fix(backend): add role guard to variety-preview and extract shared scoring method

- Add @RequiresHouseholdRole("member") to GET /{planId}/variety-preview endpoint
  to require household membership (was accessible to any authenticated user)
- Extract scoreFromSimulatedSlots() private method eliminating duplicate logic
  between simulateVarietyScore() and the old computeCurrentScore()
- Fix loose variety preview test assertions (isBetween → exact assertEquals)
- Add test verifying negative scoreDelta when candidate is a duplicate recipe

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

backend/src/main/java/com/recipeapp/planning/PlanningService.java

@@ -166,68 +166,12 @@ public class PlanningService {
 
     private double simulateVarietyScore(WeekPlan plan, Recipe candidate, LocalDate slotDate,
                                          VarietyScoreConfig config, Set<UUID> recentlyCookedIds) {
-        // Build a simulated slot list: existing slots + candidate on slotDate
         List<SimulatedSlot> simulatedSlots = new ArrayList<>();
         for (WeekPlanSlot slot : plan.getSlots()) {
             simulatedSlots.add(new SimulatedSlot(slot.getRecipe(), slot.getSlotDate()));
         }
         simulatedSlots.add(new SimulatedSlot(candidate, slotDate));
-
-        List<String> checkedTagTypes = config.getRepeatTagTypes();
-        double wTagRepeat = config.getWTagRepeat().doubleValue();
-        double wIngredientOverlap = config.getWIngredientOverlap().doubleValue();
-        double wRecentRepeat = config.getWRecentRepeat().doubleValue();
-        double wPlanDuplicate = config.getWPlanDuplicate().doubleValue();
-
-        // 1. Tag-type repeats on consecutive days
-        Map<String, List<LocalDate>> tagDays = new LinkedHashMap<>();
-        for (SimulatedSlot slot : simulatedSlots) {
-            for (Tag tag : slot.recipe.getTags()) {
-                if (checkedTagTypes.contains(tag.getTagType())) {
-                    tagDays.computeIfAbsent(tag.getName(), k -> new ArrayList<>())
-                            .add(slot.date);
-                }
-            }
-        }
-        long tagRepeatCount = tagDays.values().stream()
-                .filter(this::hasConsecutiveDays)
-                .count();
-
-        // 2. Non-staple ingredient overlaps on consecutive days
-        Map<String, List<LocalDate>> ingredientDays = new LinkedHashMap<>();
-        for (SimulatedSlot slot : simulatedSlots) {
-            for (RecipeIngredient ri : slot.recipe.getIngredients()) {
-                if (!ri.getIngredient().isStaple()) {
-                    ingredientDays.computeIfAbsent(ri.getIngredient().getName(), k -> new ArrayList<>())
-                            .add(slot.date);
-                }
-            }
-        }
-        long ingredientOverlapCount = ingredientDays.values().stream()
-                .filter(this::hasConsecutiveDays)
-                .count();
-
-        // 3. Recent repeats from cooking log
-        long recentRepeatCount = simulatedSlots.stream()
-                .map(s -> s.recipe.getId())
-                .distinct()
-                .filter(recentlyCookedIds::contains)
-                .count();
-
-        // 4. Duplicate recipes within the simulated plan
-        Map<UUID, Long> recipeCounts = simulatedSlots.stream()
-                .collect(Collectors.groupingBy(s -> s.recipe.getId(), Collectors.counting()));
-        long duplicatePenaltyCount = recipeCounts.values().stream()
-                .filter(c -> c > 1)
-                .mapToLong(c -> c - 1)
-                .sum();
-
-        double score = 10.0;
-        score -= tagRepeatCount * wTagRepeat;
-        score -= ingredientOverlapCount * wIngredientOverlap;
-        score -= recentRepeatCount * wRecentRepeat;
-        score -= duplicatePenaltyCount * wPlanDuplicate;
-        return Math.max(0, Math.min(10, score));
+        return scoreFromSimulatedSlots(simulatedSlots, config, recentlyCookedIds);
     }
 
     private record SimulatedSlot(Recipe recipe, LocalDate date) {}
@@ -247,54 +191,57 @@ public class PlanningService {
                 .map(cl -> cl.getRecipe().getId())
                 .collect(Collectors.toSet());
 
