# Phase 8 — Meal Planning & Waste Reduction

**Goal**: Enable weekly meal planning with automatic nutrition tracking vs targets. The core feature is a **suggestion engine** that recommends recipes prioritizing ingredients already in the pantry (especially those expiring soon), reducing food waste while maintaining nutritional balance.

**Depends on**: Phase 5 (products), Phase 6 (recipes), Phase 7 (pantry)

---

## Deliverables

1. `MealPlan` and `NutritionTarget` MongoDB schemas
2. Meal plan CRUD API with daily/weekly views
3. Recipe suggestion engine (algorithmic, not LLM-dependent)
4. Nutrition targets per user with daily tracking
5. Shopping gap analysis (what's needed beyond pantry)
6. Meal plan web UI with weekly calendar and suggestion panel

---

## Data Model

### MealPlan Schema

```typescript
// packages/shared/src/types/meal-plan.ts
export interface MealPlan {
  id: string;
  householdId: string;
  weekStartDate: Date; // Monday of the planning week
  days: MealPlanDay[];
  status: MealPlanStatus;
  shoppingListId?: string; // Auto-generated shopping list (Phase 9 link)
  createdBy: string;
  createdAt: Date;
  updatedAt: Date;
}

export interface MealPlanDay {
  date: Date;
  meals: PlannedMeal[];
  dailyNutritionTotal: NutritionInfo; // Computed
}

export interface PlannedMeal {
  id: string; // UUID for drag-and-drop reference
  type: MealType;
  recipeId?: string; // Linked recipe
  recipeName: string; // Denormalized
  servings: number;
  customName?: string; // For non-recipe meals
  customNutrition?: NutritionInfo; // Manual override for non-recipe meals
  perServingNutrition: NutritionInfo; // From recipe or custom
  notes?: string;
}

export enum MealType {
  BREAKFAST = 'breakfast',
  LUNCH = 'lunch',
  DINNER = 'dinner',
  SNACK = 'snack',
}

export enum MealPlanStatus {
  DRAFT = 'draft',
  ACTIVE = 'active',
  COMPLETED = 'completed',
}
```

### NutritionTarget Schema

```typescript
// packages/shared/src/types/nutrition-target.ts
export interface NutritionTarget {
  id: string;
  userId: string;
  householdId: string;
  dailyCalories: number;
  proteinG: number;
  carbsG: number;
  fatG: number;
  fiberG?: number;
  sodiumMg?: number;
  sugarG?: number;
  isActive: boolean;
  createdAt: Date;
  updatedAt: Date;
}
```

### MongoDB Indexes

```javascript
{ householdId: 1, weekStartDate: 1 }       // unique per household per week
{ householdId: 1, status: 1 }
{ householdId: 1, 'days.meals.recipeId': 1 } // Find plans using a recipe
```

---

## API Endpoints

### MealPlanModule

| Method | Path                           | Description                                    | Auth   |
| ------ | ------------------------------ | ---------------------------------------------- | ------ |
| GET    | `/meal-plans`                  | List meal plans (paginated)                    | member |
| GET    | `/meal-plans/current`          | Get current week's plan                        | member |
| GET    | `/meal-plans/:id`              | Get specific plan                              | member |
| POST   | `/meal-plans`                  | Create new week plan                           | member |
| PATCH  | `/meal-plans/:id`              | Update plan (add/move/remove meals)            | member |
| DELETE | `/meal-plans/:id`              | Delete plan (draft only)                       | admin  |
| POST   | `/meal-plans/:id/activate`     | Set plan as active                             | member |
| GET    | `/meal-plans/:id/shopping-gap` | What's needed beyond current pantry            | member |
| GET    | `/meal-plans/suggestions`      | Get recipe suggestions for current pantry      | member |
| POST   | `/meal-plans/suggest-with-llm` | LLM-powered meal plan generation (placeholder) | member |

### NutritionTargetModule

| Method | Path                     | Description                      | Auth   |
| ------ | ------------------------ | -------------------------------- | ------ |
| GET    | `/nutrition-targets`     | Get current user's active target | member |
| POST   | `/nutrition-targets`     | Set nutrition targets            | member |
| PATCH  | `/nutrition-targets/:id` | Update targets                   | member |

---

## Tasks

### 8.1 — Shared Types & Validation

- Add all types above to `packages/shared`
- Zod schemas for create/update operations
- Meal plan day validation (7 days per plan, valid dates)

### 8.2 — Meal Plan CRUD

- Standard CRUD with computed `dailyNutritionTotal` per day:
  - Sum `perServingNutrition * servings` for all meals in each day
- On meal plan creation: default to 7 empty days (Monday–Sunday)
- On update: support granular operations:
  - `addMeal(dayIndex, meal)`
  - `removeMeal(dayIndex, mealId)`
  - `moveMeal(fromDay, toDay, mealId)` — for drag-and-drop
  - `updateMeal(dayIndex, mealId, updates)`

