First step syncronization implementation

app/src/main/AndroidManifest.xml

@@ -9,6 +9,10 @@
 	<uses-permission android:name="android.permission.WAKE_LOCK" />
 	<uses-permission android:name="android.permission.VIBRATE" />
 	<uses-permission android:name="android.permission.RECEIVE_BOOT_COMPLETED" />
+	<uses-permission android:name="android.permission.GET_ACCOUNTS" />
+	<uses-permission android:name="android.permission.MANAGE_ACCOUNTS" />
+	<uses-permission android:name="android.permission.AUTHENTICATE_ACCOUNTS" />
+	<uses-permission android:name="android.permission.USE_CREDENTIALS" />
 
 	<application
 		android:name="org.koitharu.kotatsu.KotatsuApp"
@@ -53,7 +57,8 @@
 		<activity
 			android:name="org.koitharu.kotatsu.search.ui.SearchActivity"
 			android:label="@string/search" />
-		<activity android:name="org.koitharu.kotatsu.search.ui.MangaListActivity"
+		<activity
+			android:name="org.koitharu.kotatsu.search.ui.MangaListActivity"
 			android:label="@string/search_manga" />
 		<activity
 			android:name="org.koitharu.kotatsu.settings.SettingsActivity"
@@ -95,9 +100,11 @@
 			android:windowSoftInputMode="adjustResize" />
 		<activity
 			android:name="org.koitharu.kotatsu.download.ui.DownloadsActivity"
-			android:launchMode="singleTop"
+			android:label="@string/downloads"
-			android:label="@string/downloads" />
+			android:launchMode="singleTop" />
-		<activity android:name="org.koitharu.kotatsu.image.ui.ImageActivity"/>
+		<activity android:name="org.koitharu.kotatsu.image.ui.ImageActivity" />
+		<activity android:name="org.koitharu.kotatsu.sync.ui.SyncAuthActivity"
+			android:label="@string/sync"/>
 
 		<service
 			android:name="org.koitharu.kotatsu.download.ui.service.DownloadService"
@@ -109,6 +116,41 @@
 		<service
 			android:name="org.koitharu.kotatsu.widget.recent.RecentWidgetService"
 			android:permission="android.permission.BIND_REMOTEVIEWS" />
+		<service
+			android:name="org.koitharu.kotatsu.sync.ui.SyncAuthenticatorService"
+			android:exported="true"
+			tools:ignore="ExportedService">
+			<intent-filter>
+				<action android:name="android.accounts.AccountAuthenticator" />
+			</intent-filter>
+			<meta-data
+				android:name="android.accounts.AccountAuthenticator"
+				android:resource="@xml/authenticator_sync" />
+		</service>
+		<service
+			android:name="org.koitharu.kotatsu.sync.ui.favourites.FavouritesSyncService"
+			android:exported="false"
+			android:label="@string/favourites"
+			android:process=":sync">
+			<intent-filter>
+				<action android:name="android.content.SyncAdapter" />
+			</intent-filter>
+			<meta-data
+				android:name="android.content.SyncAdapter"
+				android:resource="@xml/sync_favourites" />
+		</service>
+		<service
+			android:name="org.koitharu.kotatsu.sync.ui.history.HistorySyncService"
+			android:exported="false"
+			android:label="@string/history"
+			android:process=":sync">
+			<intent-filter>
+				<action android:name="android.content.SyncAdapter" />
+			</intent-filter>
+			<meta-data
+				android:name="android.content.SyncAdapter"
+				android:resource="@xml/sync_history" />
+		</service>
 
 		<provider
 			android:name="org.koitharu.kotatsu.search.ui.MangaSuggestionsProvider"
@@ -123,6 +165,18 @@
 				android:name="android.support.FILE_PROVIDER_PATHS"
 				android:resource="@xml/filepaths" />
 		</provider>
+		<provider
+			android:name="org.koitharu.kotatsu.sync.ui.favourites.FavouritesSyncProvider"
+			android:authorities="org.koitharu.kotatsu.favourites"
+			android:exported="false"
+			android:label="@string/favourites"
+			android:syncable="true" />
+		<provider
+			android:name="org.koitharu.kotatsu.sync.ui.history.HistorySyncProvider"
+			android:authorities="org.koitharu.kotatsu.history"
+			android:exported="false"
+			android:label="@string/history"
+			android:syncable="true" />
 
 		<receiver
 			android:name="org.koitharu.kotatsu.widget.shelf.ShelfWidgetProvider"

app/src/main/java/org/koitharu/kotatsu/KotatsuApp.kt

@@ -27,6 +27,7 @@ import org.koitharu.kotatsu.remotelist.remoteListModule
 import org.koitharu.kotatsu.search.searchModule
 import org.koitharu.kotatsu.settings.settingsModule
 import org.koitharu.kotatsu.suggestions.suggestionsModule
+import org.koitharu.kotatsu.sync.syncModule
 import org.koitharu.kotatsu.tracker.trackerModule
 import org.koitharu.kotatsu.widget.WidgetUpdater
 import org.koitharu.kotatsu.widget.appWidgetModule
@@ -67,6 +68,7 @@ class KotatsuApp : Application() {
 				readerModule,
 				appWidgetModule,
 				suggestionsModule,
+				syncModule,
 			)
 		}
 	}

app/src/main/java/org/koitharu/kotatsu/core/db/MangaDatabase.kt

@@ -46,6 +46,13 @@ abstract class MangaDatabase : RoomDatabase() {
 
 	companion object {
 
+		const val TABLE_FAVOURITES = "favourites"
+		const val TABLE_MANGA = "manga"
+		const val TABLE_TAGS = "tags"
+		const val TABLE_FAVOURITE_CATEGORIES = "favourite_categories"
+		const val TABLE_HISTORY = "history"
+		const val TABLE_MANGA_TAGS = "manga_tags"
+
 		fun create(context: Context): MangaDatabase = Room.databaseBuilder(
 			context,
 			MangaDatabase::class.java,

app/src/main/java/org/koitharu/kotatsu/core/db/entity/MangaEntity.kt

@@ -3,8 +3,9 @@ package org.koitharu.kotatsu.core.db.entity
 import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.PrimaryKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA
 
-@Entity(tableName = "manga")
+@Entity(tableName = TABLE_MANGA)
 class MangaEntity(
 	@PrimaryKey(autoGenerate = false)
 	@ColumnInfo(name = "manga_id") val id: Long,

app/src/main/java/org/koitharu/kotatsu/core/db/entity/MangaTagsEntity.kt

@@ -3,25 +3,27 @@ package org.koitharu.kotatsu.core.db.entity
 import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.ForeignKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA_TAGS
 
