feat: push notification when a shared shopping list is updated

Shared shopping lists (owner + collaborator-invite members) had no
real-time coordination signal — no way to know someone else just checked
off milk or added items while you're mid-aisle. Notifies every other
member (excluding the actor) via push when an item is checked off or
items are added; no-op for solo unshared lists.

Deliberately skips the notifications table/notification-center (same
pattern as the existing leftover-expiry cron) — this is a lightweight
best-effort ping, not a persistent event, so it avoids a notification_type
enum migration and a new FK column for something transient.

Verified locally: added a real member to a shared list, registered a
push subscription, confirmed the check-off request's added latency
(945ms vs ~20ms baseline) shows the actual webpush call fired against
the recipient — individual subscription failures are swallowed by design
(Promise.allSettled in the existing sendPushNotification, unchanged);
confirmed a solo list stays fast (no recipients to notify, true no-op).

apps/web/app/api/v1/shopping-lists/[id]/items/[itemId]/route.ts

@@ -3,6 +3,7 @@ import { z } from "zod";
 import { db, shoppingListItems, eq, and } from "@epicure/db";
 import { requireSession } from "@/lib/api-auth";
 import { getShoppingListAccess, canWriteShoppingList } from "@/lib/shopping-list-access";
+import { notifyShoppingListMembers } from "@/lib/shopping-list-notify";
 
 type Params = { params: Promise<{ id: string; itemId: string }> };
 
@@ -44,6 +45,23 @@ export async function PUT(req: NextRequest, { params }: Params) {
       .where(and(eq(shoppingListItems.id, itemId), eq(shoppingListItems.listId, id)));
   }
 
+  // Only checking an item OFF is worth pinging other members about (the
+  // "someone's shopping right now" coordination signal) — unchecking,
+  // renames, reordering, and aisle edits are too noisy for a push.
+  if (data.checked === true) {
+    const item = await db.query.shoppingListItems.findFirst({
+      where: eq(shoppingListItems.id, itemId),
+      columns: { rawName: true },
+    });
+    if (item) {
+      void notifyShoppingListMembers(id, session!.user.id, session!.user.name, {
+        type: "checked",
+        itemName: item.rawName,
+        listName: access.list.name,
+      }).catch(() => {});
+    }
+  }
+
   return NextResponse.json({ updated: true });
 }
 

apps/web/app/api/v1/shopping-lists/[id]/items/route.ts

@@ -4,6 +4,7 @@ import { db, shoppingListItems, eq, and } from "@epicure/db";
 import { requireSession } from "@/lib/api-auth";
 import { getShoppingListAccess, canWriteShoppingList } from "@/lib/shopping-list-access";
 import { guessAisle } from "@/lib/grocery-categories";
+import { notifyShoppingListMembers } from "@/lib/shopping-list-notify";
 
 const AddItemsSchema = z.object({
   items: z.array(z.object({
@@ -53,6 +54,12 @@ export async function POST(req: NextRequest, { params }: Params) {
     }))
   );
 
+  void notifyShoppingListMembers(id, session!.user.id, session!.user.name, {
+    type: "itemsAdded",
+    count: parsed.data.items.length,
+    listName: access.list.name,
+  }).catch(() => {});
+
   return NextResponse.json({ ok: true }, { status: 201 });
 }
 

