apps/api/src/modules/cooking-session/cooking-session.service.ts

@@ -22,6 +22,11 @@ import { toIngredientView, toUnitView } from "../recipe/recipe.service.js";
 function cookingSessionPlanningInclude() {
   return {
     items: {
+      // A "leftovers" item (`sourcePlanningItemId` set) reserves part of an
+      // already-cooked batch — it has nothing to cook, so it must not enter
+      // the optimized cooking plan (issue #34). Excluded at the query so it
+      // never reaches `toOptimizerRecipe`.
+      where: { sourcePlanningItemId: null },
       include: {
         recipe: {
           select: {

apps/api/src/modules/planning/planning.routes.ts

@@ -1,10 +1,21 @@
 import { parseDateOnly } from "@batch-cooking/date-tools";
 import { HttpError } from "@batch-cooking/error-tools";
 import { wrapAsyncHandler } from "@batch-cooking/express-tools";
-import { addPlanningItemSchema, ErrorCode, getPlanningByDateSchema } from "@batch-cooking/shared";
+import {
+  addPlanningItemSchema,
+  assignLeftoverSchema,
+  ErrorCode,
+  getPlanningByDateSchema,
+} from "@batch-cooking/shared";
 import { Router } from "express";
 import { type AuthLocals, requireAuth } from "../../middlewares/require-auth.js";
-import { addPlanningItem, getPlanningForDate, removePlanningItem } from "./planning.service.js";
+import {
+  addPlanningItem,
+  assignLeftoverPlanningItem,
+  discardLeftover,
+  getPlanningForDate,
+  removePlanningItem,
+} from "./planning.service.js";
 
 /** Router mounted at `/planning` in app.ts. */
 export const planningRouter = Router();
@@ -69,6 +80,44 @@ planningRouter.post(
   }),
 );
 
+/**
+ * Serves part of another planning item's leftover pool on a slot — creates
+ * a "leftovers" `PlanningItem` (see {@link assignLeftoverPlanningItem}).
+ * `POST /items/leftover`, not `/items/:id/...`: the `:id` here would be the
+ * *target* slot, which doesn't exist yet — the source is in the body.
+ */
+planningRouter.post(
+  "/items/leftover",
+  requireAuth,
+  wrapAsyncHandler<unknown, AuthLocals>(async (req, res) => {
+    const input = assignLeftoverSchema.parse(req.body);
+    const date = parseDateOnly(input.date);
+    if (date === null) {
+      throw new HttpError(
+        400,
+        ErrorCode.VALIDATION_ERROR,
+        `Not a real calendar date: ${input.date}`,
+      );
+    }
+
+    const { id: viewerId, houseId } = res.locals.userProfile;
+    const item = await assignLeftoverPlanningItem(houseId, viewerId, date, input);
+    res.status(201).json(item);
+  }),
+);
+
+/** Throws away item `:id`'s whole remaining leftover pool (idempotent — see {@link discardLeftover}). */
+planningRouter.patch(
+  "/items/:id/discard-leftover",
+  requireAuth,
+  wrapAsyncHandler<unknown, AuthLocals>(async (req, res) => {
+    const id = parsePlanningItemId(req.params.id);
+    const { id: viewerId, houseId } = res.locals.userProfile;
+    const item = await discardLeftover(id, viewerId, houseId);
+    res.status(200).json(item);
+  }),
+);
+
 /** Removes one recipe from a planning slot. */
 planningRouter.delete(
   "/items/:id",

apps/api/src/modules/planning/planning.service.ts

@@ -2,6 +2,8 @@ import { type DateTime, getWeekStart, toDateOnly } from "@batch-cooking/date-too
 import { HttpError } from "@batch-cooking/error-tools";
 import {
   type AddPlanningItemInput,
+  type AssignLeftoverInput,
+  computeAvailableLeftover,
   computeBatchedPortions,
   ErrorCode,
   type PlanningItemView,
@@ -11,6 +13,35 @@ import { prisma } from "../../db/prisma.js";
 import { analytics } from "../../lib/analytics.service.js";
 import { assertRecipeVisible } from "../recipe/recipe.service.js";
 
