feat(export): dimension primitives, date members, status index

frontend/src/lib/dataExport.js

@@ -54,6 +54,54 @@ export function listExportableParams(dailyTemplate, statuses) {
   return params;
 }
 
+export const EXPORT_DIMENSIONS = [
+  { dim: 'date', label: 'Date' },
+  { dim: 'subject', label: 'Subject' },
+  { dim: 'parameter', label: 'Parameter' },
+];
+
+export function dimLabel(dim) {
+  return EXPORT_DIMENSIONS.find((d) => d.dim === dim)?.label ?? '';
+}
+
+export function otherDimension(rowDim, colDim) {
+  return EXPORT_DIMENSIONS.map((d) => d.dim).find((d) => d !== rowDim && d !== colDim) ?? null;
+}
+
+// Resolve a subject's group value for a given group field id.
+// null  -> no grouping (field is falsy or '__none__')
+// '—'   -> grouping is on but this subject has no value
+export function subjectGroupValue(animal, groupField) {
+  if (!groupField || groupField === '__none__') return null;
+  if (groupField === '__name__') return animal?.animal_name ?? '—';
+  if (groupField === '__id__') return animal?.animal_id_string ?? '—';
+  const v = animal?.subject_info?.[groupField];
+  return v === null || v === undefined || v === '' ? '—' : v;
+}
+
+export function listDateMembers(statuses) {
+  const keys = new Set();
+  for (const s of statuses ?? []) {
+    if (s?.date) keys.add(dateKey(s.date));
+  }
+  return [...keys].sort().map((k) => ({ id: k, label: k, dateKey: k }));
+}
+
+// dateKey -> Map(animalId -> status); first status per (date, animal) wins,
+// scanning in date order (matches the legacy buildMatrix tie-break).
+export function buildStatusIndex(statuses) {
+  const index = new Map();
+  const ordered = [...(statuses ?? [])].sort((a, b) => dateKey(a?.date).localeCompare(dateKey(b?.date)));
+  for (const s of ordered) {
+    if (!s?.date || s.animal_id === null || s.animal_id === undefined) continue;
+    const dk = dateKey(s.date);
+    if (!index.has(dk)) index.set(dk, new Map());
+    const byAnimal = index.get(dk);
+    if (!byAnimal.has(s.animal_id)) byAnimal.set(s.animal_id, s);
+  }
+  return index;
+}
+
 // A cell has a value unless it is null, undefined, or the empty string.
 // (0 and false are real values.)
 function hasValue(v) {