 @Entity(
-	tableName = "manga_tags", primaryKeys = ["manga_id", "tag_id"],
+	tableName = TABLE_MANGA_TAGS,
+	primaryKeys = ["manga_id", "tag_id"],
 	foreignKeys = [
 		ForeignKey(
 			entity = MangaEntity::class,
 			parentColumns = ["manga_id"],
 			childColumns = ["manga_id"],
-			onDelete = ForeignKey.CASCADE
+			onDelete = ForeignKey.CASCADE,
 		),
 		ForeignKey(
 			entity = TagEntity::class,
 			parentColumns = ["tag_id"],
 			childColumns = ["tag_id"],
-			onDelete = ForeignKey.CASCADE
+			onDelete = ForeignKey.CASCADE,
 		)
 	]
 )
 class MangaTagsEntity(
 	@ColumnInfo(name = "manga_id", index = true) val mangaId: Long,
-	@ColumnInfo(name = "tag_id", index = true) val tagId: Long
+	@ColumnInfo(name = "tag_id", index = true) val tagId: Long,
 )

app/src/main/java/org/koitharu/kotatsu/core/db/entity/TagEntity.kt

@@ -3,8 +3,9 @@ package org.koitharu.kotatsu.core.db.entity
 import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.PrimaryKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_TAGS
 
-@Entity(tableName = "tags")
+@Entity(tableName = TABLE_TAGS)
 class TagEntity(
 	@PrimaryKey(autoGenerate = false)
 	@ColumnInfo(name = "tag_id") val id: Long,

app/src/main/java/org/koitharu/kotatsu/favourites/data/FavouriteCategoryEntity.kt

@@ -3,8 +3,9 @@ package org.koitharu.kotatsu.favourites.data
 import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.PrimaryKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITE_CATEGORIES
 
-@Entity(tableName = "favourite_categories")
+@Entity(tableName = TABLE_FAVOURITE_CATEGORIES)
 class FavouriteCategoryEntity(
 	@PrimaryKey(autoGenerate = true)
 	@ColumnInfo(name = "category_id") val categoryId: Int,

app/src/main/java/org/koitharu/kotatsu/favourites/data/FavouriteEntity.kt

@@ -3,10 +3,12 @@ package org.koitharu.kotatsu.favourites.data
 import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.ForeignKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITES
 import org.koitharu.kotatsu.core.db.entity.MangaEntity
 
 @Entity(
-	tableName = "favourites", primaryKeys = ["manga_id", "category_id"], foreignKeys = [
+	tableName = TABLE_FAVOURITES, primaryKeys = ["manga_id", "category_id"],
+	foreignKeys = [
 		ForeignKey(
 			entity = MangaEntity::class,
 			parentColumns = ["manga_id"],

app/src/main/java/org/koitharu/kotatsu/history/data/HistoryDao.kt

@@ -8,9 +8,6 @@ import org.koitharu.kotatsu.core.db.entity.TagEntity
 @Dao
 abstract class HistoryDao {
 
-	/**
-	 * @hide
-	 */
 	@Transaction
 	@Query("SELECT * FROM history ORDER BY updated_at DESC LIMIT :limit OFFSET :offset")
 	abstract suspend fun findAll(offset: Int, limit: Int): List<HistoryWithManga>

app/src/main/java/org/koitharu/kotatsu/history/data/HistoryEntity.kt

@@ -4,16 +4,17 @@ import androidx.room.ColumnInfo
 import androidx.room.Entity
 import androidx.room.ForeignKey
 import androidx.room.PrimaryKey
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_HISTORY
 import org.koitharu.kotatsu.core.db.entity.MangaEntity
 
 @Entity(
-	tableName = "history",
+	tableName = TABLE_HISTORY,
 	foreignKeys = [
 		ForeignKey(
 			entity = MangaEntity::class,
 			parentColumns = ["manga_id"],
 			childColumns = ["manga_id"],
-			onDelete = ForeignKey.CASCADE
+			onDelete = ForeignKey.CASCADE,
 		)
 	]
 )

app/src/main/java/org/koitharu/kotatsu/sync/SyncModule.kt

@@ -0,0 +1,12 @@
+package org.koitharu.kotatsu.sync
+
+import org.koin.android.ext.koin.androidContext
+import org.koin.androidx.viewmodel.dsl.viewModel
+import org.koin.dsl.module
+import org.koitharu.kotatsu.sync.ui.SyncAuthViewModel
+
+val syncModule
+	get() = module {
+
+		viewModel { SyncAuthViewModel(androidContext(), get()) }
+	}

app/src/main/java/org/koitharu/kotatsu/sync/data/AccountInterceptor.kt

@@ -0,0 +1,29 @@
+package org.koitharu.kotatsu.sync.data
+
+import android.accounts.Account
+import android.accounts.AccountManager
+import android.content.Context
+import okhttp3.Credentials
+import okhttp3.Interceptor
+import okhttp3.Response
+
+class AccountInterceptor(
+	context: Context,
+	private val account: Account,
+) : Interceptor {
+
+	private val accountManager = AccountManager.get(context)
+
+	override fun intercept(chain: Interceptor.Chain): Response {
+		val password = accountManager.getPassword(account)
+		val request = if (password != null) {
+			val credential: String = Credentials.basic(account.name, password)
+			chain.request().newBuilder()
+				.header("Authorization", credential)
+				.build()
+		} else {
+			chain.request()
+		}
+		return chain.proceed(request)
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncAuthResult.kt

@@ -0,0 +1,28 @@
+package org.koitharu.kotatsu.sync.domain
+
+class SyncAuthResult(
+	val email: String,
+	val password: String,
+	val token: String,
+) {
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+
+		other as SyncAuthResult
+
+		if (email != other.email) return false
+		if (password != other.password) return false
+		if (token != other.token) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		var result = email.hashCode()
+		result = 31 * result + password.hashCode()
+		result = 31 * result + token.hashCode()
+		return result
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/domain/SyncRepository.kt

