Refactor Onboarding name validation to use state-driven UI

app/src/main/java/com/example/theloop/OnboardingViewModel.kt

@@ -18,16 +18,23 @@ class OnboardingViewModel @Inject constructor(
     private val _name = MutableStateFlow("")
     val name: StateFlow<String> = _name.asStateFlow()
 
+    private val _nameError = MutableStateFlow<Int?>(null)
+    val nameError: StateFlow<Int?> = _nameError.asStateFlow()
+
     fun onNameChange(newName: String) {
         _name.value = newName
+        _nameError.value = null
     }
 
     fun saveName(): Boolean {
         val isNameValid = name.value.isNotBlank()
         if (isNameValid) {
+            _nameError.value = null
             viewModelScope.launch {
                 userPreferencesRepository.saveUserName(name.value)
             }
+        } else {
+            _nameError.value = R.string.error_name_blank
         }
         return isNameValid
     }

app/src/main/java/com/example/theloop/ui/screens/OnboardingScreen.kt

@@ -13,6 +13,7 @@ import androidx.compose.runtime.*
 import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.res.stringResource
 import androidx.compose.ui.unit.dp
 import androidx.hilt.navigation.compose.hiltViewModel
 import androidx.health.connect.client.HealthConnectClient
@@ -28,6 +29,7 @@ fun OnboardingScreen(
     val context = LocalContext.current
     var currentStep by remember { mutableIntStateOf(0) }
     val name by viewModel.name.collectAsState()
+    val nameError by viewModel.nameError.collectAsState()
     val totalSteps = 5
 
     // Permissions state
@@ -99,7 +101,6 @@ fun OnboardingScreen(
                         if (currentStep == 0) {
                             // Save Name
                             if (!viewModel.saveName()) {
-                                Toast.makeText(context, "Name cannot be blank", Toast.LENGTH_SHORT).show()
                                 return@Button
                             }
                         }
@@ -127,7 +128,7 @@ fun OnboardingScreen(
             verticalArrangement = Arrangement.Center
         ) {
             when (currentStep) {
-                0 -> WelcomeStep(name, viewModel::onNameChange)
+                0 -> WelcomeStep(name, nameError, viewModel::onNameChange)
                 1 -> PermissionStep(
                     title = "Enable Location",
                     description = "We need your location to show local weather.",
@@ -167,7 +168,7 @@ fun OnboardingScreen(
 }
 
 @Composable
-fun WelcomeStep(name: String, onNameChange: (String) -> Unit) {
+fun WelcomeStep(name: String, nameError: Int?, onNameChange: (String) -> Unit) {
     Text("Welcome to The Loop", style = MaterialTheme.typography.displaySmall)
     Spacer(Modifier.height(16.dp))
     Text("Your daily dashboard for life.", style = MaterialTheme.typography.bodyLarge)
@@ -177,7 +178,9 @@ fun WelcomeStep(name: String, onNameChange: (String) -> Unit) {
         onValueChange = onNameChange,
         label = { Text("What's your name?") },
         singleLine = true,
-        modifier = Modifier.fillMaxWidth()
+        modifier = Modifier.fillMaxWidth(),
+        isError = nameError != null,
+        supportingText = nameError?.let { { Text(stringResource(it)) } }
     )
 }
 

app/src/main/res/values/strings.xml

@@ -2,6 +2,7 @@
     <string name="app_name">The Loop</string>
 
     <!-- UI Strings -->
+    <string name="error_name_blank">Name cannot be blank</string>
     <string name="select_temperature_unit">Select Temperature Unit</string>
     <string name="cancel">Cancel</string>
     <string name="unknown_location">Unknown Location</string>

app/src/test/java/com/example/theloop/OnboardingViewModelTest.kt

@@ -0,0 +1,58 @@
+package com.example.theloop
+
+import androidx.test.core.app.ApplicationProvider
+import com.example.theloop.data.repository.UserPreferencesRepository
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertNull
+import org.junit.Assert.assertTrue
+import org.junit.Before
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+
+@RunWith(RobolectricTestRunner::class)
+@Config(sdk = [33])
+class OnboardingViewModelTest {
+
+    private lateinit var viewModel: OnboardingViewModel
+    private lateinit var userPreferencesRepository: UserPreferencesRepository
+
+    @Before
+    fun setup() {
+        val context = ApplicationProvider.getApplicationContext<android.content.Context>()
+        userPreferencesRepository = UserPreferencesRepository(context)
+        viewModel = OnboardingViewModel(userPreferencesRepository)
+    }
+
+    @Test
+    fun saveName_withBlankName_setsErrorAndReturnsFalse() {
+        viewModel.onNameChange("   ")
+        val result = viewModel.saveName()
+
+        assertFalse(result)
+        assertEquals(R.string.error_name_blank, viewModel.nameError.value)
+    }
+
+    @Test
+    fun saveName_withValidName_clearsErrorAndReturnsTrue() {
+        viewModel.onNameChange("Valid Name")
+        val result = viewModel.saveName()
+
+        assertTrue(result)
+        assertNull(viewModel.nameError.value)
+    }
+
+    @Test
+    fun onNameChange_clearsError() {
+        // Set error first
+        viewModel.onNameChange("")
+        viewModel.saveName()
+        assertEquals(R.string.error_name_blank, viewModel.nameError.value)
+
+        // Change name
+        viewModel.onNameChange("New Name")
+        assertNull(viewModel.nameError.value)
+    }
+}