feat: enforce SKU validity, use SKU as handle

This commit enforces proper SKU validation, uses the SKU as the Shopify handle, and implements ID-based product updates to allow renaming. It also extracts the IShop interface for TDD.

src/ProductLogic.test.ts

@@ -0,0 +1,106 @@
+import { Product } from "./Product";
+import { MockSpreadsheetService } from "./services/MockSpreadsheetService";
+import { MockShop } from "./test/MockShop";
+
+describe("Product Logic (TDD)", () => {
+  let mockService: MockSpreadsheetService;
+  let mockShop: MockShop;
+
+  beforeEach(() => {
+    mockService = new MockSpreadsheetService({
+      product_inventory: [
+        ["sku", "title", "price", "shopify_id", "product_type"], // Headers
+        ["TEST-SKU-1", "Test Product", 10.99, "", "Type A"] // Data
+      ],
+      values: [
+          ["product_type", "shopify_category", "ebay_category_id"],
+          ["Type A", "Category A", "123"]
+      ]
+    });
+    mockShop = new MockShop();
+  });
+
+  test("UpdateShopifyProduct should abort if SKU is invalid", () => {
+    // Setup invalid SKU
+    mockService.setSheetData("product_inventory", [
+        ["sku", "title"],
+        ["?", "Invalid Product"]
+    ]);
+    // Allow empty sku to be passed to constructor logic check, but Product constructor throws if sku not found.
+    // So we pass a valid sku that exists in sheet, but looks invalid?
+    // The requirement is "based on the product's title... If I have a placeholder value... ensure products are not created until they have a valid SKU".
+    // In `Product.ts`, constructor takes `sku`.
+    // If I pass `?` and it's in the sheet, it constructs.
+
+    const product = new Product("?", mockService);
+
+    // Attempt update
+    product.UpdateShopifyProduct(mockShop);
+
+    // Verify no calls to creating product
+    // We expect MatchToShopifyProduct might be called (read only), but NOT productSet (writ)
+    // Actually our plan said "abort operation" at start of UpdateShopifyProduct.
+    expect(mockShop.productSetCalledWith).toBeNull();
+  });
+
+  test("ToShopifyProductSet should set handle to SKU", () => {
+    const product = new Product("TEST-SKU-1", mockService);
+    const sps = product.ToShopifyProductSet();
+
+    // We expect sps to have a 'handle' property equal to the sku
+    // This will fail compilation initially as ShopifyProductSetInput doesn't have handle
+    expect((sps as any).handle).toBe("TEST-SKU-1");
+  });
+
+  test("MatchToShopifyProduct should verify ID if present", () => {
+    // Setup data with shopify_id
+    mockService.setSheetData("product_inventory", [
+        ["sku", "shopify_id"],
+        ["TEST-SKU-OLD", "123456789"]
+    ]);
+    const product = new Product("TEST-SKU-OLD", mockService);
+
+    // Mock the response for GetProductById
+    mockShop.mockProductById = {
+        id: "123456789",
+        title: "Old Title",
+        variants: { nodes: [{ id: "gid://shopify/ProductVariant/123456789", sku: "TEST-SKU-OLD" }] },
+        options: [{ id: "opt1", optionValues: [{ id: "optval1" }] }]
+    };
+
+    // We need to call Match, but it's called inside Update usually.
+    // We can call it directly for testing.
+    product.MatchToShopifyProduct(mockShop);
+
+    // Expect GetProductById to have been called
+    expect(mockShop.getProductByIdCalledWith).toBe("123456789");
+    expect(product.shopify_id).toBe("123456789");
+  });
+
+  test("MatchToShopifyProduct should fall back to SKU if ID lookup fails", () => {
+    // Setup data with shopify_id that is invalid
+    mockService.setSheetData("product_inventory", [
+        ["sku", "shopify_id"],
+        ["TEST-SKU-FAIL", "999999999"]
+    ]);
+    const product = new Product("TEST-SKU-FAIL", mockService);
+
+    // Mock ID lookup failure (returns null/undefined)
+    mockShop.mockProductById = null;
+
+    // Mock SKU lookup success
+    mockShop.mockProductBySku = {
+        id: "555555555",
+        title: "Found By SKU",
+        variants: { nodes: [{ id: "gid://shopify/ProductVariant/555555555", sku: "TEST-SKU-FAIL" }] },
+        options: [{ id: "opt2", optionValues: [{ id: "optval2" }] }]
+    };
+
+    product.MatchToShopifyProduct(mockShop);
+
+    expect(mockShop.getProductByIdCalledWith).toBe("999999999");
+    // Should fall back to SKU
+    expect(mockShop.getProductBySkuCalledWith).toBe("TEST-SKU-FAIL");
+    expect(product.shopify_id).toBe("555555555");
+  });
+});