great appreciations to https://github.com/hadibolty/ for reporting bugs, a lot of bugs got fixed

6 files changed, 224 insertions, 38 deletions

diff --git a/app/src/main/AndroidManifest.xml b/app/src/main/AndroidManifest.xml
index 8d7bca4..74b91e0 100644
--- a/app/src/main/AndroidManifest.xml
+++ b/app/src/main/AndroidManifest.xml
@@ -3,6 +3,7 @@
     xmlns:tools="http://schemas.android.com/tools">
 
     <application
+        android:name="com.a404m.calculator.ContextHelper"
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
         android:fullBackupContent="@xml/backup_rules"
diff --git a/app/src/main/java/com/a404m/calculator/ContextHelper.kt b/app/src/main/java/com/a404m/calculator/ContextHelper.kt
new file mode 100644
index 0000000..4e5e3fc
--- /dev/null
+++ b/app/src/main/java/com/a404m/calculator/ContextHelper.kt
@@ -0,0 +1,19 @@
+package com.a404m.calculator
+
+import android.app.Application
+import android.content.Context
+
+class ContextHelper : Application() {
+    companion object {
+        var context: Context? = null
+
+        fun getAppContext(): Context? {
+            return context
+        }
+    }
+
+    override fun onCreate() {
+        super.onCreate()
+        context = applicationContext
+    }
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/a404m/calculator/model/CalcButtonModel.kt b/app/src/main/java/com/a404m/calculator/model/CalcButtonModel.kt
index c6a10da..4384448 100644
--- a/app/src/main/java/com/a404m/calculator/model/CalcButtonModel.kt
+++ b/app/src/main/java/com/a404m/calculator/model/CalcButtonModel.kt
@@ -4,98 +4,148 @@ import com.a404m.calculator.util.MathHelper
 
