Implement syncing logic (communication with server doesn't work right now)

.idea/uiDesigner.xml

@@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Palette2">
+    <group name="Swing">
+      <item class="com.intellij.uiDesigner.HSpacer" tooltip-text="Horizontal Spacer" icon="/com/intellij/uiDesigner/icons/hspacer.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="1" hsize-policy="6" anchor="0" fill="1" />
+      </item>
+      <item class="com.intellij.uiDesigner.VSpacer" tooltip-text="Vertical Spacer" icon="/com/intellij/uiDesigner/icons/vspacer.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="1" anchor="0" fill="2" />
+      </item>
+      <item class="javax.swing.JPanel" icon="/com/intellij/uiDesigner/icons/panel.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JScrollPane" icon="/com/intellij/uiDesigner/icons/scrollPane.svg" removable="false" auto-create-binding="false" can-attach-label="true">
+        <default-constraints vsize-policy="7" hsize-policy="7" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JButton" icon="/com/intellij/uiDesigner/icons/button.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="0" fill="1" />
+        <initial-values>
+          <property name="text" value="Button" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JRadioButton" icon="/com/intellij/uiDesigner/icons/radioButton.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="RadioButton" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JCheckBox" icon="/com/intellij/uiDesigner/icons/checkBox.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="3" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="CheckBox" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JLabel" icon="/com/intellij/uiDesigner/icons/label.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="0" anchor="8" fill="0" />
+        <initial-values>
+          <property name="text" value="Label" />
+        </initial-values>
+      </item>
+      <item class="javax.swing.JTextField" icon="/com/intellij/uiDesigner/icons/textField.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JPasswordField" icon="/com/intellij/uiDesigner/icons/passwordField.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JFormattedTextField" icon="/com/intellij/uiDesigner/icons/formattedTextField.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1">
+          <preferred-size width="150" height="-1" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTextArea" icon="/com/intellij/uiDesigner/icons/textArea.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTextPane" icon="/com/intellij/uiDesigner/icons/textPane.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JEditorPane" icon="/com/intellij/uiDesigner/icons/editorPane.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JComboBox" icon="/com/intellij/uiDesigner/icons/comboBox.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="2" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JTable" icon="/com/intellij/uiDesigner/icons/table.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JList" icon="/com/intellij/uiDesigner/icons/list.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="2" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTree" icon="/com/intellij/uiDesigner/icons/tree.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3">
+          <preferred-size width="150" height="50" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JTabbedPane" icon="/com/intellij/uiDesigner/icons/tabbedPane.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3">
+          <preferred-size width="200" height="200" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JSplitPane" icon="/com/intellij/uiDesigner/icons/splitPane.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="3" hsize-policy="3" anchor="0" fill="3">
+          <preferred-size width="200" height="200" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JSpinner" icon="/com/intellij/uiDesigner/icons/spinner.svg" removable="false" auto-create-binding="true" can-attach-label="true">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JSlider" icon="/com/intellij/uiDesigner/icons/slider.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="8" fill="1" />
+      </item>
+      <item class="javax.swing.JSeparator" icon="/com/intellij/uiDesigner/icons/separator.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="6" anchor="0" fill="3" />
+      </item>
+      <item class="javax.swing.JProgressBar" icon="/com/intellij/uiDesigner/icons/progressbar.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="0" fill="1" />
+      </item>
+      <item class="javax.swing.JToolBar" icon="/com/intellij/uiDesigner/icons/toolbar.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="6" anchor="0" fill="1">
+          <preferred-size width="-1" height="20" />
+        </default-constraints>
+      </item>
+      <item class="javax.swing.JToolBar$Separator" icon="/com/intellij/uiDesigner/icons/toolbarSeparator.svg" removable="false" auto-create-binding="false" can-attach-label="false">
+        <default-constraints vsize-policy="0" hsize-policy="0" anchor="0" fill="1" />
+      </item>
+      <item class="javax.swing.JScrollBar" icon="/com/intellij/uiDesigner/icons/scrollbar.svg" removable="false" auto-create-binding="true" can-attach-label="false">
+        <default-constraints vsize-policy="6" hsize-policy="0" anchor="0" fill="2" />
+      </item>
+    </group>
+  </component>
+</project>

app/build.gradle.kts

@@ -5,12 +5,12 @@ plugins {
 
 android {
     namespace = "core.notevault"
-    compileSdk = 34
+    compileSdk = 35
 
     defaultConfig {
         applicationId = "core.notevault"
         minSdk = 28
-        targetSdk = 34
+        targetSdk = 35
         versionCode = 1
         versionName = "1.0"
 