### 8.3 — Recipe Suggestion Engine (Core Algorithm)

This is the **key differentiating feature** — algorithmic, no LLM required.

```typescript
class RecipeSuggestionService {
  /**
   * Score and rank recipes based on pantry state and user preferences.
   *
   * Input:
   * - Current pantry items (with freshness urgency)
   * - Recipe catalog for the household
   * - User's nutrition targets (optional)
   * - Already planned meals this week (to avoid repetition)
   *
   * Scoring per recipe:
   *   ingredientCoverageScore  (0-40 pts): % of ingredients available in pantry
   *   freshnessUrgencyScore    (0-30 pts): bonus for using urgent/use-soon items
   *   nutritionBalanceScore    (0-20 pts): how well it complements the day's existing meals vs targets
   *   varietyScore             (0-10 pts): penalty for recently planned recipes
   *
   * Output per suggestion:
   *   - recipe (id, name, perServingNutrition)
   *   - score (total)
   *   - availableIngredients[]: items from pantry that match
   *   - missingIngredients[]: items not in pantry (with estimated cost from Phase 9 if available)
   *   - urgentIngredients[]: pantry items with urgency=urgent that this recipe would use
   *   - reasoning: human-readable explanation of why this recipe was suggested
   */
  suggestRecipes(context: SuggestionContext): Promise<RecipeSuggestion[]>;
}
```

**Ingredient matching logic**:

- Match recipe ingredient's `productId` against pantry items with `status: sealed|opened`
- Check quantity: is there enough? (approximate — compare units, flag if unclear)
- Prefer items with higher freshness urgency

**Scoring weights** (configurable per household):

```typescript
const DEFAULT_WEIGHTS = {
  ingredientCoverage: 40,
  freshnessUrgency: 30,
  nutritionBalance: 20,
  variety: 10,
};
```

### 8.4 — Shopping Gap Analysis

- `GET /meal-plans/:id/shopping-gap`:
  - For each recipe in the meal plan, list required ingredients
  - Cross-reference with current pantry (available quantity vs needed quantity)
  - Return:

```typescript
interface ShoppingGap {
  coveredByPantry: ShoppingGapItem[]; // Already have enough
  needToBuy: ShoppingGapItem[]; // Partially or fully missing
  pantryItemsUsed: PantryItemUsage[]; // Which pantry items will be consumed
}

interface ShoppingGapItem {
  productId: string;
  productName: string;
  totalNeeded: { quantity: number; unit: ServingUnit };
  availableInPantry: { quantity: number; unit: ServingUnit };
  shortfall: { quantity: number; unit: ServingUnit };
  usedInRecipes: string[]; // Recipe names
}
```

- This output feeds directly into Phase 9's auto-generated shopping lists

### 8.5 — LLM Suggestion Placeholder

- `POST /meal-plans/suggest-with-llm`:
  - Builds a context object: pantry summary, nutrition targets, dietary preferences
  - Calls `ILlmProvider.suggestMealPlan(context)`
  - With `NoOpLlmProvider`: returns `{ available: false }`
  - When wired (Phase 10): returns a full week meal plan draft

### 8.6 — Web UI: Meal Planning

- `/meal-plans` page:
  - **Weekly calendar grid**: 7 columns (Mon–Sun) × 4 rows (Breakfast, Lunch, Dinner, Snack)
  - Each cell: drop zone for recipes, shows meal name + calorie badge
  - **Drag-and-drop**: drag recipes from suggestion panel or between cells
  - **Daily nutrition summary row** at bottom: calories, protein, carbs, fat bars
    - Color-coded vs user's nutrition targets (under = blue, on-target = green, over = red)
  - **Week navigation**: previous/next week arrows
  - **Suggestion panel** (sidebar or drawer):
    - "Suggestions based on your pantry" — ranked list from suggestion engine
    - Each suggestion shows: recipe name, match score, "Uses: [urgent items]", "Need to buy: [missing items]"
    - Click to expand: full ingredient match breakdown
    - "Add to plan" button → pick day + meal type
  - **Shopping gap tab**: shows what's needed beyond pantry, "Generate shopping list" button (Phase 9 integration)
- `/nutrition-targets` settings:
  - Daily macro targets form (calories, protein, carbs, fat)
  - Preset templates: "Maintenance", "Weight loss", "Muscle gain", "Custom"
  - Visual preview: donut chart of macro ratios

---

## Acceptance Criteria

- [ ] Can create a weekly meal plan and add meals to specific days/slots
- [ ] Daily nutrition totals are computed and displayed
- [ ] Suggestion engine returns ranked recipes based on pantry state
- [ ] Suggestions prioritize recipes using soon-to-expire pantry items
- [ ] Shopping gap analysis correctly identifies missing ingredients
- [ ] Drag-and-drop works in the weekly calendar UI
- [ ] Nutrition targets can be set per user
- [ ] Daily nutrition bars show progress vs targets
- [ ] Variety scoring penalizes recently used recipes

---

## Estimated Effort

Large. The suggestion engine scoring algorithm, shopping gap analysis, and calendar UI with drag-and-drop are all significant features.