Back to ExprK.

Added more operators for calculator. Formatting and other stuff are broken.

P.S. Using my own fork of ExprK. Added square root operator to it.

app/build.gradle.kts

@@ -12,6 +12,8 @@ plugins {
 
     // Firebase Crashlytics
     id("com.google.firebase.crashlytics")
+
+//    id("io.freefair.lombok") version "6.6"
 }
 
 val composeVersion = "1.4.0-alpha02"
@@ -151,6 +153,8 @@ dependencies {
     testImplementation("junit:junit:4.13.2")
     androidTestImplementation("androidx.test:runner:1.5.1")
     androidTestImplementation("androidx.test:rules:1.5.0")
+    testImplementation("org.robolectric:robolectric:4.9")
+    testImplementation("org.jetbrains.kotlinx:kotlinx-coroutines-test:1.6.4")
 
     // Compose and navigation
     implementation("androidx.compose.ui:ui:$composeVersion")
@@ -200,6 +204,6 @@ dependencies {
     // ComposeReorderable
     implementation("org.burnoutcrew.composereorderable:reorderable:0.9.6")
 
-    // EvalEx
-    implementation("com.ezylang:EvalEx:3.0.1")
-}
+    // ExprK
+    implementation("com.github.sadellie:ExprK:e55cba8f41")
+}

app/src/main/java/com/sadellie/unitto/data/KeypadSymbols.kt

@@ -44,12 +44,26 @@ const val KEY_DIVIDE_DISPLAY = "÷"
 const val KEY_MULTIPLY = "*"
 const val KEY_MULTIPLY_DISPLAY = "×"
 
+const val KEY_LEFT_BRACKET = "("
+const val KEY_RIGHT_BRACKET = ")"
+
+const val KEY_EXPONENT = "^"
+const val KEY_EXPONENT_DISPLAY = "^"
+
+const val KEY_SQRT = "√"
+
 val OPERATORS = listOf(
     KEY_PLUS,
     KEY_MINUS,
-    KEY_MINUS_DISPLAY,
     KEY_MULTIPLY,
-    KEY_MULTIPLY_DISPLAY,
     KEY_DIVIDE,
-    KEY_DIVIDE_DISPLAY,
+    KEY_SQRT,
+    KEY_EXPONENT,
 )
+
+val INTERNAL_DISPLAY: Map<String, String> = hashMapOf(
+    KEY_MINUS to KEY_MINUS_DISPLAY,
+    KEY_MULTIPLY to KEY_MULTIPLY_DISPLAY,
+    KEY_DIVIDE to KEY_DIVIDE_DISPLAY,
+    KEY_EXPONENT to KEY_EXPONENT_DISPLAY,
+)

app/src/main/java/com/sadellie/unitto/screens/main/MainViewModel.kt

@@ -24,9 +24,10 @@ import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.setValue
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
-import com.ezylang.evalex.BaseException
-import com.ezylang.evalex.Expression
+import com.github.keelar.exprk.ExpressionException
+import com.github.keelar.exprk.Expressions
 import com.sadellie.unitto.FirebaseHelper
+import com.sadellie.unitto.data.INTERNAL_DISPLAY
 import com.sadellie.unitto.data.KEY_0
 import com.sadellie.unitto.data.KEY_1
 import com.sadellie.unitto.data.KEY_2
@@ -39,9 +40,12 @@ import com.sadellie.unitto.data.KEY_8
 import com.sadellie.unitto.data.KEY_9
 import com.sadellie.unitto.data.KEY_DIVIDE
 import com.sadellie.unitto.data.KEY_DOT
+import com.sadellie.unitto.data.KEY_LEFT_BRACKET
 import com.sadellie.unitto.data.KEY_MINUS
 import com.sadellie.unitto.data.KEY_MULTIPLY
 import com.sadellie.unitto.data.KEY_PLUS
+import com.sadellie.unitto.data.KEY_RIGHT_BRACKET
+import com.sadellie.unitto.data.KEY_SQRT
 import com.sadellie.unitto.data.OPERATORS
 import com.sadellie.unitto.data.preferences.UserPreferences
 import com.sadellie.unitto.data.preferences.UserPreferencesRepository
@@ -70,11 +74,13 @@ import javax.inject.Inject
 class MainViewModel @Inject constructor(
     private val userPrefsRepository: UserPreferencesRepository,
     private val basedUnitRepository: MyBasedUnitsRepository,
-    private val application: Application,
+    private val mContext: Application,
     private val allUnitsRepository: AllUnitsRepository
 ) : ViewModel() {
 
