Fare engine updates, seat class amount updates

apps/edr-passenger-api/src/modules/currency/currency.service.ts

@@ -30,23 +30,59 @@ export class CurrencyService {
     private readonly configService: ConfigService,
   ) {}
 
+  /**
+   * Converts a stored display-currency minor amount to the charge major amount
+   * sent to the payment provider, without hitting the DB for an exchange rate.
+   * Use this when the payment method's settlement currency matches the booking's
+   * displayCurrency — the rate is already baked into displayTotalMinor.
+   */
+  displayMinorToChargeMajor(displayMinor: number, currency: string): number {
+    const decimals = CHARGE_CURRENCY_DECIMALS[currency.toUpperCase()];
+    if (decimals === undefined) {
+      throw new BadRequestException(`Unsupported charge currency: ${currency}`);
+    }
+    return this.roundTo(displayMinor / 100, decimals);
+  }
+
+  async convertEtbMinorToChargeMinor(
+    amountMinorEtb: number,
+    targetCurrency: string,
+  ): Promise<number> {
+    const target = targetCurrency.toUpperCase();
+    if (CHARGE_CURRENCY_DECIMALS[target] === undefined) {
+      throw new BadRequestException(`Unsupported charge currency: ${targetCurrency}`);
+    }
+
+    if (target === Currency.ETB) {
+      return amountMinorEtb;
+    }
+
+    // Convert ETB minor → target minor: apply exchange rate, keep as minor units.
+    const rate = await this.getRateOrThrow(Currency.ETB, target as Currency);
+    return Math.round(amountMinorEtb * rate);
+  }
+
+  /**
+   * Converts an ETB minor-unit amount to the charge major-unit amount sent to the
+   * payment provider. Applies the exchange rate for foreign currencies then divides
+   * by 100 to yield major units (e.g. 300000 ETB minor → 3000.00 ETB major).
+   */
   async convertEtbMinorToChargeMajor(
     amountMinorEtb: number,
     targetCurrency: string,
   ): Promise<number> {
     const target = targetCurrency.toUpperCase();
-    const decimals = CHARGE_CURRENCY_DECIMALS[target];
-    if (decimals === undefined) {
+    if (CHARGE_CURRENCY_DECIMALS[target] === undefined) {
       throw new BadRequestException(`Unsupported charge currency: ${targetCurrency}`);
     }
+    const decimals = CHARGE_CURRENCY_DECIMALS[target];
 
-    const sourceMajor = amountMinorEtb / 100;
     if (target === Currency.ETB) {
-      return this.roundTo(sourceMajor, decimals);
+      return this.roundTo(amountMinorEtb / 100, decimals);
     }
 
     const rate = await this.getRateOrThrow(Currency.ETB, target as Currency);
-    return this.roundTo(sourceMajor * rate, decimals);
+    return this.roundTo((amountMinorEtb * rate) / 100, decimals);
   }
 
   async getRateOrThrow(