Implement the StartExerciseScreen with comprehensive filtering and configuration options.

app/src/main/java/eu/gaudian/translator/view/exercises/StartExerciseScreen.kt

@@ -10,7 +10,6 @@ import androidx.compose.foundation.layout.ExperimentalLayoutApi
 import androidx.compose.foundation.layout.FlowRow
 import androidx.compose.foundation.layout.Row
 import androidx.compose.foundation.layout.Spacer
-import androidx.compose.foundation.layout.fillMaxHeight
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
@@ -24,40 +23,106 @@ import androidx.compose.foundation.shape.RoundedCornerShape
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.ArrowBackIosNew
 import androidx.compose.material.icons.filled.CheckCircle
-import androidx.compose.material.icons.filled.Edit
-import androidx.compose.material.icons.filled.Hearing
-import androidx.compose.material.icons.filled.List
 import androidx.compose.material.icons.filled.PlayArrow
+import androidx.compose.material.icons.filled.Settings
 import androidx.compose.material.icons.outlined.Circle
-import androidx.compose.material3.Button
-import androidx.compose.material3.ButtonDefaults
 import androidx.compose.material3.Icon
 import androidx.compose.material3.IconButton
 import androidx.compose.material3.MaterialTheme
-import androidx.compose.material3.Slider
+import androidx.compose.material3.ModalBottomSheet
+import androidx.compose.material3.SheetState
 import androidx.compose.material3.Surface
 import androidx.compose.material3.Text
+import androidx.compose.material3.rememberModalBottomSheetState
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
-import androidx.compose.runtime.mutableFloatStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
+import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.vector.ImageVector
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.text.style.TextAlign
 import androidx.compose.ui.unit.dp
 import androidx.compose.ui.unit.sp
+import androidx.hilt.lifecycle.viewmodel.compose.hiltViewModel
 import androidx.navigation.NavHostController
+import eu.gaudian.translator.R
+import eu.gaudian.translator.model.Language
+import eu.gaudian.translator.model.TagCategory
+import eu.gaudian.translator.model.VocabularyCategory
+import eu.gaudian.translator.model.VocabularyStage
+import eu.gaudian.translator.utils.findActivity
+import eu.gaudian.translator.view.composable.AppButton
+import eu.gaudian.translator.view.composable.AppIcons
+import eu.gaudian.translator.view.composable.AppOutlinedButton
+import eu.gaudian.translator.view.composable.AppSlider
+import eu.gaudian.translator.view.composable.OptionItemSwitch
+import eu.gaudian.translator.view.dialogs.CategoryDropdown
+import eu.gaudian.translator.view.vocabulary.VocabularyExerciseType
+import eu.gaudian.translator.viewmodel.CategoryViewModel
+import eu.gaudian.translator.viewmodel.LanguageViewModel
+import eu.gaudian.translator.viewmodel.VocabularyExerciseViewModel
+import eu.gaudian.translator.viewmodel.VocabularyViewModel
+import kotlinx.coroutines.launch
 
 @Composable
 fun StartExerciseScreen(
     navController: NavHostController,
     modifier: Modifier = Modifier
 ) {
+    val activity = androidx.compose.ui.platform.LocalContext.current.findActivity()
+    val vocabularyViewModel: VocabularyViewModel = hiltViewModel(viewModelStoreOwner = activity)
+    val exerciseViewModel: VocabularyExerciseViewModel = hiltViewModel(viewModelStoreOwner = activity)
+
+    val exerciseConfig by exerciseViewModel.pendingExerciseConfig.collectAsState()
+    var selectedLanguagePairs by remember { mutableStateOf<List<Pair<Language, Language>>>(emptyList()) }
+    var selectedCategories by remember { mutableStateOf<List<VocabularyCategory>>(emptyList()) }
+    var selectedStages by remember { mutableStateOf<List<VocabularyStage>>(emptyList()) }
+
+    var selectedOriginLanguage by remember { mutableStateOf<Language?>(null) }
+    var selectedTargetLanguage by remember { mutableStateOf<Language?>(null) }
+
+    val selectedPairsIds = remember(selectedLanguagePairs) {
+        selectedLanguagePairs.map { it.first.nameResId to it.second.nameResId }
+    }
+    val selectedCategoryIds = remember(selectedCategories) {
+        selectedCategories.map { it.id }
+    }
+
+    val filteredItemsFlow = remember(
+        selectedPairsIds,
+        selectedCategoryIds,
+        selectedStages,
+        exerciseConfig.dueTodayOnly
+    ) {
+        vocabularyViewModel.filterVocabularyItemsByPairs(
+            languagePairs = selectedPairsIds.ifEmpty { null },
+            query = null,
+            categoryIds = selectedCategoryIds.ifEmpty { null },
+            stages = selectedStages.ifEmpty { null },
+            sortOrder = VocabularyViewModel.SortOrder.NEWEST_FIRST,
+            dueTodayOnly = exerciseConfig.dueTodayOnly
+        )
+    }
+    val itemsToShow by filteredItemsFlow.collectAsState(initial = emptyList())
+    val totalItemCount = itemsToShow.size
+
+    var amount by remember { mutableStateOf(0) }
+    androidx.compose.runtime.LaunchedEffect(totalItemCount) {
+        amount = totalItemCount
+    }
+
+    val updateConfig: (eu.gaudian.translator.viewmodel.ExerciseConfig) -> Unit = { config ->
+        exerciseViewModel.updatePendingExerciseConfig(config)
+    }
+
     Box(
         modifier = modifier.fillMaxSize(),
         contentAlignment = Alignment.TopCenter
@@ -67,7 +132,15 @@ fun StartExerciseScreen(
                 .widthIn(max = 700.dp) // Keeps it from over-stretching on tablets
                 .fillMaxSize()
         ) {
-            TopBarSection(onBackClick = { navController.popBackStack() })
+            TopBarSection(
+                onBackClick = { navController.popBackStack() },
+                shuffleCards = exerciseConfig.shuffleCards,
+                onShuffleCardsChanged = { updateConfig(exerciseConfig.copy(shuffleCards = it)) },
+                shuffleLanguages = exerciseConfig.shuffleLanguages,
+                onShuffleLanguagesChanged = { updateConfig(exerciseConfig.copy(shuffleLanguages = it)) },
+                trainingMode = exerciseConfig.trainingMode,
+                onTrainingModeChanged = { updateConfig(exerciseConfig.copy(trainingMode = it)) },
+            )
 
