fix: enable automatic offer discovery when customer changes

Remove guards that prevented offer reapplication when no offers are currently applied. This allows the system to automatically discover and apply eligible offers when switching to a different customer, even if the cart doesn't have any active offers yet.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Ahmed Osama

POS/src/pages/POSSale.vue

@@ -651,6 +651,13 @@ const offerReapplyTimer = ref(null)
 // Performance: Cache previous cart state to avoid unnecessary reapplications
 let previousCartHash = ''
 
+// Helper function to compute cart hash
+function computeCartHash() {
+	return cartStore.invoiceItems.map(i =>
+		`${i.item_code}-${i.quantity}-${i.rate}-${i.discount_percentage || 0}-${i.discount_amount || 0}-${i.uom || ''}-${i.warehouse || ''}`
+	).join('|')
+}
+
 // Promotion dialog
 const showPromotionManagement = ref(false)
 
@@ -749,37 +756,72 @@ watch(() => shiftStore.hasOpenShift, value => {
 	}
 })
 
-// Watch for cart changes to re-apply offers (optimized - only watch length and defer expensive calculations)
-// Performance: Only recalculate hash if cart length changed, then check if content actually changed
+// Watch for cart changes to re-apply offers
+// Comprehensive watcher that detects all cart changes including:
+// - Items added/removed (length changes)
+// - Quantity changes
+// - Rate/price changes
+// - Discount changes
+// - Item properties that affect offers
 watch(
-	() => cartStore.invoiceItems.length,
-	() => {
+	() => computeCartHash(),
+	(newHash) => {
 		// Only proceed if there are applied offers
 		if (cartStore.appliedOffers.length === 0) {
 			return
 		}
 
-		// Calculate hash only when length changes
-		const currentHash = cartStore.invoiceItems.map(i =>
-			`${i.item_code}-${i.quantity}-${i.rate}-${i.discount_percentage || 0}-${i.discount_amount || 0}`
-		).join(',')
-
 		// Skip if cart content hasn't actually changed
-		if (currentHash === previousCartHash) {
+		if (newHash === previousCartHash) {
 			return
 		}
 
-		previousCartHash = currentHash
+		previousCartHash = newHash
 
 		// Clear existing timer to prevent multiple API calls
 		if (offerReapplyTimer.value) {
 			clearTimeout(offerReapplyTimer.value)
 		}
 
-		// Set new timer - reapply offers after 800ms of no changes (increased for better performance)
+		// Set new timer - reapply offers after 500ms of no changes
 		offerReapplyTimer.value = setTimeout(async () => {
 			await cartStore.reapplyOffer(shiftStore.currentProfile)
-		}, 800)
+		}, 500)
+	}
+)
+
+// Watch for customer changes - customer affects which offers are applicable
+watch(
+	() => cartStore.customer,
+	(newCustomer, oldCustomer) => {
+		const newCustomerName = newCustomer?.name || newCustomer
+		const oldCustomerName = oldCustomer?.name || oldCustomer
+
+		// Only reapply if customer actually changed
+		if (newCustomerName !== oldCustomerName) {
+			// Clear existing timer
+			if (offerReapplyTimer.value) {
+				clearTimeout(offerReapplyTimer.value)
+			}
+
+			// Reapply offers immediately when customer changes
+			// This will discover newly eligible offers even if cart has no current offers
+			offerReapplyTimer.value = setTimeout(async () => {
+				await cartStore.reapplyOffer(shiftStore.currentProfile)
+			}, 300)
+		}
+	},
+	{ deep: true }
+)
+
+// Watch for applied offers changes - handle when offers are added/removed
+watch(
+	() => cartStore.appliedOffers.length,
+	() => {
+		// When offers are added or removed, update the cart hash to reflect new state
+		if (cartStore.invoiceItems.length > 0) {
+			previousCartHash = computeCartHash()
+		}
 	}
 )
 
@@ -998,6 +1040,8 @@ async function handlePaymentCompleted(paymentData) {
 			uiStore.showSuccess(`OFFLINE-${Date.now()}`, cartStore.grandTotal)
 			uiStore.showPaymentDialog = false
 			cartStore.clearCart()
+			// Reset cart hash after successful payment
+			previousCartHash = ''
 
 			toast.create({
 				title: "Saved Offline",
@@ -1014,6 +1058,8 @@ async function handlePaymentCompleted(paymentData) {
 
 				uiStore.showPaymentDialog = false
 				cartStore.clearCart()
+				// Reset cart hash after successful payment
+				previousCartHash = ''
 
 				if (itemsSelectorRef.value) {
 					itemsSelectorRef.value.loadItems()
@@ -1082,6 +1128,8 @@ function handleClearCart() {
 
 function confirmClearCart() {
 	cartStore.clearCart()
+	// Reset cart hash when cart is cleared
+	previousCartHash = ''
 	uiStore.showClearCartDialog = false
 	toast.create({
 		title: "Cart Cleared",
@@ -1214,6 +1262,8 @@ async function handleSaveDraft() {
 	)
 	if (success) {
 		cartStore.clearCart()
+		// Reset cart hash when cart is saved as draft and cleared
+		previousCartHash = ''
 	}
 }
 
@@ -1230,6 +1280,9 @@ async function handleLoadDraft(draft) {
 			await cartStore.reapplyOffer(shiftStore.currentProfile)
 		}
 
+		// Initialize cart hash for the loaded cart so watchers work correctly
+		previousCartHash = computeCartHash()
+
 		uiStore.showDraftDialog = false
 	} catch (error) {
 		// Error handled in store
@@ -1322,6 +1375,9 @@ async function handleEditOfflineInvoice(invoice) {
 			}
 		}
 
+		// Initialize cart hash for the loaded cart so watchers work correctly
+		previousCartHash = computeCartHash()
+
 		await offlineStore.deleteOfflineInvoice(invoice.id)
 
 		toast.create({

POS/src/stores/posCart.js

@@ -404,16 +404,16 @@ export const usePOSCartStore = defineStore('posCart', () => {
 	}
 
 	async function reapplyOffer(currentProfile) {
+		// Clear offers if cart is empty
 		if (invoiceItems.value.length === 0 && appliedOffers.value.length) {
 			appliedOffers.value = []
 			return
 		}
 
-		if (
-			invoiceItems.value.length > 0 &&
-			appliedOffers.value.length > 0 &&
-			!suppressOfferReapply.value
-		) {
+		// Reapply or discover offers when cart has items
+		// - If appliedOffers.length > 0: re-validates existing offers
+		// - If appliedOffers.length === 0: discovers new eligible offers
+		if (invoiceItems.value.length > 0 && !suppressOfferReapply.value) {
 			try {
 				const invoiceData = buildInvoiceDataForOffers(currentProfile)
 				const offerNames = getAppliedOfferCodes()