fix(bookings): apply promo discount to client-subtotal totals in guest/authenticated booking

createGuestBooking (ONE_WAY) and createGuestRoundTripBooking overwrote the
authoritative discounted total with an undiscounted client-provided subtotal
(per-seat sum or reviewedTotalMinor) whenever one was present, silently
dropping a valid promos discount at booking-creation time, even though the
same promo was correctly applied in the fare-breakdown/quote step. Only the
no-client-subtotal fallback branch subtracted discountMinor.

Mirrors the existing usedClientSubtotal fix already present in
BookingsService.createOneWayBooking (H-13): subtract discountMinor from the
client subtotal before storing it, in ETB and display currency. TRANSIT and
ROUND_TRIP_TRANSIT were unaffected since neither overrides with a client
subtotal.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/edr-passenger-api/src/modules/bookings/guest-booking.service.ts

@@ -294,8 +294,12 @@ export class GuestBookingService {
 
     let displayTotalMinor: number;
     let resolvedTotalMinor: number;
+    // True when the total came from a client-summed subtotal (per-seat sum or reviewedTotalMinor),
+    // which the portal computes UNDISCOUNTED — the promo must still be applied to it (H-13).
+    let usedClientSubtotal = false;
     if (allFaresProvided && !isPackageOneway) {
       displayTotalMinor = passengersWithFares.reduce((sum, p) => sum + p.fareMinor, 0);
+      usedClientSubtotal = true;
     } else if (isPackageOneway && dto.reviewedTotalMinor != null) {
       displayTotalMinor = dto.reviewedTotalMinor;
       if (seatedPassengers.length > 0) {
@@ -306,6 +310,7 @@ export class GuestBookingService {
       }
     } else if (dto.reviewedTotalMinor != null && dto.reviewedTotalMinor > 0) {
       displayTotalMinor = dto.reviewedTotalMinor;
+      usedClientSubtotal = true;
     } else {
       // fare engine returns ETB — convert forward to display currency
       const etbTotal = Math.max(0, totalBaseFareMinor - discountMinor);
@@ -313,6 +318,18 @@ export class GuestBookingService {
         ? await this.currencyService.convertAmount(etbTotal, Currency.ETB, displayCurrency)
         : etbTotal;
     }
+
+    // H-13: the portal sums UNDISCOUNTED per-passenger fares into a client subtotal, silently
+    // dropping the promo the fare engine recognized. Apply the authoritative discount now so the
+    // customer is charged the discounted price. The non-client-subtotal branch above already
+    // nets the discount out of etbTotal, so it's excluded here to avoid double-subtracting.
+    if (usedClientSubtotal && discountMinor > 0) {
+      const discountDisplayMinor = displayCurrency !== Currency.ETB
+        ? await this.currencyService.convertAmount(discountMinor, Currency.ETB, displayCurrency)
+        : discountMinor;
+      displayTotalMinor = Math.max(0, displayTotalMinor - discountDisplayMinor);
+    }
+
     resolvedTotalMinor = displayCurrency !== Currency.ETB
       ? await this.currencyService.convertAmount(displayTotalMinor, displayCurrency, Currency.ETB)
       : displayTotalMinor;
@@ -834,17 +851,16 @@ export class GuestBookingService {
     const allRTFaresProvided = rtSeatedPassengers.length > 0 &&
       rtSeatedPassengers.every(p => p.seatFareMinor != null && p.returnSeatFareMinor != null);
 
+    // True when the total came from a client-summed subtotal (per-seat sum or reviewedTotalMinor),
+    // which the portal computes UNDISCOUNTED — the promo must still be applied to it (H-13).
+    let usedClientSubtotal = false;
+
     if (allRTFaresProvided && !isPackageRoundTrip) {
       // Server-computed sum is authoritative — prevents race-condition under-count.
       displayTotalMinor = passengersWithFares.reduce((sum, p) => sum + p.outboundFareMinor + p.returnFareMinor, 0);
-      totalMinor = displayCurrency !== Currency.ETB
+      usedClientSubtotal = true;
-        ? await this.currencyService.convertAmount(displayTotalMinor, displayCurrency, Currency.ETB)
-        : displayTotalMinor;
     } else if (isPackageRoundTrip && dto.reviewedTotalMinor != null) {
       displayTotalMinor = dto.reviewedTotalMinor;
-      totalMinor = displayCurrency !== Currency.ETB
-        ? await this.currencyService.convertAmount(displayTotalMinor, displayCurrency, Currency.ETB)
-        : displayTotalMinor;
       const seatedCount = passengersData.filter(p => p.seatId).length;
       if (seatedCount > 0) {
         const perSeatPerLeg = Math.round(dto.reviewedTotalMinor / (seatedCount * 2));
@@ -855,11 +871,24 @@ export class GuestBookingService {
       }
     } else if (dto.reviewedTotalMinor != null && dto.reviewedTotalMinor > 0) {
       displayTotalMinor = dto.reviewedTotalMinor;
-      totalMinor = displayCurrency !== Currency.ETB
+      usedClientSubtotal = true;
-        ? await this.currencyService.convertAmount(displayTotalMinor, displayCurrency, Currency.ETB)
-        : displayTotalMinor;
     }
 
+    // H-13: the portal sums UNDISCOUNTED per-passenger fares into a client subtotal, silently
+    // dropping the promo the fare engine recognized. Apply the authoritative discount now so the
+    // customer is charged the discounted price. The no-override case above already starts from a
+    // discounted displayTotalMinor, so it's excluded here to avoid double-subtracting.
+    if (usedClientSubtotal && discountMinor > 0) {
+      const discountDisplayMinor = displayCurrency !== Currency.ETB
+        ? await this.currencyService.convertAmount(discountMinor, Currency.ETB, displayCurrency)
+        : discountMinor;
+      displayTotalMinor = Math.max(0, displayTotalMinor - discountDisplayMinor);
+    }
+
+    totalMinor = displayCurrency !== Currency.ETB
+      ? await this.currencyService.convertAmount(displayTotalMinor, displayCurrency, Currency.ETB)
+      : displayTotalMinor;
+
     // C-1 guard: never charge less than the server-recomputed authoritative round-trip fare.
     this.assertTotalNotUnderAuthoritative(totalMinor, authoritativeTotalMinor, 'createGuestRoundTripBooking');