Implemented cart service with state tracker and linked to main layout

MidrandBookshop/Services/ShoppingCart/CartService.cs

@@ -0,0 +1,153 @@
+using LiteCharms.Features.Browser;
+using LiteCharms.Features.Hasher;
+using LiteCharms.Features.MidrandBooks.Products.Models;
+using MidrandBookshop.Services.ShoppingCart.Models;
+
+namespace MidrandBookshop.Services.ShoppingCart;
+
+public sealed class CartService(LocalStorageService localStorage)
+{
+    private readonly string CartStorageKey = HashService.ToMd5Hash(nameof(Cart)).Value;
+
+    public Cart ShoppingCart { get; private set; } = new();
+
+    public event Action? OnCartChanged;
+
+    public Cart GetCart() => ShoppingCart;
+
+    public void NotifyStateChanged() => OnCartChanged?.Invoke();
+
+    public async Task LoadCartFromStorageAsync()
+    {
+        var loadResult = await localStorage.GetAsync<Cart>(CartStorageKey);
+
+        if (loadResult.IsFailed) await localStorage.SaveAsync(CartStorageKey, ShoppingCart);
+
+        if (loadResult.IsSuccess) ShoppingCart = loadResult.Value;
+
+        NotifyStateChanged();
+    }
+
+    public async Task SaveCartToStorageAsync() => await localStorage.SaveAsync(CartStorageKey, ShoppingCart);
+
+    public void AddItem(ProductPrice productPrice)
+    {
+        var itemExists = false;
+
+        for (var i = 0; i < ShoppingCart.Items.Count; i++)
+        {
+            if (ShoppingCart.Items[i].Price!.Id == productPrice.Id)
+            {
+                ShoppingCart.Items[i].Quantity++;
+                ShoppingCart.Items[i].Amount += productPrice.Amount;
+
+                itemExists = true;
+
+                break;
+            }
+        }
+
+        if (!itemExists)
+            ShoppingCart.Items.Add(new CartItem
+            {
+                Price = productPrice,
+                Amount = productPrice.Amount,
+                Quantity = 1,
+            });
+
+        CalculateTotalPrice();
+        NotifyStateChanged();
+    }
+
+    public void UpdateQuantity(long productPriceId, int newQuantity)
+    {
+        if (newQuantity <= 0)
+        {
+            RemoveAllSameItem(productPriceId);
+            NotifyStateChanged();
+
+            return;
+        }
+
+        for (var i = 0; i < ShoppingCart.Items.Count; i++)
+        {
+            if (ShoppingCart.Items[i].Price!.Id == productPriceId)
+            {
+                var oldQuantity = ShoppingCart.Items[i].Quantity;
+                var pricePerUnit = ShoppingCart.Items[i].Price!.Amount;
+
+                ShoppingCart.Items[i].Quantity = newQuantity;
+                ShoppingCart.Items[i].Amount = pricePerUnit * newQuantity;
+                break;
+            }
+        }
+
+        CalculateTotalPrice();
+        NotifyStateChanged();
+    }
+
+    public void RemoveOneItem(long productPriceId)
+    {
+        for (var i = 0; i < ShoppingCart.Items.Count; i++)
+        {
+            if (ShoppingCart.Items[i].Price!.Id == productPriceId)
+            {
+                if (ShoppingCart.Items[i].Quantity <= 1)
+                {
+                    ShoppingCart.Items.RemoveAt(i);
+                }
+                else
+                {
+                    ShoppingCart.Items[i].Quantity--;
+                    ShoppingCart.Items[i].Amount -= ShoppingCart.Items[i].Price!.Amount;
+                }
+
+                break;
+            }
+        }
+
+        CalculateTotalPrice();
+        NotifyStateChanged();
+    }
+
+    public void RemoveAllSameItem(long productPriceId)
+    {
+        if (ShoppingCart.Items.Count == 0) return;
+
+        var item = ShoppingCart.Items.FirstOrDefault(i => i.Price?.Id == productPriceId);
+
+        if (item is not null) ShoppingCart.Items.Remove(item);
+
+        CalculateTotalPrice();
+        NotifyStateChanged();
+    }
+
+    public void Clear()
+    {
+        if(ShoppingCart.CustomerId is not null || ShoppingCart.OrderId is not null)
+        {
+            ShoppingCart.TotalPrice = 0;
+            ShoppingCart.TotalVat = 0;
+            ShoppingCart.Items.Clear();
+
+            return;
+        }
+
+        ShoppingCart = new Cart();
+
+        NotifyStateChanged();
+    }
+
+    public decimal CalculateTotalPrice()
+    {
+        if (ShoppingCart.Items.Count == 0) return 0;
+
+        var gross = ShoppingCart.Items.Sum(i => i.Amount);
+
+        if (!ShoppingCart.IsVatInclusive) ShoppingCart.TotalVat = gross * ShoppingCart.VatRate;
+
+        ShoppingCart.TotalPrice = gross + ShoppingCart.TotalVat;
+
+        return ShoppingCart.TotalPrice;
+    }
+}

MidrandBookshop/Services/ShoppingCart/Models/Cart.cs

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+namespace MidrandBookshop.Services.ShoppingCart.Models;
+
+public sealed class Cart
+{
+    public long? CustomerId { get; set; }
+
+    public long? OrderId { get; set; }
+
+    public decimal TotalPrice { get; set; }
+
+    public decimal TotalVat { get; set; }
+
+    public decimal VatRate { get; set; } = 0.15m;
+
+    public bool IsVatInclusive { get; set; } = true;
+
+    public IList<CartItem> Items { get; set; } = [];
+}

MidrandBookshop/Services/ShoppingCart/Models/CartItem.cs

@@ -0,0 +1,12 @@
+using LiteCharms.Features.MidrandBooks.Products.Models;
+
+namespace MidrandBookshop.Services.ShoppingCart.Models;
+
+public sealed class CartItem
+{
+    public ProductPrice? Price { get; set; }
+
+    public long Quantity { get; set; }
+
+    public decimal Amount { get; set; }
+}