+/**
+ * One `PlanningItem` row (with its recipe resolved to `{id, name}`) shaped
+ * into the wire {@link PlanningItemView}. The three read/write paths below
+ * that return an item — `getPlanningForDate`, `addPlanningItem`,
+ * `assignLeftoverPlanningItem`, `discardLeftover` — all go through this so
+ * the shape is defined once.
+ */
+function toPlanningItemView(item: {
+  id: number;
+  weekDay: string;
+  meal: string;
+  portions: number;
+  portionsRequested: number;
+  discardedPortions: number;
+  sourcePlanningItemId: number | null;
+  recipe: { id: number; name: string };
+}): PlanningItemView {
+  return {
+    id: item.id,
+    weekDay: item.weekDay,
+    meal: item.meal,
+    portions: item.portions,
+    portionsRequested: item.portionsRequested,
+    discardedPortions: item.discardedPortions,
+    sourceItem: item.sourcePlanningItemId !== null ? { id: item.sourcePlanningItemId } : null,
+    recipe: item.recipe,
+  };
+}
+
 /**
  * Finds the household's planning that covers `date` and shapes it into a
  * {@link PlanningView} (recipes resolved to `{id, name}`). `date` is
@@ -65,16 +96,7 @@ export async function getPlanningForDate(
       id: planning.id,
       startDate: planning.startDate.toISOString(),
       finishDate: planning.finishDate.toISOString(),
-      items: planning.items.map((item) => ({
+      items: planning.items.map(toPlanningItemView),
-        id: item.id,
-        weekDay: item.weekDay,
-        meal: item.meal,
-        portions: item.portions,
-        portionsRequested: item.portionsRequested,
-        discardedPortions: item.discardedPortions,
-        sourceItem: item.sourcePlanningItemId !== null ? { id: item.sourcePlanningItemId } : null,
-        recipe: item.recipe,
-      })),
     };
   } catch (err) {
     // Rethrown as-is — `wrapAsyncHandler`/the error middleware (which
@@ -184,16 +206,7 @@ export async function addPlanningItem(
       },
     });
 
