final changes

app/src/main/kotlin/com/simplemobiletools/calculator/activities/MainActivity.kt

@@ -34,6 +34,7 @@ class MainActivity : SimpleActivity(), Calculator {
 
         calc = CalculatorImpl(this, applicationContext)
 
+        btn_factorial.setOnClickListener{ calc.handleOperation(FACTORIAL); checkHaptic(it) }
         btn_plus.setOnClickListener { calc.handleOperation(PLUS); checkHaptic(it) }
         btn_minus.setOnClickListener { calc.handleOperation(MINUS); checkHaptic(it) }
         btn_multiply.setOnClickListener { calc.handleOperation(MULTIPLY); checkHaptic(it) }

app/src/main/kotlin/com/simplemobiletools/calculator/activities/WidgetConfigureActivity.kt

@@ -111,7 +111,7 @@ class WidgetConfigureActivity : SimpleActivity() {
         config_save.setTextColor(mTextColor)
 
         val viewIds = intArrayOf(R.id.btn_0, R.id.btn_1, R.id.btn_2, R.id.btn_3, R.id.btn_4, R.id.btn_5, R.id.btn_6, R.id.btn_7, R.id.btn_8,
-                R.id.btn_9, R.id.btn_percent, R.id.btn_power, R.id.btn_root, R.id.btn_clear, R.id.btn_reset, R.id.btn_divide, R.id.btn_multiply,
+                R.id.btn_9, R.id.btn_percent, R.id.btn_power, R.id.btn_root, R.id.btn_factorial, R.id.btn_clear, R.id.btn_reset, R.id.btn_divide, R.id.btn_multiply,
                 R.id.btn_minus, R.id.btn_plus, R.id.btn_decimal, R.id.btn_equals)
         result.setTextColor(mTextColor)
         formula.setTextColor(mTextColor)

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/CalculatorImpl.kt

@@ -58,6 +58,8 @@ class CalculatorImpl(calculator: Calculator, val context: Context) {
 
         if (sign == "√") {
             setFormula(sign + first)
+        } else if (sign == "!"){
+            setFormula(first + sign)
         } else if (!sign.isEmpty()) {
             var formula = first + sign + second
             if (mWasPercentLast) {
@@ -102,6 +104,11 @@ class CalculatorImpl(calculator: Calculator, val context: Context) {
         calculateResult()
     }
 
+    private fun handleFactorial() {
+        mBaseValue = getDisplayedNumberAsDouble()
+        calculateResult()
+    }
+
     private fun calculateResult() {
         updateFormula()
         if (mWasPercentLast) {
@@ -118,7 +125,7 @@ class CalculatorImpl(calculator: Calculator, val context: Context) {
 
     fun handleOperation(operation: String) {
         mWasPercentLast = operation == PERCENT
-        if (lastKey == DIGIT && operation != ROOT) {
+        if (lastKey == DIGIT && operation != ROOT && operation!= FACTORIAL) {
             handleResult()
         }
 
@@ -130,6 +137,10 @@ class CalculatorImpl(calculator: Calculator, val context: Context) {
             handleRoot()
             mResetValue = false
         }
+        if (operation == FACTORIAL) {
+            handleFactorial()
+            mResetValue = false
+        }
     }
 
     fun handleClear() {
@@ -195,6 +206,7 @@ class CalculatorImpl(calculator: Calculator, val context: Context) {
         PERCENT -> "%"
         POWER -> "^"
         ROOT -> "√"
+        FACTORIAL -> "!"
         else -> ""
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/Constants.kt

@@ -12,6 +12,7 @@ const val ROOT = "root"
 const val DECIMAL = "decimal"
 const val CLEAR = "clear"
 const val RESET = "reset"
+const val FACTORIAL = "factorial"
 
 const val NAN = "NaN"
 const val ZERO = "zero"

app/src/main/kotlin/com/simplemobiletools/calculator/helpers/MyWidgetProvider.kt

@@ -48,6 +48,7 @@ class MyWidgetProvider : AppWidgetProvider(), Calculator {
             setupIntent(context, views, PERCENT, R.id.btn_percent)
             setupIntent(context, views, POWER, R.id.btn_power)
             setupIntent(context, views, ROOT, R.id.btn_root)
+            setupIntent(context, views, FACTORIAL, R.id.btn_factorial )
             setupIntent(context, views, CLEAR, R.id.btn_clear)
             setupIntent(context, views, RESET, R.id.btn_reset)
 
@@ -80,7 +81,7 @@ class MyWidgetProvider : AppWidgetProvider(), Calculator {
 
     private fun updateTextColors(views: RemoteViews, color: Int) {
         val viewIds = intArrayOf(R.id.formula, R.id.result, R.id.btn_0, R.id.btn_1, R.id.btn_2, R.id.btn_3, R.id.btn_4, R.id.btn_5, R.id.btn_6,
-                R.id.btn_7, R.id.btn_8, R.id.btn_9, R.id.btn_percent, R.id.btn_power, R.id.btn_root, R.id.btn_clear, R.id.btn_reset, R.id.btn_divide,
+                R.id.btn_7, R.id.btn_8, R.id.btn_9, R.id.btn_percent, R.id.btn_power, R.id.btn_root, R.id.btn_factorial, R.id.btn_clear, R.id.btn_reset, R.id.btn_divide,
                 R.id.btn_multiply, R.id.btn_minus, R.id.btn_plus, R.id.btn_decimal, R.id.btn_equals)
 
         for (i in viewIds) {
@@ -91,7 +92,7 @@ class MyWidgetProvider : AppWidgetProvider(), Calculator {
     override fun onReceive(context: Context, intent: Intent) {
         val action = intent.action
         when (action) {
-            DECIMAL, ZERO, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE, EQUALS, CLEAR, RESET, PLUS, MINUS, MULTIPLY, DIVIDE, PERCENT, POWER, ROOT -> myAction(action, context)
+            DECIMAL, ZERO, ONE, TWO, THREE, FOUR, FIVE, SIX, SEVEN, EIGHT, NINE, EQUALS, CLEAR, RESET, PLUS, MINUS, MULTIPLY, DIVIDE, PERCENT, POWER, ROOT, FACTORIAL -> myAction(action, context)
             else -> super.onReceive(context, intent)
         }
     }
@@ -116,7 +117,7 @@ class MyWidgetProvider : AppWidgetProvider(), Calculator {
             EQUALS -> calc!!.handleEquals()
             CLEAR -> calc!!.handleClear()
             RESET -> calc!!.handleReset()
-            PLUS, MINUS, MULTIPLY, DIVIDE, PERCENT, POWER, ROOT -> calc!!.handleOperation(action)
+            PLUS, MINUS, MULTIPLY, DIVIDE, PERCENT, POWER, ROOT, FACTORIAL -> calc!!.handleOperation(action)
         }
     }
 

app/src/main/kotlin/com/simplemobiletools/calculator/operation/OperationFactory.kt

@@ -14,6 +14,7 @@ object OperationFactory {
             PERCENT -> PercentOperation(baseValue, secondValue)
             POWER -> PowerOperation(baseValue, secondValue)
             ROOT -> RootOperation(baseValue)
+            FACTORIAL -> ParOperation(baseValue)
             else -> null
         }
     }