@@ -0,0 +1,206 @@
+package org.koitharu.kotatsu.sync.domain
+
+import android.accounts.Account
+import android.content.ContentProviderClient
+import android.content.ContentProviderOperation
+import android.content.Context
+import android.content.SyncResult
+import android.net.Uri
+import androidx.annotation.WorkerThread
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import org.json.JSONArray
+import org.json.JSONObject
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITES
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITE_CATEGORIES
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_HISTORY
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA_TAGS
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_TAGS
+import org.koitharu.kotatsu.parsers.util.json.mapJSONTo
+import org.koitharu.kotatsu.parsers.util.parseJson
+import org.koitharu.kotatsu.sync.data.AccountInterceptor
+import org.koitharu.kotatsu.utils.ext.toContentValues
+import org.koitharu.kotatsu.utils.ext.toJson
+import org.koitharu.kotatsu.utils.ext.toRequestBody
+
+private const val AUTHORITY_HISTORY = "org.koitharu.kotatsu.history"
+private const val AUTHORITY_FAVOURITES = "org.koitharu.kotatsu.favourites"
+/**
+ * Warning! This class may be used in another process
+ */
+class SyncRepository(
+	context: Context,
+	account: Account,
+	private val provider: ContentProviderClient,
+) {
+
+	private val httpClient = OkHttpClient.Builder()
+		.addInterceptor(AccountInterceptor(context, account))
+		.build()
+	private val baseUrl = context.getString(R.string.url_sync_server)
+
+	@WorkerThread
+	fun syncFavouriteCategories(syncResult: SyncResult) {
+		val uri = uri(AUTHORITY_FAVOURITES, TABLE_FAVOURITE_CATEGORIES)
+		val data = JSONObject()
+		provider.query(uri, null, null, null, null)?.use { cursor ->
+			val favourites = JSONArray()
+			if (cursor.moveToFirst()) {
+				do {
+					favourites.put(cursor.toJson())
+				} while (cursor.moveToNext())
+			}
+			data.put(TABLE_FAVOURITES, favourites)
+		}
+		data.put("timestamp", System.currentTimeMillis())
+		val request = Request.Builder()
+			.url("$baseUrl/resource/$TABLE_FAVOURITE_CATEGORIES")
+			.post(data.toRequestBody())
+			.build()
+		val response = httpClient.newCall(request).execute().parseJson()
+		val operations = ArrayList<ContentProviderOperation>()
+		val timestamp = response.getLong("timestamp")
+		operations += ContentProviderOperation.newDelete(uri)
+			.withSelection("created_at < ?", arrayOf(timestamp.toString()))
+			.build()
+		val ja = response.getJSONArray(TABLE_FAVOURITE_CATEGORIES)
+		ja.mapJSONTo(operations) { jo ->
+			ContentProviderOperation.newInsert(uri)
+				.withValues(jo.toContentValues())
+				.build()
+		}
+
+		val result = provider.applyBatch(operations)
+		syncResult.stats.numDeletes = result.first().count?.toLong() ?: 0L
+		syncResult.stats.numInserts = result.drop(1).sumOf { it.count?.toLong() ?: 0L }
+	}
+
+	@WorkerThread
+	fun syncFavourites(syncResult: SyncResult) {
+		val uri = uri(AUTHORITY_FAVOURITES, TABLE_FAVOURITES)
+		val data = JSONObject()
+		provider.query(uri, null, null, null, null)?.use { cursor ->
+			val jsonArray = JSONArray()
+			if (cursor.moveToFirst()) {
+				do {
+					val jo = cursor.toJson()
+					jo.put("manga", getManga(AUTHORITY_FAVOURITES, jo.getLong("manga_id")))
+					jsonArray.put(jo)
+				} while (cursor.moveToNext())
+			}
+			data.put(TABLE_FAVOURITES, jsonArray)
+		}
+		data.put("timestamp", System.currentTimeMillis())
+		val request = Request.Builder()
+			.url("$baseUrl/resource/$TABLE_FAVOURITES")
+			.post(data.toRequestBody())
+			.build()
+		val response = httpClient.newCall(request).execute().parseJson()
+		val operations = ArrayList<ContentProviderOperation>()
+		val timestamp = response.getLong("timestamp")
+		operations += ContentProviderOperation.newDelete(uri)
+			.withSelection("created_at < ?", arrayOf(timestamp.toString()))
+			.build()
+		val ja = response.getJSONArray(TABLE_FAVOURITES)
+		ja.mapJSONTo(operations) { jo ->
+			ContentProviderOperation.newInsert(uri)
+				.withValues(jo.toContentValues())
+				.build()
+		}
+
+		val result = provider.applyBatch(operations)
+		syncResult.stats.numDeletes = result.first().count?.toLong() ?: 0L
+		syncResult.stats.numInserts = result.drop(1).sumOf { it.count?.toLong() ?: 0L }
+	}
+
+	@WorkerThread
+	fun syncHistory(syncResult: SyncResult) {
+		val uri = uri(AUTHORITY_HISTORY, TABLE_HISTORY)
+		val data = JSONObject()
+		provider.query(uri, null, null, null, null)?.use { cursor ->
+			val jsonArray = JSONArray()
+			if (cursor.moveToFirst()) {
+				do {
+					val jo = cursor.toJson()
+					jo.put("manga", getManga(AUTHORITY_HISTORY, jo.getLong("manga_id")))
+					jsonArray.put(jo)
+				} while (cursor.moveToNext())
+			}
+			data.put(TABLE_HISTORY, jsonArray)
+		}
+		data.put("timestamp", System.currentTimeMillis())
+		val request = Request.Builder()
+			.url("$baseUrl/resource/$TABLE_HISTORY")
+			.post(data.toRequestBody())
+			.build()
+		val response = httpClient.newCall(request).execute().parseJson()
+		val operations = ArrayList<ContentProviderOperation>()
+		val timestamp = response.getLong("timestamp")
+		operations += ContentProviderOperation.newDelete(uri)
+			.withSelection("updated_at < ?", arrayOf(timestamp.toString()))
+			.build()
+		val ja = response.getJSONArray(TABLE_HISTORY)
+		ja.mapJSONTo(operations) { jo ->
+			ContentProviderOperation.newInsert(uri)
+				.withValues(jo.toContentValues())
+				.build()
+		}
+
+		val result = provider.applyBatch(operations)
+		syncResult.stats.numDeletes = result.first().count?.toLong() ?: 0L
+		syncResult.stats.numInserts = result.drop(1).sumOf { it.count?.toLong() ?: 0L }
+	}
+
+	private fun getManga(authority: String, id: Long): JSONObject {
+		val manga = provider.query(
+			uri(authority, TABLE_MANGA),
+			null,
+			"manga_id = ?",
+			arrayOf(id.toString()),
+			null,
+		)?.use { cursor ->
+			cursor.moveToFirst()
+			cursor.toJson()
+		}
+		requireNotNull(manga)
+		val tags = provider.query(
+			uri(authority, TABLE_MANGA_TAGS),
+			arrayOf("tag_id"),
+			"manga_id = ?",
+			arrayOf(id.toString()),
+			null,
+		)?.use { cursor ->
+			val json = JSONArray()
+			if (cursor.moveToFirst()) {
+				do {
+					val tagId = cursor.getLong(0)
+					json.put(getTag(authority, tagId))
+				} while (cursor.moveToNext())
+			}
+			json
+		}
+		manga.put("tags", requireNotNull(tags))
+		return manga
+	}
+
+	private fun getTag(authority: String, tagId: Long): JSONObject {
+		val tag = provider.query(
+			uri(authority, TABLE_TAGS),
+			null,
+			"tag_id = ?",
+			arrayOf(tagId.toString()),
+			null,
+		)?.use { cursor ->
+			if (cursor.moveToFirst()) {
+				cursor.toJson()
+			} else {
+				null
+			}
+		}
+		return requireNotNull(tag)
+	}
+
+	private fun uri(authority: String, table: String) = Uri.parse("content://$authority/$table")
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncAuthActivity.kt