-    return {
+    return toPlanningItemView(item);
-      id: item.id,
-      weekDay: item.weekDay,
-      meal: item.meal,
-      portions: item.portions,
-      portionsRequested: item.portionsRequested,
-      discardedPortions: item.discardedPortions,
-      sourceItem: item.sourcePlanningItemId !== null ? { id: item.sourcePlanningItemId } : null,
-      recipe: item.recipe,
-    };
   } catch (err) {
     throw err; // see getPlanningForDate()'s catch comment above
   }
@@ -221,3 +234,139 @@ export async function removePlanningItem(id: number, houseId: number | null): Pr
     throw err; // see getPlanningForDate()'s catch comment above
   }
 }
+
+/**
+ * Loads a `PlanningItem` (scoped to `houseId`) with everything
+ * {@link computeAvailableLeftover} needs — its own portion fields plus how
+ * much of its pool has already been served elsewhere (`leftoverUses`) — or
+ * throws `404 PLANNING_ITEM_NOT_FOUND` (same "don't confirm what exists"
+ * posture as `removePlanningItem`). Shared by
+ * {@link assignLeftoverPlanningItem} and {@link discardLeftover}.
+ */
+async function loadItemWithLeftoverPool(id: number, houseId: number | null) {
+  const item = await prisma.planningItem.findUnique({
+    where: { id },
+    include: {
+      planning: { select: { houseId: true } },
+      leftoverUses: { select: { portions: true } },
+      recipe: { select: { id: true, name: true } },
+    },
+  });
+  if (!item || houseId === null || item.planning.houseId !== houseId) {
+    throw new HttpError(404, ErrorCode.PLANNING_ITEM_NOT_FOUND, `Planning item ${id} not found`);
+  }
+  return item;
+}
+
+/**
+ * Serves `input.portions` of another item's leftover pool on the
+ * `(date, weekDay, meal)` slot — creates a "leftovers" `PlanningItem`
+ * (`sourcePlanningItemId` set) on the same recipe as its source. Nothing
+ * new is cooked for it, so `portions === portionsRequested` and it excludes
+ * itself from the shopping list / cooking session (see those services'
+ * `where: { sourcePlanningItemId: null }`).
+ *
+ * The source's `recipeId` is copied, never taken from the client (a
+ * leftovers item can only be its source's recipe). `input.portions` is
+ * re-checked against the pool actually still available
+ * ({@link computeAvailableLeftover}) — trusting a client value here would
+ * let a household conjure portions it never cooked.
+ *
+ * @throws {HttpError} `404 HOUSE_NOT_FOUND` if `houseId` is `null`.
+ * @throws {HttpError} `404 PLANNING_ITEM_NOT_FOUND` if `sourceItemId` doesn't exist, belongs to another household, or is itself a leftovers item (no leftovers-on-leftovers).
+ * @throws {HttpError} `409 LEFTOVER_QUANTITY_EXCEEDED` if `portions` exceeds the source's still-available pool.
+ */
+export async function assignLeftoverPlanningItem(
+  houseId: number | null,
+  viewerId: number,
+  date: DateTime,
+  input: AssignLeftoverInput,
+): Promise<PlanningItemView> {
+  try {
+    if (houseId === null) {
+      throw new HttpError(404, ErrorCode.HOUSE_NOT_FOUND, "Profile has no household");
+    }
+
+    const source = await loadItemWithLeftoverPool(input.sourceItemId, houseId);
+    if (source.sourcePlanningItemId !== null) {
+      // A leftovers item has no pool of its own — serving leftovers cooks
+      // nothing, so it can't be a source for more.
+      throw new HttpError(
+        404,
+        ErrorCode.PLANNING_ITEM_NOT_FOUND,
+        `Planning item ${input.sourceItemId} is not a leftovers source`,
+      );
+    }
+
+    const available = computeAvailableLeftover(source);
+    if (input.portions > available) {
+      throw new HttpError(
+        409,
+        ErrorCode.LEFTOVER_QUANTITY_EXCEEDED,
+        `Item ${source.id} has ${available} leftover portion(s) available, asked for ${input.portions}`,
+      );
+    }
+
+    const weekStart = getWeekStart(toDateOnly(date));
+    const planning = await findOrCreatePlanningForWeek(houseId, weekStart);
+
+    const item = await prisma.planningItem.create({
+      data: {
+        planningId: planning.id,
+        weekDay: input.weekDay,
+        meal: input.meal,
+        recipeId: source.recipeId,
+        portions: input.portions,
+        portionsRequested: input.portions,
+        sourcePlanningItemId: source.id,
+      },
+      include: { recipe: { select: { id: true, name: true } } },
+    });
+
+    analytics.recordEvent("planning.leftover_assigned", {
+      actorId: viewerId,
+      context: { recipeId: source.recipeId, portions: input.portions, sourceItemId: source.id },
+    });
+
+    return toPlanningItemView(item);
+  } catch (err) {
+    throw err; // see getPlanningForDate()'s catch comment above
+  }
+}
+
+/**
+ * Throws away the whole still-available leftover pool of item `id`
+ * (`discardedPortions += available`) — the basket's "jeter" button.
+ * Idempotent: an item with nothing left to discard is returned unchanged,
+ * no event recorded.
+ *
+ * @throws {HttpError} `404 PLANNING_ITEM_NOT_FOUND` — same guard as `removePlanningItem`.
+ */
+export async function discardLeftover(
+  id: number,
+  viewerId: number,
+  houseId: number | null,
+): Promise<PlanningItemView> {
+  try {
+    const item = await loadItemWithLeftoverPool(id, houseId);
+    const available = computeAvailableLeftover(item);
+    if (available === 0) {
+      return toPlanningItemView(item);
+    }
+
+    const updated = await prisma.planningItem.update({
+      where: { id },
+      data: { discardedPortions: item.discardedPortions + available },
+      include: { recipe: { select: { id: true, name: true } } },
+    });
+
+    analytics.recordEvent("planning.leftover_discarded", {
+      actorId: viewerId,
+      context: { recipeId: item.recipe.id, portions: available },
+    });
+
+    return toPlanningItemView(updated);
+  } catch (err) {
+    throw err; // see getPlanningForDate()'s catch comment above
+  }
+}