-        // Current score: simulate with only existing slots
-        double currentScore = computeCurrentScore(plan, config, recentlyCookedIds);
-
-        // Projected score: add candidate on the given date
+        List<SimulatedSlot> currentSlots = plan.getSlots().stream()
+                .map(s -> new SimulatedSlot(s.getRecipe(), s.getSlotDate()))
+                .toList();
+        double currentScore = currentSlots.isEmpty() ? 10.0
+                : scoreFromSimulatedSlots(currentSlots, config, recentlyCookedIds);
         double projectedScore = simulateVarietyScore(plan, candidate, date, config, recentlyCookedIds);
 
         return new VarietyPreviewResponse(currentScore, projectedScore, projectedScore - currentScore);
     }
 
-    private double computeCurrentScore(WeekPlan plan, VarietyScoreConfig config, Set<UUID> recentlyCookedIds) {
-        List<WeekPlanSlot> slots = plan.getSlots();
-        if (slots.isEmpty()) return 10.0;
-
+    private double scoreFromSimulatedSlots(List<SimulatedSlot> slots, VarietyScoreConfig config,
+                                            Set<UUID> recentlyCookedIds) {
         List<String> checkedTagTypes = config.getRepeatTagTypes();
         double wTagRepeat = config.getWTagRepeat().doubleValue();
         double wIngredientOverlap = config.getWIngredientOverlap().doubleValue();
         double wRecentRepeat = config.getWRecentRepeat().doubleValue();
         double wPlanDuplicate = config.getWPlanDuplicate().doubleValue();
 
+        // 1. Tag-type repeats on consecutive days
         Map<String, List<LocalDate>> tagDays = new LinkedHashMap<>();
-        for (WeekPlanSlot slot : slots) {
-            for (Tag tag : slot.getRecipe().getTags()) {
+        for (SimulatedSlot slot : slots) {
+            for (Tag tag : slot.recipe.getTags()) {
                 if (checkedTagTypes.contains(tag.getTagType())) {
-                    tagDays.computeIfAbsent(tag.getName(), k -> new ArrayList<>()).add(slot.getSlotDate());
+                    tagDays.computeIfAbsent(tag.getName(), k -> new ArrayList<>()).add(slot.date);
                 }
             }
         }
         long tagRepeatCount = tagDays.values().stream().filter(this::hasConsecutiveDays).count();
 
+        // 2. Non-staple ingredient overlaps on consecutive days
         Map<String, List<LocalDate>> ingredientDays = new LinkedHashMap<>();
-        for (WeekPlanSlot slot : slots) {
-            for (RecipeIngredient ri : slot.getRecipe().getIngredients()) {
+        for (SimulatedSlot slot : slots) {
+            for (RecipeIngredient ri : slot.recipe.getIngredients()) {
                 if (!ri.getIngredient().isStaple()) {
                     ingredientDays.computeIfAbsent(ri.getIngredient().getName(), k -> new ArrayList<>())
-                            .add(slot.getSlotDate());
+                            .add(slot.date);
                 }
             }
         }
         long ingredientOverlapCount = ingredientDays.values().stream().filter(this::hasConsecutiveDays).count();
 
+        // 3. Recent repeats from cooking log
         long recentRepeatCount = slots.stream()
-                .map(s -> s.getRecipe().getId())
+                .map(s -> s.recipe.getId())
                 .distinct()
                 .filter(recentlyCookedIds::contains)
                 .count();
 
+        // 4. Duplicate recipes within the plan
         Map<UUID, Long> recipeCounts = slots.stream()
-                .collect(Collectors.groupingBy(s -> s.getRecipe().getId(), Collectors.counting()));
+                .collect(Collectors.groupingBy(s -> s.recipe.getId(), Collectors.counting()));
         long duplicatePenaltyCount = recipeCounts.values().stream()
                 .filter(c -> c > 1)
                 .mapToLong(c -> c - 1)

backend/src/main/java/com/recipeapp/planning/WeekPlanController.java

@@ -98,6 +98,7 @@ public class WeekPlanController {
     }
 
     @GetMapping("/{planId}/variety-preview")
+    @RequiresHouseholdRole("member")
     public VarietyPreviewResponse getVarietyPreview(
             Principal principal,
             @PathVariable UUID planId,

backend/src/test/java/com/recipeapp/planning/PlanningServiceTest.java

@@ -447,34 +447,65 @@ class PlanningServiceTest {
     // ── Variety preview ──
 
     @Test
-    void getVarietyPreviewShouldReturnScoreDelta() {
+    void getVarietyPreviewShouldReturnScoreDeltaForDifferentRecipe() {
         var household = testHousehold();
         var plan = testWeekPlan(household);
         var planId = plan.getId();
 