@@ -65,4 +65,5 @@ dependencies {
     // Optional: Unterstützung für Kotlin Coroutines oder RxJava
     implementation("androidx.room:room-ktx:$room_version") // Für Kotlin-Extensions
     implementation("androidx.room:room-rxjava3:$room_version") // Für RxJava-Unterstützung
+    implementation("androidx.work:work-runtime:2.10.0")
 }

app/src/main/java/core/notevault/MainActivity.java

@@ -12,6 +12,8 @@ import android.widget.Toast;
 import androidx.fragment.app.Fragment;
 import androidx.fragment.app.FragmentManager;
 import androidx.navigation.fragment.NavHostFragment;
+import androidx.work.OneTimeWorkRequest;
+import androidx.work.WorkManager;
 import com.google.android.material.snackbar.Snackbar;
 import com.google.android.material.navigation.NavigationView;
 import androidx.navigation.NavController;
@@ -22,6 +24,7 @@ import androidx.drawerlayout.widget.DrawerLayout;
 import androidx.appcompat.app.AppCompatActivity;
 import core.notevault.data.*;
 import core.notevault.databinding.ActivityMainBinding;
+import core.notevault.sync.SyncWorker;
 import core.notevault.sync.auth.AuthRepository;
 import core.notevault.sync.auth.LoginCallback;
 import core.notevault.ui.gallery.GalleryFragment;
@@ -35,8 +38,10 @@ import core.notevault.util.NoteSheetsUtil;
 import java.io.*;
 import java.nio.file.Files;
 import java.util.ArrayList;
+import java.util.Calendar;
 import java.util.Date;
 import java.util.List;
+import java.util.concurrent.TimeUnit;
 
 public class MainActivity extends AppCompatActivity implements MetaDataDialog.OnMetadataListener,
         ConcertEditorDialog.OnConcertEditorListener, ConcertSongSelector.OnSongSelectedListener, LoginCallback {
@@ -68,6 +73,25 @@ public class MainActivity extends AppCompatActivity implements MetaDataDialog.On
 
         setupLoginButton();
         musicDB = MusicDatabase.getDatabase(this);
+        scheduleSync();
+    }
+
+    public void scheduleSync() {
+        // Setze eine Uhrzeit für die Synchronisation
+        Calendar calendar = Calendar.getInstance();
+        calendar.set(Calendar.HOUR_OF_DAY,11);
+        calendar.set(Calendar.MINUTE, 32);
+        calendar.set(Calendar.SECOND, 0);
+
+        long triggerTime = calendar.getTimeInMillis(); // Zeitstempel für den Trigger
+
+        // Erstelle die OneTimeWorkRequest für den SyncWorker
+        OneTimeWorkRequest syncRequest = new OneTimeWorkRequest.Builder(SyncWorker.class)
+                .setInitialDelay(triggerTime - System.currentTimeMillis(), TimeUnit.MILLISECONDS) // Verzögerung bis zur Ausführung
+                .build();
+
+        // Planen des Workers mit WorkManager
+        WorkManager.getInstance(getBaseContext()).enqueue(syncRequest);
     }
 
     @Override

app/src/main/java/core/notevault/data/Concert.java

@@ -1,26 +1,33 @@
 package core.notevault.data;
 
-import androidx.room.Entity;
+import androidx.room.*;
-import androidx.room.Ignore;
+import core.notevault.data.sync.SyncStatus;
-import androidx.room.PrimaryKey;
+import core.notevault.data.sync.SyncStatusConverter;
 
 import java.text.SimpleDateFormat;
+import java.time.LocalDateTime;
 import java.util.Date;
 import java.util.Locale;
 
 @Entity(tableName = "concerts")
+@TypeConverters(SyncStatusConverter.class)
 public class Concert {
 
     @PrimaryKey(autoGenerate = true)
     private int id;
 
+    private String serverSpecificConcertID;
     private String title;
     private String concertDate;
+    private SyncStatus syncStatus;
+
+    private LocalDateTime lastModified;
 
