSectionGeometry via extends/type aliases. There are no functional changes — only structural deduplication of previously inline type declarations.

• New diffSpatial.ts introduces VerticalBounds (top, height) and the generic SectionGeometry<THunkBounds extends VerticalBounds>.
• PlannedHunkBounds now extends VerticalBounds and PlannedSectionGeometry becomes a type alias for SectionGeometry<PlannedHunkBounds>.
• DiffSectionRowBounds and DiffSectionGeometry similarly adopt the shared base types while preserving their extra fields (rowBounds, rowBoundsByKey).
• The private rowContributesToHunkBounds helper remains duplicated in both plannedReviewRows.ts and diffSectionGeometry.ts; since the PR is already consolidating shared spatial code, extracting this helper as a follow-up would complete the unification.

Confidence Score: 5/5

Safe to merge — this is a pure type-level refactor with no functional changes to runtime logic.

All three changed files produce structurally identical TypeScript shapes to their pre-PR versions; the only change is where the top/height/bodyHeight/hunkAnchorRows/hunkBounds properties are declared. No logic, caching, or measurement code was altered. The single P2 comment flags a pre-existing duplicate helper that could be consolidated but does not block merging.

No files require special attention.

Important Files Changed

Filename	Overview
src/ui/lib/diffSpatial.ts	New file introducing the shared VerticalBounds and generic SectionGeometry<THunkBounds> types extracted from both geometry modules; clean and well-documented.
src/ui/diff/plannedReviewRows.ts	PlannedHunkBounds now extends VerticalBounds and PlannedSectionGeometry is aliased to SectionGeometry<PlannedHunkBounds>; structurally identical to the previous inline declarations, no functional change.
src/ui/lib/diffSectionGeometry.ts	DiffSectionRowBounds and DiffSectionGeometry now derive from the shared types; all fields preserved, caching and measurement logic unchanged.

Class Diagram

%%{init: {'theme': 'neutral'}}%%
classDiagram
    class VerticalBounds {
        +number top
        +number height
    }

    class SectionGeometry~THunkBounds~ {
        +number bodyHeight
        +Map~number,number~ hunkAnchorRows
        +Map~number,THunkBounds~ hunkBounds
    }

    class PlannedHunkBounds {
        +string startRowId
        +string endRowId
    }

    class PlannedSectionGeometry

    class DiffSectionRowBounds {
        +string key
    }

    class DiffSectionGeometry {
        +DiffSectionRowBounds[] rowBounds
        +Map~string,DiffSectionRowBounds~ rowBoundsByKey
    }

    VerticalBounds <|-- PlannedHunkBounds : extends
    VerticalBounds <|-- DiffSectionRowBounds : extends
    SectionGeometry <|.. PlannedSectionGeometry : alias (THunkBounds=PlannedHunkBounds)
    SectionGeometry <|-- DiffSectionGeometry : extends (THunkBounds=PlannedHunkBounds)

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Comments Outside Diff (1)

1. src/ui/diff/plannedReviewRows.ts, line 28-32 (link)

   Duplicated rowContributesToHunkBounds function

   An identical rowContributesToHunkBounds function lives in both src/ui/diff/plannedReviewRows.ts (lines 28–32) and src/ui/lib/diffSectionGeometry.ts (lines 83–87). Since this PR is already extracting shared spatial utilities into diffSpatial.ts, this helper could be moved there (or a sibling shared module) and imported by both callers, keeping the rule consistent in one place.

_{Reviews (1): Last reviewed commit: "Extract shared diff spatial types" | Re-trigger Greptile}