-    private val _inputValue: MutableStateFlow<String> = MutableStateFlow(KEY_0)
+    val inputValue: MutableStateFlow<String> = MutableStateFlow(KEY_0)
+    private val latestInputStack: MutableList<String> = mutableListOf(KEY_0)
+    private val _inputDisplayValue: MutableStateFlow<String> = MutableStateFlow(KEY_0)
     private val _deleteButtonEnabled: MutableStateFlow<Boolean> = MutableStateFlow(false)
     private val _negateButtonEnabled: MutableStateFlow<Boolean> = MutableStateFlow(false)
     private val _isLoadingDatabase: MutableStateFlow<Boolean> = MutableStateFlow(true)
@@ -88,15 +94,13 @@ class MainViewModel @Inject constructor(
     )
 
     val mainFlow = combine(
-        _inputValue, _isLoadingDatabase, _isLoadingNetwork, _showError, _userPrefs
-    ) { inputValue, isLoadingDatabase, isLoadingNetwork, showError, _ ->
+        _inputDisplayValue, _isLoadingDatabase, _isLoadingNetwork, _showError, _userPrefs
+    ) { inputDisplayValue, isLoadingDatabase, isLoadingNetwork, showError, _ ->
         return@combine MainScreenUIState(
-            inputValue = inputValue,
+            inputValue = inputDisplayValue,
             resultValue = convertValue(),
-            deleteButtonEnabled = _deleteButtonEnabled.value,
-            dotButtonEnabled = !_inputValue.value.takeLastWhile {
-                it.toString() !in OPERATORS.minus(KEY_DOT)
-            }.contains(KEY_DOT),
+            deleteButtonEnabled = inputValue.value != KEY_0,
+            dotButtonEnabled = canEnterDot(),
             negateButtonEnabled = _negateButtonEnabled.value,
             isLoadingDatabase = isLoadingDatabase,
             isLoadingNetwork = isLoadingNetwork,
@@ -122,31 +126,37 @@ class MainViewModel @Inject constructor(
      */
     private fun convertValue(): String {
 
-        val cleanInput = _inputValue.value.dropLastWhile { !it.isDigit() }
+        var cleanInput = inputValue.value.dropLastWhile { !it.isDigit() }
+
+        // AUTOCLOSE ALL BRACKETS
+        val leftBrackets = inputValue.value.count { it.toString() == KEY_LEFT_BRACKET }
+        val rightBrackets = inputValue.value.count { it.toString() == KEY_RIGHT_BRACKET }
+
+        val neededBrackets = leftBrackets - rightBrackets
+        if (neededBrackets > 0) {
+            cleanInput += KEY_RIGHT_BRACKET.repeat(neededBrackets)
+        }
 
         // Kotlin doesn't have a multi catch
         val calculatedInput = try {
-            val evaluated = Expression(cleanInput)
+            val evaluated = Expressions()
                 // Optimal precision, not too low, not too high. Balanced for performance and UX.
-                .evaluate()
-                .numberValue
+                .eval(cleanInput)
                 .setScale(_userPrefs.value.digitsPrecision, RoundingMode.HALF_EVEN)
                 .stripTrailingZeros()
             if (evaluated.compareTo(BigDecimal.ZERO) == 0) BigDecimal.ZERO else evaluated
         } catch (e: Exception) {
             // Kotlin doesn't have a multi catch
             when (e) {
-                is BaseException, is ArrayIndexOutOfBoundsException, is NumberFormatException, is ArithmeticException -> return mainFlow.value.resultValue
+                is ExpressionException, is ArrayIndexOutOfBoundsException, is IndexOutOfBoundsException, is NumberFormatException, is ArithmeticException -> return mainFlow.value.resultValue
                 else -> throw e
             }
         }
 