             LazyColumn(
                 modifier = Modifier
@@ -76,27 +149,107 @@ fun StartExerciseScreen(
                 verticalArrangement = Arrangement.spacedBy(32.dp)
             ) {
                 item { Spacer(modifier = Modifier.height(8.dp)) }
-                item { LanguagePairSection() }
-                item { CategoriesSection() }
-                item { DifficultySection() }
-                item { NumberOfCardsSection() }
-                item { QuestionTypesSection() }
+                item {
+                    LanguagePairSection(
+                        selectedPairs = selectedLanguagePairs,
+                        onPairsChanged = { selectedLanguagePairs = it },
+                        onOriginLanguageSelected = { language ->
+                            selectedOriginLanguage = language
+                            if (selectedTargetLanguage?.nameResId == language?.nameResId) {
+                                selectedTargetLanguage = null
+                            }
+                            updateConfig(exerciseConfig.copy(originLanguageId = language?.nameResId))
+                        },
+                        onTargetLanguageSelected = { language ->
+                            selectedTargetLanguage = language
+                            if (selectedOriginLanguage?.nameResId == language?.nameResId) {
+                                selectedOriginLanguage = null
+                            }
+                            updateConfig(exerciseConfig.copy(targetLanguageId = language?.nameResId))
+                        },
+                        selectedOriginLanguage = selectedOriginLanguage,
+                        selectedTargetLanguage = selectedTargetLanguage
+                    )
+                }
+                item {
+                    CategoriesSection(
+                        selectedCategories = selectedCategories,
+                        onCategoriesChanged = { selectedCategories = it }
+                    )
+                }
+                item {
+                    DifficultySection(
+                        selectedStages = selectedStages,
+                        onStagesChanged = { selectedStages = it }
+                    )
+                }
+                item {
+                    NumberOfCardsSection(
+                        totalAvailable = totalItemCount,
+                        amount = amount,
+                        onAmountChanged = { amount = it },
+                        dueTodayOnly = exerciseConfig.dueTodayOnly,
+                        onDueTodayOnlyChanged = { updateConfig(exerciseConfig.copy(dueTodayOnly = it)) }
+                    )
+                }
+                item {
+                    QuestionTypesSection(
+                        selectedTypes = exerciseConfig.selectedExerciseTypes,
+                        onTypeSelected = { type ->
+                            val current = exerciseConfig.selectedExerciseTypes.toMutableSet()
+                            if (type in current) {
+                                if (current.size > 1) current.remove(type)
+                            } else {
+                                current.add(type)
+                            }
+                            updateConfig(exerciseConfig.copy(selectedExerciseTypes = current))
+                        }
+                    )
+                }
                 item { Spacer(modifier = Modifier.height(24.dp)) }
             }
 
-            BottomButtonSection()
+            BottomButtonSection(
+                enabled = totalItemCount > 0 && amount > 0,
+                amount = amount,
+                onStart = {
+                    val finalItems = if (exerciseConfig.shuffleCards) {
+                        itemsToShow.shuffled().take(amount)
+                    } else {
+                        itemsToShow.take(amount)
+                    }
+
+                    exerciseViewModel.startExerciseWithConfig(
+                        finalItems,
+                        exerciseConfig.copy(
+                            exerciseItemCount = finalItems.size,
+                            originalExerciseItems = finalItems,
+                            originLanguageId = selectedOriginLanguage?.nameResId,
+                            targetLanguageId = selectedTargetLanguage?.nameResId
+                        )
+                    )
+
+                    navController.navigate("vocabulary_exercise/false")
+                }
+            )
         }
     }
 }
 
-//TODO add a settings icon here (top right), this should open a modal bottom sheed with our
-// OptionItemSwitch from startscreen
-//change the behavior: shuffle cards, default: on
-//shuffle languages, default: on
-//training mode, default: off
-//due today will be place more prominent, not in the bottom sheet
 @Composable
-fun TopBarSection(onBackClick: () -> Unit) {
+fun TopBarSection(
+    onBackClick: () -> Unit,
+    shuffleCards: Boolean,
+    onShuffleCardsChanged: (Boolean) -> Unit,
+    shuffleLanguages: Boolean,
+    onShuffleLanguagesChanged: (Boolean) -> Unit,
+    trainingMode: Boolean,
+    onTrainingModeChanged: (Boolean) -> Unit
+) {
+    var showSettings by remember { mutableStateOf(false) }
+    val sheetState = rememberModalBottomSheetState(skipPartiallyExpanded = true)
+    val scope = rememberCoroutineScope()
+
     Row(
         modifier = Modifier
             .fillMaxWidth()
@@ -118,15 +271,45 @@ fun TopBarSection(onBackClick: () -> Unit) {
         }
 
         Text(
-            text = "Start Exercise",
+            text = stringResource(R.string.label_start_exercise),
             style = MaterialTheme.typography.titleLarge,
             fontWeight = FontWeight.Bold,
             modifier = Modifier.weight(1f),
-            textAlign = androidx.compose.ui.text.style.TextAlign.Center
+            textAlign = TextAlign.Center
         )
 
