refactor(collections): parsing and writing a list's links moves into collections helpers

server/src/nest/collections/collections.helpers.ts

@@ -0,0 +1,22 @@
+import type { CollectionLink } from '@trek/shared';
+
+/**
+ * Pure helpers of the collections domain, moved verbatim out of
+ * collections.service.ts. Nothing here touches the DB, so they stay plain
+ * exports rather than methods on CollectionsService.
+ */
+
+/** Links are stored as a JSON TEXT column; parse on read, stringify on write. */
+export function parseLinks(raw: unknown): CollectionLink[] | undefined {
+  if (typeof raw !== 'string' || !raw) return undefined;
+  try {
+    const v = JSON.parse(raw);
+    return Array.isArray(v) ? (v as CollectionLink[]) : undefined;
+  } catch {
+    return undefined;
+  }
+}
+
+export function serializeLinks(links: CollectionLink[] | undefined): string | null {
+  return links && links.length ? JSON.stringify(links) : null;
+}

server/src/nest/collections/collections.service.ts

@@ -62,7 +62,6 @@ import type {
   CollectionMember,
   CollectionMembership,
   CollectionPlace,
-  CollectionLink,
   CollectionCreateRequest,
   CollectionUpdateRequest,
   CollectionSavePlaceRequest,
@@ -76,22 +75,7 @@ import type {
 import { NotificationsService } from '../notifications/notifications.service';
 import { PlaceImportService, type ExportedCollectionFile } from '../place-import/place-import.service';
 import { UnitOfWork } from '../database/unit-of-work';
-
-/** Links are stored as a JSON TEXT column; parse on read, stringify on write. */
-function parseLinks(raw: unknown): CollectionLink[] | undefined {
-  if (typeof raw !== 'string' || !raw) return undefined;
-  try {
-    const v = JSON.parse(raw);
-    return Array.isArray(v) ? (v as CollectionLink[]) : undefined;
-  } catch {
-    return undefined;
-  }
-}
-
-function serializeLinks(links: CollectionLink[] | undefined): string | null {
-  return links && links.length ? JSON.stringify(links) : null;
-}
-
+import { parseLinks, serializeLinks } from './collections.helpers';
 
 // ---------------------------------------------------------------------------
 // Errors — thrown as plain Errors carrying a status; TrekExceptionFilter maps

server/tests/unit/nest/collections.helpers.test.ts

@@ -0,0 +1,31 @@
+/**
+ * The link helpers of the collections domain, which read and write the JSON
+ * TEXT column a list or a saved place keeps its links in.
+ * COLLECTIONS-HELPERS-001 to 003.
+ */
+import { parseLinks, serializeLinks } from '../../../src/nest/collections/collections.helpers';
+
+import { describe, expect, it } from 'vitest';
+
+const links = [{ url: 'https://menu.example/', label: 'Menu' }];
+
+describe('parseLinks', () => {
+  it('COLLECTIONS-HELPERS-001: reads a stored array of links back', () => {
+    expect(parseLinks(JSON.stringify(links))).toEqual(links);
+  });
+
+  it('COLLECTIONS-HELPERS-002: answers undefined for a missing, empty, unreadable or non-array value', () => {
+    expect(parseLinks(null)).toBeUndefined();
+    expect(parseLinks('')).toBeUndefined();
+    expect(parseLinks('{not json')).toBeUndefined();
+    expect(parseLinks(JSON.stringify(links[0]))).toBeUndefined();
+  });
+});
+
+describe('serializeLinks', () => {
+  it('COLLECTIONS-HELPERS-003: writes links as JSON and no links as null', () => {
+    expect(serializeLinks(links)).toBe(JSON.stringify(links));
+    expect(serializeLinks([])).toBeNull();
+    expect(serializeLinks(undefined)).toBeNull();
+  });
+});