feat: remember previously used unit per unit converter category

Author: Bnyro

app/src/main/java/net/youapps/calcyou/persistence/FavoriteUnitsRepository.kt

@@ -8,7 +8,7 @@ import net.you_apps.calcyou.Unit
 class FavoriteUnitsRepository(val context: Context) {
     val dataStore get() = context.favoriteUnitsDataStore
 
-    val unitsFlow = dataStore.data.map { it.categoriesList }
+    val unitConverterCategoriesFlow = dataStore.data.map { it.categoriesList }
 
     suspend fun addFavoriteUnit(categoryKey: String, unitKey: String) {
         dataStore.updateData { data ->
@@ -52,4 +52,34 @@ class FavoriteUnitsRepository(val context: Context) {
                 .build()
         }
     }
+
+    suspend fun setSelectedUnit(categoryKey: String, unitKey: String?) {
+        dataStore.updateData { data ->
+            var builder = data.toBuilder()
+
+            // although it's not currently needed, it's possible to clear
+            // the selected unit to reset it to default
+            val unit = unitKey?.let { Unit.newBuilder().setKey(it).build() }
+
+            // add category if it doesn't exist yet
+            if (data.categoriesList.none { it.key == categoryKey }) {
+                builder = builder.addCategories(
+                    FavoriteUnitCategory.newBuilder()
+                        .setKey(categoryKey)
+                        .setSelectedUnit(unit)
+                        .build()
+                )
+            } else {
+                val categoryIndex = data.categoriesList.indexOfFirst { category ->
+                    category.key == categoryKey
+                }
+                val updatedCategory = data.categoriesList[categoryIndex].toBuilder()
+                updatedCategory.setSelectedUnit(unit)
+
+                builder.setCategories(categoryIndex, updatedCategory)
+            }
+
+            builder.build()
+        }
+    }
 }

app/src/main/java/net/youapps/calcyou/ui/screens/ConverterScreen.kt

@@ -28,6 +28,7 @@ import androidx.compose.material3.TextField
 import androidx.compose.material3.TextFieldDefaults
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
@@ -80,7 +81,11 @@ inline fun <reified T> ConverterScreen(
         verticalArrangement = Arrangement.spacedBy(16.dp)
     ) {
         var expanded by remember { mutableStateOf(false) }
-        var selectedUnit by remember { mutableStateOf(converter.units.first()) }
+        val selectedUnitKey by converterModel.selectedUnit.collectAsState(null)
+        val selectedUnit = remember(selectedUnitKey) {
+            converter.units.firstOrNull { converterModel.unitKey(it) == selectedUnitKey?.key }
+                ?: converter.units.first()
+        }
         var converted: List<Pair<ConverterUnit<T>, T>> by remember { mutableStateOf(listOf()) }
         var textFieldValue by remember { mutableStateOf("") }
 
@@ -153,9 +158,6 @@ inline fun <reified T> ConverterScreen(
                     converterModel,
                     converter.units,
                     selectedUnit,
-                    { unit ->
-                        selectedUnit = unit
-                    },
                     onDismissRequest = {
                         showUnitPickerScreen = false
                     }

app/src/main/java/net/youapps/calcyou/ui/screens/ConverterUnitPickerScreen.kt

@@ -47,7 +47,6 @@ fun <T> ConverterUnitPickerScreen(
     converterViewModel: UnitConverterViewModel,
     availableUnits: List<ConverterUnit<T>>,
     selectedUnit: ConverterUnit<T>,
-    onUnitSelected: (ConverterUnit<T>) -> Unit,
     onDismissRequest: () -> Unit
 ) {
     val context = LocalContext.current
@@ -64,6 +63,11 @@ fun <T> ConverterUnitPickerScreen(
 
     val scrollBehavior = SearchBarDefaults.enterAlwaysSearchBarScrollBehavior()
 
+    fun setSelectedUnit(unit: ConverterUnit<T>) {
+        converterViewModel.saveSelectedUnitForCategory(unit)
+        onDismissRequest()
+    }
+
     FullscreenDialog(onDismissRequest = onDismissRequest) {
         Scaffold(
             topBar = {
@@ -76,9 +80,7 @@ fun <T> ConverterUnitPickerScreen(
                         SearchBarDefaults.InputField(
                             query = query,
                             onQueryChange = { query = it },
-                            onSearch = {
-
-                            },
+                            onSearch = { /* do nothing, search is automatically triggered by onQueryChange */ },
                             expanded = true,
                             onExpandedChange = {},
                             placeholder = { Text(stringResource(R.string.search)) },
@@ -120,8 +122,7 @@ fun <T> ConverterUnitPickerScreen(
                                         isSelected = unit == selectedUnit,
                                         isFavorite = true,
                                         onClicked = {
-                                            onUnitSelected(unit)
-                                            onDismissRequest()
+                                            setSelectedUnit(unit)
                                         },
                                         toggleIsFavorited = {
                                             converterViewModel.removeFavoriteUnit(unit)
@@ -139,8 +140,7 @@ fun <T> ConverterUnitPickerScreen(
                         isSelected = unit == selectedUnit,
                         isFavorite = false,
                         onClicked = {
-                            onUnitSelected(unit)
-                            onDismissRequest()
+                            setSelectedUnit(unit)
                         },
                         toggleIsFavorited = {
                             converterViewModel.addFavoriteUnit(unit)

app/src/main/java/net/youapps/calcyou/viewmodels/UnitConverterViewModel.kt

@@ -19,8 +19,11 @@ class UnitConverterViewModel(application: Application): AndroidViewModel(applica
     private val favoriteUnitsRepository = FavoriteUnitsRepository(application)
 
     val currentCategoryKey = MutableStateFlow<String?>(null)
-    val favoriteUnits = combine(favoriteUnitsRepository.unitsFlow, currentCategoryKey) { favoriteUnits, category ->
-        favoriteUnits.firstOrNull { it.key == category }?.favoritesList.orEmpty()
+    val favoriteUnits = combine(favoriteUnitsRepository.unitConverterCategoriesFlow, currentCategoryKey) { categories, category ->
+        categories.firstOrNull { it.key == category }?.favoritesList.orEmpty()
+    }
+    val selectedUnit = combine(favoriteUnitsRepository.unitConverterCategoriesFlow, currentCategoryKey) { categories, category ->
+        categories.firstOrNull { it.key == category }?.selectedUnit
     }
 
     fun <T> unitKey(unit: ConverterUnit<T>): String {
@@ -38,6 +41,10 @@ class UnitConverterViewModel(application: Application): AndroidViewModel(applica
         favoriteUnitsRepository.removeFavoriteUnit(currentCategoryKey.value!!, unitKey(unit))
     }
 
+    fun <T> saveSelectedUnitForCategory(unit: ConverterUnit<T>) = viewModelScope.launch {
+        favoriteUnitsRepository.setSelectedUnit(currentCategoryKey.value!!, unitKey(unit))
+    }
+
     companion object {
         val Factory = viewModelFactory {
             initializer {

app/src/main/proto/favorite_units.proto

@@ -10,6 +10,7 @@ message Unit {
 message FavoriteUnitCategory {
   string key = 1;
   repeated Unit favorites = 2;
+  optional Unit selected_unit = 3;
 }
 
 message FavoriteUnits {