-        // Spacer to balance the back button for centering
-        Spacer(modifier = Modifier.size(48.dp))
+        IconButton(
+            onClick = { showSettings = true },
+            modifier = Modifier
+                .clip(CircleShape)
+                .background(MaterialTheme.colorScheme.surfaceVariant.copy(alpha = 0.5f))
+        ) {
+            Icon(
+                imageVector = Icons.Default.Settings,
+                contentDescription = "Settings",
+                modifier = Modifier.size(20.dp),
+                tint = MaterialTheme.colorScheme.primary
+            )
+        }
+    }
+
+    if (showSettings) {
+        StartExerciseSettingsBottomSheet(
+            sheetState = sheetState,
+            shuffleCards = shuffleCards,
+            onShuffleCardsChanged = onShuffleCardsChanged,
+            shuffleLanguages = shuffleLanguages,
+            onShuffleLanguagesChanged = onShuffleLanguagesChanged,
+            trainingMode = trainingMode,
+            onTrainingModeChanged = onTrainingModeChanged,
+            onDismiss = {
+                scope.launch { sheetState.hide() }.invokeOnCompletion {
+                    if (!sheetState.isVisible) {
+                        showSettings = false
+                    }
+                }
+            }
+        )
     }
 }
 
@@ -156,27 +339,129 @@ fun SectionHeader(title: String, actionText: String? = null, onActionClick: () -
     }
 }
 
-//TODO Get our (exisiting) language pairs from the viewmodel, user should be able to select 0,1 , or several, also order by more popular (amount of flashcard in one language)
-// so that more used/popular language pairs appear first
 @Composable
-fun LanguagePairSection() {
-    var selectedPair by remember { mutableStateOf(0) }
+fun LanguagePairSection(
+    selectedPairs: List<Pair<Language, Language>>,
+    onPairsChanged: (List<Pair<Language, Language>>) -> Unit,
+    onOriginLanguageSelected: (Language?) -> Unit,
+    onTargetLanguageSelected: (Language?) -> Unit,
+    selectedOriginLanguage: Language?,
+    selectedTargetLanguage: Language?
+) {
+    val activity = androidx.compose.ui.platform.LocalContext.current.findActivity()
+    val vocabularyViewModel: VocabularyViewModel = hiltViewModel(viewModelStoreOwner = activity)
+    val languageViewModel: LanguageViewModel = hiltViewModel(viewModelStoreOwner = activity)
+    val languagesPresent by vocabularyViewModel.languagesPresent.collectAsState(initial = emptySet())
+    val allLanguages by languageViewModel.allLanguages.collectAsState(initial = emptyList())
+
+    val availableLanguages = remember(languagesPresent, allLanguages) {
+        val presentIds = languagesPresent.filterNotNull().toSet()
+        allLanguages.filter { it.nameResId in presentIds }
+    }
+
+    val allItems by vocabularyViewModel.vocabularyItems.collectAsState(initial = emptyList())
+    val pairCounts = remember(allItems) {
+        allItems.mapNotNull { item ->
+            val first = item.languageFirstId
+            val second = item.languageSecondId
+            if (first != null && second != null) {
+                val pair = if (first < second) first to second else second to first
+                pair
+            } else {
+                null
+            }
+        }.groupingBy { it }.eachCount()
+    }
+
+    val availablePairs = remember(pairCounts, allLanguages) {
+        pairCounts.entries
+            .sortedByDescending { it.value }
+            .mapNotNull { (pairIds, _) ->
+                val first = allLanguages.find { it.nameResId == pairIds.first }
+                val second = allLanguages.find { it.nameResId == pairIds.second }
+                if (first != null && second != null) first to second else null
+            }
+    }
 
     Column {
-        SectionHeader(title = "Language Pair", actionText = "Change")
-        Row(horizontalArrangement = Arrangement.spacedBy(16.dp)) {
-            LanguageChip(
-                text = "EN → ES",
-                isSelected = selectedPair == 0,
-                modifier = Modifier.weight(1f),
-                onClick = { selectedPair = 0 }
-            )
-            LanguageChip(
-                text = "EN → FR",
-                isSelected = selectedPair == 1,
-                modifier = Modifier.weight(1f),
-                onClick = { selectedPair = 1 }
+        SectionHeader(title = stringResource(R.string.language_pair))
+
+        if (availablePairs.isEmpty()) {
+            Text(
+                text = stringResource(R.string.text_no_dictionary_language_pairs_found),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant
             )
+        } else {
+            FlowRow(
+                horizontalArrangement = Arrangement.spacedBy(12.dp),
+                verticalArrangement = Arrangement.spacedBy(12.dp)
+            ) {
+                availablePairs.forEach { pair ->
+                    val isSelected = selectedPairs.contains(pair)
+                    LanguageChip(
+                        text = "${pair.first.name} → ${pair.second.name}",
+                        isSelected = isSelected,
+                        modifier = Modifier.widthIn(min = 160.dp),
+                        onClick = {
+                            val updated = if (isSelected) {
+                                selectedPairs - pair
+                            } else {
+                                selectedPairs + pair
+                            }
+                            onPairsChanged(updated)
+                        }
+                    )
+                }
+            }
+        }
+
+        Spacer(modifier = Modifier.height(16.dp))
+        Text(
+            text = stringResource(R.string.label_language_direction),
+            style = MaterialTheme.typography.titleMedium,
+            fontWeight = FontWeight.Bold
+        )
+        Text(
+            text = stringResource(R.string.text_language_direction_explanation),
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant
+        )
+        Spacer(modifier = Modifier.height(12.dp))
+        Row(
+            horizontalArrangement = Arrangement.spacedBy(16.dp),
+            modifier = Modifier.fillMaxWidth()
+        ) {
+            Column(modifier = Modifier.weight(1f)) {
+                Text(
+                    text = stringResource(R.string.label_origin_language),
+                    style = MaterialTheme.typography.bodyMedium,
+                    modifier = Modifier.padding(bottom = 8.dp)
+                )
+                eu.gaudian.translator.view.composable.SingleLanguageDropDown(
+                    modifier = Modifier.fillMaxWidth(),
+                    languageViewModel = languageViewModel,
+                    selectedLanguage = selectedOriginLanguage,
+                    onLanguageSelected = onOriginLanguageSelected,
+                    showNoneOption = true,
+                    alternateLanguages = availableLanguages
+                )
+            }
+            Column(modifier = Modifier.weight(1f)) {
+                Text(
+                    text = stringResource(R.string.label_target_language),
+                    style = MaterialTheme.typography.bodyMedium,
+                    modifier = Modifier.padding(bottom = 8.dp)
+                )
+                eu.gaudian.translator.view.composable.SingleLanguageDropDown(
+                    modifier = Modifier.fillMaxWidth(),
+                    languageViewModel = languageViewModel,
+                    selectedLanguage = selectedTargetLanguage,
+                    onLanguageSelected = onTargetLanguageSelected,
+                    showNoneOption = true,
+                    alternateLanguages = availableLanguages
+                )
+            }
         }
     }
 }
@@ -207,32 +492,93 @@ fun LanguageChip(text: String, isSelected: Boolean, modifier: Modifier = Modifie
     }
 }
 