         // Ugly way of determining when to hide calculated value
-        _calculatedValue.value = if (calculatedInput.toPlainString() != cleanInput) {
-            // Expression is not same as the result, show result
+        _calculatedValue.value = if (!latestInputStack.none { it in OPERATORS }) {
             calculatedInput.toStringWith(_userPrefs.value.outputFormat)
         } else {
-            // Expression is same as the result, don't show result, the input text is enough
             null
         }
 
@@ -182,7 +192,7 @@ class MainViewModel @Inject constructor(
         _negateButtonEnabled.update { clickedUnit.group.canNegate }
         // Now we change to positive if the group we switched to supports negate
         if (!clickedUnit.group.canNegate) {
-            _inputValue.update { _inputValue.value.removePrefix(KEY_MINUS) }
+            inputValue.update { inputValue.value.removePrefix(KEY_MINUS) }
         }
 
         // Now setting up right unit (pair for the left one)
@@ -293,90 +303,146 @@ class MainViewModel @Inject constructor(
      * @param[symbolToAdd] Digit/Symbol we want to add, can be any digit 0..9 or a dot symbol
      */
     fun processInput(symbolToAdd: String) {
-        val lastSymbol = _inputValue.value.last().toString()
-        val lastSecondSymbol = _inputValue.value.takeLast(2).dropLast(1)
+        val lastTwoSymbols = latestInputStack.takeLast(2)
+        val lastSymbol: String = lastTwoSymbols.getOrNull(1) ?: lastTwoSymbols[0]
+        val lastSecondSymbol: String? = lastTwoSymbols.getOrNull(0)
         _deleteButtonEnabled.update { true }
 
