feat(planner): add sortEasiestFirst utility for J4 swap context

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/planner/week.test.ts

@@ -6,7 +6,8 @@ import {
 	weekDays,
 	isToday,
 	formatWeekRange,
-	formatDayLabel
+	formatDayLabel,
+	sortEasiestFirst
 } from './week';
 
 describe('getWeekStart', () => {
@@ -144,3 +145,52 @@ describe('formatDayLabel', () => {
 		expect(formatDayLabel('2026-03-30')).toContain(',');
 	});
 });
+
+describe('sortEasiestFirst', () => {
+	it('sorts easy before medium before hard', () => {
+		const recipes = [
+			{ id: '1', name: 'Hard', effort: 'hard', cookTimeMin: 10 },
+			{ id: '2', name: 'Easy', effort: 'easy', cookTimeMin: 10 },
+			{ id: '3', name: 'Medium', effort: 'medium', cookTimeMin: 10 }
+		];
+		const sorted = sortEasiestFirst(recipes);
+		expect(sorted.map((r) => r.effort)).toEqual(['easy', 'medium', 'hard']);
+	});
+
+	it('sorts by cookTimeMin ascending within same effort', () => {
+		const recipes = [
+			{ id: '1', name: 'Slow Easy', effort: 'easy', cookTimeMin: 60 },
+			{ id: '2', name: 'Fast Easy', effort: 'easy', cookTimeMin: 15 }
+		];
+		const sorted = sortEasiestFirst(recipes);
+		expect(sorted[0].name).toBe('Fast Easy');
+	});
+
+	it('treats missing effort as after hard', () => {
+		const recipes = [
+			{ id: '1', name: 'No effort', effort: undefined, cookTimeMin: 5 },
+			{ id: '2', name: 'Hard', effort: 'hard', cookTimeMin: 5 }
+		];
+		const sorted = sortEasiestFirst(recipes);
+		expect(sorted[0].effort).toBe('hard');
+	});
+
+	it('treats missing cookTimeMin as after defined values', () => {
+		const recipes = [
+			{ id: '1', name: 'No time', effort: 'easy', cookTimeMin: undefined },
+			{ id: '2', name: 'Has time', effort: 'easy', cookTimeMin: 30 }
+		];
+		const sorted = sortEasiestFirst(recipes);
+		expect(sorted[0].name).toBe('Has time');
+	});
+
+	it('does not mutate the original array', () => {
+		const recipes = [
+			{ id: '1', name: 'Hard', effort: 'hard', cookTimeMin: 10 },
+			{ id: '2', name: 'Easy', effort: 'easy', cookTimeMin: 10 }
+		];
+		const original = [...recipes];
+		sortEasiestFirst(recipes);
+		expect(recipes[0].effort).toBe(original[0].effort);
+	});
+});

frontend/src/lib/planner/week.ts

@@ -75,6 +75,25 @@ export function isToday(dateStr: string): boolean {
 	return dateStr === todayStr;
 }
 
+const EFFORT_ORDER: Record<string, number> = { easy: 0, medium: 1, hard: 2 };
+
+/**
+ * Returns a new array of recipes sorted easiest first (effort ASC, cookTimeMin ASC).
+ * Used for the J4 mid-week swap context — different from variety-first sorting in J2.
+ */
+export function sortEasiestFirst<T extends { effort?: string | null; cookTimeMin?: number | null }>(
+	recipes: T[]
+): T[] {
+	return [...recipes].sort((a, b) => {
+		const ea = a.effort != null ? (EFFORT_ORDER[a.effort] ?? 99) : 99;
+		const eb = b.effort != null ? (EFFORT_ORDER[b.effort] ?? 99) : 99;
+		if (ea !== eb) return ea - eb;
+		const ta = a.cookTimeMin ?? Infinity;
+		const tb = b.cookTimeMin ?? Infinity;
+		return ta - tb;
+	});
+}
+
 /**
  * Formats a week range: "30. Mär – 5. Apr 2026".
  */