Extract reverse-lookup scan to core/relationships (one shared impl)

src/app/components/DatasetsModal.tsx

@@ -16,6 +16,7 @@ import { useState } from 'react';
 import { useShallow } from 'zustand/react/shallow';
 import { datasetReference, type DataSource, type Dataset } from '@core/dataset';
 import { detectFormat, detectFormatFromUrl, type DataFormat } from '@core/format-detection';
+import { datasetUsageCounts, snippetsReferencingDataset } from '@core/relationships';
 import { closeModal, openModal, resnapshot } from '../modals/ModalCoordinator';
 import { confirm } from '../stores/ConfirmStore';
 import { notify } from '../stores/NotificationStore';
@@ -44,18 +45,6 @@ function humanBytes(bytes: number): string {
   return `${mb < 10 ? mb.toFixed(1) : Math.round(mb)} MB`;
 }
 
-/** Map of dataset name (lower-cased) → how many snippets reference it. */
-function usageByName(snippets: ReadonlyArray<{ datasetRefs: string[] }>): Map<string, number> {
-  const counts = new Map<string, number>();
-  for (const s of snippets) {
-    for (const ref of s.datasetRefs) {
-      const key = ref.toLowerCase();
-      counts.set(key, (counts.get(key) ?? 0) + 1);
-    }
-  }
-  return counts;
-}
-
 const SOURCE_OPTIONS: ReadonlyArray<SegmentedOption<DataSource>> = [
   { value: 'inline', label: 'Inline' },
   { value: 'url', label: 'URL' },
@@ -70,7 +59,7 @@ export function DatasetsModal() {
   const select = useDatasetStore((s) => s.select);
   const startCreate = useDatasetStore((s) => s.startCreate);
 
-  const usage = usageByName(snippets);
+  const usage = datasetUsageCounts(snippets);
   const ordered = [...datasets].sort(byModifiedDesc);
 
   const handleNew = () => {
@@ -165,8 +154,7 @@ function DatasetDetail({
   const selectSnippet = useSnippetStore((s) => s.selectSnippet);
   const [copied, setCopied] = useState(false);
 
-  const lower = dataset.name.toLowerCase();
-  const linked = snippets.filter((s) => s.datasetRefs.some((r) => r.toLowerCase() === lower));
+  const linked = snippetsReferencingDataset(snippets, dataset.name);
 
   const handleEdit = () => {
     startEdit();

src/app/services/RelationshipService.test.ts

@@ -45,23 +45,21 @@ describe('reverse lookup', () => {
 
 describe('renameDatasetEverywhere', () => {
   test('renames the dataset record and every referencing snippet', () => {
-    useDatasetStore
-      .getState()
-      .add(
-        createDataset({
-          name: 'Sales',
-          data: [{ a: 1 }],
-          format: 'json',
-          source: 'inline',
-          now: T,
-        }),
-      );
+    useDatasetStore.getState().add(
+      createDataset({
+        name: 'Sales',
+        data: [{ a: 1 }],
+        format: 'json',
+        source: 'inline',
+        now: T,
+      }),
+    );
     useSnippetStore.getState().hydrate([seedSnippet('a', 'Sales')], 'a');
     useSnippetStore.getState().publish(T);
 
-    const updated = renameDatasetEverywhere('Sales', 'Revenue', new Date('2026-07-01T00:00:00Z'));
+    const result = renameDatasetEverywhere('Sales', 'Revenue', new Date('2026-07-01T00:00:00Z'));
 
-    expect(updated).toBe(1);
+    expect(result).toEqual({ updated: 1 });
     expect(useDatasetStore.getState().datasets[0].name).toBe('Revenue');
     const s = useSnippetStore.getState().snippets[0];
     expect(s.datasetRefs).toEqual(['Revenue']);
@@ -69,6 +67,6 @@ describe('renameDatasetEverywhere', () => {
   });
 
   test('is a no-op when old and new names are equal', () => {
-    expect(renameDatasetEverywhere('Sales', 'Sales')).toBe(0);
+    expect(renameDatasetEverywhere('Sales', 'Sales')).toEqual({ updated: 0 });
   });
 });

src/app/services/RelationshipService.ts

@@ -13,25 +13,19 @@
  */
 
 import type { Snippet } from '@core/snippet';
+import { snippetsReferencingDataset } from '@core/relationships';
 import { useDatasetStore } from '../stores/DatasetStore';
 import { useSnippetStore } from '../stores/SnippetStore';
 
-// TODO: nothing in production calls this service yet — DatasetsModal derives
-// usage/linked-snippets inline (it must read `snippets` reactively, not via the
-// getState snapshot these use), and DatasetStore.save propagates rename itself
-// (it updates other fields besides the name, so it can't delegate cleanly).
-// `renameDatasetEverywhere` also matches by exact name, unlike the rest of the
-// case-insensitive naming policy, and arch/07 documents it returning `{ updated }`
-// not a bare number. Either reconcile the duplication (extract a reactive-friendly
-// pure `snippetsReferencing(snippets, name)` helper both sides share) or fold this
-// service in when M4's "Build Chart from dataset" needs a non-reactive caller.
+// The reverse-lookup scan itself is the pure `snippetsReferencingDataset`
+// (`core/relationships`) — the *one* implementation arch/07 §6 calls for. These
+// wrappers just bind it to a store snapshot for non-reactive callers (e.g. a
+// programmatic rename); the reactive UI calls the core helper directly with its
+// live `snippets` selection, so neither side duplicates the matching logic.
 
-/** Snippets whose `datasetRefs` include `name` (case-insensitive). */
+/** Snippets whose `datasetRefs` include `name` (case-insensitive), from the store. */
 export function findSnippetsReferencingDataset(name: string): Snippet[] {
-  const lower = name.toLowerCase();
-  return useSnippetStore
-    .getState()
-    .snippets.filter((s) => s.datasetRefs.some((ref) => ref.toLowerCase() === lower));
+  return snippetsReferencingDataset(useSnippetStore.getState().snippets, name);
 }
 
 /** Count for the dataset usage badge (spec §05 → List item). */
@@ -42,13 +36,18 @@ export function datasetUsageCount(name: string): number {
 /**
  * Rename a dataset and propagate everywhere (docs/architecture/07 §6): renames
  * the dataset record, then rewrites every referencing snippet's spec, draftSpec,
- * and datasetRefs. The caller is responsible for collision policy on `newName`
- * (the edit form rejects a taken name; programmatic paths pre-resolve a unique
- * one). Returns the number of snippets updated.
+ * and datasetRefs (via `SnippetStore.renameDatasetRefs`, the single rename impl).
+ * The caller is responsible for collision policy on `newName` (the edit form
+ * rejects a taken name; programmatic paths pre-resolve a unique one). Returns the
+ * number of snippets updated, as `{ updated }` (arch/07 §6).
  */
-export function renameDatasetEverywhere(oldName: string, newName: string, now?: Date): number {
-  if (oldName === newName) return 0;
+export function renameDatasetEverywhere(
+  oldName: string,
+  newName: string,
+  now?: Date,
+): { updated: number } {
+  if (oldName === newName) return { updated: 0 };
   const dataset = useDatasetStore.getState().datasets.find((d) => d.name === oldName);
   if (dataset) useDatasetStore.getState().update(dataset.id, { name: newName }, now);
-  return useSnippetStore.getState().renameDatasetRefs(oldName, newName, now);
+  return { updated: useSnippetStore.getState().renameDatasetRefs(oldName, newName, now) };
 }