         when (symbolToAdd) {
-            KEY_0 -> {
-                // Don't add zero if the input is already a zero
-                if (_inputValue.value == KEY_0) return
-                // Don't add zero if there is a zero and operator in front
-                if ((lastSecondSymbol in OPERATORS) and (lastSymbol == KEY_0)) return
-                _inputValue.update { _inputValue.value + symbolToAdd }
-            }
-            KEY_1, KEY_2, KEY_3, KEY_4, KEY_5, KEY_6, KEY_7, KEY_8, KEY_9 -> {
-                // Replace single zero (default input) if it's here
-                if (_inputValue.value == KEY_0) {
-                    _inputValue.update { symbolToAdd }
-                } else {
-                    _inputValue.update { _inputValue.value + symbolToAdd }
-                }
-            }
-            KEY_DOT -> {
-                _inputValue.update { _inputValue.value + symbolToAdd }
-            }
-            KEY_MINUS -> {
-                when {
-                    // Replace single zero with minus (to support negative numbers)
-                    (_inputValue.value == KEY_0) -> {
-                        if (symbolToAdd == KEY_MINUS) _inputValue.update { symbolToAdd }
-                    }
-                    // Don't allow multiple minuses near each other
-                    (lastSymbol == KEY_MINUS) -> {}
-                    // Don't allow plus and minus be near each other
-                    (lastSymbol == KEY_PLUS) -> {
-                        _inputValue.update { _inputValue.value.dropLast(1) + symbolToAdd }
-                    }
-                    else -> {
-                        _inputValue.update { _inputValue.value + symbolToAdd }
-                    }
-                }
-            }
             KEY_PLUS, KEY_DIVIDE, KEY_MULTIPLY -> {
                 when {
                     // Don't need expressions that start with zero
-                    (_inputValue.value == KEY_0) or (_inputValue.value == KEY_MINUS) -> {}
+                    (inputValue.value == KEY_0) or (inputValue.value == KEY_MINUS) -> {}
                     /**
                      * For situations like "50+-", when user clicks "/" we delete "-" so it becomes
                      * "50+". We don't add "/' here. User will click "/" second time and the input
                      * will be "50/".
                      */
-                    (lastSecondSymbol in OPERATORS) and (lastSymbol == KEY_MINUS) -> {
+                    (lastSecondSymbol in OPERATORS) and (lastSymbol == KEY_MINUS)-> {
                         deleteDigit()
                     }
                     // Don't allow multiple operators near each other
                     (lastSymbol in OPERATORS) -> {
-                        _inputValue.update { _inputValue.value.dropLast(1) + symbolToAdd }
+                        deleteDigit()
+                        setInputSymbols(symbolToAdd)
                     }
                     else -> {
-                        _inputValue.update { _inputValue.value + symbolToAdd }
+                        setInputSymbols(symbolToAdd)
+                    }
+                }
+            }
+            KEY_0 -> {
+                // Don't add zero if the input is already a zero
+                if (inputValue.value == KEY_0) return
+                // Prevents things like "-00" and "4+000"
+                if ((lastSecondSymbol in OPERATORS) and (lastSymbol == KEY_0)) return
+                setInputSymbols(symbolToAdd)
+            }
+            KEY_1, KEY_2, KEY_3, KEY_4, KEY_5, KEY_6, KEY_7, KEY_8, KEY_9 -> {
+                // Replace single zero (default input) if it's here
+                if (inputValue.value == KEY_0) {
+                    setInputSymbols(symbolToAdd, false)
+                } else {
+                    setInputSymbols(symbolToAdd)
+                }
+            }
+            KEY_MINUS -> {
+                when {
+                    // Replace single zero with minus (to support negative numbers)
+                    (inputValue.value == KEY_0) -> {
+                        setInputSymbols(symbolToAdd, false)
+                    }
+                    // Don't allow multiple minuses near each other
+                    (lastSymbol.compareTo(KEY_MINUS) == 0) -> {}
+                    // Don't allow plus and minus be near each other
+                    (lastSymbol == KEY_PLUS) -> {
+                        deleteDigit()
+                        setInputSymbols(symbolToAdd)
+                    }
+                    else -> {
+                        setInputSymbols(symbolToAdd)
+                    }
+                }
+            }
+            KEY_DOT -> {
+                setInputSymbols(symbolToAdd)
+            }
+            KEY_LEFT_BRACKET, KEY_RIGHT_BRACKET -> {
+                when {
+                    // Replace single zero with minus (to support negative numbers)
+                    (inputValue.value == KEY_0) -> {
+                        setInputSymbols(symbolToAdd, false)
+                    }
+                    else -> {
+                        setInputSymbols(symbolToAdd)
+                    }
+                }
+            }
+            KEY_SQRT -> {
+                when {
+                    // Replace single zero with minus (to support negative numbers)
+                    (inputValue.value == KEY_0) -> {
+                        setInputSymbols(symbolToAdd, false)
+                    }
+                    else -> {
+                        setInputSymbols(symbolToAdd)
+                    }
+                }
+            }
+            else -> {
+                when {
+                    // Replace single zero with minus (to support negative numbers)
+                    (inputValue.value == KEY_0) -> {
+                        setInputSymbols(symbolToAdd, false)
+                    }
+                    else -> {
+                        setInputSymbols(symbolToAdd)
                     }
                 }
             }
         }
+
     }
 
     /**
      * Deletes last symbol from input and handles buttons state (enabled/disabled)
      */
     fun deleteDigit() {
-        // Deleting last symbol
-        var inputToSet = _inputValue.value.dropLast(1)
+        val lastSymbol = latestInputStack.removeLast()
 
-        /*
-        Now we check what we have left
-        We deleted last symbol and we got Empty string, just minus symbol, or zero
-        Do not allow deleting anything beyond this (disable button)
-        Set input to default (zero)
-        Skipping this block means that we are left we acceptable value, i.e. 123.03
-        */
-        if (inputToSet in listOf(String(), KEY_MINUS, KEY_0)) {
-            _deleteButtonEnabled.update { false }
-            inputToSet = KEY_0
+        // We will need to delete last symbol from both values
+        val displayRepresentation: String = INTERNAL_DISPLAY[lastSymbol] ?: lastSymbol
+
+        // If this value are same, it means that after deleting there will be no symbols left, set to default
+        if (lastSymbol == inputValue.value) {
+            setInputSymbols(KEY_0, false)
+        } else {
+            inputValue.update { it.removeSuffix(lastSymbol) }
+            _inputDisplayValue.update { it.removeSuffix(displayRepresentation) }
         }
+    }
 
