Optimize data processing with caching, single-pass algorithms, and O(1) lookups

src/components/inventory/AddItemForm.tsx

@@ -59,6 +59,9 @@ const statusMessages = {
 
 
 export const AddItemForm = ({ onAddItem, onCancel, existingSkus }: AddItemFormProps) => {
+  // Convert to Set for O(1) lookup performance
+  const existingSkusSet = new Set(existingSkus);
+
   const [formData, setFormData] = useState<Omit<Product, 'id' | 'lastUpdated' | 'expiryDate'>>({
     name: '',
     price: 0,
@@ -85,7 +88,7 @@ export const AddItemForm = ({ onAddItem, onCancel, existingSkus }: AddItemFormPr
 
   const handleSubmit = (e: React.FormEvent) => {
     e.preventDefault();
-    if (existingSkus.includes(formData.sku)) {
+    if (existingSkusSet.has(formData.sku)) {
       setSkuError('SKU already exists');
       return;
     }
@@ -105,7 +108,7 @@ export const AddItemForm = ({ onAddItem, onCancel, existingSkus }: AddItemFormPr
   const handleSkuChange = (e: React.ChangeEvent<HTMLInputElement>) => {
     const value = e.target.value;
     setFormData(prev => ({ ...prev, sku: value }));
-    if (existingSkus.includes(value)) {
+    if (existingSkusSet.has(value)) {
       setSkuError('SKU already exists');
     } else {
       setSkuError(null);

src/components/inventory/EditItemForm.tsx

@@ -12,11 +12,13 @@ interface EditItemFormProps {
 }
 
 export const EditItemForm = ({ item, onEditItem, onCancel, existingSkus }: EditItemFormProps) => {
+  // Convert to Set for O(1) lookup performance
+  const existingSkusSet = new Set(existingSkus);
   const [skuError, setSkuError] = useState<string | null>(null);
   const [category, setCategory] = useState(item.category || '');
 
   const validateSku = (sku: string): boolean => {
-    if (existingSkus.includes(sku)) {
+    if (existingSkusSet.has(sku)) {
       setSkuError('SKU already exists. Please enter a unique SKU.');
       return false;
     }

src/components/reports/DailySalesReport.tsx

@@ -6,12 +6,20 @@ import { useEffect, useState } from "react";
 
 const DailySalesReport = () => {
   const [sales, setSales] = useState<Sale[]>([]);
-  const today = new Date().toISOString().split("T")[0];
+  const today = new Date();
+  today.setHours(0, 0, 0, 0);
+  const todayTime = today.getTime();
+  const tomorrowTime = todayTime + 24 * 60 * 60 * 1000;
 
   useEffect(() => {
     setSales(salesService.getAll());
   }, []);
-  const dailySales = sales.filter((sale) => sale.date.startsWith(today));
+
+  // Use timestamp comparison for better performance
+  const dailySales = sales.filter((sale) => {
+    const saleTime = new Date(sale.date).getTime();
+    return saleTime >= todayTime && saleTime < tomorrowTime;
+  });
 
   const totalSales = dailySales.reduce((total, sale) => total + sale.total, 0);
 

src/components/reports/ExpiringItemsReport.tsx

@@ -5,18 +5,20 @@ import { useEffect, useState } from "react";
 
 const ExpiringItemsReport = () => {
   const [products, setProducts] = useState<Product[]>([]);
-  const today = new Date();
 
   useEffect(() => {
     setProducts(inventoryService.getAll());
   }, []);
-  const next30Days = new Date();
-  next30Days.setDate(today.getDate() + 30);
+
+  // Calculate dates once for better performance
+  const todayTime = new Date().getTime();
+  const next30DaysTime = todayTime + (30 * 24 * 60 * 60 * 1000);
 