     @Ignore
     public Concert(String title, String concertDate) {
         this.title = title;
         this.concertDate = concertDate;
+        this.lastModified = LocalDateTime.now();
     }
 
     public Concert() {
@@ -56,4 +63,28 @@ public class Concert {
     public void setConcertDate(String concertDate) {
         this.concertDate = concertDate;
     }
+
+    public String getServerSpecificConcertID() {
+        return serverSpecificConcertID;
+    }
+
+    public void setServerSpecificConcertID(String serverSpecificConcertID) {
+        this.serverSpecificConcertID = serverSpecificConcertID;
+    }
+
+    public SyncStatus getSyncStatus() {
+        return syncStatus;
+    }
+
+    public void setSyncStatus(SyncStatus syncStatus) {
+        this.syncStatus = syncStatus;
+    }
+
+    public LocalDateTime getLastModified() {
+        return lastModified;
+    }
+
+    public void setLastModified(LocalDateTime lastModified) {
+        this.lastModified = lastModified;
+    }
 }

app/src/main/java/core/notevault/data/DateConverter.java

@@ -0,0 +1,20 @@
+package core.notevault.data;
+
+import androidx.room.TypeConverter;
+
+import java.time.LocalDateTime;
+import java.time.format.DateTimeFormatter;
+
+public class DateConverter {
+    // Konvertiere LocalDateTime in String
+    @TypeConverter
+    public static String fromLocalDateTime(LocalDateTime localDateTime) {
+        return localDateTime == null ? null : localDateTime.format(DateTimeFormatter.ISO_LOCAL_DATE_TIME);
+    }
+
+    // Konvertiere String zurück in LocalDateTime
+    @TypeConverter
+    public static LocalDateTime toLocalDateTime(String dateTimeString) {
+        return dateTimeString == null ? null : LocalDateTime.parse(dateTimeString, DateTimeFormatter.ISO_LOCAL_DATE_TIME);
+    }
+}

app/src/main/java/core/notevault/data/MusicDatabase.java

@@ -1,11 +1,12 @@
 package core.notevault.data;
 
 import android.content.Context;
-import androidx.room.Room;
+import androidx.room.*;
-import androidx.room.RoomDatabase;
+import core.notevault.data.sync.SyncResponse;
-import androidx.room.Database;
+import core.notevault.data.sync.SyncStatusConverter;
 
-@Database(entities = {MusicNote.class, NoteSheet.class, Concert.class, ConcertSong.class}, version = 2, exportSchema = false)
+@Database(entities = {MusicNote.class, NoteSheet.class, Concert.class, ConcertSong.class, SyncResponse.class}, version = 2, exportSchema = false)
+@TypeConverters(DateConverter.class)
 public abstract class MusicDatabase extends RoomDatabase {
     public abstract MusicNoteDAO musicNoteDao();
 

app/src/main/java/core/notevault/data/MusicNoteDAO.java

@@ -1,7 +1,10 @@
 package core.notevault.data;
 
 import androidx.room.*;
+import core.notevault.data.sync.SyncResponse;
+import core.notevault.data.sync.SyncStatus;
 
+import java.time.LocalDateTime;
 import java.util.List;
 
 @Dao
@@ -19,6 +22,9 @@ public interface MusicNoteDAO {
     @Query("SELECT * FROM note_sheets WHERE musicNoteId = :musicNoteId")
     List<NoteSheet> getNoteSheetsForMusicSong(long musicNoteId);
 
+    @Query("SELECT * FROM concerts WHERE syncStatus = :status")
+    List<Concert> getConcertsWithSyncStatus(SyncStatus status);
+
     @Insert
     void insertConcert(Concert concert);
 
@@ -43,5 +49,18 @@ public interface MusicNoteDAO {
     @Query("DELETE FROM concert_songs WHERE concertID = :concertID AND musicNoteID = :songID")
     void deleteConcertSong(long songID, int concertID);
 
+    @Query("UPDATE concerts SET serverSpecificConcertID = :serverUUID WHERE id = :concertID")
+    @Transaction
+    void updateConcertServerUUID(String serverUUID, int concertID);
 