-//TODO uSe our real categories here
-//If there are too many categories (+15) use CategoryDropDown instead of FlowRow
 @OptIn(ExperimentalLayoutApi::class)
 @Composable
-fun CategoriesSection() {
-    val categories = listOf("Travel", "Business", "Food", "Technology", "Slang", "Academic", "Relationships")
-    var selectedCategories by remember { mutableStateOf(setOf("Travel", "Food")) }
+fun CategoriesSection(
+    selectedCategories: List<VocabularyCategory>,
+    onCategoriesChanged: (List<VocabularyCategory>) -> Unit
+) {
+    val activity = androidx.compose.ui.platform.LocalContext.current.findActivity()
+    val categoryViewModel: CategoryViewModel = hiltViewModel(viewModelStoreOwner = activity)
+    val categories by categoryViewModel.categories.collectAsState(initial = emptyList())
 
     Column {
-        SectionHeader(title = "Categories")
+        SectionHeader(title = stringResource(R.string.label_categories))
+
+        val tagCategories = categories.filterIsInstance<TagCategory>()
+        if (tagCategories.size > 15) {
+            CategoryDropdown(
+                onCategorySelected = { selections ->
+                    onCategoriesChanged(selections.filterNotNull())
+                },
+                multipleSelectable = true,
+                onlyLists = false,
+                addCategory = false,
+                modifier = Modifier.fillMaxWidth(),
+                enableSearch = true
+            )
+        } else {
+            FlowRow(
+                horizontalArrangement = Arrangement.spacedBy(8.dp),
+                verticalArrangement = Arrangement.spacedBy(8.dp),
+                modifier = Modifier.fillMaxWidth()
+            ) {
+                tagCategories.forEach { category ->
+                    val isSelected = selectedCategories.contains(category)
+                    Surface(
+                        shape = RoundedCornerShape(20.dp),
+                        color = if (isSelected) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.surfaceVariant,
+                        onClick = {
+                            val updated = if (isSelected) {
+                                selectedCategories - category
+                            } else {
+                                selectedCategories + category
+                            }
+                            onCategoriesChanged(updated)
+                        }
+                    ) {
+                        Text(
+                            text = category.name,
+                            color = if (isSelected) MaterialTheme.colorScheme.onPrimary else MaterialTheme.colorScheme.onSurfaceVariant,
+                            modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp),
+                            style = MaterialTheme.typography.bodyMedium,
+                            fontWeight = if (isSelected) FontWeight.Bold else FontWeight.Normal
+                        )
+                    }
+                }
+            }
+        }
+    }
+}
+//Make it a flow row, as all stages in one row does not work
+@Composable
+fun DifficultySection(
+    selectedStages: List<VocabularyStage>,
+    onStagesChanged: (List<VocabularyStage>) -> Unit
+) {
+    val context = androidx.compose.ui.platform.LocalContext.current
+    Column {
+        SectionHeader(title = stringResource(R.string.label_filter_by_stage))
         FlowRow(
             horizontalArrangement = Arrangement.spacedBy(8.dp),
-            verticalArrangement = Arrangement.spacedBy(8.dp),
-            modifier = Modifier.fillMaxWidth()
+            verticalArrangement = Arrangement.spacedBy(8.dp)
         ) {
-            categories.forEach { category ->
-                val isSelected = selectedCategories.contains(category)
+            VocabularyStage.entries.forEach { stage ->
+                val isSelected = selectedStages.contains(stage)
                 Surface(
                     shape = RoundedCornerShape(20.dp),
                     color = if (isSelected) MaterialTheme.colorScheme.primary else MaterialTheme.colorScheme.surfaceVariant,
                     onClick = {
-                        selectedCategories = if (isSelected) selectedCategories - category else selectedCategories + category
+                        val updated = if (isSelected) {
+                            selectedStages - stage
+                        } else {
+                            selectedStages + stage
+                        }
+                        onStagesChanged(updated)
                     }
                 ) {
                     Text(
-                        text = category,
+                        text = stage.toString(context),
                         color = if (isSelected) MaterialTheme.colorScheme.onPrimary else MaterialTheme.colorScheme.onSurfaceVariant,
                         modifier = Modifier.padding(horizontal = 16.dp, vertical = 8.dp),
                         style = MaterialTheme.typography.bodyMedium,
@@ -244,63 +590,46 @@ fun CategoriesSection() {
     }
 }
 
