perf(planning): reuse immutable non-working date counts

src/app/services/planning-objectives.spec.ts

@@ -75,6 +75,29 @@ describe('composable planning objectives', () => {
 		).toEqual([3, 7, 4, 6, 5, 2]);
 	});
 
+	it.each(['sum', 'count', 'maximum'] as const)(
+		'keeps %s distinct-date scores current with frozen and mutable period dates',
+		(aggregation) => {
+			const mutableDates = ['2024-05-08'];
+			const observations: OptimizationObservations = {
+				...empty,
+				timeOffPeriods: Object.freeze([
+					Object.freeze({
+						nonWorkingDates: Object.freeze(['2024-01-06', '2024-01-07', '2024-01-07']),
+					}),
+					Object.freeze({ nonWorkingDates: mutableDates }),
+				]),
+			};
+			const configuration = { ...OPTIMIZATION_PRESETS.nonWorkingDayGain, aggregation };
+			const initial = { sum: 3, count: 2, maximum: 2 };
+			expect(evaluateOptimization(configuration, observations)).toBe(initial[aggregation]);
+			expect(evaluateOptimization(configuration, observations)).toBe(initial[aggregation]);
+			mutableDates.push('2024-05-09', '2024-05-09', '2024-05-11');
+			const updated = { sum: 5, count: 2, maximum: 3 };
+			expect(evaluateOptimization(configuration, observations)).toBe(updated[aggregation]);
+		},
+	);
+
 	it.each(['sum', 'count', 'maximum'] as const)(
 		'defines empty %s as zero for every measure',
 		(aggregation) => {

src/app/services/planning-objectives.ts

@@ -203,6 +203,9 @@ export interface OptimizationObservations {
 	leavePlacements: readonly { supporting: boolean }[];
 }
 
+// Calendar geometry reuses frozen date arrays across candidate plans.
+const nonWorkingDateCounts = new WeakMap<readonly string[], number>();
+
 export function evaluateOptimization(
 	configuration: OptimizationConfiguration,
 	observations: OptimizationObservations,
@@ -224,9 +227,14 @@ export function evaluateOptimization(
 				.map((week) => week.value);
 			break;
 		case 'time-off-periods':
-			values = observations.timeOffPeriods.map(
-				(period) => new Set(period.nonWorkingDates).size,
-			);
+			values = observations.timeOffPeriods.map(({ nonWorkingDates }) => {
+				const cached = nonWorkingDateCounts.get(nonWorkingDates);
+				if (cached !== undefined) return cached;
+				const count = new Set(nonWorkingDates).size;
+				if (Object.isFrozen(nonWorkingDates))
+					nonWorkingDateCounts.set(nonWorkingDates, count);
+				return count;
+			});
 			break;
 		case 'work-sequences':
 			values = observations.workSequences