@@ -0,0 +1,159 @@
+package org.koitharu.kotatsu.sync.ui
+
+import android.accounts.Account
+import android.accounts.AccountAuthenticatorResponse
+import android.accounts.AccountManager
+import android.os.Bundle
+import android.text.Editable
+import android.text.TextWatcher
+import android.view.View
+import android.widget.Button
+import androidx.core.graphics.Insets
+import androidx.core.view.isGone
+import androidx.core.view.isVisible
+import androidx.transition.Fade
+import androidx.transition.TransitionManager
+import com.google.android.material.dialog.MaterialAlertDialogBuilder
+import org.koin.androidx.viewmodel.ext.android.viewModel
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.base.ui.BaseActivity
+import org.koitharu.kotatsu.databinding.ActivitySyncAuthBinding
+import org.koitharu.kotatsu.sync.domain.SyncAuthResult
+import org.koitharu.kotatsu.utils.ext.getDisplayMessage
+
+class SyncAuthActivity : BaseActivity<ActivitySyncAuthBinding>(), View.OnClickListener {
+
+	private var accountAuthenticatorResponse: AccountAuthenticatorResponse? = null
+	private var resultBundle: Bundle? = null
+
+	private val viewModel by viewModel<SyncAuthViewModel>()
+
+	override fun onCreate(savedInstanceState: Bundle?) {
+		super.onCreate(savedInstanceState)
+		setContentView(ActivitySyncAuthBinding.inflate(layoutInflater))
+		accountAuthenticatorResponse = intent.getParcelableExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE)
+		accountAuthenticatorResponse?.onRequestContinued()
+		binding.buttonCancel.setOnClickListener(this)
+		binding.buttonNext.setOnClickListener(this)
+		binding.buttonBack.setOnClickListener(this)
+		binding.buttonDone.setOnClickListener(this)
+		binding.editEmail.addTextChangedListener(EmailTextWatcher(binding.buttonNext))
+		binding.editPassword.addTextChangedListener(PasswordTextWatcher(binding.buttonDone))
+
+		viewModel.onTokenObtained.observe(this, ::onTokenReceived)
+		viewModel.onError.observe(this, ::onError)
+		viewModel.isLoading.observe(this, ::onLoadingStateChanged)
+	}
+
+	override fun onWindowInsetsChanged(insets: Insets) {
+		val basePadding = resources.getDimensionPixelOffset(R.dimen.screen_padding)
+		binding.root.setPadding(
+			basePadding + insets.left,
+			basePadding + insets.top,
+			basePadding + insets.right,
+			basePadding + insets.bottom,
+		)
+	}
+
+	override fun onBackPressed() {
+		if (binding.switcher.isVisible && binding.switcher.displayedChild > 0) {
+			binding.switcher.showPrevious()
+		} else {
+			super.onBackPressed()
+		}
+	}
+
+	override fun onClick(v: View) {
+		when (v.id) {
+			R.id.button_cancel -> {
+				setResult(RESULT_CANCELED)
+				finish()
+			}
+			R.id.button_next -> {
+				binding.switcher.showNext()
+			}
+			R.id.button_back -> {
+				binding.switcher.showPrevious()
+			}
+			R.id.button_done -> {
+				viewModel.obtainToken(
+					email = binding.editEmail.text.toString(),
+					password = binding.editPassword.text.toString(),
+				)
+			}
+		}
+	}
+
+	override fun finish() {
+		accountAuthenticatorResponse?.let { response ->
+			resultBundle?.also {
+				response.onResult(it)
+			} ?: response.onError(AccountManager.ERROR_CODE_CANCELED, getString(R.string.canceled))
+		}
+		super.finish()
+	}
+
+	private fun onLoadingStateChanged(isLoading: Boolean) {
+		if (isLoading == binding.layoutProgress.isVisible) {
+			return
+		}
+		TransitionManager.beginDelayedTransition(binding.root, Fade())
+		binding.switcher.isGone = isLoading
+		binding.layoutProgress.isVisible = isLoading
+	}
+
+	private fun onError(error: Throwable) {
+		MaterialAlertDialogBuilder(this)
+			.setTitle(R.string.error)
+			.setMessage(error.getDisplayMessage(resources))
+			.setNegativeButton(R.string.close, null)
+			.show()
+	}
+
+	private fun onTokenReceived(authResult: SyncAuthResult) {
+		val am = AccountManager.get(this)
+		val account = Account(authResult.email, getString(R.string.account_type_sync))
+		val result = Bundle()
+		if (am.addAccountExplicitly(account, authResult.password, Bundle())) {
+			result.putString(AccountManager.KEY_ACCOUNT_NAME, account.name)
+			result.putString(AccountManager.KEY_ACCOUNT_TYPE, account.type)
+			result.putString(AccountManager.KEY_AUTHTOKEN, authResult.token)
+			am.setAuthToken(account, account.type, authResult.token)
+		} else {
+			result.putString(AccountManager.KEY_ERROR_MESSAGE, getString(R.string.account_already_exists))
+		}
+		resultBundle = result
+		setResult(RESULT_OK)
+		finish()
+	}
+
+	private class EmailTextWatcher(
+		private val button: Button,
+	) : TextWatcher {
+
+		private val regexEmail = Regex("^[A-Z0-9._%+-]+@[A-Z0-9.-]+\\.[A-Z]{2,6}$", RegexOption.IGNORE_CASE)
+
+		override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) = Unit
+
+		override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) = Unit
+
+		override fun afterTextChanged(s: Editable?) {
+			val text = s?.toString()
+			button.isEnabled = !text.isNullOrEmpty() && regexEmail.matches(text)
+		}
+	}
+
+	private class PasswordTextWatcher(
+		private val button: Button,
+	) : TextWatcher {
+
+		override fun beforeTextChanged(s: CharSequence?, start: Int, count: Int, after: Int) = Unit
+
+		override fun onTextChanged(s: CharSequence?, start: Int, before: Int, count: Int) = Unit
+
+		override fun afterTextChanged(s: Editable?) {
+			val text = s?.toString()
+			button.isEnabled = text != null && text.length >= 4
+		}
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncAuthViewModel.kt

