Init

Prefab.Web/Pricing/FromPriceCalculator.cs

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+using System.Collections.Generic;
+using System.Linq;
+using Prefab.Catalog.Domain.Entities;
+
+namespace Prefab.Web.Pricing;
+
+public sealed record FromPriceResult(decimal? Amount, string? Currency, bool IsPriced);
+
+/// <summary>
+/// Computes a display-friendly "from price" for catalog products by examining model and variant pricing.
+/// </summary>
+public sealed class FromPriceCalculator
+{
+    private const string DefaultCurrency = "USD";
+    private readonly string _currencyCode;
+
+    public FromPriceCalculator(string? currencyCode = null)
+    {
+        _currencyCode = string.IsNullOrWhiteSpace(currencyCode) ? DefaultCurrency : currencyCode.Trim();
+    }
+
+    public FromPriceResult Compute(Product product)
+    {
+        ArgumentNullException.ThrowIfNull(product);
+
+        if (product.Price.HasValue)
+        {
+            return new FromPriceResult(product.Price.Value, _currencyCode, true);
+        }
+
+        var variantPrices = ExtractVariantPrices(product.Variants);
+        if (variantPrices.Count > 0)
+        {
+            var minimum = variantPrices.Min();
+            return new FromPriceResult(minimum, _currencyCode, true);
+        }
+
+        return new FromPriceResult(null, null, false);
+    }
+
+    private static List<decimal> ExtractVariantPrices(IEnumerable<Product> variants) =>
+        variants
+            .Where(variant => variant is { Kind: ProductKind.Variant, Price: not null })
+            .Select(variant => variant.Price!.Value)
+            .ToList();
+}