fix(cashout): make JMD exchange-rate conversion decimal-safe [ENG-509]

src/domain/shared/MoneyAmount.ts

@@ -146,7 +146,13 @@ export class JMDAmount extends MoneyAmount {
 
   static dollars(d: number): JMDAmount | BigIntConversionError {
     try {
-      return new JMDAmount(BigInt(d) * 100n)
+      // Mirror USDAmount.dollars: use the Money lib for a decimal-safe conversion.
+      // BigInt(d) throws on any fractional rate (e.g. an NCB rate of 155.5), which
+      // is what the exchange-rate value virtually always is.
+      const dollarAmt = new Money(d.toString(), "JMDollars", Round.HALF_TO_EVEN)
+      const cents = JMDAmount.cents("100")
+      if (cents instanceof BigIntConversionError) return cents // should never happen
+      return new JMDAmount(cents.money.multiply(dollarAmt).toFixed(2))
     } catch (error) {
       return new BigIntConversionError(
         error instanceof Error ? error.message : String(error),

src/graphql/error-map.ts

@@ -921,6 +921,11 @@ export const mapError = (error: ApplicationError): CustomApolloError => {
       message = "No upgrade request found for this account"
       return new NotFoundError({ message, logger: baseLogger })
 
+    case "ExchangeRateQueryError":
+      message =
+        "Cashout is temporarily unavailable while we refresh the exchange rate. Please try again shortly."
+      return new UnexpectedClientError({ message, logger: baseLogger })
+
     case "InvalidLnurlError":
       return new InvalidLnurlError({ message: error.message, logger: baseLogger })