Add optional room areas

src/frontend/utils/building-structure.ts

@@ -18,6 +18,19 @@ type FloorLike = Pick<FloorDto, "id" | "name"> & {
   buildingId?: string | null;
 };
 type RoomLike = Pick<RoomDto, "floorId">;
+type RoomAreaLike = Pick<RoomDto, "floorId" | "areaM2">;
+
+export interface RoomAreaSummary {
+  areaM2: number;
+  roomCount: number;
+  missingAreaCount: number;
+}
+
+export interface StructureAreaSummaries {
+  total: RoomAreaSummary;
+  byBuilding: Map<string | null, RoomAreaSummary>;
+  byFloor: Map<string | null, RoomAreaSummary>;
+}
 
 export interface FloorGroup<TFloor extends FloorLike = FloorLike> {
   /** null for floors without (known) building. */
@@ -262,6 +275,59 @@ export function countRoomsByFloor(
   return counts;
 }
 
+/**
+ * Sums only known room areas and counts missing values separately. Rooms with
+ * no known floor/building are grouped under null for the corresponding UI
+ * entries "Ohne Etage" and "Ohne Gebäude".
+ */
+export function summarizeRoomAreas(
+  rooms: ReadonlyArray<RoomAreaLike>,
+  floors: ReadonlyArray<FloorLike>,
+  buildings: ReadonlyArray<BuildingLike>
+): StructureAreaSummaries {
+  const buildingIds = toIdSet(buildings);
+  const floorsById = new Map(floors.map((floor) => [floor.id, floor]));
+  const byBuilding = new Map<string | null, RoomAreaSummary>();
+  const byFloor = new Map<string | null, RoomAreaSummary>();
+  const total = emptyAreaSummary();
+
+  for (const room of rooms) {
+    const floor = room.floorId === null ? undefined : floorsById.get(room.floorId);
+    const floorId = floor?.id ?? null;
+    const buildingId = floor
+      ? resolveFloorBuildingId(floor, buildingIds)
+      : null;
+    addRoomArea(total, room.areaM2);
+    addRoomArea(summaryFor(byFloor, floorId), room.areaM2);
+    addRoomArea(summaryFor(byBuilding, buildingId), room.areaM2);
+  }
+  return { total, byBuilding, byFloor };
+}
+
+function emptyAreaSummary(): RoomAreaSummary {
+  return { areaM2: 0, roomCount: 0, missingAreaCount: 0 };
+}
+
+function summaryFor(
+  summaries: Map<string | null, RoomAreaSummary>,
+  key: string | null
+) {
+  const existing = summaries.get(key);
+  if (existing) return existing;
+  const created = emptyAreaSummary();
+  summaries.set(key, created);
+  return created;
+}
+
+function addRoomArea(summary: RoomAreaSummary, areaM2: number | null) {
+  summary.roomCount += 1;
+  if (areaM2 === null) {
+    summary.missingAreaCount += 1;
+  } else {
+    summary.areaM2 += areaM2;
+  }
+}
+
 /** "EG · Haus A", "EG" (floor without building) or "Ohne Etage". */
 export function describeRoomLocation(
   room: RoomLike,