fix(facets): export label and count columns in facet CSV download

src/components/SearchFacet/SearchFacetModal/SearchFacetModal.tsx

@@ -31,9 +31,9 @@ import { SelectedList } from './SelectedList';
 import { useDebounce } from '@/lib/useDebounce';
 import { FACET_DEFAULT_PREFIX, useGetFacetData } from '../useGetFacetData';
 import { useDownloadFile } from '@/lib/useDownloadFile';
-import { join, last, map, pipe, pluck, split } from 'ramda';
 import { parseAPIError } from '@/utils/common/parseAPIError';
-import { FacetItem, FacetLogic } from '../types';
+import { formatFacetCSV } from '../helpers';
+import { FacetLogic } from '../types';
 
 interface ISearchFacetModalProps extends Omit<IFacetListProps, 'onError'> {
   children: (props: { searchTerm: string }) => ReactNode;
@@ -199,16 +199,8 @@ const FacetDownloadButton = () => {
     enabled,
   });
 
-  const formatData = useCallback(
-    () =>
-      pipe<[FacetItem[]], string[], string[], string>(
-        pluck('val'),
-        map((s: string) => last(split('/', s)) ?? ''),
-        join('\n'),
-      )(treeData),
-    [treeData],
-  );
-  const { onDownload } = useDownloadFile(formatData, { filename: 'fulllist.txt' });
+  const formatData = useCallback(() => formatFacetCSV(treeData), [treeData]);
+  const { onDownload } = useDownloadFile(formatData, { filename: 'fulllist.csv', type: 'CSV' });
 
   useEffect(() => {
     if (enabled && !isFetching && isSuccess) {

src/components/SearchFacet/__tests__/helpers.test.ts

@@ -0,0 +1,67 @@
+import { describe, expect, it } from 'vitest';
+import { formatFacetCSV } from '../helpers';
+import { FacetItem } from '../types';
+
+const item = (val: string, count: number): FacetItem => ({
+  id: val,
+  val,
+  count,
+  parentId: null,
+  level: 0,
+});
+
+describe('formatFacetCSV', () => {
+  it('returns only the header for an empty list', () => {
+    expect(formatFacetCSV([])).toBe('Label,Count');
+  });
+
+  it('strips the hierarchical prefix from the label', () => {
+    const result = formatFacetCSV([item('0/Smith, J', 42)]);
+    expect(result).toBe('Label,Count\n"Smith, J",42');
+  });
+
+  it('includes the count column', () => {
+    const result = formatFacetCSV([item('0/Jones, B', 7)]);
+    expect(result).toContain(',7');
+  });
+
+  it('handles deeper hierarchy levels', () => {
+    const result = formatFacetCSV([item('1/Smith, J/Smith, John', 5)]);
+    expect(result).toBe('Label,Count\n"Smith, John",5');
+  });
+
+  it('escapes double-quotes in labels per RFC 4180', () => {
+    const result = formatFacetCSV([item('0/He said "hi"', 1)]);
+    expect(result).toBe('Label,Count\n"He said ""hi""",1');
+  });
+
+  it('wraps labels containing commas in quotes', () => {
+    const result = formatFacetCSV([item('0/Doe, Jane', 10)]);
+    expect(result).toBe('Label,Count\n"Doe, Jane",10');
+  });
+
+  it('handles non-hierarchical keys (no slash)', () => {
+    const result = formatFacetCSV([item('astronomy', 100)]);
+    expect(result).toBe('Label,Count\n"astronomy",100');
+  });
+
+  it('handles a key with an empty last segment (e.g. "0/")', () => {
+    const result = formatFacetCSV([item('0/', 5)]);
+    expect(result).toBe('Label,Count\n"",5');
+  });
+
+  it('handles an empty string key', () => {
+    const result = formatFacetCSV([item('', 0)]);
+    expect(result).toBe('Label,Count\n"",0');
+  });
+
+  it('produces one row per item', () => {
+    const items = [item('0/Alpha', 3), item('0/Beta', 7), item('0/Gamma', 1)];
+    const lines = formatFacetCSV(items).split('\n');
+    expect(lines).toHaveLength(4); // header + 3 rows
+    expect(lines[0]).toBe('Label,Count');
+    expect(lines[1]).toBe('"Alpha",3');
+    expect(lines[2]).toBe('"Beta",7');
+    expect(lines[3]).toBe('"Gamma",1');
+  });
+});

src/components/SearchFacet/helpers.ts

@@ -34,7 +34,7 @@ import {
   when,
 } from 'ramda';
 import { isNonEmptyString } from 'ramda-adjunct';
-import { FacetLogic, OnFilterArgs } from './types';
+import { FacetItem, FacetLogic, OnFilterArgs } from './types';
 import { isString } from '@/utils/common/guards';
 import { FacetField, IADSApiSearchParams } from '@/api/search/types';
 import { OBJECTS_API_KEYS } from '@/api/objects/objects';
@@ -249,6 +249,24 @@ export const getFilters = (query: IADSApiSearchParams): FilterTuple[] =>
     ]),
   )(query);
 
+/**
+ * Formats a list of facet items as a CSV string with Label and Count columns.
+ * Labels are always double-quoted; embedded double-quotes are doubled.
+ * Uses LF line endings (consistent with other CSV exports in this codebase).
+ *
+ * @example
+ * formatFacetCSV([{ val: '0/Smith, J', count: 42, ... }])
+ * // => "Label,Count\n\"Smith, J\",42"
+ */
+export const formatFacetCSV = (items: FacetItem[]): string => {
+  const rows = items.map((item) => {
+    const label = parseTitleFromKey(item.val) as string;
+    const escaped = label.replace(/"/g, '""');
+    return `"${escaped}",${item.count}`;
+  });
+  return ['Label,Count', ...rows].join('\n');
+};
+
 // get object name from react query cache
 export const getObjectName = (id: string, queryClient: QueryClient) => {
   const queryCache = queryClient.getQueryCache();

src/lib/useDownloadFile.ts

@@ -24,7 +24,7 @@ export const useDownloadFile = (value: string | (() => string), options: IUseDow
   const href = useMemo(() => {
     const content = typeof value === 'function' ? [value()] : [value];
     if (typeof window !== 'undefined' && isNonEmptyString(content[0])) {
-      const blob = new window.Blob(content, { type });
+      const blob = new window.Blob(content, { type: meta[0] });
       return window.URL.createObjectURL(blob);
     }
     return '';