apps/api/src/modules/shopping-list/shopping-list.service.ts

@@ -13,6 +13,11 @@ import { toIngredientView, toUnitView } from "../recipe/recipe.service.js";
 function shoppingListPlanningInclude() {
   return {
     items: {
+      // "Leftovers" items (`sourcePlanningItemId` set) reserve a portion of
+      // an already-cooked batch — nothing new to buy for them. Excluded
+      // here so they never reach `aggregateShoppingList`; counting them
+      // would double up the source recipe's ingredients (issue #34).
+      where: { sourcePlanningItemId: null },
       include: {
         recipe: {
           select: {

apps/api/test/cooking-session.test.ts

@@ -328,5 +328,42 @@ describe("Cooking session", () => {
         180, 210,
       ]);
     });
+
+    it("leaves a leftovers item out of the cooking plan — it has nothing to cook (issue #34)", async () => {
+      const agent = request.agent(app);
+      await agent.post("/auth/signup").send(buildSignupPayload());
+      const houseRes = await agent.post("/house").send({ name: "Chez moi" });
+
+      const recipe = await prisma.recipe.create({
+        data: {
+          name: "Soupe",
+          authorId: houseRes.body.adminId,
+          portions: 4,
+          steps: { create: [{ order: 0, description: "Faire mijoter la soupe." }] },
+        },
+      });
+
+      // One real slot (12 prepared for 10 requested), then a leftovers slot
+      // reusing 2 of it — the plan must still contain only "Soupe" once.
+      const source = await agent.post("/planning/items").send({
+        date: today(),
+        weekDay: "lundi",
+        meal: "diner",
+        recipeId: recipe.id,
+        portionsRequested: 10,
+      });
+      await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.body.id,
+        portions: 2,
+      });
+
+      const res = await agent.get("/cooking-session").query({ date: today() });
+
+      expect(res.status).to.equal(200);
+      expect(res.body.recipes.map((r: { name: string }) => r.name)).to.deep.equal(["Soupe"]);
+    });
   });
 });