@@ -0,0 +1,44 @@
+package org.koitharu.kotatsu.sync.ui
+
+import android.content.Context
+import kotlinx.coroutines.Dispatchers
+import okhttp3.OkHttpClient
+import okhttp3.Request
+import org.json.JSONObject
+import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.base.ui.BaseViewModel
+import org.koitharu.kotatsu.parsers.util.await
+import org.koitharu.kotatsu.parsers.util.parseJson
+import org.koitharu.kotatsu.sync.domain.SyncAuthResult
+import org.koitharu.kotatsu.utils.SingleLiveEvent
+import org.koitharu.kotatsu.utils.ext.toRequestBody
+import java.util.*
+
+class SyncAuthViewModel(
+	context: Context,
+	private val okHttpClient: OkHttpClient,
+) : BaseViewModel() {
+
+	private val baseUrl = context.getString(R.string.url_sync_server)
+	val onTokenObtained = SingleLiveEvent<SyncAuthResult>()
+
+	fun obtainToken(email: String, password: String) {
+		launchLoadingJob(Dispatchers.Default) {
+			authenticate(email, password)
+			val token = UUID.randomUUID().toString()
+			val result = SyncAuthResult(email, password, token)
+			onTokenObtained.postCall(result)
+		}
+	}
+
+	private suspend fun authenticate(email: String, password: String) {
+		val body = JSONObject(
+			mapOf("email" to email, "password" to password)
+		).toRequestBody()
+		val request = Request.Builder()
+			.url("$baseUrl/register")
+			.post(body)
+			.build()
+		val response = okHttpClient.newCall(request).await().parseJson()
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncAuthenticator.kt

@@ -0,0 +1,79 @@
+package org.koitharu.kotatsu.sync.ui
+
+import android.accounts.AbstractAccountAuthenticator
+import android.accounts.Account
+import android.accounts.AccountAuthenticatorResponse
+import android.accounts.AccountManager
+import android.content.Context
+import android.content.Intent
+import android.os.Bundle
+import android.text.TextUtils
+
+class SyncAuthenticator(private val context: Context) : AbstractAccountAuthenticator(context) {
+
+	override fun editProperties(response: AccountAuthenticatorResponse?, accountType: String?): Bundle? = null
+
+	override fun addAccount(
+		response: AccountAuthenticatorResponse?,
+		accountType: String?,
+		authTokenType: String?,
+		requiredFeatures: Array<out String>?,
+		options: Bundle?,
+	): Bundle {
+		val intent = Intent(context, SyncAuthActivity::class.java)
+		intent.putExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE, response)
+		val bundle = Bundle()
+		if (options != null) {
+			bundle.putAll(options)
+		}
+		bundle.putParcelable(AccountManager.KEY_INTENT, intent)
+		return bundle
+	}
+
+	override fun confirmCredentials(
+		response: AccountAuthenticatorResponse?,
+		account: Account?,
+		options: Bundle?,
+	): Bundle? = null
+
+	override fun getAuthToken(
+		response: AccountAuthenticatorResponse?,
+		account: Account,
+		authTokenType: String?,
+		options: Bundle?,
+	): Bundle {
+		val result = Bundle()
+		val am = AccountManager.get(context.applicationContext)
+		val authToken = am.peekAuthToken(account, authTokenType)
+		if (!TextUtils.isEmpty(authToken)) {
+			result.putString(AccountManager.KEY_ACCOUNT_NAME, account.name)
+			result.putString(AccountManager.KEY_ACCOUNT_TYPE, account.type)
+			result.putString(AccountManager.KEY_AUTHTOKEN, authToken)
+		} else {
+			val intent = Intent(context, SyncAuthActivity::class.java)
+			intent.putExtra(AccountManager.KEY_ACCOUNT_AUTHENTICATOR_RESPONSE, response)
+			// intent.putExtra(SyncAuthActivity.EXTRA_TOKEN_TYPE, authTokenType)
+			val bundle = Bundle()
+			if (options != null) {
+				bundle.putAll(options)
+			}
+			bundle.putParcelable(AccountManager.KEY_INTENT, intent)
+		}
+		return result
+	}
+
+	override fun getAuthTokenLabel(authTokenType: String?): String? = null
+
+	override fun updateCredentials(
+		response: AccountAuthenticatorResponse?,
+		account: Account?,
+		authTokenType: String?,
+		options: Bundle?,
+	): Bundle? = null
+
+	override fun hasFeatures(
+		response: AccountAuthenticatorResponse?,
+		account: Account?,
+		features: Array<out String>?,
+	): Bundle? = null
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncAuthenticatorService.kt

@@ -0,0 +1,19 @@
+package org.koitharu.kotatsu.sync.ui
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+
+class SyncAuthenticatorService : Service() {
+
+	private lateinit var authenticator: SyncAuthenticator
+
+	override fun onCreate() {
+		super.onCreate()
+		authenticator = SyncAuthenticator(this)
+	}
+
+	override fun onBind(intent: Intent?): IBinder? {
+		return authenticator.iBinder
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/SyncProvider.kt

