feat(excel): group entries by date, join names with ' & '

js/excel.js

@@ -8,16 +8,31 @@ export function readEmployeeNames(arrayBuffer) {
     .filter(name => name.length > 0);
 }
 
+// Pure helper: returns { names: [...], dates: [...] } columns for a schedule.
+// Multiple employees per date are joined alphabetically with " & ".
+export function buildScheduleColumns(assignments, employees) {
+  const nameById = Object.fromEntries(employees.map(e => [e.id, e.name]));
+  const byDate = new Map();
+  for (const a of assignments) {
+    if (!byDate.has(a.date)) byDate.set(a.date, []);
+    byDate.get(a.date).push(nameById[a.employeeId] ?? '');
+  }
+  const sortedDates = [...byDate.keys()].sort();
+  const names = sortedDates.map(d =>
+    byDate.get(d).slice().sort((x, y) => x.localeCompare(y, 'de')).join(' & ')
+  );
+  const dates = sortedDates.map(d => {
+    const [y, m, day] = d.split('-');
+    return day + '.' + m + '.' + y;
+  });
+  return { names, dates };
+}
+
 // Exports schedule as xlsx blob
-// assignments: [{ date: "2026-04-01", employeeId }]
+// assignments: [{ date: "2026-04-01", employeeId }] — multiple entries per date allowed
 // employees: [{ id, name }]
 export function exportSchedule(assignments, employees) {
-  const nameById = Object.fromEntries(employees.map(e => [e.id, e.name]));
-  const names = assignments.map(a => nameById[a.employeeId] ?? '');
-  const dates = assignments.map(a => {
-    const [y, m, d] = a.date.split('-');
-    return d + '.' + m + '.' + y;
-  });
+  const { names, dates } = buildScheduleColumns(assignments, employees);
   const ws = XLSX.utils.aoa_to_sheet([names, dates]);
   const wb = XLSX.utils.book_new();
   XLSX.utils.book_append_sheet(wb, ws, 'Moderationsplan');