-        // Plan already has one slot (Mon)
+        // Plan already has one slot (Mon) with Spaghetti
         var existingRecipe = testRecipe(household, "Spaghetti");
         var slot = new WeekPlanSlot(plan, existingRecipe, WEEK_START);
         setId(slot, WeekPlanSlot.class, UUID.randomUUID());
         plan.getSlots().add(slot);
 
+        // Candidate is Lachsfilet (different recipe, no shared tags/ingredients)
         var candidate = testRecipe(household, "Lachsfilet");
         var candidateId = candidate.getId();
 
         when(weekPlanRepository.findById(planId)).thenReturn(Optional.of(plan));
         when(recipeRepository.findByIdAndHouseholdIdAndDeletedAtIsNull(candidateId, HOUSEHOLD_ID))
                 .thenReturn(Optional.of(candidate));
-        when(varietyScoreConfigRepository.findByHouseholdId(HOUSEHOLD_ID))
-                .thenReturn(Optional.empty());
+        when(varietyScoreConfigRepository.findByHouseholdId(HOUSEHOLD_ID)).thenReturn(Optional.empty());
         when(cookingLogRepository.findByHouseholdIdAndCookedOnAfter(eq(HOUSEHOLD_ID), any()))
                 .thenReturn(List.of());
 
         var result = planningService.getVarietyPreview(HOUSEHOLD_ID, planId, candidateId, WEEK_START.plusDays(1));
 
-        // With no penalties, projected score should be 10.0; current (1 slot, no conflicts) is also 10.0
-        assertThat(result.projectedScore()).isBetween(0.0, 10.0);
-        assertThat(result.scoreDelta()).isEqualTo(result.projectedScore() - result.currentScore());
-        assertThat(result.currentScore()).isBetween(0.0, 10.0);
+        // 1 existing slot with no conflicts → currentScore = 10.0
+        // Adding a different recipe with no tags/ingredients → projectedScore = 10.0, delta = 0
+        assertThat(result.currentScore()).isEqualTo(10.0);
+        assertThat(result.projectedScore()).isEqualTo(10.0);
+        assertThat(result.scoreDelta()).isEqualTo(0.0);
+    }
+
+    @Test
+    void getVarietyPreviewShouldReturnNegativeDeltaForDuplicateRecipe() {
+        var household = testHousehold();
+        var plan = testWeekPlan(household);
+        var planId = plan.getId();
+
+        // Plan already has Spaghetti on Mon
+        var existingRecipe = testRecipe(household, "Spaghetti");
+        var slot = new WeekPlanSlot(plan, existingRecipe, WEEK_START);
+        setId(slot, WeekPlanSlot.class, UUID.randomUUID());
+        plan.getSlots().add(slot);
+
+        // Candidate is the same Spaghetti recipe → triggers duplicate penalty (wPlanDuplicate = 2.0)
+        when(weekPlanRepository.findById(planId)).thenReturn(Optional.of(plan));
+        when(recipeRepository.findByIdAndHouseholdIdAndDeletedAtIsNull(existingRecipe.getId(), HOUSEHOLD_ID))
+                .thenReturn(Optional.of(existingRecipe));
+        when(varietyScoreConfigRepository.findByHouseholdId(HOUSEHOLD_ID)).thenReturn(Optional.empty());
+        when(cookingLogRepository.findByHouseholdIdAndCookedOnAfter(eq(HOUSEHOLD_ID), any()))
+                .thenReturn(List.of());
+
+        var result = planningService.getVarietyPreview(
+                HOUSEHOLD_ID, planId, existingRecipe.getId(), WEEK_START.plusDays(1));
+
+        // currentScore = 10.0 (1 slot, no conflicts)
+        // projectedScore = 10.0 - 1 * 2.0 (duplicate penalty) = 8.0
+        assertThat(result.currentScore()).isEqualTo(10.0);
+        assertThat(result.projectedScore()).isEqualTo(8.0);
+        assertThat(result.scoreDelta()).isEqualTo(-2.0);
     }
 
     @Test

backend/src/test/java/com/recipeapp/planning/WeekPlanControllerTest.java

@@ -265,4 +265,5 @@ class WeekPlanControllerTest {
                         .principal(() -> "member@example.com"))
                 .andExpect(status().isForbidden());
     }
+
 }