+    // Methode für das batchweise Update der Konzert-ServerUUIDs
+    @Query("DELETE FROM concerts WHERE serverSpecificConcertID IN (:serverSpecificIDs)")
+    void deleteConcerts(List<String> serverSpecificIDs);
+
+    @Insert
+    @Transaction
+    void insertSyncResponses(List<SyncResponse> syncResponses);
+
+    @Query("SELECT MAX(lastModified) FROM concerts")
+    LocalDateTime getLatestSyncTimestamp();
 }

app/src/main/java/core/notevault/data/sync/SyncAction.java

@@ -0,0 +1,6 @@
+package core.notevault.data.sync;
+
+public enum SyncAction {
+    TOBEUPLOADED,
+    TOBEDOWNLOADED
+}

app/src/main/java/core/notevault/data/sync/SyncActionConverter.java

@@ -0,0 +1,15 @@
+package core.notevault.data.sync;
+
+import androidx.room.TypeConverter;
+
+public class SyncActionConverter {
+    @TypeConverter
+    public static SyncAction fromInt(int value) {
+        return SyncAction.values()[value];
+    }
+
+    @TypeConverter
+    public static int toInt(SyncAction action) {
+        return action.ordinal();
+    }
+}

app/src/main/java/core/notevault/data/sync/SyncObject.java

@@ -0,0 +1,5 @@
+package core.notevault.data.sync;
+
+public enum SyncObject {
+    CONCERT
+}

app/src/main/java/core/notevault/data/sync/SyncObjectConverter.java

@@ -0,0 +1,15 @@
+package core.notevault.data.sync;
+
+import androidx.room.TypeConverter;
+
+public class SyncObjectConverter {
+    @TypeConverter
+    public static SyncObject fromInt(int value) {
+        return SyncObject.values()[value];
+    }
+
+    @TypeConverter
+    public static int toInt(SyncObject object) {
+        return object.ordinal();
+    }
+}

app/src/main/java/core/notevault/data/sync/SyncResponse.java

@@ -0,0 +1,59 @@
+package core.notevault.data.sync;
+
+
+import androidx.room.Entity;
+import androidx.room.Ignore;
+import androidx.room.PrimaryKey;
+import androidx.room.TypeConverters;
+
+@Entity(tableName = "sync_actions")
+@TypeConverters({SyncStatusConverter.class, SyncObjectConverter.class})
+public class SyncResponse {
+    @PrimaryKey(autoGenerate = true)
+    private long id;
+    private String serverUUID;
+    private SyncAction syncAction;
+    private SyncObject syncObject;
+
+    @Ignore
+    public SyncResponse(String serverUUID, SyncAction syncAction, SyncObject syncObject) {
+        this.serverUUID = serverUUID;
+        this.syncAction = syncAction;
+        this.syncObject = syncObject;
+    }
+
+    public SyncResponse() {
+    }
+
+    public String getServerUUID() {
+        return serverUUID;
+    }
+
+    public void setServerUUID(String serverUUID) {
+        this.serverUUID = serverUUID;
+    }
+
+    public SyncAction getSyncAction() {
+        return syncAction;
+    }
+
+    public void setSyncAction(SyncAction syncAction) {
+        this.syncAction = syncAction;
+    }
+
+    public SyncObject getSyncObject() {
+        return syncObject;
+    }
+
+    public void setSyncObject(SyncObject syncObject) {
+        this.syncObject = syncObject;
+    }
+
+    public long getId() {
+        return id;
+    }
+
+    public void setId(long id) {
+        this.id = id;
+    }
+}

app/src/main/java/core/notevault/data/sync/SyncStatus.java

@@ -0,0 +1,9 @@
+package core.notevault.data.sync;
+
+public enum SyncStatus {
+    CREATED,
+    DELETED,
+    MODIFIED,
+    REMOTE_MODIFIED,
+    SYNCED;
+}

app/src/main/java/core/notevault/data/sync/SyncStatusConverter.java

@@ -0,0 +1,15 @@
+package core.notevault.data.sync;
+
+import androidx.room.TypeConverter;
+
+public class SyncStatusConverter {
+    @TypeConverter
+    public static SyncStatus fromInt(int value) {
+        return SyncStatus.values()[value];
+    }
+
+    @TypeConverter
+    public static int toInt(SyncStatus syncStatus) {
+        return syncStatus.ordinal();
+    }
+}

app/src/main/java/core/notevault/sync/ApiClient.java

@@ -4,6 +4,7 @@ import android.content.Context;
 import android.content.SharedPreferences;
 import core.notevault.sync.auth.AuthInterceptor;
 import okhttp3.OkHttpClient;
+import okhttp3.logging.HttpLoggingInterceptor;
 import retrofit2.Retrofit;
 import retrofit2.converter.gson.GsonConverterFactory;
 