-//TODO use our real stages here
-//Make it a flow row, as all stages in one row does not work
 @Composable
-fun DifficultySection() {
-    val stages = listOf("New", "Stage 1", "Stage 2", "Stage 3", "Stage 4", "Stage 5", "Learned")
-    var selectedDifficulty by remember { mutableStateOf("Medium") }
-
+fun NumberOfCardsSection(
+    totalAvailable: Int,
+    amount: Int,
+    onAmountChanged: (Int) -> Unit,
+    dueTodayOnly: Boolean,
+    onDueTodayOnlyChanged: (Boolean) -> Unit
+) {
     Column {
-        SectionHeader(title = "Difficulty Level")
-        Surface(
-            shape = RoundedCornerShape(50),
-            color = MaterialTheme.colorScheme.surfaceVariant,
-            modifier = Modifier.fillMaxWidth().height(56.dp)
-        ) {
-            Row(
-                modifier = Modifier.fillMaxSize().padding(4.dp),
-                verticalAlignment = Alignment.CenterVertically
-            ) {
-                stages.forEach { level ->
-                    val isSelected = selectedDifficulty == level
-                    Box(
-                        modifier = Modifier
-                            .weight(1f)
-                            .fillMaxHeight()
-                            .clip(RoundedCornerShape(50))
-                            .background(if (isSelected) MaterialTheme.colorScheme.primary else Color.Transparent)
-                            .clickable { selectedDifficulty = level },
-                        contentAlignment = Alignment.Center
-                    ) {
-                        Text(
-                            text = level,
-                            color = if (isSelected) MaterialTheme.colorScheme.onPrimary else MaterialTheme.colorScheme.onSurfaceVariant,
-                            fontWeight = if (isSelected) FontWeight.Bold else FontWeight.Normal,
-                            style = MaterialTheme.typography.bodyMedium
-                        )
-                    }
-                }
-            }
+        OptionItemSwitch(
+            title = stringResource(R.string.text_due_today_only),
+            description = stringResource(R.string.text_due_today_only_description),
+            checked = dueTodayOnly,
+            onCheckedChange = onDueTodayOnlyChanged
+        )
+
+        Spacer(modifier = Modifier.height(16.dp))
+
+        if (totalAvailable == 0) {
+            Text(
+                text = stringResource(R.string.no_cards_found_for_the_selected_filters),
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.error
+            )
+            return@Column
         }
-    }
-}
 
-//TODO add optionitemswitch "Die Today Only", make sure that the amount of cards displayed is correct
+        val maxAvailable = totalAvailable.coerceAtLeast(1)
+        val coercedAmount = amount.coerceIn(1, maxAvailable)
+        if (coercedAmount != amount) {
+            onAmountChanged(coercedAmount)
+        }
 
-//TODO use the slider from ImportVocabulary dialog here, also with the quick selection of cards
-@Composable
-fun NumberOfCardsSection() {
-    var sliderPosition by remember { mutableFloatStateOf(25f) }
-
-    Column {
         Row(
             modifier = Modifier.fillMaxWidth().padding(bottom = 8.dp),
             horizontalArrangement = Arrangement.SpaceBetween,
             verticalAlignment = Alignment.CenterVertically
         ) {
             Text(
-                text = "NUMBER OF CARDS",
+                text = stringResource(R.string.text_amount_of_cards).uppercase(),
                 style = MaterialTheme.typography.labelMedium,
                 fontWeight = FontWeight.Bold,
                 letterSpacing = 1.sp,
@@ -311,7 +640,7 @@ fun NumberOfCardsSection() {
                 color = MaterialTheme.colorScheme.primary,
             ) {
                 Text(
-                    text = sliderPosition.toInt().toString(),
+                    text = "$coercedAmount / $totalAvailable",
                     color = MaterialTheme.colorScheme.onPrimary,
                     style = MaterialTheme.typography.labelMedium,
                     fontWeight = FontWeight.Bold,
@@ -320,59 +649,73 @@ fun NumberOfCardsSection() {
             }
         }
 
-        Slider(
-            value = sliderPosition,
-            onValueChange = { sliderPosition = it },
-            valueRange = 5f..50f,
-            steps = 45
+        AppSlider(
+            value = coercedAmount.toFloat(),
+            onValueChange = { onAmountChanged(it.toInt().coerceIn(1, maxAvailable)) },
+            valueRange = 1f..maxAvailable.toFloat(),
+            steps = if (maxAvailable > 1) maxAvailable - 2 else 0,
+            modifier = Modifier.fillMaxWidth()
         )
 
-        Row(
-            modifier = Modifier.fillMaxWidth(),
-            horizontalArrangement = Arrangement.SpaceBetween
-        ) {
-            Text("5 CARDS", style = MaterialTheme.typography.labelSmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
-            Text("50 CARDS", style = MaterialTheme.typography.labelSmall, color = MaterialTheme.colorScheme.onSurfaceVariant)
+        val quickSelectValues = listOf(10, 25, 50, 100)
+        val availableQuickSelections = quickSelectValues.filter { it <= maxAvailable }
+        if (availableQuickSelections.isNotEmpty()) {
+            Spacer(modifier = Modifier.height(12.dp))
+            Row(
+                modifier = Modifier.fillMaxWidth(),
+                horizontalArrangement = Arrangement.spacedBy(8.dp)
+            ) {
+                availableQuickSelections.forEach { value ->
+                    AppOutlinedButton(
+                        onClick = { onAmountChanged(value) },
+                        modifier = Modifier.weight(1f)
+                    ) {
+                        Text(value.toString())
+                    }
+                }
+            }
         }
     }
 }
-
-//TODO use our four question types here, from StartScreen.kt
+//TODO use our four question types here, from StartScreen.kt, user must select at least one
 @Composable
-fun QuestionTypesSection() {
-    var selectedTypes by remember { mutableStateOf(setOf("Multiple Choice", "Spelling")) }
-
+fun QuestionTypesSection(
+    selectedTypes: Set<VocabularyExerciseType>,
+    onTypeSelected: (VocabularyExerciseType) -> Unit
+) {
     Column {
-        SectionHeader(title = "Question Types")
+        SectionHeader(title = stringResource(R.string.text_question_types))
 
