fix: preserve calculator btc on rate failure

Author: ovitrif

Bitkit/Components/Widgets/CalculatorWidget.swift

@@ -271,7 +271,7 @@ struct CalculatorWidget: View {
         guard let source = values.refreshSource(activeInput: preferredSource) else { return }
 
         if source == .fiat {
-            refreshBitcoinFromFiat()
+            refreshBitcoinFromFiat(preserveBitcoinOnConversionFailure: true)
         } else {
             refreshFiatFromBitcoin()
         }
@@ -296,20 +296,13 @@ struct CalculatorWidget: View {
         }
     }
 
-    private func refreshBitcoinFromFiat() {
+    private func refreshBitcoinFromFiat(preserveBitcoinOnConversionFailure: Bool = false) {
         guard !values.fiatValue.isEmpty else {
             values.bitcoinValue = ""
             return
         }
 
-        let fiatValue = CalculatorWidgetFormatter.fiatDecimalValue(values.fiatValue)
-        if NSDecimalNumber(decimal: fiatValue).compare(NSDecimalNumber.zero) == .orderedSame {
-            values.bitcoinValue = CalculatorWidgetFormatter.fiatConversionBitcoinValue(0, displayUnit: currency.displayUnit)
-            return
-        }
-
-        let fiatDouble = NSDecimalNumber(decimal: fiatValue).doubleValue
-        if let sats = currency.convert(fiatAmount: fiatDouble) {
+        if let sats = CalculatorWidgetFormatter.convertedSatsFromFiat(values.fiatValue, convert: { currency.convert(fiatAmount: $0) }) {
             let cappedSats = min(sats, CalculatorWidgetFormatter.maxBitcoinSats)
             values.bitcoinValue = CalculatorWidgetFormatter.fiatConversionBitcoinValue(cappedSats, displayUnit: currency.displayUnit)
 
@@ -320,9 +313,11 @@ struct CalculatorWidget: View {
                     values.fiatValue = ""
                 }
             }
-        } else {
-            values.bitcoinValue = ""
+            return
         }
+
+        guard !preserveBitcoinOnConversionFailure else { return }
+        values.bitcoinValue = ""
     }
 
     private func persistValues() {

Bitkit/Models/CalculatorWidgetData.swift

@@ -227,6 +227,15 @@ enum CalculatorWidgetFormatter {
         sats == 0 ? "0" : satsToBitcoinValue(sats, displayUnit: displayUnit)
     }
 
+    static func convertedSatsFromFiat(_ rawValue: String, convert: (Double) -> UInt64?) -> UInt64? {
+        let fiatValue = fiatDecimalValue(rawValue)
+        if NSDecimalNumber(decimal: fiatValue).compare(NSDecimalNumber.zero) == .orderedSame {
+            return 0
+        }
+
+        return convert(NSDecimalNumber(decimal: fiatValue).doubleValue)
+    }
+
     static func fiatDecimalValue(_ rawValue: String) -> Decimal {
         decimalValue(sanitizeDecimalInput(raw: rawValue, maxDecimalPlaces: fiatDecimalPlaces))
     }

BitkitTests/CalculatorWidgetTests.swift

@@ -166,6 +166,18 @@ final class CalculatorWidgetTests: XCTestCase {
         XCTAssertEqual(CalculatorWidgetFormatter.fiatConversionBitcoinValue(0, displayUnit: .classic), "0")
     }
 
+    func testFiatConversionReturnsNilWhenRateUnavailable() {
+        let sats = CalculatorWidgetFormatter.convertedSatsFromFiat("12.34") { _ in nil }
+
+        XCTAssertNil(sats)
+    }
+
+    func testZeroFiatConversionDoesNotRequireRate() {
+        let sats = CalculatorWidgetFormatter.convertedSatsFromFiat("0") { _ in nil }
+
+        XCTAssertEqual(sats, 0)
+    }
+
     func testClassicBitcoinRejectsValuesAboveSupply() {
         XCTAssertTrue(CalculatorWidgetFormatter.exceedsMaxBitcoin("21000000.00000001", displayUnit: .classic))
         XCTAssertFalse(CalculatorWidgetFormatter.exceedsMaxBitcoin("21000000", displayUnit: .classic))