feat: Add media details sidebar and date handling features, including media grouping by date

libertas-frontend/src/lib/date-utils.ts

@@ -0,0 +1,36 @@
+import { format, parseISO, isToday, isYesterday } from "date-fns";
+import type { Media } from "@/domain/types";
+
+/**
+ * Groups a flat array of media items into a Map
+ * where keys are human-readable date strings.
+ * Assumes the media array is already sorted chronologically.
+ */
+export const groupMediaByDate = (
+  media: Media[],
+): Map<string, Media[]> => { // <-- Return a Map
+  return media.reduce(
+    (acc, m) => {
+      const dateString = m.date_taken ?? m.created_at;
+      const date = parseISO(dateString);
+
+      let groupTitle: string;
+
+      if (isToday(date)) {
+        groupTitle = "Today";
+      } else if (isYesterday(date)) {
+        groupTitle = "Yesterday";
+      } else {
+        // e.g., "November 2025"
+        groupTitle = format(date, "MMMM yyyy");
+      }
+
+      if (!acc.has(groupTitle)) { 
+        acc.set(groupTitle, []); 
+      }
+      acc.get(groupTitle)!.push(m);
+      return acc;
+    },
+    new Map<string, Media[]>(),
+  );
+};