@@ -0,0 +1,96 @@
+package org.koitharu.kotatsu.sync.ui
+
+import android.content.ContentProvider
+import android.content.ContentProviderOperation
+import android.content.ContentProviderResult
+import android.content.ContentValues
+import android.database.Cursor
+import android.database.sqlite.SQLiteDatabase
+import android.net.Uri
+import androidx.sqlite.db.SupportSQLiteQueryBuilder
+import java.util.concurrent.Callable
+import org.koin.android.ext.android.inject
+import org.koitharu.kotatsu.core.db.MangaDatabase
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITES
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_FAVOURITE_CATEGORIES
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_HISTORY
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_MANGA_TAGS
+import org.koitharu.kotatsu.core.db.MangaDatabase.Companion.TABLE_TAGS
+
+abstract class SyncProvider : ContentProvider() {
+
+	private val database by inject<MangaDatabase>()
+	private val supportedTables = setOf(
+		TABLE_FAVOURITES,
+		TABLE_MANGA,
+		TABLE_TAGS,
+		TABLE_FAVOURITE_CATEGORIES,
+		TABLE_HISTORY,
+		TABLE_MANGA_TAGS,
+	)
+
+	override fun onCreate(): Boolean {
+		return true
+	}
+
+	override fun query(
+		uri: Uri,
+		projection: Array<out String>?,
+		selection: String?,
+		selectionArgs: Array<out String>?,
+		sortOrder: String?
+	): Cursor? = if (getTableName(uri) != null) {
+		val sqlQuery = SupportSQLiteQueryBuilder.builder(uri.lastPathSegment)
+			.columns(projection)
+			.selection(selection, selectionArgs)
+			.orderBy(sortOrder)
+			.create()
+		database.openHelper.readableDatabase.query(sqlQuery)
+	} else {
+		null
+	}
+
+	override fun getType(uri: Uri): String? {
+		return getTableName(uri)?.let { "vnd.android.cursor.dir/" }
+	}
+
+	override fun insert(uri: Uri, values: ContentValues?): Uri? {
+		val table = getTableName(uri)
+		if (values == null || table == null) {
+			return null
+		}
+		val db = database.openHelper.writableDatabase
+		db.insert(table, SQLiteDatabase.CONFLICT_REPLACE, values)
+		return null
+	}
+
+	override fun delete(uri: Uri, selection: String?, selectionArgs: Array<out String>?): Int {
+		val table = getTableName(uri)
+		if (table == null) {
+			return 0
+		}
+		return database.openHelper.writableDatabase.delete(table, selection, selectionArgs)
+	}
+
+	override fun update(uri: Uri, values: ContentValues?, selection: String?, selectionArgs: Array<out String>?): Int {
+		val table = getTableName(uri)
+		if (values == null || table == null) {
+			return 0
+		}
+		return database.openHelper.writableDatabase
+			.update(table, SQLiteDatabase.CONFLICT_IGNORE, values, selection, selectionArgs)
+	}
+
+	override fun applyBatch(operations: ArrayList<ContentProviderOperation>): Array<ContentProviderResult> {
+		return database.runInTransaction(Callable { super.applyBatch(operations) })
+	}
+
+	override fun bulkInsert(uri: Uri, values: Array<out ContentValues>): Int {
+		return database.runInTransaction(Callable { super.bulkInsert(uri, values) })
+	}
+
+	private fun getTableName(uri: Uri): String? {
+		return uri.pathSegments.singleOrNull()?.takeIf { it in supportedTables }
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/favourites/FavouritesSyncAdapter.kt

@@ -0,0 +1,28 @@
+package org.koitharu.kotatsu.sync.ui.favourites
+
+import android.accounts.Account
+import android.content.AbstractThreadedSyncAdapter
+import android.content.ContentProviderClient
+import android.content.Context
+import android.content.SyncResult
+import android.os.Bundle
+import org.koitharu.kotatsu.sync.domain.SyncRepository
+import org.koitharu.kotatsu.utils.ext.onError
+
+class FavouritesSyncAdapter(context: Context) : AbstractThreadedSyncAdapter(context, true) {
+
+	override fun onPerformSync(
+		account: Account,
+		extras: Bundle,
+		authority: String,
+		provider: ContentProviderClient,
+		syncResult: SyncResult,
+	) {
+		// Debug.waitForDebugger()
+		val repository = SyncRepository(context, account, provider)
+		runCatching {
+			repository.syncFavouriteCategories(syncResult)
+			repository.syncFavourites(syncResult)
+		}.onFailure(syncResult::onError)
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/favourites/FavouritesSyncProvider.kt

@@ -0,0 +1,5 @@
+package org.koitharu.kotatsu.sync.ui.favourites
+
+import org.koitharu.kotatsu.sync.ui.SyncProvider
+
+class FavouritesSyncProvider : SyncProvider()

app/src/main/java/org/koitharu/kotatsu/sync/ui/favourites/FavouritesSyncService.kt

@@ -0,0 +1,19 @@
+package org.koitharu.kotatsu.sync.ui.favourites
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+
+class FavouritesSyncService : Service() {
+
+	private lateinit var syncAdapter: FavouritesSyncAdapter
+
+	override fun onCreate() {
+		super.onCreate()
+		syncAdapter = FavouritesSyncAdapter(applicationContext)
+	}
+
+	override fun onBind(intent: Intent?): IBinder {
+		return syncAdapter.syncAdapterBinder
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/history/HistorySyncAdapter.kt

@@ -0,0 +1,27 @@
+package org.koitharu.kotatsu.sync.ui.history
+
+import android.accounts.Account
+import android.content.AbstractThreadedSyncAdapter
+import android.content.ContentProviderClient
+import android.content.Context
+import android.content.SyncResult
+import android.os.Bundle
+import org.koitharu.kotatsu.sync.domain.SyncRepository
+import org.koitharu.kotatsu.utils.ext.onError
+
+class HistorySyncAdapter(context: Context) : AbstractThreadedSyncAdapter(context, true) {
+
+	override fun onPerformSync(
+		account: Account,
+		extras: Bundle,
+		authority: String,
+		provider: ContentProviderClient,
+		syncResult: SyncResult,
+	) {
+		// Debug.waitForDebugger()
+		val repository = SyncRepository(context, account, provider)
+		runCatching {
+			repository.syncHistory(syncResult)
+		}.onFailure(syncResult::onError)
+	}
+}

app/src/main/java/org/koitharu/kotatsu/sync/ui/history/HistorySyncProvider.kt

@@ -0,0 +1,5 @@
+package org.koitharu.kotatsu.sync.ui.history
+
+import org.koitharu.kotatsu.sync.ui.SyncProvider
+
+class HistorySyncProvider : SyncProvider()

app/src/main/java/org/koitharu/kotatsu/sync/ui/history/HistorySyncService.kt

@@ -0,0 +1,19 @@
+package org.koitharu.kotatsu.sync.ui.history
+
+import android.app.Service
+import android.content.Intent
+import android.os.IBinder
+
+class HistorySyncService : Service() {
+
+	private lateinit var syncAdapter: HistorySyncAdapter
+
+	override fun onCreate() {
+		super.onCreate()
+		syncAdapter = HistorySyncAdapter(applicationContext)
+	}
+
+	override fun onBind(intent: Intent?): IBinder {
+		return syncAdapter.syncAdapterBinder
+	}
+}