-        _inputValue.update { inputToSet }
+    /**
+     * Adds given [symbol] to [inputValue] and [_inputDisplayValue] and updates [latestInputStack].
+     *
+     * By default add symbol, but if [add] is False, will replace current input (when replacing
+     * default [KEY_0] input).
+     */
+    private fun setInputSymbols(symbol: String, add: Boolean = true) {
+        val displaySymbol: String = INTERNAL_DISPLAY[symbol] ?: symbol
+
+        when {
+            add -> {
+                inputValue.update { it + symbol }
+                _inputDisplayValue.update { it + displaySymbol }
+                latestInputStack.add(symbol)
+            }
+            else -> {
+                inputValue.update { symbol }
+                _inputDisplayValue.update { displaySymbol }
+                latestInputStack.add(symbol)
+            }
+        }
     }
 
     /**
@@ -384,7 +450,7 @@ class MainViewModel @Inject constructor(
      */
     fun clearInput() {
         _deleteButtonEnabled.update { false }
-        _inputValue.update { KEY_0 }
+        setInputSymbols(KEY_0, false)
     }
 
     /**
@@ -392,6 +458,13 @@ class MainViewModel @Inject constructor(
      */
     fun inputValue() = (mainFlow.value.calculatedValue ?: mainFlow.value.inputValue).toBigDecimal()
 
+    /**
+     * Returns True if can be placed.
+     */
+    private fun canEnterDot(): Boolean = !inputValue.value.takeLastWhile {
+        it.toString() !in OPERATORS.minus(KEY_DOT)
+    }.contains(KEY_DOT)
+
     /**
      * Saves latest pair of units into datastore
      */
@@ -418,7 +491,7 @@ class MainViewModel @Inject constructor(
 
             // Now we load units data from database
             val allBasedUnits = basedUnitRepository.getAll()
-            allUnitsRepository.loadFromDatabase(application, allBasedUnits)
+            allUnitsRepository.loadFromDatabase(mContext, allBasedUnits)
 
             // User is free to convert values and units on units screen can be sorted properly
             _negateButtonEnabled.update { unitFrom.group.canNegate }

app/src/main/java/com/sadellie/unitto/screens/main/components/Keyboard.kt

@@ -39,11 +39,16 @@ import com.sadellie.unitto.data.KEY_CLEAR
 import com.sadellie.unitto.data.KEY_DIVIDE
 import com.sadellie.unitto.data.KEY_DIVIDE_DISPLAY
 import com.sadellie.unitto.data.KEY_DOT
+import com.sadellie.unitto.data.KEY_EXPONENT
+import com.sadellie.unitto.data.KEY_EXPONENT_DISPLAY
+import com.sadellie.unitto.data.KEY_LEFT_BRACKET
 import com.sadellie.unitto.data.KEY_MINUS
 import com.sadellie.unitto.data.KEY_MINUS_DISPLAY
 import com.sadellie.unitto.data.KEY_MULTIPLY
 import com.sadellie.unitto.data.KEY_MULTIPLY_DISPLAY
 import com.sadellie.unitto.data.KEY_PLUS
+import com.sadellie.unitto.data.KEY_RIGHT_BRACKET
+import com.sadellie.unitto.data.KEY_SQRT
 import com.sadellie.unitto.screens.Formatter
 