@@ -12,9 +13,13 @@ public class ApiClient {
 
     public static Retrofit getRetrofitInstance(Context context) {
         if (retrofit == null) {
+            HttpLoggingInterceptor loggingInterceptor = new HttpLoggingInterceptor();
+            loggingInterceptor.setLevel(HttpLoggingInterceptor.Level.BODY);
+
             SharedPreferences sharedPreferences = context.getSharedPreferences("app_prefs", Context.MODE_PRIVATE);
             OkHttpClient client = new OkHttpClient.Builder()
                     .addInterceptor(new AuthInterceptor(sharedPreferences))
+                    .addInterceptor(loggingInterceptor)
                     .build();
 
             retrofit = new Retrofit.Builder()

app/src/main/java/core/notevault/sync/SyncWorker.java

@@ -0,0 +1,127 @@
+package core.notevault.sync;
+import android.content.Context;
+import android.util.Log;
+import androidx.annotation.NonNull;
+import androidx.work.Worker;
+import androidx.work.WorkerParameters;
+import core.notevault.data.Concert;
+import core.notevault.data.MusicDatabase;
+import core.notevault.data.MusicNoteDAO;
+import core.notevault.data.sync.SyncAction;
+import core.notevault.data.sync.SyncObject;
+import core.notevault.data.sync.SyncResponse;
+import core.notevault.data.sync.SyncStatus;
+import core.notevault.sync.synchronisation.*;
+import retrofit2.Call;
+import retrofit2.Callback;
+import retrofit2.Response;
+
+import java.io.IOException;
+import java.time.LocalDateTime;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CountDownLatch;
+import java.util.stream.Collectors;
+
+public class SyncWorker extends Worker{
+    private SyncService syncService;
+    private MusicNoteDAO database;
+    public SyncWorker(@NonNull Context context, @NonNull WorkerParameters workerParams) {
+        super(context, workerParams);
+        this.syncService = ApiClient.getRetrofitInstance(context).create(SyncService.class);
+        MusicDatabase musicDatabase = MusicDatabase.getDatabase(context);
+        database = musicDatabase.musicNoteDao();
+    }
+
+    @NonNull
+    @Override
+    public Result doWork() {
+        SyncRequest concertSync = buildConcertSyncRequest();
+
+        final CountDownLatch latch = new CountDownLatch(1);
+        final Result[] result = {Result.failure()};
+
+        syncWithServer(concertSync, new Callback<SyncResponseModel>() {
+            @Override
+            public void onResponse(Call<SyncResponseModel> call, Response<SyncResponseModel> response) {
+                if(response.isSuccessful()) {
+                    result[0] = Result.success();
+                    Log.d("SyncWorker", "Sync finished, process now");
+                    processConcertSynResponse(response.body());
+                } else {
+                    Log.d("SyncWorker", "Sync failed");
+                    if (response.errorBody() != null) {
+                        try {
+                            String errorBody = response.errorBody().string();
+                            Log.d("SyncWorker", "Error Body: " + errorBody);
+                        } catch (IOException e) {
+                            e.printStackTrace();
+                        }
+                    }
+                    result[0] = Result.failure();
+                }
+                latch.countDown();
+            }
+
+            @Override
+            public void onFailure(Call<SyncResponseModel> call, Throwable throwable) {
+                result[0] = Result.failure();
+                Log.d("SyncWorker", "Sync failure");
+                latch.countDown();
+            }
+        });
+
+        try {
+            latch.await();
+        } catch (InterruptedException e) {
+//            throw new RuntimeException(e);
+        }
+        return result[0];
+    }
+
+    private SyncRequest buildConcertSyncRequest() {
+        List<Concert> createdConcerts = database.getConcertsWithSyncStatus(SyncStatus.CREATED);
+        List<Concert> deletedConcerts = database.getConcertsWithSyncStatus(SyncStatus.DELETED);
+        List<Concert> modifiedConcerts = database.getConcertsWithSyncStatus(SyncStatus.MODIFIED);
+
+
+        List<Integer> deviceIDsCreatedConcerts = createdConcerts.stream().map(Concert::getId).collect(Collectors.toList());
+        List<SyncChangeRequest> modifiedSyncRequests = modifiedConcerts.stream().map(concert ->
+                new SyncChangeRequest(concert.getServerSpecificConcertID(), concert.getLastModified())).collect(Collectors.toList());
+        List<SyncChangeRequest> deletedSyncRequests = deletedConcerts.stream().map(concert ->
+                new SyncChangeRequest(concert.getServerSpecificConcertID(), concert.getLastModified())).collect(Collectors.toList());
+
+        Log.d("SyncWorker", "Build SyncRequest");
+        // Datenbankabfrage: Nur IDs mit Zustand "Modified" oder "Deleted" abrufen
+        // Dies ist abhängig von der spezifischen Implementierung der Datenbank
+        return new SyncRequest(database.getLatestSyncTimestamp(), deletedSyncRequests, modifiedSyncRequests, deviceIDsCreatedConcerts);
+    }
+
+    private void syncWithServer(SyncRequest syncRequest, Callback<SyncResponseModel> callback) {
+        syncService.syncConcerts(syncRequest).enqueue(callback);
+    }
+
+    private void processConcertSynResponse(SyncResponseModel syncResponse) {
+        Log.d("SyncWorker", "Process SyncResponse");
+        //Assign local Concert entries the provided Server ID
+        List<SyncResponse> syncResponses = new ArrayList<>();
+        for(SyncCreateResponse createResponse : syncResponse.getCreateResonses()) {
+            database.updateConcertServerUUID(createResponse.getServerObjectUUID(), createResponse.getDeviceSpecificObjectID());
+            syncResponses.add(new SyncResponse(createResponse.getServerObjectUUID(), SyncAction.TOBEUPLOADED, SyncObject.CONCERT));
+        }
+
+        //Delete Concerts that the server has marked as deleted
+        database.deleteConcerts(syncResponse.getToBeDeleted());
+
+        //Persist SyncResponse
+
+        for(String toBeDownloaded : syncResponse.getToBeDownloaded()) {
+            syncResponses.add(new SyncResponse(toBeDownloaded, SyncAction.TOBEDOWNLOADED, SyncObject.CONCERT));
+        }
+
+        for(String toBeUploaded : syncResponse.getToBeUploaded()) {
+            syncResponses.add(new SyncResponse(toBeUploaded, SyncAction.TOBEUPLOADED, SyncObject.CONCERT));
+        }
+        database.insertSyncResponses(syncResponses);
+    }
+}