apps/api/test/planning.test.ts

@@ -271,4 +271,182 @@ describe("Planning", () => {
       expect(res.body.code).to.equal(ErrorCode.VALIDATION_ERROR);
     });
   });
+
+  describe("leftovers — POST /planning/items/leftover and PATCH .../discard-leftover", () => {
+    /**
+     * Signs up + creates a household, saves a 4-portion recipe, and plans
+     * it once with `requested` portions — so the resulting item has a
+     * leftover pool of `ceil(requested/4)*4 - requested`. Returns the agent,
+     * the recipe, and that source item.
+     */
+    async function setupWithSource(requested: number) {
+      const agent = request.agent(app);
+      await agent.post("/auth/signup").send(buildSignupPayload());
+      const houseRes = await agent.post("/house").send({ name: "Chez moi" });
+      const recipe = await prisma.recipe.create({
+        data: { name: "Lasagnes", authorId: houseRes.body.adminId, portions: 4 },
+      });
+      const addRes = await agent.post("/planning/items").send({
+        date: today(),
+        weekDay: "lundi",
+        meal: "diner",
+        recipeId: recipe.id,
+        portionsRequested: requested,
+      });
+      return { agent, recipe, source: addRes.body };
+    }
+
+    it("serves part of a source item's leftover pool as a new leftovers item on another slot", async () => {
+      // 10 requested on a 4-portion recipe -> 12 prepared, pool of 2.
+      const { agent, recipe, source } = await setupWithSource(10);
+      expect(source.portions).to.equal(12);
+
+      const res = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 2,
+      });
+
+      expect(res.status).to.equal(201);
+      expect(res.body).to.include({
+        weekDay: "mardi",
+        meal: "dejeuner",
+        portions: 2,
+        portionsRequested: 2,
+        discardedPortions: 0,
+      });
+      expect(res.body.sourceItem).to.deep.equal({ id: source.id });
+      // The recipe is copied from the source, not sent by the client.
+      expect(res.body.recipe.id).to.equal(recipe.id);
+    });
+
+    it("rejects assigning more portions than the source pool still has, with 409 LEFTOVER_QUANTITY_EXCEEDED", async () => {
+      const { agent, source } = await setupWithSource(10); // pool of 2
+
+      // Take 2 of the 2 available...
+      await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 2,
+      });
+      // ...then ask for 1 more — nothing left.
+      const res = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mercredi",
+        meal: "diner",
+        sourceItemId: source.id,
+        portions: 1,
+      });
+
+      expect(res.status).to.equal(409);
+      expect(res.body.code).to.equal(ErrorCode.LEFTOVER_QUANTITY_EXCEEDED);
+    });
+
+    it("404s when the source item belongs to another household", async () => {
+      const { source } = await setupWithSource(10);
+
+      const stranger = request.agent(app);
+      await stranger.post("/auth/signup").send(buildSignupPayload());
+      await stranger.post("/house").send({ name: "Ailleurs" });
+
+      const res = await stranger.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 1,
+      });
+
+      expect(res.status).to.equal(404);
+      expect(res.body.code).to.equal(ErrorCode.PLANNING_ITEM_NOT_FOUND);
+    });
+
+    it("404s when the source item is itself a leftovers item (no leftovers-on-leftovers)", async () => {
+      const { agent, source } = await setupWithSource(10);
+      const leftover = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 1,
+      });
+
+      const res = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mercredi",
+        meal: "diner",
+        sourceItemId: leftover.body.id,
+        portions: 1,
+      });
+
+      expect(res.status).to.equal(404);
+      expect(res.body.code).to.equal(ErrorCode.PLANNING_ITEM_NOT_FOUND);
+    });
+
+    it("deleting the source item cascades to every leftovers item served from it", async () => {
+      const { agent, source } = await setupWithSource(10);
+      const leftover = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 2,
+      });
+
+      await agent.delete(`/planning/items/${source.id}`).expect(204);
+
+      const stillThere = await prisma.planningItem.findUnique({ where: { id: leftover.body.id } });
+      expect(stillThere).to.equal(null);
+    });
+
+    it("discards the whole remaining pool, and is idempotent", async () => {
+      const { agent, source } = await setupWithSource(10); // pool of 2
+
+      const first = await agent.patch(`/planning/items/${source.id}/discard-leftover`);
+      expect(first.status).to.equal(200);
+      expect(first.body.discardedPortions).to.equal(2);
+
+      // Nothing left — a second call changes nothing.
+      const second = await agent.patch(`/planning/items/${source.id}/discard-leftover`);
+      expect(second.status).to.equal(200);
+      expect(second.body.discardedPortions).to.equal(2);
+
+      // And the pool is now empty for an assignment too.
+      const assign = await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 1,
+      });
+      expect(assign.status).to.equal(409);
+    });
+
+    it("only discards what's still available after some was already served", async () => {
+      const { agent, source } = await setupWithSource(10); // pool of 2
+      await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.id,
+        portions: 1,
+      });
+
+      const res = await agent.patch(`/planning/items/${source.id}/discard-leftover`);
+      expect(res.status).to.equal(200);
+      // 1 of the 2 was served; only the other 1 gets discarded.
+      expect(res.body.discardedPortions).to.equal(1);
+    });
+
+    it("404s discarding an unknown planning item", async () => {
+      const { agent } = await setupWithSource(4);
+      const res = await agent.patch("/planning/items/999999/discard-leftover");
+      expect(res.status).to.equal(404);
+      expect(res.body.code).to.equal(ErrorCode.PLANNING_ITEM_NOT_FOUND);
+    });
+  });
 });

apps/api/test/shopping-list.test.ts

@@ -172,6 +172,48 @@ describe("Shopping list", () => {
       expect(res.body.items[0].quantity).to.equal(400);
     });
 