 data class CalcButtonModel(
     val text: String,
-    val weight:Float = 1F,
+    val weight: Float = 1F,
     val op: (expression: String) -> String,
 ) {
     companion object {
         val K_0 = CalcButtonModel(
             text = "0",
             op = {
-                it + '0'
+                addNumber(
+                    it,
+                    '0'
+                )
             }
         )
         val K_1 = CalcButtonModel(
             text = "1",
             op = {
-                it + '1'
+                addNumber(
+                    it,
+                    '1'
+                )
             }
         )
         val K_2 = CalcButtonModel(
             text = "2",
             op = {
-                it + '2'
+                addNumber(
+                    it,
+                    '2'
+                )
             }
         )
         val K_3 = CalcButtonModel(
             text = "3",
             op = {
-                it + '3'
+                addNumber(
+                    it,
+                    '3'
+                )
             }
         )
         val K_4 = CalcButtonModel(
             text = "4",
             op = {
-                it + '4'
+                addNumber(
+                    it,
+                    '4'
+                )
             }
         )
         val K_5 = CalcButtonModel(
             text = "5",
             op = {
-                it + '5'
+                addNumber(
+                    it,
+                    '5'
+                )
             }
         )
         val K_6 = CalcButtonModel(
             text = "6",
             op = {
-                it + '6'
+                addNumber(
+                    it,
+                    '6'
+                )
             }
         )
         val K_7 = CalcButtonModel(
             text = "7",
             op = {
-                it + '7'
+                addNumber(
+                    it,
+                    '7'
+                )
             }
         )
         val K_8 = CalcButtonModel(
             text = "8",
             op = {
-                it + '8'
+                addNumber(
+                    it,
+                    '8'
+                )
             }
         )
         val K_9 = CalcButtonModel(
             text = "9",
             op = {
-                it + '9'
+                addNumber(
+                    it,
+                    '9'
+                )
             }
         )
         val K_PLUS = CalcButtonModel(
             text = "+",
             op = {
-                it + '+'
+                addOperator(
+                    it,
+                    '+',
+                    true
+                )
             }
         )
         val K_MINUS = CalcButtonModel(
             text = "-",
             op = {
-                it + '-'
+                addOperator(
+                    it,
+                    '-',
+                    true
+                )
             }
         )
         val K_MULTIPLY = CalcButtonModel(
             text = "×",
             op = {
-                it + '×'
+                addOperator(
+                    it,
+                    '×',
+                    false
+                )
             }
         )
         val K_DIVISION = CalcButtonModel(
             text = "÷",
             op = {
-                it + '÷'
+                addOperator(
+                    it,
+                    '÷',
+                    false
+                )
             }
         )
         val K_REMINDER = CalcButtonModel(
             text = "%",
             op = {
-                it + '%'
+                addOperator(
+                    it,
+                    '%',
+                    false
+                )
             }
         )
         val K_EQUAL = CalcButtonModel(
@@ -107,20 +157,25 @@ data class CalcButtonModel(
         val K_DOT = CalcButtonModel(
             text = ".",
             op = {
-                it + '.'
+                when (MathHelper.getInWriting(it)) {
+                    MathHelper.InWriting.NONE -> "0."
+                    MathHelper.InWriting.NUMBER_INT -> "$it."
+                    MathHelper.InWriting.NUMBER_FLOAT -> it
+                    MathHelper.InWriting.OPERATOR -> "${it}0."
+                }
             }
         )
         val K_C = CalcButtonModel(
             text = "C",
             op = {
-                ""
+                "0"
             }
         )
         val K_BACKSPACE = CalcButtonModel(
             text = "⌫",
             op = {
                 if (it.length <= 1) {
-                    ""
+                    "0"
                 } else {
                     it.substring(
                         0,
@@ -135,5 +190,50 @@ data class CalcButtonModel(
                 it
             }
         )
+
+        private fun addOperator(
+            expression: String,
+            operator: Char,
+            canBePrefix: Boolean
+        ): String {
+            return if (expression == "0") {
+                if (canBePrefix) operator.toString()
+                else expression + operator
+            } else {
+                when (MathHelper.getInWriting(expression)) {
+                    MathHelper.InWriting.NONE ->
+                        if (canBePrefix) operator.toString()
+                        else ""
+
+                    MathHelper.InWriting.NUMBER_INT ->
+                        expression + operator
+
+                    MathHelper.InWriting.NUMBER_FLOAT ->
+                        if (expression.last() == '.') "${expression}0$operator"
+                        else expression + operator
+
+                    MathHelper.InWriting.OPERATOR -> expression.substring(
+                        0,
+                        expression.length - 1
+                    ) + operator
+                }
+            }
+        }
+
+        private fun addNumber(
+            expression: String,
+            number: Char
+        ): String {
+            val value = MathHelper.getLastNumber(expression)
+
+            return if (value == "0") {
+                expression.substring(
+                    0,
+                    expression.length - 1
+                ) + number
+            } else {
+                expression + number
+            }
+        }
     }
 }
diff --git a/app/src/main/java/com/a404m/calculator/ui/page/Home.kt b/app/src/main/java/com/a404m/calculator/ui/page/Home.kt
index ba9a21e..a2c4846 100644
--- a/app/src/main/java/com/a404m/calculator/ui/page/Home.kt
+++ b/app/src/main/java/com/a404m/calculator/ui/page/Home.kt
@@ -34,7 +34,7 @@ import com.a404m.calculator.ui.util.CalcGrid
 @Composable
 fun HomePage(modifier: Modifier = Modifier) {
     var expression by rememberSaveable {
-        mutableStateOf("")
+        mutableStateOf("0")
     }
     Scaffold(
         modifier = modifier,
diff --git a/app/src/main/java/com/a404m/calculator/ui/util/Toast.kt b/app/src/main/java/com/a404m/calculator/ui/util/Toast.kt
new file mode 100644
index 0000000..5041472
--- /dev/null
+++ b/app/src/main/java/com/a404m/calculator/ui/util/Toast.kt
@@ -0,0 +1,12 @@
+package com.a404m.calculator.ui.util
+
+import android.widget.Toast
+import com.a404m.calculator.ContextHelper
+
+fun showToast(text:String){
+    Toast.makeText(
+        ContextHelper.context,
+        text,
+        Toast.LENGTH_SHORT
+    ).show()
+}
\ No newline at end of file
diff --git a/app/src/main/java/com/a404m/calculator/util/MathHelper.kt b/app/src/main/java/com/a404m/calculator/util/MathHelper.kt
index d0c3ee3..77244b0 100644
--- a/app/src/main/java/com/a404m/calculator/util/MathHelper.kt
+++ b/app/src/main/java/com/a404m/calculator/util/MathHelper.kt
@@ -1,9 +1,13 @@
 package com.a404m.calculator.util
 
 import android.util.Log
+import com.a404m.calculator.ui.util.showToast
 import com.a404m.calculator.util.MathHelper.Operator.Kind
+import java.math.BigDecimal
 import java.nio.charset.UnsupportedCharsetException
 