 /**
@@ -76,24 +81,28 @@ fun Keyboard(
         // Column modifier
         val cModifier = Modifier.weight(1f)
         Column(cModifier) {
+            KeyboardButton(bModifier, KEY_LEFT_BRACKET, isPrimary = false, onClick = addDigit)
             KeyboardButton(bModifier, KEY_7, onClick = addDigit)
             KeyboardButton(bModifier, KEY_4, onClick = addDigit)
             KeyboardButton(bModifier, KEY_1, onClick = addDigit)
             KeyboardButton(bModifier, KEY_0, onClick = addDigit)
         }
         Column(cModifier) {
+            KeyboardButton(bModifier, KEY_RIGHT_BRACKET, isPrimary = false, onClick = addDigit)
             KeyboardButton(bModifier, KEY_8, onClick = addDigit)
             KeyboardButton(bModifier, KEY_5, onClick = addDigit)
             KeyboardButton(bModifier, KEY_2, onClick = addDigit)
             KeyboardButton(bModifier, Formatter.fractional, enabled = dotButtonEnabled) { addDigit(KEY_DOT) }
         }
         Column(cModifier) {
+            KeyboardButton(bModifier, KEY_EXPONENT_DISPLAY, isPrimary = false, onClick = { addDigit(KEY_EXPONENT) })
             KeyboardButton(bModifier, KEY_9, onClick = addDigit)
             KeyboardButton(bModifier, KEY_6, onClick = addDigit)
             KeyboardButton(bModifier, KEY_3, onClick = addDigit)
             KeyboardButton(bModifier, KEY_CLEAR, enabled = deleteButtonEnabled, onLongClick = clearInput) { deleteDigit() }
         }
         Column(cModifier) {
+            KeyboardButton(bModifier, KEY_SQRT, isPrimary = false, onClick = { addDigit(KEY_SQRT) })
             KeyboardButton(bModifier, KEY_DIVIDE_DISPLAY, isPrimary = false) { addDigit(KEY_DIVIDE) }
             KeyboardButton(bModifier, KEY_MULTIPLY_DISPLAY, isPrimary = false) { addDigit(KEY_MULTIPLY) }
             KeyboardButton(bModifier, KEY_MINUS_DISPLAY, isPrimary = false) { addDigit(KEY_MINUS) }

app/src/main/java/com/sadellie/unitto/screens/main/components/TopScreen.kt

@@ -85,7 +85,7 @@ fun TopScreenPart(
 
     Column(
         modifier = modifier,
-        verticalArrangement = Arrangement.spacedBy(24.dp)
+        verticalArrangement = Arrangement.spacedBy(8.dp)
     ) {
         MyTextField(
             Modifier.fillMaxWidth(),

