Implemented network-based authentication and secure token storage

- Replaced mock login logic in `LoginViewModel` with actual API calls using Retrofit.
- Integrated `EncryptedSharedPreferences` via a new `TokenStorage` class to securely persist access and refresh tokens.
- Added `RetrofitProvider` and `APIService` to handle network requests and JSON serialization.
- Updated `Account` entity and database schema (version 2) to include user roles, enabling destructive migration for development.
- Added necessary internet permissions and allowed cleartext traffic in `AndroidManifest.xml`.
- Included dependencies for Retrofit, OkHttp logging, and AndroidX Security.

app/build.gradle.kts

@@ -65,4 +65,12 @@ dependencies {
     val room_version = "2.8.4"
     implementation("androidx.room:room-runtime:$room_version")
     ksp("androidx.room:room-compiler:$room_version")
+
+    // Retrofit + Gson
+    implementation("com.squareup.retrofit2:retrofit:2.9.0")
+    implementation("com.squareup.retrofit2:converter-gson:2.9.0")
+    // OkHttp logging (debug)
+    implementation("com.squareup.okhttp3:logging-interceptor:4.9.3")
+    // AndroidX Security (EncryptedSharedPreferences)
+    implementation("androidx.security:security-crypto:1.1.0-alpha03")
 }

app/src/main/AndroidManifest.xml

@@ -2,6 +2,8 @@
 <manifest xmlns:android="http://schemas.android.com/apk/res/android"
     xmlns:tools="http://schemas.android.com/tools">
 
+    <uses-permission android:name="android.permission.INTERNET" />
+
     <application
         android:allowBackup="true"
         android:dataExtractionRules="@xml/data_extraction_rules"
@@ -10,6 +12,7 @@
         android:label="@string/app_name"
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
+        android:usesCleartextTraffic="true"
         android:theme="@style/Theme.ShapPlanner">
         <activity
             android:name=".activities.MainActivity"

app/src/main/java/de/miaurizius/shap_planner/TokenStorage.kt

@@ -0,0 +1,39 @@
+package de.miaurizius.shap_planner
+
+import android.content.Context
+import androidx.security.crypto.EncryptedSharedPreferences
+import androidx.security.crypto.MasterKey
+
+class TokenStorage(context: Context) {
+
+    private val masterKey = MasterKey.Builder(context)
+        .setKeyScheme(MasterKey.KeyScheme.AES256_GCM)
+        .build()
+
+    private val prefs = EncryptedSharedPreferences.create(
+        context,
+        "wg_token_prefs",
+        masterKey,
+        EncryptedSharedPreferences.PrefKeyEncryptionScheme.AES256_SIV,
+        EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
+    )
+
+    fun saveTokens(accountId: String, accessToken: String, refreshToken: String) {
+        prefs.edit()
+            .putString("access_$accountId", accessToken)
+            .putString("refresh_$accountId", refreshToken)
+            .apply()
+    }
+
+    fun getAccess(accountId: String): String? = prefs.getString("access_$accountId", null)
+    fun getRefresh(accountId: String): String? = prefs.getString("refresh_$accountId", null)
+
+    fun clearTokens(accountId: String) {
+        prefs.edit()
+            .remove("access_$accountId")
+            .remove("refresh_$accountId")
+            .apply()
+    }
+
+
+}

app/src/main/java/de/miaurizius/shap_planner/activities/MainActivity.kt

@@ -53,7 +53,7 @@ class MainActivity : ComponentActivity() {
 //        enableEdgeToEdge()
 
         val prefs = UserPreferences(this)
-        val loginViewModel = LoginViewModel(prefs)
+        val loginViewModel = LoginViewModel(prefs, applicationContext)
 
         val database = AppDatabase.getDatabase(applicationContext)
         val dao = database.accountDao()

app/src/main/java/de/miaurizius/shap_planner/entities/Account.kt

@@ -17,6 +17,7 @@ data class Account (
     val wgName: String,
     val avatarUrl: String? = null,
     val serverUrl: String,
+    val role: String,
 )
 
