fix: prevent invalid state after percentage calculation (#178)

Refs: #160

Author: aricodeine

CHANGELOG.md

@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+- Fixed issue that occurs after doing a percent operation ([#160])
+
 ## [1.2.0] - 2025-10-29
 ### Changed
 - Compatibility updates for Android 15 & 16
@@ -60,6 +63,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 [#31]: https://github.com/FossifyOrg/Calculator/issues/31
 [#44]: https://github.com/FossifyOrg/Calculator/issues/44
 [#64]: https://github.com/FossifyOrg/Calculator/issues/64
+[#160]: https://github.com/FossifyOrg/Calculator/issues/160
 
 [Unreleased]: https://github.com/FossifyOrg/Calculator/compare/1.2.0...HEAD
 [1.2.0]: https://github.com/FossifyOrg/Calculator/compare/1.1.0...1.2.0

app/src/main/kotlin/org/fossify/math/helpers/CalculatorImpl.kt

@@ -114,6 +114,7 @@ class CalculatorImpl(
         if (lastKey == DIGIT || lastKey == DECIMAL) {
             if (lastOperation != "" && operation == PERCENT) {
                 handlePercent()
+                lastOperation = ""
             } else {
                 // split to multiple lines just to see when does the crash happen
                 secondValue = when (operation) {
@@ -140,7 +141,7 @@ class CalculatorImpl(
         if (getSecondValue() == BigDecimal.ZERO && inputDisplayedFormula.contains("÷")) {
             lastKey = DIVIDE
             lastOperation = DIVIDE
-        } else {
+        } else if(operation != PERCENT) {
             lastKey = operation
             lastOperation = operation
         }
@@ -376,6 +377,7 @@ class CalculatorImpl(
         if (newValue == "" || newValue == "0") {
             newValue = "0"
             lastKey = CLEAR
+            resetValues()
         } else {
             if (operations.contains(lastDeletedValue) || lastKey == EQUALS) {
                 lastOperation = ""