+  // Use timestamp comparison for better performance
   const expiringItems = products.filter((product) => {
     if (!product.expiryDate) return false;
-    const expiryDate = new Date(product.expiryDate);
-    return expiryDate >= today && expiryDate <= next30Days;
+    const expiryTime = new Date(product.expiryDate).getTime();
+    return expiryTime >= todayTime && expiryTime <= next30DaysTime;
   });
 
   return (

src/components/reports/MonthlySalesReport.tsx

@@ -19,11 +19,17 @@ interface Sale {
 const MonthlySalesReport = () => {
   const [sales, setSales] = useState<Sale[]>([]);
   const currentMonth = new Date().getMonth();
+  const currentYear = new Date().getFullYear();
 
   useEffect(() => {
     setSales(salesService.getAll());
   }, []);
-  const monthlySales = sales.filter((sale) => new Date(sale.date).getMonth() === currentMonth);
+
+  // Optimize by checking both month and year for accuracy
+  const monthlySales = sales.filter((sale) => {
+    const saleDate = new Date(sale.date);
+    return saleDate.getMonth() === currentMonth && saleDate.getFullYear() === currentYear;
+  });
 
   const totalSales = monthlySales.reduce((total, sale) => total + sale.total, 0);
 

src/context/AuthContext.tsx

@@ -1,4 +1,4 @@
-import React, { createContext, useState, useEffect } from 'react';
+import React, { createContext, useState, useEffect, useCallback } from 'react';
 import type { ReactNode } from 'react';
 import { useNavigate } from 'react-router-dom';
 import { userService } from '@/services/storage';
@@ -35,14 +35,15 @@ export const AuthProvider = ({ children }: { children: ReactNode }) => {
     setLoading(false);
   }, []);
 
-  const login = async (username: string, password: string, role: UserRole) => {
+  const login = useCallback(async (username: string, password: string, role: UserRole) => {
     try {
       const user = userService.validateCredentials(username, password);
 
       // Check if user exists and has the correct role
       if (user && user.role === role) {
-        // Remove password before storing in state
-        const { password: _, ...userData } = user;
+        // Remove password before storing in state for security
+        // eslint-disable-next-line @typescript-eslint/no-unused-vars
+        const { password: unusedPassword, ...userData } = user; // Remove password from user data
         localStorage.setItem('currentUser', JSON.stringify(userData));
         setUser(userData);
         return true;
@@ -58,13 +59,13 @@ export const AuthProvider = ({ children }: { children: ReactNode }) => {
       console.error('Login error:', error);
       return false;
     }
-  };
+  }, []);
 
-  const logout = () => {
+  const logout = useCallback(() => {
     localStorage.removeItem('currentUser');
     setUser(null);
     navigate('/login');
-  };
+  }, [navigate]);
 
   return (
     <AuthContext.Provider value={{ user, login, logout, loading }}>

src/pages/admin/Dashboard.tsx

@@ -80,79 +80,87 @@ const Dashboard = () => {
 
   // Calculate metrics
   const metrics = useMemo(() => {
-    const today = new Date();
-    const yesterday = new Date(today);
-    yesterday.setDate(yesterday.getDate() - 1);
+    const todayStart = new Date();
+    todayStart.setHours(0, 0, 0, 0);
+    const todayStartTime = todayStart.getTime();
 
-    const todaySales = sales.filter(sale => {
-      const saleDate = new Date(sale.date);
-      return saleDate.toDateString() === today.toDateString();
-    });
+    const yesterdayStart = new Date(todayStart);
+    yesterdayStart.setDate(yesterdayStart.getDate() - 1);
+    const yesterdayStartTime = yesterdayStart.getTime();
+    const yesterdayEndTime = todayStartTime;
 