app/src/main/java/core/notevault/sync/auth/AuthInterceptor.java

@@ -1,6 +1,7 @@
 package core.notevault.sync.auth;
 
 import android.content.SharedPreferences;
+import android.util.Log;
 import okhttp3.Interceptor;
 import okhttp3.Request;
 import okhttp3.Response;
@@ -13,12 +14,17 @@ public class AuthInterceptor implements Interceptor {
 
     public AuthInterceptor(SharedPreferences sharedPreferences) {
         this.sharedPreferences = sharedPreferences;
+        String token = sharedPreferences.getString("jwt_token", null);
     }
 
     @Override
     public Response intercept(Chain chain) throws IOException {
         Request originalRequest = chain.request();
 
+        if(originalRequest.url().encodedPath().equals("/api/v1/auth/login")) {
+            return chain.proceed(originalRequest);
+        }
+
         String token = sharedPreferences.getString("jwt_token", null);
         if (token == null) {
             return chain.proceed(originalRequest);

app/src/main/java/core/notevault/sync/synchronisation/SyncChangeRequest.java

@@ -0,0 +1,29 @@
+package core.notevault.sync.synchronisation;
+
+import java.time.LocalDateTime;
+
+public class SyncChangeRequest {
+    private String serverUUID;
+    private LocalDateTime lastModified;
+
+    public SyncChangeRequest(String serverUUID, LocalDateTime lastModified) {
+        this.serverUUID = serverUUID;
+        this.lastModified = lastModified;
+    }
+
+    public String getServerUUID() {
+        return serverUUID;
+    }
+
+    public void setServerUUID(String serverUUID) {
+        this.serverUUID = serverUUID;
+    }
+
+    public LocalDateTime getLastModified() {
+        return lastModified;
+    }
+
+    public void setLastModified(LocalDateTime lastModified) {
+        this.lastModified = lastModified;
+    }
+}

