fix: preserve active calculator input on rate refresh

Author: ovitrif

Bitkit/Components/Widgets/CalculatorWidget.swift

@@ -64,20 +64,20 @@ struct CalculatorWidget: View {
         }
         .onChange(of: currency.selectedCurrency) {
             refreshCurrencyFields()
-            refreshDerivedValue()
+            refreshDerivedValue(preferredSource: calculatorInput.activeInput)
             refreshNumberPadConfiguration()
             persistValues()
         }
         .onChange(of: currency.displayUnit) { _, newUnit in
             convertBitcoinValue(to: newUnit)
             refreshCurrencyFields()
-            refreshDerivedValue()
+            refreshDerivedValue(preferredSource: calculatorInput.activeInput)
             refreshNumberPadConfiguration()
             persistValues()
         }
         .onChange(of: currency.rates) {
             refreshCurrencyFields()
-            refreshDerivedValue()
+            refreshDerivedValue(preferredSource: calculatorInput.activeInput)
             persistValues()
         }
         .onChange(of: calculatorInput.submittedKey?.id) {
@@ -264,8 +264,8 @@ struct CalculatorWidget: View {
         previousDisplayUnit = newUnit
     }
 
-    private func refreshDerivedValue() {
-        if values.shouldRefreshBitcoinFromFiat {
+    private func refreshDerivedValue(preferredSource: CalculatorMoneyType? = nil) {
+        if values.refreshSource(activeInput: preferredSource) == .fiat {
             refreshBitcoinFromFiat()
         } else {
             refreshFiatFromBitcoin()

Bitkit/Models/CalculatorWidgetData.swift

@@ -24,9 +24,14 @@ struct CalculatorWidgetValues: Codable, Equatable {
     var shouldRefreshBitcoinFromFiat: Bool {
         bitcoinValue.isEmpty && !fiatValue.isEmpty
     }
+
+    func refreshSource(activeInput: CalculatorMoneyType?) -> CalculatorMoneyType {
+        if let activeInput { return activeInput }
+        return shouldRefreshBitcoinFromFiat ? .fiat : .bitcoin
+    }
 }
 
-enum CalculatorMoneyType {
+enum CalculatorMoneyType: Equatable {
     case bitcoin
     case fiat
 }

BitkitTests/CalculatorWidgetTests.swift

@@ -100,6 +100,30 @@ final class CalculatorWidgetTests: XCTestCase {
         XCTAssertTrue(values.shouldRefreshBitcoinFromFiat)
     }
 
+    func testFiatActiveInputStaysRefreshSourceWhenBothValuesExist() {
+        let values = CalculatorWidgetValues(bitcoinValue: "10000", fiatValue: "12.34")
+
+        XCTAssertEqual(values.refreshSource(activeInput: .fiat), .fiat)
+    }
+
+    func testBitcoinActiveInputStaysRefreshSourceWhenFiatOnlyWouldOtherwiseWin() {
+        let values = CalculatorWidgetValues(bitcoinValue: "", fiatValue: "12.34")
+
+        XCTAssertEqual(values.refreshSource(activeInput: .bitcoin), .bitcoin)
+    }
+
+    func testRefreshSourceFallsBackToFiatOnlyValue() {
+        let values = CalculatorWidgetValues(bitcoinValue: "", fiatValue: "12.34")
+
+        XCTAssertEqual(values.refreshSource(activeInput: nil), .fiat)
+    }
+
+    func testRefreshSourceFallsBackToBitcoinWhenBothValuesExist() {
+        let values = CalculatorWidgetValues(bitcoinValue: "10000", fiatValue: "12.34")
+
+        XCTAssertEqual(values.refreshSource(activeInput: nil), .bitcoin)
+    }
+
     func testPreviewPreservesPersistedFiatOnlyValue() {
         let values = CalculatorWidgetValues(bitcoinValue: "", fiatValue: "12.34")