         QuestionTypeCard(
-            title = "Multiple Choice",
-            subtitle = "Choose the correct meaning",
-            icon = Icons.Default.List,
-            isSelected = selectedTypes.contains("Multiple Choice"),
-            onClick = {
-                selectedTypes = if (selectedTypes.contains("Multiple Choice")) selectedTypes - "Multiple Choice" else selectedTypes + "Multiple Choice"
-            }
+            title = stringResource(R.string.label_guessing_exercise),
+            subtitle = stringResource(R.string.flip_card),
+            icon = AppIcons.Guessing,
+            isSelected = selectedTypes.contains(VocabularyExerciseType.GUESSING),
+            onClick = { onTypeSelected(VocabularyExerciseType.GUESSING) }
         )
         Spacer(modifier = Modifier.height(12.dp))
         QuestionTypeCard(
-            title = "Spelling",
-            subtitle = "Type the translated word",
-            icon = Icons.Default.Edit,
-            isSelected = selectedTypes.contains("Spelling"),
-            onClick = {
-                selectedTypes = if (selectedTypes.contains("Spelling")) selectedTypes - "Spelling" else selectedTypes + "Spelling"
-            }
+            title = stringResource(R.string.label_spelling_exercise),
+            subtitle = stringResource(R.string.type_the_translation),
+            icon = AppIcons.SpellCheck,
+            isSelected = selectedTypes.contains(VocabularyExerciseType.SPELLING),
+            onClick = { onTypeSelected(VocabularyExerciseType.SPELLING) }
         )
         Spacer(modifier = Modifier.height(12.dp))
         QuestionTypeCard(
-            title = "Listening",
-            subtitle = "Recognize spoken words",
-            icon = Icons.Default.Hearing,
-            isSelected = selectedTypes.contains("Listening"),
-            onClick = {
-                selectedTypes = if (selectedTypes.contains("Listening")) selectedTypes - "Listening" else selectedTypes + "Listening"
-            }
+            title = stringResource(R.string.label_multiple_choice_exercise),
+            subtitle = stringResource(R.string.label_choose_exercise_types),
+            icon = AppIcons.CheckList,
+            isSelected = selectedTypes.contains(VocabularyExerciseType.MULTIPLE_CHOICE),
+            onClick = { onTypeSelected(VocabularyExerciseType.MULTIPLE_CHOICE) }
+        )
+        Spacer(modifier = Modifier.height(12.dp))
+        QuestionTypeCard(
+            title = stringResource(R.string.label_word_jumble_exercise),
+            subtitle = stringResource(R.string.text_assemble_the_word_here),
+            icon = AppIcons.Extension,
+            isSelected = selectedTypes.contains(VocabularyExerciseType.WORD_JUMBLE),
+            onClick = { onTypeSelected(VocabularyExerciseType.WORD_JUMBLE) }
         )
     }
 }
@@ -413,36 +756,88 @@ fun QuestionTypeCard(title: String, subtitle: String, icon: ImageVector, isSelec
     }
 }
 @Composable
-fun BottomButtonSection() {
+fun BottomButtonSection(
+    enabled: Boolean,
+    amount: Int,
+    onStart: () -> Unit
+) {
     Box(
         modifier = Modifier
             .fillMaxWidth()
             .padding(24.dp)
     ) {
-        Button(
-            onClick = { /* TODO: Start Session */ },
+        AppButton(
+            onClick = onStart,
             modifier = Modifier
                 .fillMaxWidth()
                 .height(56.dp),
-            shape = RoundedCornerShape(28.dp),
-            colors = ButtonDefaults.buttonColors(containerColor = MaterialTheme.colorScheme.primary)
+            enabled = enabled,
+            shape = RoundedCornerShape(28.dp)
         ) {
             Row(
                 horizontalArrangement = Arrangement.Center,
                 verticalAlignment = Alignment.CenterVertically
             ) {
                 Text(
-                    text = "Start Session",
+                    text = stringResource(R.string.label_start_exercise_2d, amount),
                     style = MaterialTheme.typography.titleMedium,
                     fontWeight = FontWeight.Bold
                 )
                 Spacer(modifier = Modifier.width(8.dp))
                 Icon(
                     imageVector = Icons.Default.PlayArrow,
-                    contentDescription = "Play",
+                    contentDescription = stringResource(R.string.cd_play),
                     modifier = Modifier.size(20.dp)
                 )
             }
         }
     }
+}
+
+@Composable
+private fun StartExerciseSettingsBottomSheet(
+    sheetState: SheetState,
+    shuffleCards: Boolean,
+    onShuffleCardsChanged: (Boolean) -> Unit,
+    shuffleLanguages: Boolean,
+    onShuffleLanguagesChanged: (Boolean) -> Unit,
+    trainingMode: Boolean,
+    onTrainingModeChanged: (Boolean) -> Unit,
+    onDismiss: () -> Unit
+) {
+    ModalBottomSheet(
+        onDismissRequest = onDismiss,
+        sheetState = sheetState
+    ) {
+        Column(
+            modifier = Modifier
+                .fillMaxWidth()
+                .padding(horizontal = 20.dp, vertical = 16.dp),
+            verticalArrangement = Arrangement.spacedBy(12.dp)
+        ) {
+            Text(
+                text = stringResource(R.string.options),
+                style = MaterialTheme.typography.titleMedium,
+                fontWeight = FontWeight.Bold
+            )
+            OptionItemSwitch(
+                title = stringResource(R.string.shuffle_cards),
+                description = stringResource(R.string.text_shuffle_card_order_description),
+                checked = shuffleCards,
+                onCheckedChange = onShuffleCardsChanged
+            )
+            OptionItemSwitch(
+                title = stringResource(R.string.text_shuffle_languages),
+                description = stringResource(R.string.text_shuffle_languages_description),
+                checked = shuffleLanguages,
+                onCheckedChange = onShuffleLanguagesChanged
+            )
+            OptionItemSwitch(
+                title = stringResource(R.string.label_training_mode),
+                description = stringResource(R.string.text_training_mode_description),
+                checked = trainingMode,
+                onCheckedChange = onTrainingModeChanged
+            )
+        }
+    }
 }

app/src/main/java/eu/gaudian/translator/view/vocabulary/VocabularyExerciseHostScreen.kt