app/src/test/java/com/sadellie/unitto/screens/MainViewModelTest.kt

@@ -0,0 +1,394 @@
+/*
+ * Unitto is a unit converter for Android
+ * Copyright (c) 2022-2022 Elshan Agaev
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+package com.sadellie.unitto.screens
+
+import android.os.StrictMode
+import androidx.room.Room
+import com.sadellie.unitto.data.KEY_0
+import com.sadellie.unitto.data.KEY_1
+import com.sadellie.unitto.data.KEY_2
+import com.sadellie.unitto.data.KEY_3
+import com.sadellie.unitto.data.KEY_4
+import com.sadellie.unitto.data.KEY_5
+import com.sadellie.unitto.data.KEY_6
+import com.sadellie.unitto.data.KEY_7
+import com.sadellie.unitto.data.KEY_8
+import com.sadellie.unitto.data.KEY_9
+import com.sadellie.unitto.data.KEY_COMMA
+import com.sadellie.unitto.data.KEY_DIVIDE
+import com.sadellie.unitto.data.KEY_DOT
+import com.sadellie.unitto.data.KEY_EXPONENT
+import com.sadellie.unitto.data.KEY_LEFT_BRACKET
+import com.sadellie.unitto.data.KEY_MINUS
+import com.sadellie.unitto.data.KEY_MULTIPLY
+import com.sadellie.unitto.data.KEY_PLUS
+import com.sadellie.unitto.data.KEY_RIGHT_BRACKET
+import com.sadellie.unitto.data.KEY_SQRT
+import com.sadellie.unitto.data.preferences.DataStoreModule
+import com.sadellie.unitto.data.preferences.UserPreferencesRepository
+import com.sadellie.unitto.data.units.AllUnitsRepository
+import com.sadellie.unitto.data.units.database.MyBasedUnitDatabase
+import com.sadellie.unitto.data.units.database.MyBasedUnitsRepository
+import com.sadellie.unitto.screens.main.MainViewModel
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.test.TestDispatcher
+import kotlinx.coroutines.test.UnconfinedTestDispatcher
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.test.setMain
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TestWatcher
+import org.junit.runner.Description
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.RuntimeEnvironment
+import org.robolectric.annotation.Config
+
+
+@ExperimentalCoroutinesApi
+class CoroutineTestRule(private val dispatcher: TestDispatcher = UnconfinedTestDispatcher()) :
+    TestWatcher() {
+
+    override fun starting(description: Description) {
+        super.starting(description)
+        Dispatchers.setMain(dispatcher)
+    }
+
+    override fun finished(description: Description) {
+        super.finished(description)
+        Dispatchers.resetMain()
+    }
+
+}
+
+
+@OptIn(ExperimentalCoroutinesApi::class)
+@Config(manifest = Config.NONE)
+@RunWith(RobolectricTestRunner::class)
+class MainViewModelTest {
+
+    @ExperimentalCoroutinesApi
+    @get:Rule
+    val coroutineTestRule = CoroutineTestRule()
+
+    private lateinit var viewModel: MainViewModel
+    private val allUnitsRepository = AllUnitsRepository()
+
+    @Before
+    fun setUp() {
+        viewModel = MainViewModel(
+            UserPreferencesRepository(
+                DataStoreModule().provideUserPreferencesDataStore(
+                    RuntimeEnvironment.getApplication()
+                )
+            ), MyBasedUnitsRepository(
+                Room.inMemoryDatabaseBuilder(
+                    RuntimeEnvironment.getApplication(), MyBasedUnitDatabase::class.java
+                ).build().myBasedUnitDao()
+            ), RuntimeEnvironment.getApplication(), allUnitsRepository
+        )
+    }
+
+    @Test
+    fun processInputTest() = runTest {
+        // https://github.com/robolectric/robolectric/issues/6377#issuecomment-843779001
+        StrictMode.enableDefaults()
+        val testDispatcher = UnconfinedTestDispatcher(testScheduler)
+        Dispatchers.setMain(testDispatcher)
+        viewModel.mainFlow.launchIn(CoroutineScope(testDispatcher))
+
+        /**
+         * For simplicity comments will have structure:
+         * currentInput | userInput | processed internal input | processed display output
+         */
+        `test 0`()
+        `test digits from 1 to 9`()
+        `test plus, divide and multiply operators`()
+        `test dot`()
+        `test minus`()
+        `test brackets`()
+
+        Dispatchers.resetMain()
+    }
+
+    private fun `test 0`() {
+        // 0 | 000 | 0 | 0
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("0", viewModel.inputValue.value)
+        assertEquals("0", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 123 | 000 | 123000
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_3)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("123000", viewModel.inputValue.value)
+        assertEquals("123000", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 123. | 000 | 123.000
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_3)
+        viewModel.processInput(KEY_DOT)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("123.000", viewModel.inputValue.value)
+        assertEquals("123.000", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // - | 000 | -0
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("-0", viewModel.inputValue.value)
+        assertEquals("–0", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 12+ | 000 | 12+0
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("12+0", viewModel.inputValue.value)
+        assertEquals("12+0", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // √0 | 000 | √0
+        viewModel.processInput(KEY_SQRT)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_0)
+        assertEquals("√0", viewModel.inputValue.value)
+        assertEquals("√0", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+    }
+
+    private fun `test digits from 1 to 9`() {
+        // 0 | 123456789 | 123456789
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_3)
+        viewModel.processInput(KEY_4)
+        viewModel.processInput(KEY_5)
+        viewModel.processInput(KEY_6)
+        viewModel.processInput(KEY_7)
+        viewModel.processInput(KEY_8)