+    it("ignores a leftovers item — nothing new to buy for a slot that just reserves an already-cooked batch (issue #34)", async () => {
+      const agent = request.agent(app);
+      await agent.post("/auth/signup").send(buildSignupPayload());
+      const houseRes = await agent.post("/house").send({ name: "Chez moi" });
+      const authorId: number = houseRes.body.adminId;
+
+      const tomatoId = await ingredientId("tomato");
+      const gramId = await unitId("gram");
+      const recipe = await prisma.recipe.create({
+        data: {
+          name: "Salade de tomates",
+          authorId,
+          portions: 4,
+          ingredients: { create: [{ ingredientId: tomatoId, quantity: 100, unitId: gramId }] },
+        },
+      });
+
+      // One real slot at 12 prepared (10 requested), then a leftovers slot
+      // reusing 2 of that batch — the shopping list must still be 300g
+      // (100 × 12/4), not 350g.
+      const source = await agent.post("/planning/items").send({
+        date: today(),
+        weekDay: "lundi",
+        meal: "diner",
+        recipeId: recipe.id,
+        portionsRequested: 10,
+      });
+      await agent.post("/planning/items/leftover").send({
+        date: today(),
+        weekDay: "mardi",
+        meal: "dejeuner",
+        sourceItemId: source.body.id,
+        portions: 2,
+      });
+
+      const res = await agent.get("/shopping-list").query({ date: today() });
+
+      expect(res.status).to.equal(200);
+      expect(res.body.items).to.have.length(1);
+      expect(res.body.items[0].quantity).to.equal(300);
+    });
+
     it("sums the same ingredient across two different recipes sharing a unit", async () => {
       const agent = request.agent(app);
       await agent.post("/auth/signup").send(buildSignupPayload());

apps/web/src/locales/fr/translation.json

@@ -47,7 +47,8 @@
     "UTENSIL_NOT_FOUND": "Un des ustensiles sélectionnés n'existe pas",
     "INVALID_CORRECTION_SPAN": "La sélection ne correspond plus au texte de l'étape",
     "INTERNAL_ERROR": "Une erreur est survenue, réessayez plus tard",
-    "RETRAIN_ALREADY_RUNNING": "Un ré-entraînement est déjà en cours"
+    "RETRAIN_ALREADY_RUNNING": "Un ré-entraînement est déjà en cours",
+    "LEFTOVER_QUANTITY_EXCEEDED": "Il ne reste plus assez de portions disponibles"
   },
   "auth": {
     "login": {

packages/shared/src/errors/error-codes.ts

@@ -42,6 +42,9 @@ export enum ErrorCode {
   RECIPE_ALREADY_IMPORTED = 4022,
   /** `POST /admin/api/tech-steps/retrain` attempted while a previous retrain (F1 gate + backfill) is still running — it holds a process-wide lock so two can't overlap. */
   RETRAIN_ALREADY_RUNNING = 4023,
+
+  /** `POST /planning/items/leftover` asked to assign more portions than the source item's leftover pool still has available (`computeAvailableLeftover`, revalidated server-side). */
+  LEFTOVER_QUANTITY_EXCEEDED = 4024,
   /** A household action reserved to its admin (delete the household, remove a member) attempted by a non-admin member. */
   NOT_HOUSE_ADMIN = 4030,
   /** `PATCH /recipes/:id` or `DELETE /recipes/:id` attempted by someone other than the recipe's author — visibility controls reading, not writing. */

packages/shared/src/schemas/planning.ts

@@ -42,3 +42,23 @@ export const addPlanningItemSchema = z.object({
 });
 /** Inferred TS type for {@link addPlanningItemSchema}'s validated output. */
 export type AddPlanningItemInput = z.infer<typeof addPlanningItemSchema>;
+
+/**
+ * Payload accepted by `POST /planning/items/leftover` — serves `portions`
+ * of another item's leftover pool on the `(date, weekDay, meal)` slot,
+ * creating a "leftovers" `PlanningItem` (see `planning.service.ts`'s
+ * `assignLeftoverPlanningItem`). `recipeId` is deliberately **not** here:
+ * a leftovers item can only be the same recipe as its source, so the
+ * server copies it from `sourceItemId` rather than trusting the client.
+ * `portions` is re-checked against the pool actually still available
+ * server-side — a client value over that is a `409 LEFTOVER_QUANTITY_EXCEEDED`.
+ */
+export const assignLeftoverSchema = z.object({
+  date: z.string().regex(/^\d{4}-\d{2}-\d{2}$/, "Date invalide"),
+  weekDay: z.enum(WEEK_DAYS),
+  meal: z.enum(MEALS),
+  sourceItemId: z.number().int().positive(),
+  portions: z.number().int().positive("Le nombre de portions doit être positif"),
+});
+/** Inferred TS type for {@link assignLeftoverSchema}'s validated output. */
+export type AssignLeftoverInput = z.infer<typeof assignLeftoverSchema>;

