Refine catalog cart controls and show cart badge in header

app/composables/useClientCart.ts

@@ -12,8 +12,8 @@ export type ClientCartItem = {
 };
 
 function normalizeQuantity(value: number) {
-  if (!Number.isFinite(value) || value < 1) {
-    return 1;
+  if (!Number.isFinite(value) || value < 0) {
+    return 0;
   }
 
   return Math.floor(value);
@@ -64,7 +64,13 @@ export function useClientCart() {
       return;
     }
 
-    existing.quantity = normalizeQuantity(quantity);
+    const normalizedQuantity = normalizeQuantity(quantity);
+    if (normalizedQuantity === 0) {
+      removeProduct(productId);
+      return;
+    }
+
+    existing.quantity = normalizedQuantity;
   }
 
   function incrementQuantity(productId: string) {
@@ -82,7 +88,13 @@ export function useClientCart() {
       return;
     }
 
-    existing.quantity = normalizeQuantity(existing.quantity - 1);
+    const normalizedQuantity = normalizeQuantity(existing.quantity - 1);
+    if (normalizedQuantity === 0) {
+      removeProduct(productId);
+      return;
+    }
+
+    existing.quantity = normalizedQuantity;
   }
 
   function removeProduct(productId: string) {