feat(pdf): add poSubtotal helper for PO PDF totals

Co-authored-by: Orca <help@stably.ai>

src/lib/pdf/format.test.ts

@@ -5,6 +5,7 @@ import {
   addDays,
   quoteSubtotal,
   vatAmount,
+  poSubtotal,
   QUOTE_VALID_DAYS,
   effectiveQuoteDate,
   effectiveValidityDays,
@@ -109,6 +110,8 @@ describe("effectiveQuoteDate", () => {
   });
 });
 
+
+
 describe("effectiveValidityDays", () => {
   it("uses quote.validity_days when set to a number", () => {
     expect(effectiveValidityDays({ validity_days: 60 })).toBe(60);
@@ -119,4 +122,35 @@ describe("effectiveValidityDays", () => {
   it("falls back to QUOTE_VALID_DAYS (30) when undefined", () => {
     expect(effectiveValidityDays({})).toBe(QUOTE_VALID_DAYS);
   });
-});
+});
+
+describe("poSubtotal", () => {
+  it("sums order_qty × cost_price when order_qty is set", () => {
+    expect(poSubtotal([{ order_qty: 3, quantity: 1, cost_price: 100 }])).toBe(300);
+  });
+  it("falls back to quantity when order_qty is missing", () => {
+    expect(poSubtotal([{ quantity: 4, cost_price: 50 }])).toBe(200);
+  });
+  it("falls back to quantity when order_qty is 0 (blank treated as missing)", () => {
+    expect(poSubtotal([{ order_qty: 0, quantity: 2, cost_price: 75 }])).toBe(150);
+  });
+  it("sums across multiple items", () => {
+    expect(poSubtotal([
+      { order_qty: 3, quantity: 1, cost_price: 100 },
+      { order_qty: 5, quantity: 1, cost_price: 40 },
+    ])).toBe(500);
+  });
+  it("rounds to 2 decimal places (avoids floating-point dust)", () => {
+    expect(poSubtotal([
+      { quantity: 3, cost_price: 33.33 },
+      { quantity: 3, cost_price: 33.33 },
+      { quantity: 3, cost_price: 33.34 },
+    ])).toBe(300);
+  });
+  it("returns 0 for an empty array", () => {
+    expect(poSubtotal([])).toBe(0);
+  });
+  it("treats non-numeric cost_price as 0", () => {
+    expect(poSubtotal([{ quantity: 5, cost_price: NaN }])).toBe(0);
+  });
+});

src/lib/pdf/format.ts

@@ -39,6 +39,26 @@ export function quoteSubtotal(items: { quantity: number; selling_price: number }
   return items.reduce((sum, it) => sum + it.quantity * it.selling_price, 0);
 }
 
+/**
+ * Sum of (order_qty ?? quantity) * cost_price across PO items. Differs
+ * from `quoteSubtotal()` in using supplier-facing cost and order quantity.
+ * A blank or zero order_qty falls back to quantity so it never zeroes a line.
+ * Rounds to 2dp so the printed table doesn't show floating-point dust.
+ */
+export function poSubtotal(
+  items: { order_qty?: number | null; quantity: number; cost_price: number }[]
+): number {
+  return Math.round(
+    items.reduce(
+      (sum, it) =>
+        sum +
+        (Number(it.order_qty) || Number(it.quantity) || 0) *
+          (Number(it.cost_price) || 0),
+      0
+    ) * 100
+  ) / 100;
+}
+
 /** ZAR VAT is 15% — round to 2dp so the printed total matches the line items. */
 export function vatAmount(subtotal: number): number {
   return Math.round(subtotal * 0.15 * 100) / 100;