online cart with Optimistic state

src/app/[name]/(Dialogs)/cart/hooks/useCartData.ts

@@ -1,5 +1,6 @@
 import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import * as api from "../service/CartService";
+import type { CartResponse } from "../types/Types";
 
 export const useBulkCart = () => {
   const queryClient = useQueryClient();
@@ -15,7 +16,48 @@ export const useIncrementCart = () => {
   const queryClient = useQueryClient();
   return useMutation({
     mutationFn: api.increment,
-    onSuccess: () => {
+    onMutate: async (id: string | number) => {
+      await queryClient.cancelQueries({ queryKey: ["cart-items"] });
+
+      const previousCart = queryClient.getQueryData<CartResponse>([
+        "cart-items",
+      ]);
+
+      if (previousCart?.data) {
+        const existingItem = previousCart.data.items.find(
+          (item) => item.foodId === String(id)
+        );
+
+        if (existingItem) {
+          const updatedItems = previousCart.data.items.map((item) => {
+            if (item.foodId === String(id)) {
+              return {
+                ...item,
+                quantity: item.quantity + 1,
+              };
+            }
+            return item;
+          });
+
+          queryClient.setQueryData<CartResponse>(["cart-items"], {
+            ...previousCart,
+            data: {
+              ...previousCart.data,
+              items: updatedItems,
+              totalItems: previousCart.data.totalItems + 1,
+            },
+          });
+        }
+      }
+
+      return { previousCart };
+    },
+    onError: (_err, _id, context) => {
+      if (context?.previousCart) {
+        queryClient.setQueryData(["cart-items"], context.previousCart);
+      }
+    },
+    onSettled: () => {
       queryClient.invalidateQueries({ queryKey: ["cart-items"] });
     },
   });
@@ -25,7 +67,48 @@ export const useDecrementCart = () => {
   const queryClient = useQueryClient();
   return useMutation({
     mutationFn: api.decrement,
-    onSuccess: () => {
+    onMutate: async (id: string | number) => {
+      await queryClient.cancelQueries({ queryKey: ["cart-items"] });
+
+      const previousCart = queryClient.getQueryData<CartResponse>([
+        "cart-items",
+      ]);
+
+      if (previousCart?.data) {
+        const updatedItems = previousCart.data.items
+          .map((item) => {
+            if (item.foodId === String(id)) {
+              const newQuantity = item.quantity - 1;
+              if (newQuantity <= 0) {
+                return null;
+              }
+              return {
+                ...item,
+                quantity: newQuantity,
+              };
+            }
+            return item;
+          })
+          .filter((item): item is NonNullable<typeof item> => item !== null);
+
+        queryClient.setQueryData<CartResponse>(["cart-items"], {
+          ...previousCart,
+          data: {
+            ...previousCart.data,
+            items: updatedItems,
+            totalItems: Math.max(0, previousCart.data.totalItems - 1),
+          },
+        });
+      }
+
+      return { previousCart };
+    },
+    onError: (_err, _id, context) => {
+      if (context?.previousCart) {
+        queryClient.setQueryData(["cart-items"], context.previousCart);
+      }
+    },
+    onSettled: () => {
       queryClient.invalidateQueries({ queryKey: ["cart-items"] });
     },
   });
@@ -35,15 +118,43 @@ export const useClearCart = () => {
   const queryClient = useQueryClient();
   return useMutation({
     mutationFn: api.clear,
-    onSuccess: () => {
+    onMutate: async () => {
+      await queryClient.cancelQueries({ queryKey: ["cart-items"] });
+
+      const previousCart = queryClient.getQueryData<CartResponse>([
+        "cart-items",
+      ]);
+
+      if (previousCart?.data) {
+        queryClient.setQueryData<CartResponse>(["cart-items"], {
+          ...previousCart,
+          data: {
+            ...previousCart.data,
+            items: [],
+            totalItems: 0,
+            subTotal: 0,
+            total: 0,
+          },
+        });
+      }
+
+      return { previousCart };
+    },
+    onError: (_err, _variables, context) => {
+      if (context?.previousCart) {
+        queryClient.setQueryData(["cart-items"], context.previousCart);
+      }
+    },
+    onSettled: () => {
       queryClient.invalidateQueries({ queryKey: ["cart-items"] });
     },
   });
 };
 
-export const useGetCartItems = () => {
+export const useGetCartItems = (enabled = true) => {
   return useQuery({
     queryKey: ["cart-items"],
     queryFn: api.getCartItems,
+    enabled,
   });
 };