feat(stock): write stock_ledger audit row when cost_price changes

src/lib/server/stock-pricing-service.test.ts

@@ -47,3 +47,100 @@ describe("updateStockItemsPricing — happy path", () => {
     });
   });
 });
+
+describe("updateStockItemsPricing — stock_ledger audit on cost change", () => {
+  const stubPb = (before: Record<string, unknown>, updated: Record<string, unknown>) => {
+    const ledgerCreates: Array<Record<string, unknown>> = [];
+    return {
+      pb: {
+        collection: (name: string) => {
+          if (name === "stock_items") {
+            return {
+              getOne: vi.fn().mockResolvedValue(before),
+              update: vi.fn().mockResolvedValue(updated),
+              create: vi.fn(),
+            };
+          }
+          if (name === "stock_ledger") {
+            return {
+              create: vi.fn().mockImplementation(async (row) => {
+                ledgerCreates.push(row);
+                return { id: "ledger1", ...row };
+              }),
+              _creates: ledgerCreates,
+            };
+          }
+          throw new Error(`unexpected ${name}`);
+        },
+      },
+      ledgerCreates,
+    } as const;
+  };
+
+  it("writes a stock_ledger row with reason=adjustment when costPrice changes", async () => {
+    const before = {
+      id: "abcdefghijklmno",
+      cost_price: 2.5,
+      selling_price: 3.25,
+      markup: 30,
+    };
+    const updated = { ...before, cost_price: 3.2 };
+    const { pb, ledgerCreates } = stubPb(before, updated);
+
+    await updateStockItemsPricing({
+      pb: pb as never,
+      updates: [{ id: "abcdefghijklmno", costPrice: 3.2 }],
+      actor: { id: "useropid1234567", name: "Gary" },
+    } as UpdateStockItemsPricingInput);
+
+    expect(ledgerCreates).toEqual([
+      expect.objectContaining({
+        stock_item: "abcdefghijklmno",
+        change_qty: 0,
+        unit_cost: 3.2,
+        reason: "adjustment",
+        reference_type: "manual",
+      }),
+    ]);
+  });
+
+  it("does NOT write a stock_ledger row when costPrice is omitted", async () => {
+    const before = {
+      id: "abcdefghijklmno",
+      cost_price: 2.5,
+      selling_price: 3.25,
+      markup: 30,
+    };
+    const updated = { ...before, selling_price: 4.16 };
+    const { pb, ledgerCreates } = stubPb(before, updated);
+
+    await updateStockItemsPricing({
+      pb: pb as never,
+      updates: [{ id: "abcdefghijklmno", sellingPrice: 4.16 }],
+      actor: { id: "useropid1234567", name: "Gary" },
+    } as UpdateStockItemsPricingInput);
+
+    expect(ledgerCreates).toEqual([]);
+  });
+
+  it("does NOT write a stock_ledger row when costPrice equals the existing cost", async () => {
+    const before = {
+      id: "abcdefghijklmno",
+      cost_price: 2.5,
+      selling_price: 3.25,
+      markup: 30,
+    };
+    const updated = before;
+    const { pb, ledgerCreates } = stubPb(before, updated);
+
+    await updateStockItemsPricing({
+      pb: pb as never,
+      updates: [
+        { id: "abcdefghijklmno", costPrice: 2.5, sellingPrice: 5 },
+      ],
+      actor: { id: "useropid1234567", name: "Gary" },
+    } as UpdateStockItemsPricingInput);
+
+    expect(ledgerCreates).toEqual([]);
+  });
+});

src/lib/server/stock-pricing-service.ts

@@ -151,6 +151,36 @@ export async function updateStockItemsPricing(
       continue;
     }
 
+    // 3.5. Cost audit — write a stock_ledger row ONLY when costPrice was
+    //      supplied and differs from the existing cost_price. Side-effect:
+    //      a failed ledger write aborts THIS row (we won't half-write the
+    //      patch without recording the audit trail).
+    if (
+      update.costPrice !== undefined &&
+      before.cost_price !== update.costPrice
+    ) {
+      try {
+        await input.pb.collection("stock_ledger").create({
+          stock_item: update.id,
+          change_qty: 0,
+          unit_cost: update.costPrice,
+          reason: "adjustment",
+          reference_type: "manual",
+          notes: `${input.actor.name} edited cost from /stock`,
+          created_by: input.actor.id,
+        });
+      } catch (err) {
+        const message = err instanceof Error ? err.message : String(err);
+        results.push({
+          id: update.id,
+          ok: false,
+          reason: "pb_error",
+          message: `Patched row but failed to write stock_ledger: ${message}`,
+        });
+        continue;
+      }
+    }
+
     // 4. Capture previous snapshot for the response.
     const previous: StockItemPricingSnapshot = {
       cost_price: before.cost_price,