app/src/main/java/org/koitharu/kotatsu/utils/ext/AndroidExt.kt

@@ -1,14 +1,20 @@
 package org.koitharu.kotatsu.utils.ext
 
 import android.content.Context
+import android.content.OperationApplicationException
+import android.content.SyncResult
+import android.database.SQLException
 import android.net.ConnectivityManager
 import android.net.Network
 import android.net.NetworkRequest
 import android.net.Uri
 import android.os.Build
 import androidx.work.CoroutineWorker
-import kotlin.coroutines.resume
 import kotlinx.coroutines.suspendCancellableCoroutine
+import okio.IOException
+import org.json.JSONException
+import org.koitharu.kotatsu.BuildConfig
+import kotlin.coroutines.resume
 
 val Context.connectivityManager: ConnectivityManager
 	get() = getSystemService(Context.CONNECTIVITY_SERVICE) as ConnectivityManager
@@ -40,4 +46,14 @@ fun String.toUriOrNull() = if (isEmpty()) null else Uri.parse(this)
 suspend fun CoroutineWorker.trySetForeground(): Boolean = runCatching {
 	val info = getForegroundInfo()
 	setForeground(info)
-}.isSuccess
+}.isSuccess
+
+fun SyncResult.onError(error: Throwable) {
+	when (error) {
+		is IOException -> stats.numIoExceptions++
+		is OperationApplicationException,
+		is SQLException -> databaseError = true
+		is JSONException -> stats.numParseExceptions++
+		else -> if (BuildConfig.DEBUG) throw error
+	}
+}

app/src/main/java/org/koitharu/kotatsu/utils/ext/CursorExt.kt

@@ -0,0 +1,39 @@
+package org.koitharu.kotatsu.utils.ext
+
+import android.content.ContentValues
+import android.database.Cursor
+import org.json.JSONObject
+
+fun Cursor.toJson(): JSONObject {
+	val jo = JSONObject()
+	for (i in 0 until columnCount) {
+		val name = getColumnName(i)
+		when (getType(i)) {
+			Cursor.FIELD_TYPE_STRING -> jo.put(name, getString(i))
+			Cursor.FIELD_TYPE_FLOAT -> jo.put(name, getDouble(i))
+			Cursor.FIELD_TYPE_INTEGER -> jo.put(name, getLong(i))
+			Cursor.FIELD_TYPE_NULL -> jo.put(name, null)
+			Cursor.FIELD_TYPE_BLOB -> jo.put(name, getBlob(i))
+		}
+	}
+	return jo
+}
+
+fun JSONObject.toContentValues(): ContentValues {
+	val cv = ContentValues(length())
+	for (key in keys()) {
+		val name = key.escapeName()
+		when (val value = get(key)) {
+			null -> cv.putNull(name)
+			is String -> cv.put(name, value)
+			is Float -> cv.put(name, value)
+			is Double -> cv.put(name, value)
+			is Int -> cv.put(name, value)
+			is Long -> cv.put(name, value)
+			else -> throw IllegalArgumentException("Value $value cannot be putted in ContentValues")
+		}
+	}
+	return cv
+}
+
+private fun String.escapeName() = "`$this`"

app/src/main/java/org/koitharu/kotatsu/utils/ext/HttpExt.kt

@@ -0,0 +1,9 @@
+package org.koitharu.kotatsu.utils.ext
+
+import okhttp3.MediaType.Companion.toMediaType
+import okhttp3.RequestBody.Companion.toRequestBody
+import org.json.JSONObject
+
+private val TYPE_JSON = "application/json".toMediaType()
+
+fun JSONObject.toRequestBody() = toString().toRequestBody(TYPE_JSON)

app/src/main/res/drawable/ic_sync.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<vector
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	android:width="24dp"
+	android:height="24dp"
+	android:tint="?colorControlNormal"
+	android:viewportWidth="24"
+	android:viewportHeight="24">
+	<path
+		android:fillColor="#000"
+		android:pathData="M12,18A6,6 0 0,1 6,12C6,11 6.25,10.03 6.7,9.2L5.24,7.74C4.46,8.97 4,10.43 4,12A8,8 0 0,0 12,20V23L16,19L12,15M12,4V1L8,5L12,9V6A6,6 0 0,1 18,12C18,13 17.75,13.97 17.3,14.8L18.76,16.26C19.54,15.03 20,13.57 20,12A8,8 0 0,0 12,4Z" />
+</vector>