specs/backend-architecture.md

@@ -232,6 +232,18 @@ Router `/planning` (`planning.routes.ts`/`.service.ts`), `requireAuth`.
   par l'appelant (`assertRecipeVisible`, `recipe.service.ts`) → 404
   `RECIPE_NOT_FOUND` sinon.
 - `DELETE /planning/items/:id` → `removePlanningItem`, 204.
+- `POST /planning/items/leftover` → `assignLeftoverPlanningItem`, 201. Body
+  `assignLeftoverSchema` = `{ date, weekDay, meal, sourceItemId, portions }`.
+  Crée un item « restes » (`sourcePlanningItemId` non nul) sur le créneau
+  cible, **même recette que la source** (`recipeId` copié, jamais envoyé par
+  le client). `portions` est revérifié contre le pool réellement disponible
+  (`computeAvailableLeftover`) → 409 `LEFTOVER_QUANTITY_EXCEEDED` si dépassé,
+  404 `PLANNING_ITEM_NOT_FOUND` si `sourceItemId` inconnu / d'un autre foyer /
+  lui-même un item « restes » (pas de restes-sur-restes).
+- `PATCH /planning/items/:id/discard-leftover` → `discardLeftover`, 200. Jette
+  tout le pool encore disponible de l'item (`discardedPortions += disponible`) ;
+  idempotent (rien à jeter → renvoyé inchangé, aucun évènement). 404 même
+  garde que `removePlanningItem`.
 
 **Portions demandées vs préparées (issue #34)** — le client n'envoie que
 `portionsRequested` (« combien ce créneau doit nourrir »). `addPlanningItem`
@@ -240,12 +252,18 @@ en dérive `portions` (ce qui est **réellement préparé**) via
 (`@batch-cooking/shared`, pur) : on arrondit au multiple supérieur du
 rendement de la recette (`ceil(demandées / recette.portions) × recette.portions`)
 — on cuisine des lots entiers, jamais une fraction de plat. L'écart
-`portions − portionsRequested` est le **pool de restes** de cet item.
+`portions − portionsRequested` est le **pool de restes** de cet item,
-`getPlanningForDate` renvoie les deux valeurs plus `discardedPortions` et
+consommé par les items « restes » (`sourcePlanningItemId` pointant vers lui)
-`sourceItem` (dérivé de `sourcePlanningItemId`) dans chaque
+et par `discardedPortions`. `getPlanningForDate` renvoie les deux valeurs
-`PlanningItemView`, sans `include` Prisma supplémentaire. Les routes
+plus `discardedPortions` et `sourceItem` dans chaque `PlanningItemView`,
-d'attribution/jet de restes et l'exclusion des items « restes » de la liste
+sans `include` Prisma supplémentaire (le front reconstitue `leftoverUses` à
-de courses / session de cuisine arrivent dans une itération ultérieure.
+partir du tableau plat `planning.items` pour l'affichage du panier).
+
+**Exclusion des items « restes »** — `shopping-list.service.ts` et
+`cooking-session.service.ts` filtrent `items: { where: { sourcePlanningItemId:
+null } }` dans leur `include` : un créneau qui ne fait que resservir un plat
+déjà cuisiné n'a rien à acheter ni à cuisiner. `getPlanningForDate` **ne**
+filtre pas — la grille affiche bien ces items (badge « restes »).
 
 **Création de la semaine** — `findOrCreatePlanningForWeek` est le seul
 endroit qui crée une ligne `Planning`, retrouvée par `startDate` exact (un