-    const yesterdaySales = sales.filter(sale => {
-      const saleDate = new Date(sale.date);
-      return saleDate.toDateString() === yesterday.toDateString();
-    });
+    const weekAgoTime = todayStartTime - (7 * 24 * 60 * 60 * 1000);
+    const monthAgoTime = todayStartTime - (30 * 24 * 60 * 60 * 1000);
+
+    // Single pass through sales for all time-based calculations
+    let totalTodaySales = 0;
+    let totalYesterdaySales = 0;
+    let totalWeeklySales = 0;
+    let totalMonthlySales = 0;
+    let totalAllSales = 0;
+
+    for (const sale of sales) {
+      const saleTime = new Date(sale.date).getTime();
+      totalAllSales += sale.total;
+
+      if (saleTime >= todayStartTime) {
+        totalTodaySales += sale.total;
+        totalWeeklySales += sale.total;
+        totalMonthlySales += sale.total;
+      } else if (saleTime >= yesterdayStartTime && saleTime < yesterdayEndTime) {
+        totalYesterdaySales += sale.total;
+        totalWeeklySales += sale.total;
+        totalMonthlySales += sale.total;
+      } else if (saleTime >= weekAgoTime) {
+        totalWeeklySales += sale.total;
+        totalMonthlySales += sale.total;
+      } else if (saleTime >= monthAgoTime) {
+        totalMonthlySales += sale.total;
+      }
+    }
 
-    const totalTodaySales = todaySales.reduce((sum, sale) => sum + sale.total, 0);
-    const totalYesterdaySales = yesterdaySales.reduce((sum, sale) => sum + sale.total, 0);
     const salesChange = totalYesterdaySales > 0 
       ? ((totalTodaySales - totalYesterdaySales) / totalYesterdaySales) * 100 
       : 0;
-
-    // Calculate weekly sales (last 7 days)
-    const oneWeekAgo = new Date(today);
-    oneWeekAgo.setDate(oneWeekAgo.getDate() - 7);
-    const weeklySales = sales.filter(sale => {
-      const saleDate = new Date(sale.date);
-      return saleDate >= oneWeekAgo;
-    });
-    const totalWeeklySales = weeklySales.reduce((sum, sale) => sum + sale.total, 0);
 
-    // Calculate monthly sales (last 30 days)
-    const oneMonthAgo = new Date(today);
-    oneMonthAgo.setDate(oneMonthAgo.getDate() - 30);
-    const monthlySales = sales.filter(sale => {
-      const saleDate = new Date(sale.date);
-      return saleDate >= oneMonthAgo;
-    });
-    const totalMonthlySales = monthlySales.reduce((sum, sale) => sum + sale.total, 0);
+    // Single pass through inventory for all calculations
+    let criticalItemsCount = 0;
+    let totalStock = 0;
+    let totalInventoryValue = 0;
+    let lowStockItemsCount = 0;
+    let lowStockValue = 0;
+    const inventoryByCategory: Record<string, { count: number; value: number }> = {};
 
-    const criticalItems = inventory.filter(item => 
-      item.quantity <= (item.criticalLevel || 5)
-    );
-
-    // Calculate total stock across all items
-    const totalStock = inventory.reduce((sum, item) => sum + item.quantity, 0);
-
-    // Calculate price-related metrics
-    const totalInventoryValue = inventory.reduce((sum, item) => {
+    for (const item of inventory) {
+      const quantity = item.quantity;
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
       const price = (item as any).price || 0;
-      return sum + (price * item.quantity);
-    }, 0);
-
-    const avgProductPrice = inventory.length > 0 
-      ? totalInventoryValue / inventory.reduce((sum, item) => sum + item.quantity, 0)
-      : 0;
-
-    const lowStockValue = inventory
-      .filter(item => item.quantity < 10)
-      .reduce((sum, item) => {
-        const price = (item as any).price || 0;
-        return sum + (price * item.quantity);
-      }, 0);
-
-    // Group inventory by category for the pie chart
-    const inventoryByCategory = inventory.reduce<Record<string, { count: number; value: number }>>((acc, item) => {
+      const itemValue = price * quantity;
+
+      totalStock += quantity;
+      totalInventoryValue += itemValue;
+
+      if (quantity <= (item.criticalLevel || 5)) {
+        criticalItemsCount++;
+      }
+
+      if (quantity < 10) {
+        lowStockItemsCount++;
+        lowStockValue += itemValue;
+      }
+
+      // eslint-disable-next-line @typescript-eslint/no-explicit-any
       const category = (item as any).category || 'Uncategorized';
-      const price = (item as any).price || 0;
-      if (!acc[category]) {
-        acc[category] = { count: 0, value: 0 };
+      if (!inventoryByCategory[category]) {
+        inventoryByCategory[category] = { count: 0, value: 0 };
       }
-      acc[category].count += item.quantity;
-      acc[category].value += price * item.quantity;
-      return acc;
-    }, {});
+      inventoryByCategory[category].count += quantity;
+      inventoryByCategory[category].value += itemValue;
+    }
+
+    const avgProductPrice = totalStock > 0 
+      ? totalInventoryValue / totalStock
+      : 0;
 