 @Dao

app/src/main/java/de/miaurizius/shap_planner/network/APIService.kt

@@ -0,0 +1,17 @@
+package de.miaurizius.shap_planner.network
+
+import retrofit2.Response
+import retrofit2.http.Body
+import retrofit2.http.POST
+
+data class LoginRequest(val username: String, val password: String)
+data class LoginUser(val id: String, val username: String, val role: String, val avatarUrl: String?)
+data class LoginResponse(val access_token: String, val refresh_token: String, val user: LoginUser, val wgName: String)
+
+interface APIService {
+    @POST("api/login")
+    suspend fun login(@Body req: LoginRequest): Response<LoginResponse>
+
+    @POST("api/refresh")
+    suspend fun refresh(@Body req: Map<String, String>): Response<Map<String, String>>
+}

app/src/main/java/de/miaurizius/shap_planner/network/RetrofitProvider.kt

@@ -0,0 +1,28 @@
+package de.miaurizius.shap_planner.network
+
+import okhttp3.OkHttpClient
+import okhttp3.logging.HttpLoggingInterceptor
+import retrofit2.Retrofit
+import retrofit2.converter.gson.GsonConverterFactory
+
+object RetrofitProvider {
+
+    fun create(serverUrl: String): APIService {
+        val base = if (serverUrl.endsWith("/")) serverUrl else "$serverUrl/"
+
+        val logger = HttpLoggingInterceptor().apply { level = HttpLoggingInterceptor.Level.BASIC }
+
+        val client = OkHttpClient.Builder()
+            .addInterceptor(logger)
+            .build()
+
+        val retrofit = Retrofit.Builder()
+            .baseUrl(base)
+            .client(client)
+            .addConverterFactory(GsonConverterFactory.create())
+            .build()
+
+        return retrofit.create(APIService::class.java)
+    }
+
+}

app/src/main/java/de/miaurizius/shap_planner/room/AppDatabase.kt

@@ -7,7 +7,7 @@ import androidx.room.RoomDatabase
 import de.miaurizius.shap_planner.entities.Account
 import de.miaurizius.shap_planner.entities.AccountDao
 
-@Database(entities = [Account::class], version = 1)
+@Database(entities = [Account::class], version = 2)
 abstract class AppDatabase : RoomDatabase() {
     abstract fun accountDao(): AccountDao
     companion object {
@@ -20,7 +20,7 @@ abstract class AppDatabase : RoomDatabase() {
                     context.applicationContext,
                     AppDatabase::class.java,
                     "shap_planner_database"
-                ).build()
+                ).fallbackToDestructiveMigration(true).build()
                 INSTANCE = instance
                 instance
             }

app/src/main/java/de/miaurizius/shap_planner/viewmodels/LoginViewModel.kt

@@ -1,25 +1,65 @@
 package de.miaurizius.shap_planner.viewmodels
 
+import android.content.Context
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
+import de.miaurizius.shap_planner.TokenStorage
 import de.miaurizius.shap_planner.UserPreferences
 import de.miaurizius.shap_planner.entities.Account
+import de.miaurizius.shap_planner.network.LoginRequest
+import de.miaurizius.shap_planner.network.RetrofitProvider
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
 import java.util.UUID
 
-class LoginViewModel(private val prefs: UserPreferences) : ViewModel() {
+class LoginViewModel(private val prefs: UserPreferences, private val appContext: Context) : ViewModel() {
+
+    private val tokenStorage = TokenStorage(appContext)
 
     val isLoggedIn = prefs.isLoggedInFlow.stateIn(viewModelScope, SharingStarted.Lazily, false)
     val lastUserId = prefs.lastUserLoginFlow.stateIn(viewModelScope, SharingStarted.Lazily, null)
 
     fun login(serverUrl: String, username: String, password: String, viewModel: MainViewModel) {
-        val uuid = UUID.randomUUID();
-        val acc = Account(uuid, username, "Pfadi-WG", null, serverUrl) //TODO: get data from backend
-        viewModel.addAccount(acc)
-        println("Logged in as ${username} in ${serverUrl}")
-        viewModelScope.launch { prefs.saveLogin(uuid.toString()) }
+        viewModelScope.launch {
+            val api = RetrofitProvider.create(serverUrl)
+
+            try {
+                val response = withContext(Dispatchers.IO) {
+                    api.login(LoginRequest(username, password))
+                }
+
+                if(response.isSuccessful) {
+                    val body = response.body() ?: run {
+                        return@launch
+                    }
+
+                    val access = body.access_token
+                    val refresh = body.refresh_token
+
+                    tokenStorage.saveTokens(body.user.id, access, refresh)
+
+                    val account = Account(
+                        id = UUID.fromString(body.user.id),
+                        name = username,
+                        wgName = body.wgName,
+                        avatarUrl = null,
+                        serverUrl = serverUrl,
+                        role = body.user.role
+                    )
+
+                    viewModel.addAccount(account)
+
+                    prefs.saveLogin(body.user.id)
+                } else {
+                    println("Login failed: ${response.code()} ${response.errorBody()?.toString()}")
+                }
+            } catch(e: Exception) {
+                e.printStackTrace()
+            }
+        }
     }
 
     fun logout() {