app/src/main/res/layout/activity_sync_auth.xml

@@ -0,0 +1,177 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	xmlns:app="http://schemas.android.com/apk/res-auto"
+	xmlns:tools="http://schemas.android.com/tools"
+	android:layout_width="match_parent"
+	android:layout_height="match_parent"
+	android:orientation="vertical"
+	android:padding="@dimen/screen_padding">
+
+	<TextView
+		android:id="@+id/textView_title"
+		android:layout_width="match_parent"
+		android:layout_height="wrap_content"
+		android:layout_marginTop="8dp"
+		android:drawablePadding="16dp"
+		android:gravity="center_horizontal"
+		android:text="@string/sync_title"
+		android:textAppearance="?textAppearanceHeadline5"
+		app:drawableTint="?colorPrimary"
+		app:drawableTopCompat="@drawable/ic_sync"
+		app:layout_constraintEnd_toEndOf="parent"
+		app:layout_constraintStart_toStartOf="parent"
+		app:layout_constraintTop_toTopOf="parent" />
+
+	<ViewSwitcher
+		android:id="@+id/switcher"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent">
+
+		<RelativeLayout
+			android:id="@+id/page_email"
+			android:layout_width="match_parent"
+			android:layout_height="match_parent">
+
+			<TextView
+				android:id="@+id/textView_subtitle"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentTop="true"
+				android:layout_alignParentEnd="true"
+				android:layout_marginTop="12dp"
+				android:gravity="center_horizontal"
+				android:text="@string/email_enter_hint"
+				android:textAppearance="?textAppearanceSubtitle1" />
+
+			<com.google.android.material.textfield.TextInputLayout
+				android:id="@+id/layout_email"
+				style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_below="@id/textView_subtitle"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentEnd="true"
+				android:layout_marginTop="30dp"
+				app:errorIconDrawable="@null"
+				app:helperText="You can sign in into an existing account or create a new one"
+				app:hintEnabled="false">
+
+				<com.google.android.material.textfield.TextInputEditText
+					android:id="@+id/edit_email"
+					android:layout_width="match_parent"
+					android:layout_height="wrap_content"
+					android:autofillHints="emailAddress"
+					android:imeOptions="actionDone"
+					android:inputType="textEmailAddress"
+					android:singleLine="true"
+					android:textSize="16sp"
+					tools:text="test@mail.com" />
+
+			</com.google.android.material.textfield.TextInputLayout>
+
+			<Button
+				android:id="@+id/button_cancel"
+				style="@style/Widget.Material3.Button.OutlinedButton"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentBottom="true"
+				android:text="@android:string/cancel" />
+
+			<Button
+				android:id="@+id/button_next"
+				style="@style/Widget.Material3.Button.TonalButton"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:layout_alignParentEnd="true"
+				android:layout_alignParentBottom="true"
+				android:enabled="false"
+				android:text="@string/next"
+				tools:ignore="RelativeOverlap" />
+
+		</RelativeLayout>
+
+		<RelativeLayout
+			android:id="@+id/page_password"
+			android:layout_width="match_parent"
+			android:layout_height="match_parent">
+
+			<TextView
+				android:id="@+id/textView_subtitle_2"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentTop="true"
+				android:layout_alignParentEnd="true"
+				android:layout_marginTop="12dp"
+				android:gravity="center_horizontal"
+				android:text="Enter your email to continue"
+				android:textAppearance="?textAppearanceSubtitle1" />
+
+			<com.google.android.material.textfield.TextInputLayout
+				android:id="@+id/layout_password"
+				style="@style/Widget.MaterialComponents.TextInputLayout.OutlinedBox"
+				android:layout_width="0dp"
+				android:layout_height="wrap_content"
+				android:layout_below="@id/textView_subtitle_2"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentEnd="true"
+				android:layout_marginTop="30dp"
+				app:errorIconDrawable="@null"
+				app:helperText="You can sign in into an existing account or create a new one"
+				app:hintEnabled="false">
+
+				<com.google.android.material.textfield.TextInputEditText
+					android:id="@+id/edit_password"
+					android:layout_width="match_parent"
+					android:layout_height="wrap_content"
+					android:autofillHints="password"
+					android:imeOptions="actionDone"
+					android:inputType="textPassword"
+					android:maxLength="24"
+					android:singleLine="true"
+					android:textSize="16sp"
+					tools:text="qwerty" />
+
+			</com.google.android.material.textfield.TextInputLayout>
+
+			<Button
+				android:id="@+id/button_back"
+				style="@style/Widget.Material3.Button.OutlinedButton"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:layout_alignParentStart="true"
+				android:layout_alignParentBottom="true"
+				android:text="@string/back" />
+
+			<Button
+				android:id="@+id/button_done"
+				style="@style/Widget.Material3.Button.TonalButton"
+				android:layout_width="wrap_content"
+				android:layout_height="wrap_content"
+				android:layout_alignParentEnd="true"
+				android:layout_alignParentBottom="true"
+				android:enabled="false"
+				android:text="@string/done"
+				tools:ignore="RelativeOverlap" />
+
+		</RelativeLayout>
+	</ViewSwitcher>
+
+	<FrameLayout
+		android:id="@+id/layout_progress"
+		android:layout_width="match_parent"
+		android:layout_height="match_parent"
+		android:visibility="gone">
+
+		<com.google.android.material.progressindicator.CircularProgressIndicator
+			android:layout_width="wrap_content"
+			android:layout_height="wrap_content"
+			android:layout_gravity="center"
+			android:indeterminate="true" />
+
+	</FrameLayout>
+
+</LinearLayout>

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

@@ -1,9 +1,11 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
-	<string name="url_github_issues">https://github.com/nv95/Kotatsu/issues</string>
+	<string name="url_github_issues" translatable="false">https://github.com/nv95/Kotatsu/issues</string>
-	<string name="url_discord">https://discord.gg/NNJ5RgVBC5</string>
+	<string name="url_discord" translatable="false">https://discord.gg/NNJ5RgVBC5</string>
-	<string name="url_forpda">https://4pda.to/forum/index.php?showtopic=697669</string>
+	<string name="url_forpda" translatable="false">https://4pda.to/forum/index.php?showtopic=697669</string>
-	<string name="url_weblate">https://hosted.weblate.org/engage/kotatsu</string>
+	<string name="url_weblate" translatable="false">https://hosted.weblate.org/engage/kotatsu</string>
+	<string name="account_type_sync" translatable="false">org.kotatsu.sync</string>
+	<string name="url_sync_server" translatable="false">http://192.168.0.113:8080</string>
 	<string-array name="values_theme" translatable="false">
 		<item>-1</item>
 		<item>1</item>

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

@@ -279,4 +279,10 @@
 	<string name="download_slowdown_summary">Helps avoid blocking your IP address</string>
 	<string name="local_manga_processing">Saved manga processing</string>
 	<string name="chapters_will_removed_background">Chapters will be removed in the background. It can take some time</string>
+	<string name="canceled">Canceled</string>
+	<string name="account_already_exists">Account already exists</string>
+	<string name="back">Back</string>
+	<string name="sync">Synchronization</string>
+	<string name="sync_title">Sync your data</string>
+	<string name="email_enter_hint">Enter your email to continue</string>
 </resources>

app/src/main/res/xml/authenticator_sync.xml

@@ -0,0 +1,7 @@
+<?xml version="1.0" encoding="utf-8"?>
+<account-authenticator
+	xmlns:android="http://schemas.android.com/apk/res/android"
+	android:accountPreferences="@xml/pref_sync"
+	android:accountType="@string/account_type_sync"
+	android:icon="@mipmap/ic_launcher"
+	android:label="@string/app_name" />

app/src/main/res/xml/pref_sync.xml

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="utf-8"?>
+<PreferenceScreen
+	xmlns:android="http://schemas.android.com/apk/res/android">
+
+	<Preference
+		android:persistent="false"
+		android:summary="Preference stub"
+		android:title="TODO" />
+
+</PreferenceScreen>

app/src/main/res/xml/sync_favourites.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<sync-adapter xmlns:android="http://schemas.android.com/apk/res/android"
+	android:accountType="@string/account_type_sync"
+	android:allowParallelSyncs="false"
+	android:contentAuthority="org.koitharu.kotatsu.favourites"
+	android:isAlwaysSyncable="true"
+	android:supportsUploading="true"
+	android:userVisible="true" />

app/src/main/res/xml/sync_history.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="utf-8"?>
+<sync-adapter xmlns:android="http://schemas.android.com/apk/res/android"
+	android:accountType="@string/account_type_sync"
+	android:allowParallelSyncs="false"
+	android:contentAuthority="org.koitharu.kotatsu.history"
+	android:isAlwaysSyncable="true"
+	android:supportsUploading="true"
+	android:userVisible="true" />