app/src/main/java/core/notevault/sync/synchronisation/SyncCreateResponse.java

@@ -0,0 +1,22 @@
+package core.notevault.sync.synchronisation;
+
+public class SyncCreateResponse {
+    private String serverObjectUUID;
+    private int deviceSpecificObjectID;
+
+    public String getServerObjectUUID() {
+        return serverObjectUUID;
+    }
+
+    public void setServerObjectUUID(String serverObjectUUID) {
+        this.serverObjectUUID = serverObjectUUID;
+    }
+
+    public int getDeviceSpecificObjectID() {
+        return deviceSpecificObjectID;
+    }
+
+    public void setDeviceSpecificObjectID(int deviceSpecificObjectID) {
+        this.deviceSpecificObjectID = deviceSpecificObjectID;
+    }
+}

app/src/main/java/core/notevault/sync/synchronisation/SyncRequest.java

@@ -0,0 +1,50 @@
+package core.notevault.sync.synchronisation;
+
+import java.time.LocalDateTime;
+import java.util.List;
+
+public class SyncRequest {
+    private LocalDateTime lastSync;
+    private List<SyncChangeRequest> deletedConcerts;
+    private List<SyncChangeRequest> modifiedConcerts;
+    private List<Integer> createdConcerts;
+
+    public SyncRequest(LocalDateTime lastSync, List<SyncChangeRequest> deletedConcerts, List<SyncChangeRequest> modifiedConcerts, List<Integer> createdConcerts) {
+        this.lastSync = lastSync;
+        this.deletedConcerts = deletedConcerts;
+        this.modifiedConcerts = modifiedConcerts;
+        this.createdConcerts = createdConcerts;
+    }
+
+    public LocalDateTime getLastSync() {
+        return lastSync;
+    }
+
+    public void setLastSync(LocalDateTime lastSync) {
+        this.lastSync = lastSync;
+    }
+
+    public List<SyncChangeRequest> getDeletedConcerts() {
+        return deletedConcerts;
+    }
+
+    public void setDeletedConcerts(List<SyncChangeRequest> deletedConcerts) {
+        this.deletedConcerts = deletedConcerts;
+    }
+
+    public List<SyncChangeRequest> getModifiedConcerts() {
+        return modifiedConcerts;
+    }
+
+    public void setModifiedConcerts(List<SyncChangeRequest> modifiedConcerts) {
+        this.modifiedConcerts = modifiedConcerts;
+    }
+
+    public List<Integer> getCreatedConcerts() {
+        return createdConcerts;
+    }
+
+    public void setCreatedConcerts(List<Integer> createdConcerts) {
+        this.createdConcerts = createdConcerts;
+    }
+}

app/src/main/java/core/notevault/sync/synchronisation/SyncResponseModel.java

@@ -0,0 +1,42 @@
+package core.notevault.sync.synchronisation;
+
+import java.util.List;
+
+public class SyncResponseModel {
+    private List<String> toBeUploaded;
+    private List<String> toBeDownloaded;
+    private List<String> toBeDeleted;
+    private List<SyncCreateResponse> createResonses;
+
+    public List<String> getToBeUploaded() {
+        return toBeUploaded;
+    }
+
+    public void setToBeUploaded(List<String> toBeUploaded) {
+        this.toBeUploaded = toBeUploaded;
+    }
+
+    public List<String> getToBeDownloaded() {
+        return toBeDownloaded;
+    }
+
+    public void setToBeDownloaded(List<String> toBeDownloaded) {
+        this.toBeDownloaded = toBeDownloaded;
+    }
+
+    public List<String> getToBeDeleted() {
+        return toBeDeleted;
+    }
+
+    public void setToBeDeleted(List<String> toBeDeleted) {
+        this.toBeDeleted = toBeDeleted;
+    }
+
+    public List<SyncCreateResponse> getCreateResonses() {
+        return createResonses;
+    }
+
+    public void setCreateResonses(List<SyncCreateResponse> createResonses) {
+        this.createResonses = createResonses;
+    }
+}

app/src/main/java/core/notevault/sync/synchronisation/SyncService.java

@@ -0,0 +1,12 @@
+package core.notevault.sync.synchronisation;
+
+import core.notevault.data.sync.SyncResponse;
+import retrofit2.Call;
+import retrofit2.http.Body;
+import retrofit2.http.POST;
+
+public interface SyncService {
+
+    @POST("api/v1/sync/concerts")
+    Call<SyncResponseModel> syncConcerts(@Body SyncRequest syncRequest);
+}