observe live data for auth token existence in root view

android/Omnivore/app/build.gradle

@@ -71,6 +71,7 @@ dependencies {
     implementation("androidx.lifecycle:lifecycle-viewmodel-compose:$lifecycle_version")
     // LiveData
     implementation("androidx.lifecycle:lifecycle-livedata-ktx:$lifecycle_version")
+    implementation("androidx.compose.runtime:runtime-livedata:1.2.1")
 
     // Saved state module for ViewModel
     implementation("androidx.lifecycle:lifecycle-viewmodel-savedstate:$lifecycle_version")

android/Omnivore/app/src/main/java/app/omnivore/omnivore/DatastoreRepository.kt

@@ -2,12 +2,15 @@ package app.omnivore.omnivore
 
 import android.content.Context
 import androidx.datastore.core.DataStore
-import androidx.datastore.preferences.core.Preferences
-import androidx.datastore.preferences.core.edit
-import androidx.datastore.preferences.core.intPreferencesKey
-import androidx.datastore.preferences.core.stringPreferencesKey
+import androidx.datastore.dataStore
+import androidx.datastore.preferences.core.*
 import androidx.datastore.preferences.preferencesDataStore
+import androidx.lifecycle.asLiveData
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.flow.first
+import kotlinx.coroutines.flow.map
+import java.io.IOException
 import javax.inject.Inject
 
 private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(
@@ -15,6 +18,7 @@ private val Context.dataStore: DataStore<Preferences> by preferencesDataStore(
 )
 
 interface DatastoreRepository {
+  val hasAuthTokenFlow: Flow<Boolean>
   suspend fun putString(key: String, value: String)
   suspend fun putInt(key: String, value: Int)
   suspend fun getString(key: String): String?
@@ -49,4 +53,11 @@ class OmnivoreDatastore @Inject constructor(
     val preferences = context.dataStore.data.first()
     return preferences[preferencesKey]
   }
+
+  override val hasAuthTokenFlow: Flow<Boolean> = context
+    .dataStore.data.map { preferences ->
+      val key = stringPreferencesKey(DatastoreKeys.omnivoreAuthToken)
+      val token = preferences[key]
+      token != null
+    }
 }

android/Omnivore/app/src/main/java/app/omnivore/omnivore/LoginViewModel.kt

@@ -2,9 +2,12 @@ package app.omnivore.omnivore
 
 import android.content.ContentValues
 import android.util.Log
-import androidx.lifecycle.ViewModel
-import androidx.lifecycle.viewModelScope
+import androidx.compose.runtime.getValue
+import androidx.compose.runtime.mutableStateOf
+import androidx.compose.runtime.setValue
+import androidx.lifecycle.*
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.launch
 import javax.inject.Inject
 
@@ -12,6 +15,11 @@ import javax.inject.Inject
 class LoginViewModel @Inject constructor(
   private val datastoreRepo: DatastoreRepository
 ): ViewModel() {
+  val hasAuthTokenLiveData: LiveData<Boolean> = datastoreRepo
+    .hasAuthTokenFlow
+    .distinctUntilChanged()
+    .asLiveData()
+
   fun login(email: String, password: String) {
     val emailLogin = RetrofitHelper.getInstance().create(EmailLoginSubmit::class.java)
 

android/Omnivore/app/src/main/java/app/omnivore/omnivore/MainActivity.kt

@@ -22,6 +22,7 @@ import androidx.compose.ui.text.input.PasswordVisualTransformation
 import androidx.compose.ui.unit.dp
 import app.omnivore.omnivore.ui.theme.OmnivoreTheme
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.livedata.observeAsState
 import androidx.compose.runtime.setValue
 import dagger.hilt.android.AndroidEntryPoint
 
@@ -36,13 +37,37 @@ class MainActivity : ComponentActivity() {
       OmnivoreTheme {
         // A surface container using the 'background' color from the theme
         Surface(modifier = Modifier.fillMaxSize(), color = MaterialTheme.colors.background) {
-          LoginView(viewModel)
+          rootView(viewModel)
         }
       }
     }
   }
 }
 
+@Composable
+fun rootView(viewModel: LoginViewModel) {
+  val hasAuthToken: Boolean by viewModel.hasAuthTokenLiveData.observeAsState(false)
+
+  if (hasAuthToken) {
+    loggedInView()
+  } else {
+    LoginView(viewModel)
+  }
+}
+
+@Composable
+fun loggedInView() {
+  Column(
+    verticalArrangement = Arrangement.Center,
+    horizontalAlignment = Alignment.CenterHorizontally,
+    modifier = Modifier
+      .background(MaterialTheme.colors.background)
+      .fillMaxSize()
+  ) {
+    Text("You have a valid auth token. Nice. Go save something in Chrome!")
+  }
+}
+
 @Composable
 fun LoginView(viewModel: LoginViewModel) {
   var email by rememberSaveable { mutableStateOf("") }