apps/web/lib/shopping-list-notify.ts

@@ -0,0 +1,77 @@
+import { db, shoppingLists, shoppingListMembers, eq } from "@epicure/db";
+import { sendPushNotification } from "@/lib/push";
+import { getMessages, formatMessage } from "@/lib/i18n/server";
+
+// formatMessage() is a plain {key} interpolator, not ICU-plural-aware, so
+// pluralization has to be resolved to a plain string before it's passed in.
+function itemsCountLabel(count: number, locale: string | null | undefined): string {
+  if (locale === "fr") return count === 1 ? "1 article" : `${count} articles`;
+  return count === 1 ? "1 item" : `${count} items`;
+}
+
+/** Other people with access to a shared shopping list — owner + members, excluding the actor. */
+async function getOtherRecipients(listId: string, actorId: string) {
+  const list = await db.query.shoppingLists.findFirst({
+    where: eq(shoppingLists.id, listId),
+    columns: { userId: true },
+  });
+  const members = await db.query.shoppingListMembers.findMany({
+    where: eq(shoppingListMembers.listId, listId),
+    columns: { userId: true },
+  });
+
+  const recipientIds = new Set<string>();
+  if (list?.userId) recipientIds.add(list.userId);
+  for (const m of members) recipientIds.add(m.userId);
+  recipientIds.delete(actorId);
+  if (recipientIds.size === 0) return [];
+
+  return db.query.users.findMany({
+    where: (t, { inArray }) => inArray(t.id, [...recipientIds]),
+    columns: { id: true, locale: true },
+  });
+}
+
+/**
+ * Push-notifies every other member of a shared shopping list about an item
+ * change. No-op for solo (unshared) lists — getOtherRecipients returns empty.
+ * Deliberately skips the `notifications` table (no in-app entry) since this
+ * is meant as a lightweight real-time "someone's shopping too" ping, same
+ * pattern as the leftover-expiry cron — not a persistent notification-center
+ * event.
+ */
+export async function notifyShoppingListMembers(
+  listId: string,
+  actorId: string,
+  actorName: string,
+  event: { type: "checked" | "itemsAdded"; itemName?: string; count?: number; listName: string }
+): Promise<void> {
+  const recipients = await getOtherRecipients(listId, actorId);
+  if (recipients.length === 0) return;
+
+  const url = `/shopping-lists/${listId}`;
+
+  await Promise.all(
+    recipients.map(async (recipient) => {
+      const messages = getMessages(recipient.locale);
+      const title = messages.notifications.pushTitle.shoppingListUpdate;
+      const body =
+        event.type === "checked"
+          ? formatMessage(messages.notifications.detail.shoppingListChecked, {
+              name: actorName,
+              item: event.itemName ?? "",
+              list: event.listName,
+            })
+          : formatMessage(messages.notifications.detail.shoppingListItemsAdded, {
+              name: actorName,
+              countLabel: itemsCountLabel(event.count ?? 1, recipient.locale),
+              list: event.listName,
+            });
+
+      await sendPushNotification(recipient.id, { title, body, url }).catch((err) => {
+        console.error("[shopping-list-notify] push failed", err);
+      });
+    })
+  );
+}
+

apps/web/messages/en.json

@@ -41,7 +41,9 @@
     "detail": {
       "comment": "{name} commented on your recipe \"{title}\"",
       "rating": "{name} rated your recipe \"{title}\" {stars} stars",
-      "leftoverExpiring": "Your \"{dish}\" from \"{title}\" is about to expire — eat it soon!"
+      "leftoverExpiring": "Your \"{dish}\" from \"{title}\" is about to expire — eat it soon!",
+      "shoppingListChecked": "{name} checked off \"{item}\" in \"{list}\"",
+      "shoppingListItemsAdded": "{name} added {countLabel} to \"{list}\""
     },
     "pushTitle": {
       "follow": "New follower",
@@ -50,7 +52,8 @@
       "reaction": "New reaction",
       "rating": "New rating",
       "mention": "You were mentioned",
-      "leftoverExpiring": "Leftovers expiring soon"
+      "leftoverExpiring": "Leftovers expiring soon",
+      "shoppingListUpdate": "Shopping list update"
     }
   },
   "recipe": {

apps/web/messages/fr.json

@@ -41,7 +41,9 @@
     "detail": {
       "comment": "{name} a commenté votre recette « {title} »",
       "rating": "{name} a noté votre recette « {title} » {stars} étoiles",
-      "leftoverExpiring": "Votre « {dish} » de « {title} » arrive à expiration — à manger vite !"
+      "leftoverExpiring": "Votre « {dish} » de « {title} » arrive à expiration — à manger vite !",
+      "shoppingListChecked": "{name} a coché « {item} » dans « {list} »",
+      "shoppingListItemsAdded": "{name} a ajouté {countLabel} à « {list} »"
     },
     "pushTitle": {
       "follow": "Nouvel abonné",
@@ -50,7 +52,8 @@
       "reaction": "Nouvelle réaction",
       "rating": "Nouvelle note",
       "mention": "Vous avez été mentionné",
-      "leftoverExpiring": "Restes bientôt périmés"
+      "leftoverExpiring": "Restes bientôt périmés",
+      "shoppingListUpdate": "Mise à jour de la liste de courses"
     }
   },
   "recipe": {