From dfe3938afc5580a2b07a63f1be5f3646fbc4fe1a Mon Sep 17 00:00:00 2001
From: Experiments DB Dev <dev@experiments-db.local>
Date: Mon, 6 Jul 2026 15:40:24 -0400
Subject: [PATCH] feat(frontend): toCSV + csvFilename for data export

---
 frontend/src/lib/dataExport.js    | 20 ++++++++++++++++++++
 frontend/tests/dataExport.test.js | 30 ++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/frontend/src/lib/dataExport.js b/frontend/src/lib/dataExport.js
index ee52e49..d32649a 100644
--- a/frontend/src/lib/dataExport.js
+++ b/frontend/src/lib/dataExport.js
@@ -112,3 +112,23 @@ export function buildMatrix(statuses, animals, param) {
 
   return { columns, rows };
 }
+
+function escapeCsvCell(value) {
+  const s = value === null || value === undefined ? '' : String(value);
+  return /[",\n]/.test(s) ? `"${s.replace(/"/g, '""')}"` : s;
+}
+
+// Serialize a matrix to an RFC-4180-ish CSV string (LF line endings).
+// First column is the date; remaining columns follow matrix.columns order.
+export function toCSV(matrix) {
+  const header = ['Date', ...matrix.columns.map((c) => c.header)].map(escapeCsvCell).join(',');
+  const lines = matrix.rows.map((r) => [r.date, ...r.values].map(escapeCsvCell).join(','));
+  return [header, ...lines].join('\n');
+}
+
+// Build a download filename from the experiment title and parameter label.
+export function csvFilename(title, label) {
+  const slug = (s) => String(s ?? '').replace(/[^a-z0-9]+/gi, '-').replace(/^-+|-+$/g, '');
+  const base = [slug(title), slug(label)].filter(Boolean).join('-');
+  return `${base || 'export'}.csv`;
+}
diff --git a/frontend/tests/dataExport.test.js b/frontend/tests/dataExport.test.js
index 7be93a3..4f01f2a 100644
--- a/frontend/tests/dataExport.test.js
+++ b/frontend/tests/dataExport.test.js
@@ -125,3 +125,33 @@ describe('buildMatrix', () => {
     expect(m.columns.length).toBe(2);
   });
 });
+
+import { toCSV, csvFilename } from '../src/lib/dataExport';
+
+describe('toCSV', () => {
+  it('writes a header row of Date + column headers, then data rows', () => {
+    const matrix = {
+      columns: [{ id: 'a1', header: 'Alpha' }, { id: 'a2', header: 'Beta' }],
+      rows: [{ date: '2026-07-01', values: [5, ''] }, { date: '2026-07-02', values: ['', 9] }],
+    };
+    expect(toCSV(matrix)).toBe('Date,Alpha,Beta\n2026-07-01,5,\n2026-07-02,,9');
+  });
+  it('escapes commas, quotes, and newlines per RFC 4180', () => {
+    const matrix = {
+      columns: [{ id: 'a1', header: 'Note, field' }],
+      rows: [{ date: '2026-07-01', values: ['he said "hi"'] }, { date: '2026-07-02', values: ['line1\nline2'] }],
+    };
+    expect(toCSV(matrix)).toBe(
+      'Date,"Note, field"\n2026-07-01,"he said ""hi"""\n2026-07-02,"line1\nline2"',
+    );
+  });
+});
+
+describe('csvFilename', () => {
+  it('slugifies the experiment title and parameter label', () => {
+    expect(csvFilename('My Study #1', 'Success rate')).toBe('My-Study-1-Success-rate.csv');
+  });
+  it('falls back to "export" when both slugs are empty', () => {
+    expect(csvFilename('', '')).toBe('export.csv');
+  });
+});