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road-compiler/.trellis/spec/backend/direct-edit-api.md

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Direct Edit Solver And API

1. Scope / Trigger

This contract covers the pure direct-edit resolver and the workbench endpoints that preview, persist, checkpoint, and rebase native-road-edits/v2 documents. It is required because the feature crosses compiler, storage, and HTTP layers.

2. Signatures

resolveDirectEditConstraints(model, editDocument, context)
// -> { roadProfiles, junctionPlans, constraintStates, handles, diagnostics }

GET  /api/edit-state
POST /api/edit-preview
POST /api/edits
POST /api/revisions
POST /api/revisions/:id/rebase

3. Contracts

  • The resolver is deterministic and must not import fs, path, http, or write files. It accepts a baseline model, an optional validated v2 document, and { revisionId, compilerGeometryVersion, previewSeq } context.
  • GET /api/edit-state returns the active document, documentVersion, active revision, constraint states, diagnostics, and road-edit-handles/v1 manifest.
  • POST /api/edit-preview accepts document (or replacement constraints and operations) and optional integer previewSeq. It returns the same manifest/state data plus compiled layers, echoes previewSeq, and never changes active files. Work over the 300ms budget sets degraded: true.
  • POST /api/edits requires integer expectedDocumentVersion and either a complete document or replacement arrays. Saves through a staging file and rename, increments documentVersion, and returns the active revision.
  • A version mismatch returns HTTP 409 with { ok: false, error, current } and leaves the active document byte-identical.
  • POST /api/revisions requires a non-empty label; it creates an immutable checkpoint and returns its manifest plus current edit state.
  • POST /api/revisions/:id/rebase is read-only and returns status counts plus per-constraint details. pending, conflicted, and stale constraints do not enter geometry solving.

4. Validation & Error Matrix

Condition Required behavior
Missing or invalid v2 document fields Reject with a field-specific 400 error
Missing expectedDocumentVersion Reject with 400; do not write
Expected version differs from active version Return 409 and current version; do not write
Empty checkpoint label Reject with 400; no revision is created
Missing active workspace for preview Reject with 400; no files are created
Solver replay anchor cannot resolve Mark stale or conflicted with diagnostic; never silently apply
Compiler geometry version differs Mark all replayable constraints recheck without changing values
Invariant violation (lane width, crossing boundaries, self-intersection, connector bounds) Return a blocking diagnostic; do not clamp or silently repair

5. Good / Base / Bad Cases

  • Good: preview the same document later saved with the same active baseline; compiled layers and solver diagnostics agree, while tracked file bytes and mtimes remain unchanged.
  • Base: an empty v2 document yields byte-for-byte baseline geometry and an empty constraint-state list.
  • Bad: two tabs save version N; the second save with N receives 409 and cannot overwrite the first tab's document.

6. Tests Required

  • Unit: resolver purity, empty-document identity, five replay statuses, handle manifest fields, and blocking invariant diagnostics.
  • Integration: preview file bytes/mtimes unchanged, previewSeq echoed, preview layers matching formal compilation, and degraded represented as a boolean.
  • Persistence: atomic save, version-409 no-write path, checkpoint parent and digest integrity, and rebase counts/details.

7. Wrong vs Correct

Wrong

fs.writeFileSync(activeEdits, JSON.stringify(draft));

This permits half-written documents and allows a stale browser tab to overwrite newer edits.

Correct

if (expectedDocumentVersion !== current.documentVersion) throw conflict409();
saveEditDocument(activeEdits, { ...draft, documentVersion: current.documentVersion });

The service checks the version before the atomic version-bumping write, while the pure resolver remains reusable by preview and formal compilation.