@@ -19,7 +19,6 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.mutableIntStateOf
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
-import androidx.compose.runtime.saveable.rememberSaveable
 import androidx.compose.runtime.setValue
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
@@ -28,10 +27,8 @@ import androidx.compose.ui.res.stringResource
 import androidx.hilt.lifecycle.viewmodel.compose.hiltViewModel
 import androidx.navigation.NavController
 import eu.gaudian.translator.R
-import eu.gaudian.translator.model.Language
 import eu.gaudian.translator.utils.findActivity
 import eu.gaudian.translator.view.composable.AppAlertDialog
-import eu.gaudian.translator.viewmodel.ExerciseConfig
 import eu.gaudian.translator.viewmodel.ScreenState
 import eu.gaudian.translator.viewmodel.VocabularyExerciseViewModel
 import eu.gaudian.translator.viewmodel.VocabularyViewModel
@@ -57,14 +54,7 @@ fun VocabularyExerciseHostScreen(
 
     val cardSet by vocabularyViewModel.cardSet.collectAsState()
     val screenState by exerciseViewModel.screenState.collectAsState()
-
-    var shuffleCards by rememberSaveable { mutableStateOf(false) }
-    var shuffleLanguages by remember { mutableStateOf(false) }
-    var trainingMode by remember { mutableStateOf(false) }
-    var dueTodayOnly by remember { mutableStateOf(false) }
-    var selectedExerciseTypes by remember { mutableStateOf(setOf(VocabularyExerciseType.GUESSING)) }
-    var selectedOriginLanguage by remember { mutableStateOf<Language?>(null) }
-    var selectedTargetLanguage by remember { mutableStateOf<Language?>(null) }
+    val pendingConfig by exerciseViewModel.pendingExerciseConfig.collectAsState()
 
     var finalScore by remember { mutableIntStateOf(0) }
     var finalWrongAnswers by remember { mutableIntStateOf(0) }
@@ -76,16 +66,40 @@ fun VocabularyExerciseHostScreen(
         false
     }
 
-    LaunchedEffect(Unit) {
-        // Reset exercise state when starting fresh
-        exerciseViewModel.resetExercise()
-        
-        vocabularyViewModel.prepareExercise(
-            categoryIdsAsJson,
-            stageNamesAsJson,
-            languageIdsAsJson,
-            dailyOnly = dailyOnly,
-        )
+    LaunchedEffect(categoryIdsAsJson, stageNamesAsJson, languageIdsAsJson, dailyOnly) {
+        // Only reset and prepare if the host is opened via explicit filters.
+        if (!categoryIdsAsJson.isNullOrBlank() || !stageNamesAsJson.isNullOrBlank() || !languageIdsAsJson.isNullOrBlank() || dailyOnly) {
+            exerciseViewModel.resetExercise()
+            vocabularyViewModel.prepareExercise(
+                categoryIdsAsJson,
+                stageNamesAsJson,
+                languageIdsAsJson,
+                dailyOnly = dailyOnly,
+            )
+        }
+    }
+
+    LaunchedEffect(cardSet, screenState, pendingConfig) {
+        if (cardSet != null && screenState == ScreenState.START) {
+            val items = cardSet?.cards.orEmpty()
+            if (items.isNotEmpty()) {
+                val selectedCount = pendingConfig.exerciseItemCount
+                    .takeIf { it > 0 }
+                    ?: items.size
+                val finalItems = if (pendingConfig.shuffleCards) {
+                    items.shuffled().take(selectedCount)
+                } else {
+                    items.take(selectedCount)
+                }
+                exerciseViewModel.startExerciseWithConfig(
+                    finalItems,
+                    pendingConfig.copy(
+                        exerciseItemCount = finalItems.size,
+                        originalExerciseItems = finalItems
+                    )
+                )
+            }
+        }
     }
 
     if (cardSet == null && screenState != ScreenState.START) {
@@ -95,68 +109,9 @@ fun VocabularyExerciseHostScreen(
     } else {
         when (screenState) {
             ScreenState.START -> {
-                StartScreen(
-                    cardSet = cardSet,
-                    onStartClicked = { finalItems ->
-                        exerciseViewModel.startExerciseWithConfig(
-                            finalItems,
-                            ExerciseConfig(
-                                shuffleCards = shuffleCards,
-                                shuffleLanguages = shuffleLanguages,
-                                trainingMode = trainingMode,
-                                dueTodayOnly = dueTodayOnly,
-                                selectedExerciseTypes = selectedExerciseTypes,
-                                exerciseItemCount = finalItems.size,
-                                originalExerciseItems = finalItems,
-                                originLanguageId = selectedOriginLanguage?.nameResId,
-                                targetLanguageId = selectedTargetLanguage?.nameResId
-                            )
-                        )
-                    },
-                    onClose = onClose,
-                    shuffleCards = shuffleCards,
-                    onShuffleCardsChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        shuffleCards = it
-                    },
-                    shuffleLanguages = shuffleLanguages,
-                    onShuffleLanguagesChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        shuffleLanguages = it
-                    },
-                    trainingMode = trainingMode,
-                    onTrainingModeChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        trainingMode = it
-                        exerciseViewModel.onTrainingModeChanged(it)
-                    },
-                    hideTodayOnlySwitch = dailyOnly,
-                    dueTodayOnly = dueTodayOnly,
-                    onDueTodayOnlyChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        dueTodayOnly = it
-                    },
-                    selectedExerciseTypes = selectedExerciseTypes,
-                    onExerciseTypeSelected = { type ->
-                        val currentTypes = selectedExerciseTypes.toMutableSet()
-                        if (type in currentTypes) {
-                            if (currentTypes.size > 1) currentTypes.remove(type)
-                        } else {
-                            currentTypes.add(type)
-                        }
-                        selectedExerciseTypes = currentTypes
-                    },
-                    selectedOriginLanguage = selectedOriginLanguage,
-                    onOriginLanguageChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        selectedOriginLanguage = it
-                    },
-                    selectedTargetLanguage = selectedTargetLanguage,
-                    onTargetLanguageChanged = {
-                        @Suppress("AssignedValueIsNeverRead")
-                        selectedTargetLanguage = it
-                    }
-                )
+                Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+                    CircularProgressIndicator()
+                }
             }
             ScreenState.EXERCISE -> {
                 ExerciseScreen(