+typealias MathNumberType = BigDecimal
+
 object MathHelper {
     private val operatorStrings = arrayOf(
         '+',
@@ -44,35 +48,35 @@ object MathHelper {
         '+',
         Kind.INFIX,
         {
-            Operand(it.first().value+it.last().value)
+            Operand(it.first().value + it.last().value)
         }
     )
     private val sub = Operator(
         '-',
         Kind.INFIX,
         {
-            Operand(it.first().value-it.last().value)
+            Operand(it.first().value - it.last().value)
         }
     )
     private val mul = Operator(
         '×',
         Kind.INFIX,
         {
-            Operand(it.first().value*it.last().value)
+            Operand(it.first().value * it.last().value)
         }
     )
     private val div = Operator(
         '÷',
         Kind.INFIX,
         {
-            Operand(it.first().value/it.last().value)
+            Operand(it.first().value / it.last().value)
         }
     )
     private val rem = Operator(
         '%',
         Kind.INFIX,
         {
-            Operand(it.first().value%it.last().value)
+            Operand(it.first().value % it.last().value)
         }
     )
     private val operatorOrders = arrayOf(
@@ -104,7 +108,8 @@ object MathHelper {
         return try {
             parse(lex(expression)).eval().toString()
         } catch (e: Exception) {
-            e.message ?: "Exception"
+            showToast(e.message ?: "Exception")
+            expression
         }
     }
 
@@ -114,7 +119,7 @@ object MathHelper {
                 break
             }
             var i = -1
-            while(++i < lexed.size) {
+            while (++i < lexed.size) {
                 val item = lexed[i]
                 if (item is BasicOperator) {
                     var op = item.toOperator(
@@ -175,7 +180,7 @@ object MathHelper {
                             value = expression.substring(
                                 start,
                                 i
-                            ).toDouble()
+                            ).toBigDecimal()
                         )
                     )
                     --i
@@ -198,7 +203,7 @@ object MathHelper {
     private class Operator(
         val operator: Char,
         val kind: Kind,
-        val operate: (operands:List<Operand>)-> Operand,
+        val operate: (operands: List<Operand>) -> Operand,
         val operands: ArrayList<Any> = arrayListOf(),
     ) {
         fun cloneWithoutOperands(): Operator {
@@ -223,14 +228,14 @@ object MathHelper {
                 "A404M",
                 "eval: $operator $operands"
             )
-            if(operandSize() != operands.size){
+            if (operandSize() != operands.size) {
                 throw UnsupportedOperationException("Not enough operands")
             }
 
             val evaledOperands = operands.map {
-                if(it is Operator){
+                if (it is Operator) {
                     it.eval()
-                }else{
+                } else {
                     it as Operand
                 }
             }
@@ -277,7 +282,7 @@ object MathHelper {
             )
             val right = rightItem is Operand || rightItem is Operator
 
-            val k:Kind
+            val k: Kind
 
             if (left) {
                 if (right) {
@@ -302,13 +307,62 @@ object MathHelper {
     }
 
     private class Operand(
-        val value: Double,
-    ){
+        val value: MathNumberType,
+    ) {
         override fun toString(): String {
-            if(value % 1 == 0.0){
-                return "%.0f".format(value)
+            var str = value.toString()
+            if(str.contains('.')){
+                while (str.last() == '0'){
+                    str = str.removeRange(str.length-1,str.length)
+                }
+                if(str.last() == '.'){
+                    str = str.removeRange(str.length-1,str.length)
+                }
+            }
+            return str
+        }
+    }
+
+    enum class InWriting {
+        NONE,
+        NUMBER_INT,
+        NUMBER_FLOAT,
+        OPERATOR,
+    }
+
+    fun getInWriting(expression: String): InWriting {
+        return when (expression.lastOrNull()) {
+            in operatorStrings -> InWriting.OPERATOR
+            in numberStrings -> {
+                var i = expression.length
+                var hasDot = false
+                while (--i >= 0 && expression[i] in numberStrings) {
+                    if (expression[i] == '.') {
+                        hasDot = true
+                    }
+                }
+
+                if (hasDot) InWriting.NUMBER_FLOAT
+                else InWriting.NUMBER_INT
             }
-            return value.toString()
+
+            else -> InWriting.NONE
+        }
+    }
+
+    fun getLastNumber(expression: String): String? {
+        return when (expression.lastOrNull()) {
+            in numberStrings -> {
+                var i = expression.length
+                var number = ""
+                while (--i >= 0 && expression[i] in numberStrings) {
+                    number = "${expression[i]}$number"
+                }
+
+                number
+            }
+
+            else -> null
         }
     }
 }
\ No newline at end of file