feat(shopping): addRecipeToCart (idempotent via ON CONFLICT)

src/lib/server/shopping/repository.ts

@@ -25,12 +25,20 @@ export type ShoppingListSnapshot = {
 };
 
 export function addRecipeToCart(
-  _db: Database.Database,
-  _recipeId: number,
-  _profileId: number | null,
-  _servings?: number
+  db: Database.Database,
+  recipeId: number,
+  profileId: number | null,
+  servings?: number
 ): void {
-  throw new Error('not implemented');
+  const row = db
+    .prepare('SELECT servings_default FROM recipe WHERE id = ?')
+    .get(recipeId) as { servings_default: number | null } | undefined;
+  const resolved = servings ?? row?.servings_default ?? 4;
+  db.prepare(
+    `INSERT INTO shopping_cart_recipe (recipe_id, servings, added_by_profile_id)
+     VALUES (?, ?, ?)
+     ON CONFLICT(recipe_id) DO UPDATE SET servings = excluded.servings`
+  ).run(recipeId, resolved, profileId);
 }
 
 export function removeRecipeFromCart(_db: Database.Database, _recipeId: number): void {
@@ -45,8 +53,17 @@ export function setCartServings(
   throw new Error('not implemented');
 }
 
-export function listShoppingList(_db: Database.Database): ShoppingListSnapshot {
-  throw new Error('not implemented');
+export function listShoppingList(db: Database.Database): ShoppingListSnapshot {
+  const recipes = db
+    .prepare(
+      `SELECT cr.recipe_id, r.title, r.image_path, cr.servings,
+              COALESCE(r.servings_default, cr.servings) AS servings_default
+         FROM shopping_cart_recipe cr
+         JOIN recipe r ON r.id = cr.recipe_id
+        ORDER BY cr.added_at ASC`
+    )
+    .all() as ShoppingCartRecipe[];
+  return { recipes, rows: [], uncheckedCount: 0 };
 }
 
 export function toggleCheck(

tests/integration/shopping-repository.test.ts

@@ -0,0 +1,65 @@
+import { describe, it, expect } from 'vitest';
+import { openInMemoryForTest } from '../../src/lib/server/db';
+import { insertRecipe } from '../../src/lib/server/recipes/repository';
+import {
+  addRecipeToCart,
+  listShoppingList
+} from '../../src/lib/server/shopping/repository';
+import type { Recipe } from '../../src/lib/types';
+
+function recipe(overrides: Partial<Recipe> = {}): Recipe {
+  return {
+    id: null,
+    title: 'Test',
+    description: null,
+    source_url: null,
+    source_domain: null,
+    image_path: null,
+    servings_default: 4,
+    servings_unit: null,
+    prep_time_min: null,
+    cook_time_min: null,
+    total_time_min: null,
+    cuisine: null,
+    category: null,
+    ingredients: [],
+    steps: [],
+    tags: [],
+    ...overrides
+  };
+}
+
+describe('addRecipeToCart', () => {
+  it('inserts recipe with default servings from recipe.servings_default', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe({ title: 'Pasta', servings_default: 4 }));
+    addRecipeToCart(db, id, null);
+    const snap = listShoppingList(db);
+    expect(snap.recipes).toHaveLength(1);
+    expect(snap.recipes[0].servings).toBe(4);
+  });
+
+  it('respects explicit servings override', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe({ servings_default: 4 }));
+    addRecipeToCart(db, id, null, 2);
+    expect(listShoppingList(db).recipes[0].servings).toBe(2);
+  });
+
+  it('is idempotent: second insert updates servings, not fails', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe({ servings_default: 4 }));
+    addRecipeToCart(db, id, null, 2);
+    addRecipeToCart(db, id, null, 6);
+    const snap = listShoppingList(db);
+    expect(snap.recipes).toHaveLength(1);
+    expect(snap.recipes[0].servings).toBe(6);
+  });
+
+  it('falls back to servings=4 when recipe has no default', () => {
+    const db = openInMemoryForTest();
+    const id = insertRecipe(db, recipe({ servings_default: null }));
+    addRecipeToCart(db, id, null);
+    expect(listShoppingList(db).recipes[0].servings).toBe(4);
+  });
+});