+        viewModel.processInput(KEY_9)
+        assertEquals("123456789", viewModel.inputValue.value)
+        assertEquals("123456789", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+    }
+
+    private fun `test plus, divide and multiply operators`() {
+        // 0 | +++ | 0
+        viewModel.processInput(KEY_PLUS)
+        assertEquals("0", viewModel.inputValue.value)
+        assertEquals("0", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 123 | +++ | 123+
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_3)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_PLUS)
+        assertEquals("123+", viewModel.inputValue.value)
+        assertEquals("123+", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 1- | *** | 1*
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MULTIPLY)
+        viewModel.processInput(KEY_MULTIPLY)
+        viewModel.processInput(KEY_MULTIPLY)
+        assertEquals("1*", viewModel.inputValue.value)
+        assertEquals("1×", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 1/- | +++ | 1+
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_DIVIDE)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_PLUS)
+        assertEquals("1+", viewModel.inputValue.value)
+        assertEquals("1+", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+    }
+
+    private fun `test dot`() {
+        // 0 | . | 0.
+        viewModel.processInput(KEY_DOT)
+        assertEquals("0.", viewModel.inputValue.value)
+        assertEquals("0.", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 1 | . | 1.
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_DOT)
+        assertEquals("1.", viewModel.inputValue.value)
+        assertEquals("1.", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 1+ | . | 1+.
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_DOT)
+        assertEquals("1+.", viewModel.inputValue.value)
+        assertEquals("1+.", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // √ | . | √.
+        viewModel.processInput(KEY_SQRT)
+        viewModel.processInput(KEY_DOT)
+        assertEquals("√.", viewModel.inputValue.value)
+        assertEquals("√.", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+    }
+
+    private fun `test minus`() {
+        // 0 | --- | -
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        assertEquals("-", viewModel.inputValue.value)
+        assertEquals("–", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 12 | --- | 12-
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        assertEquals("12-", viewModel.inputValue.value)
+        assertEquals("12–", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 12+ | --- | 12-
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        assertEquals("12-", viewModel.inputValue.value)
+        assertEquals("12–", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 12/ | --- | 12/-
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_DIVIDE)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        assertEquals("12/-", viewModel.inputValue.value)
+        assertEquals("12÷–", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // √ | --- | √-
+        viewModel.processInput(KEY_SQRT)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        viewModel.processInput(KEY_MINUS)
+        assertEquals("√-", viewModel.inputValue.value)
+        assertEquals("√–", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+    }
+
+    private fun `test brackets`() {
+        // 0 | ( | (
+        viewModel.processInput(KEY_LEFT_BRACKET)
+        assertEquals("(", viewModel.inputValue.value)
+        assertEquals("(", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // 0 | ((( | (((
+        viewModel.processInput(KEY_LEFT_BRACKET)
+        viewModel.processInput(KEY_LEFT_BRACKET)
+        viewModel.processInput(KEY_LEFT_BRACKET)
+        assertEquals("(((", viewModel.inputValue.value)
+        assertEquals("(((", viewModel.mainFlow.value.inputValue)
+        viewModel.clearInput()
+
+        // √ | (10+2) | √(10+2)
+        viewModel.processInput(KEY_SQRT)
+        viewModel.processInput(KEY_LEFT_BRACKET)
+        viewModel.processInput(KEY_1)
+        viewModel.processInput(KEY_0)
+        viewModel.processInput(KEY_PLUS)
+        viewModel.processInput(KEY_2)
+        viewModel.processInput(KEY_RIGHT_BRACKET)
+        assertEquals("√(10+2)", viewModel.inputValue.value)
+        assertEquals("√(10+2)", viewModel.mainFlow.value.inputValue)
+    }
+
+    @Test
+    fun deleteSymbolTest() = runTest {
+        // https://github.com/robolectric/robolectric/issues/6377#issuecomment-843779001
+        StrictMode.enableDefaults()
+        val testDispatcher = UnconfinedTestDispatcher(testScheduler)
+        Dispatchers.setMain(testDispatcher)
+        viewModel.mainFlow.launchIn(CoroutineScope(testDispatcher))
+
+        listOf(
+            KEY_1, KEY_2, KEY_3, KEY_4, KEY_5, KEY_6, KEY_7, KEY_8, KEY_9, KEY_0,
+            KEY_DOT, KEY_COMMA, KEY_LEFT_BRACKET, KEY_RIGHT_BRACKET,
+            KEY_PLUS, KEY_MINUS, KEY_DIVIDE, KEY_MULTIPLY, KEY_EXPONENT, KEY_SQRT,
+        ).forEach {
+            // We enter one symbol and delete it, should be default as a result
+            viewModel.processInput(it)
+            viewModel.deleteDigit()
+            assertEquals("0", viewModel.mainFlow.value.inputValue)
+            assertEquals("0", viewModel.inputValue.value)
+        }
+        viewModel.clearInput()
+
+        // Now we check that we can delete multiple values
+        viewModel.processInput(KEY_3)
+        viewModel.processInput(KEY_SQRT)
+        viewModel.processInput(KEY_9)
+        viewModel.deleteDigit()
+        assertEquals("3√", viewModel.inputValue.value)
+        assertEquals("3√", viewModel.mainFlow.value.inputValue)
+
+        Dispatchers.resetMain()
+    }
+
+}