feat(19-02): add COALESCE merge for reference items in item service

- getAllItems and getItemById LEFT JOIN globalItems with COALESCE for name, weight, price, image
- createItem accepts globalItemId and purchasePriceCents, stores brand+model as fallback name
- duplicateItem preserves globalItemId and purchasePriceCents
- updateItem type includes globalItemId and purchasePriceCents
- 10 new tests for reference item creation and merged data retrieval

tests/services/item.service.test.ts

@@ -1,4 +1,5 @@
 import { beforeEach, describe, expect, it } from "bun:test";
+import { globalItems } from "../../src/db/schema.ts";
 import {
 	createItem,
 	deleteItem,
@@ -168,6 +169,216 @@ describe("Item Service", () => {
 		});
 	});
 
+	describe("reference items (globalItemId)", () => {
+		async function insertGlobalItem(
+			testDb: any,
+			data: {
+				brand: string;
+				model: string;
+				weightGrams?: number;
+				priceCents?: number;
+				imageUrl?: string;
+			},
+		) {
+			const [row] = await testDb
+				.insert(globalItems)
+				.values(data)
+				.returning();
+			return row;
+		}
+
+		it("createItem with globalItemId creates a reference item with globalItemId set", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Big Agnes",
+				model: "Copper Spur HV UL2",
+				weightGrams: 1270,
+				priceCents: 44995,
+			});
+
+			const item = await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			expect(item).toBeDefined();
+			expect(item?.globalItemId).toBe(gi.id);
+		});
+
+		it("createItem with globalItemId stores brand+model as fallback name", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "MSR",
+				model: "Hubba Hubba",
+				weightGrams: 1540,
+			});
+
+			const item = await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			expect(item?.name).toBe("MSR Hubba Hubba");
+		});
+
+		it("getAllItems returns merged name from global item for reference items", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				weightGrams: 425,
+				priceCents: 17995,
+			});
+
+			await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all).toHaveLength(1);
+			expect(all[0].name).toBe("Nemo Tensor");
+		});
+
+		it("getAllItems returns merged weightGrams from global item for reference items", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				weightGrams: 425,
+				priceCents: 17995,
+			});
+
+			await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all[0].weightGrams).toBe(425);
+		});
+
+		it("getAllItems returns merged priceCents from global item for reference items", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				weightGrams: 425,
+				priceCents: 17995,
+			});
+
+			await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all[0].priceCents).toBe(17995);
+		});
+
+		it("getAllItems returns item's own imageFilename when set, ignoring global imageUrl", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				imageUrl: "https://example.com/global.jpg",
+			});
+
+			await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+				imageFilename: "local.jpg",
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all[0].imageFilename).toBe("local.jpg");
+		});
+
+		it("getAllItems falls back to global imageUrl when item has no imageFilename", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Nemo",
+				model: "Tensor",
+				imageUrl: "https://example.com/global.jpg",
+			});
+
+			await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all[0].imageFilename).toBe("https://example.com/global.jpg");
+		});
+
+		it("getAllItems returns standalone item data unchanged", async () => {
+			await createItem(db, userId, {
+				name: "My Manual Tent",
+				weightGrams: 1500,
+				priceCents: 25000,
+				categoryId: 1,
+			});
+
+			const all = await getAllItems(db, userId);
+			expect(all).toHaveLength(1);
+			expect(all[0].name).toBe("My Manual Tent");
+			expect(all[0].weightGrams).toBe(1500);
+			expect(all[0].priceCents).toBe(25000);
+			expect(all[0].globalItemId).toBeNull();
+		});
+
+		it("getItemById returns merged data for a reference item", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "Thermarest",
+				model: "NeoAir XLite",
+				weightGrams: 340,
+				priceCents: 20995,
+			});
+
+			const created = await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const item = await getItemById(db, userId, created?.id);
+			expect(item).toBeDefined();
+			expect(item?.name).toBe("Thermarest NeoAir XLite");
+			expect(item?.weightGrams).toBe(340);
+			expect(item?.priceCents).toBe(20995);
+			expect(item?.globalItemId).toBe(gi.id);
+		});
+
+		it("duplicateItem on a reference item preserves globalItemId", async () => {
+			const gi = await insertGlobalItem(db, {
+				brand: "MSR",
+				model: "PocketRocket 2",
+				weightGrams: 73,
+				priceCents: 4995,
+			});
+
+			const original = await createItem(db, userId, {
+				name: "placeholder",
+				categoryId: 1,
+				globalItemId: gi.id,
+			});
+
+			const copy = await duplicateItem(db, userId, original?.id);
+			expect(copy).toBeDefined();
+			expect(copy?.globalItemId).toBe(gi.id);
+		});
+
+		it("createItem with purchasePriceCents stores the value", async () => {
+			const item = await createItem(db, userId, {
+				name: "Discounted Tent",
+				categoryId: 1,
+				purchasePriceCents: 29999,
+			});
+
+			expect(item?.purchasePriceCents).toBe(29999);
+		});
+	});
+
 	describe("cross-user isolation", () => {
 		it("user cannot see other user's items", async () => {
 			const userId2 = await createSecondTestUser(db);