     // Convert to array for the pie chart
     const pieChartData = Object.entries(inventoryByCategory).map(([name, data]) => ({
@@ -162,16 +170,16 @@ const Dashboard = () => {
     }));
 
     return {
-      totalSales: sales.reduce((sum, sale) => sum + sale.total, 0),
+      totalSales: totalAllSales,
       weeklySales: totalWeeklySales,
       monthlySales: totalMonthlySales,
       totalProducts: inventory.length,
       totalStock,
       totalInventoryValue,
       avgProductPrice,
       lowStockValue,
-      lowStockItems: inventory.filter(item => item.quantity < 10).length,
-      criticalItems: criticalItems.length,
+      lowStockItems: lowStockItemsCount,
+      criticalItems: criticalItemsCount,
       todaySales: totalTodaySales,
       salesChange,
       pieChartData

src/pages/admin/Inventory.tsx

@@ -19,7 +19,7 @@ const Inventory = () => {
   const [showAddItemForm, setShowAddItemForm] = useState(false);
   const [editingItem, setEditingItem] = useState<Product | null>(null);
 
-  // Get unique categories from inventory items
+  // Get unique categories from inventory items  
   const categories = useMemo(() => {
     const categorySet = new Set<string>();
     inventoryItems.forEach(item => {
@@ -29,6 +29,11 @@ const Inventory = () => {
     });
     return Array.from(categorySet).sort();
   }, [inventoryItems]);
+
+  // Create SKU set for fast validation
+  const existingSkusSet = useMemo(() => {
+    return new Set(inventoryItems.map(item => item.sku).filter(Boolean));
+  }, [inventoryItems]);
 
   // Load inventory items on component mount
   useEffect(() => {
@@ -157,7 +162,7 @@ const Inventory = () => {
             <AddItemForm 
               onAddItem={handleAddItem} 
               onCancel={() => setShowAddItemForm(false)}
-              existingSkus={inventoryItems.map(item => item.sku).filter(Boolean) as string[]}
+              existingSkus={Array.from(existingSkusSet)}
             />
           </CardContent>
         </Card>
@@ -173,10 +178,7 @@ const Inventory = () => {
               item={editingItem}
               onEditItem={handleUpdateItem}
               onCancel={() => setEditingItem(null)}
-              existingSkus={inventoryItems
-                .filter(item => item.id !== editingItem.id) // Exclude current item's SKU
-                .map(item => item.sku)
-                .filter(Boolean) as string[]}
+              existingSkus={Array.from(existingSkusSet).filter(sku => sku !== editingItem.sku)}
             />
           </CardContent>
         </Card>

src/pages/admin/NewSale.tsx

@@ -89,9 +89,12 @@ const NewSale: React.FC = () => {
     if (cart.length === 0) return;
 
     try {
+      // Create a product map for O(1) lookups instead of O(n) for each item
+      const productMap = new Map(products.map(p => [p.id, p]));
+
       // First, validate all items have sufficient stock
       for (const item of cart) {
-        const product = products.find(p => p.id === item.productId);
+        const product = productMap.get(item.productId);
         if (!product) {
           throw new Error(`Product ${item.name} not found`);
         }
@@ -102,7 +105,7 @@ const NewSale: React.FC = () => {
 
       // Process inventory updates
       for (const item of cart) {
-        const product = products.find(p => p.id === item.productId)!;
+        const product = productMap.get(item.productId)!;
         const newQuantity = product.quantity - item.quantity;
 
         await inventoryService.update(product.id, {