app/src/main/java/eu/gaudian/translator/viewmodel/VocabularyExerciseViewModel.kt

@@ -90,6 +90,9 @@ class VocabularyExerciseViewModel @Inject constructor(
 
     // Exercise configuration state
     private val _exerciseConfig = MutableStateFlow(ExerciseConfig())
+    private val _pendingExerciseConfig = MutableStateFlow(ExerciseConfig())
+
+    val pendingExerciseConfig: StateFlow<ExerciseConfig> = _pendingExerciseConfig.asStateFlow()
 
     // Exercise results state
     private val _exerciseResults = MutableStateFlow(ExerciseResults())
@@ -399,12 +402,17 @@ class VocabularyExerciseViewModel @Inject constructor(
         config: ExerciseConfig
     ) {
         _exerciseConfig.value = config
+        _pendingExerciseConfig.value = config
         _totalItems.value = items.size
         _originalItems.value = items
         startExercise(items, config.selectedExerciseTypes, config.shuffleLanguages)
         _screenState.value = ScreenState.EXERCISE
     }
 
+    fun updatePendingExerciseConfig(config: ExerciseConfig) {
+        _pendingExerciseConfig.value = config
+    }
+
     fun finishExercise(score: Int, wrongAnswers: Int) {
         _exerciseResults.value = ExerciseResults(score, wrongAnswers)
         _screenState.value = ScreenState.RESULT

app/src/main/java/eu/gaudian/translator/viewmodel/VocabularyViewModel.kt

@@ -617,6 +617,56 @@ class VocabularyViewModel @Inject constructor(
         }
     }
 
+    fun filterVocabularyItemsByPairs(
+        languagePairs: List<Pair<Int, Int>>?,
+        query: String?,
+        categoryIds: List<Int>?,
+        stages: List<VocabularyStage>?,
+        wordClass: String? = null,
+        dueTodayOnly: Boolean = false,
+        sortOrder: SortOrder
+    ): Flow<List<VocabularyItem>> {
+        val baseFlow = filterVocabularyItems(
+            languages = null,
+            query = query,
+            categoryIds = categoryIds,
+            stage = null,
+            wordClass = wordClass,
+            dueTodayOnly = dueTodayOnly,
+            sortOrder = sortOrder
+        )
+
+        val normalizedPairs = languagePairs
+            ?.map { pair -> if (pair.first < pair.second) pair else pair.second to pair.first }
+            ?.toSet()
+
+        return combine(baseFlow, stageMapping) { items, stageMap ->
+            var filteredItems = items
+
+            if (!normalizedPairs.isNullOrEmpty()) {
+                filteredItems = filteredItems.filter { item ->
+                    val firstId = item.languageFirstId
+                    val secondId = item.languageSecondId
+                    if (firstId == null || secondId == null) {
+                        false
+                    } else {
+                        val normalizedPair = if (firstId < secondId) firstId to secondId else secondId to firstId
+                        normalizedPairs.contains(normalizedPair)
+                    }
+                }
+            }
+
+            if (!stages.isNullOrEmpty()) {
+                filteredItems = filteredItems.filter { item ->
+                    val stage = stageMap[item.id] ?: VocabularyStage.NEW
+                    stage in stages
+                }
+            }
+
+            filteredItems
+        }
+    }
+
     suspend fun generateVocabularyItems(category: String, amount: Int) {
         val selectedSourceLanguage = languageRepository.loadSelectedSourceLanguage().first()
         val selectedTargetLanguage = languageRepository.loadSelectedTargetLanguage().first()

app/src/main/res/values-de-rDE/strings.xml

@@ -292,7 +292,7 @@
     <string name="label_start_exercise_2d">Übung starten (%1$d)</string>
     <string name="number_of_cards">Anzahl der Karten: %1$d / %2$d</string>
     <string name="no_cards_found_for_the_selected_filters">Keine Karten für die gewählten Filter gefunden.</string>
-    <string name="label_choose_exercise_types">Übungstypen wählen</string>
+    <string name="label_choose_exercise_types">Die richtige Antwort wählen</string>
     <string name="options">Optionen</string>
     <string name="shuffle_cards">Karten mischen</string>
     <string name="quit">Beenden</string>
@@ -338,7 +338,7 @@
     <string name="statistics_are_loading">Statistiken werden geladen…</string>
     <string name="to_d">nach %1$s</string>
     <string name="label_translate_from_2d">Übersetze von %1$s</string>
-    <string name="text_assemble_the_word_here">Bilde das Wort hier</string>
+    <string name="text_assemble_the_word_here">Bringe die Buchstaben in Reihenfolge</string>
     <string name="correct_answer">Richtige Antwort: %1$s</string>
     <string name="label_quit_exercise_qm">Übung beenden?</string>
     <string name="text_are_you_sure_you_want_to_quit_your_progress_in_this_session_will_be_lost">Möchtest du wirklich beenden? Dein Fortschritt in dieser Sitzung geht verloren.</string>
@@ -680,7 +680,7 @@
     <string name="label_language_direction">Sprachenrichtung
 </string>
     <string name="text_language_direction_explanation">Du kannst eine optionale Einstellung vornehmen, welche Sprache zuerst oder zweit kommen soll.</string>
-    <string name="label_guessing_exercise">Vermutung</string>
+    <string name="label_guessing_exercise">Raten</string>
     <string name="label_spelling_exercise">Rechtschreibung</string>
     <string name="label_multiple_choice_exercise">Multiple Choice</string>
     <string name="label_word_jumble_exercise">Wortwirrwarr</string>