eims integration master test complete

apps/edr-freight-api/src/modules/billing/eims-invoice.mapper.ts

@@ -183,6 +183,12 @@ export interface EimsLineTax {
   code: string;
   ratePercent: number;
   exciseTaxValue: number;
+  /**
+   * Line-level `Discount`. Its effect on `TotalLineAmount` has never been observed live (every
+   * prior test ran it at 0), so the total below still sums PreTax + Tax + Excise only — do not
+   * start subtracting this without a confirmed MoR example.
+   */
+  discount: number;
 }
 
 export interface EimsMapperContext {
@@ -336,7 +342,13 @@ export function toEimsInvoice(
   const ItemList: EimsInvoiceItem[] = invoice.lines.map((line, index) => {
     const lineNumber = index + 1;
     const tax = context.taxForLine(line, lineNumber);
-    if (!tax || !tax.code || !Number.isFinite(tax.ratePercent) || !Number.isFinite(tax.exciseTaxValue)) {
+    if (
+      !tax ||
+      !tax.code ||
+      !Number.isFinite(tax.ratePercent) ||
+      !Number.isFinite(tax.exciseTaxValue) ||
+      !Number.isFinite(tax.discount)
+    ) {
       throw new Error(
         `EIMS mapping: unresolved tax treatment for line ${lineNumber} (${line.chargeType}) ` +
           `on invoice ${invoice.invoiceNumber}`,
@@ -349,7 +361,7 @@ export function toEimsInvoice(
     const unit = typeof line.metadata?.unit === "string" ? line.metadata.unit : context.unitDefault;
 
     return {
-      Discount: 0,
+      Discount: round2(tax.discount),
       ExciseTaxValue,
       HarmonizationCode: null,
       NatureOfSupplies: natureOfSupplies,