Merge feature/settings-validation (server validation, cache/TTS scaffold) into feature/ui-polish

app/src/main/java/org/dueattendant149/bookshelf/data/di/AppModule.kt

@@ -8,6 +8,7 @@ package org.dueattendant149.bookshelf.data.di
 
 import android.app.Application
 import androidx.room.Room
+import androidx.work.WorkManager
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
@@ -46,6 +47,10 @@ object AppModule {
             .build()
     }
 
+    @Provides
+    @Singleton
+    fun provideWorkManager(app: Application): WorkManager = WorkManager.getInstance(app)
+
     @Provides
     @Singleton
     fun provideBookDatabase(app: Application): BookDatabase {

app/src/main/java/org/dueattendant149/bookshelf/data/di/RepositoryModule.kt

@@ -29,6 +29,7 @@ import org.dueattendant149.bookshelf.data.parser.file.FileParserImpl
 import org.dueattendant149.bookshelf.data.parser.text.TextParser
 import org.dueattendant149.bookshelf.data.parser.text.TextParserImpl
 import org.dueattendant149.bookshelf.data.repository.BookRepositoryImpl
+import org.dueattendant149.bookshelf.data.repository.CacheRepositoryImpl
 import org.dueattendant149.bookshelf.data.repository.CategoryRepositoryImpl
 import org.dueattendant149.bookshelf.data.repository.ColorPresetRepositoryImpl
 import org.dueattendant149.bookshelf.data.repository.FileSystemRepositoryImpl

app/src/main/java/org/dueattendant149/bookshelf/data/local/room/CachedFileDao.kt

@@ -12,16 +12,26 @@ import androidx.room.Insert
 import androidx.room.OnConflictStrategy
 import androidx.room.Query
 import androidx.room.Update
+import kotlinx.coroutines.flow.Flow
 import org.dueattendant149.bookshelf.data.local.dto.CachedFileEntity
 
 @Dao
 interface CachedFileDao {
     @Insert(onConflict = OnConflictStrategy.REPLACE)
-    suspend fun insert(file: CachedFileEntity)
+    suspend fun insert(file: CachedFileEntity): Long
 
     @Query("SELECT * FROM cached_file WHERE bookId = :bookId AND type = :type")
     suspend fun getByBookIdAndType(bookId: Int, type: String): List<CachedFileEntity>
 
+    @Query("SELECT * FROM cached_file WHERE bookId = :bookId AND type = :type LIMIT 1")
+    suspend fun getByBookIdAndTypeSingle(bookId: Int, type: String): CachedFileEntity?
+
+    @Query("SELECT * FROM cached_file WHERE bookId = :bookId")
+    suspend fun getByBookId(bookId: Int): List<CachedFileEntity>
+
+    @Query("SELECT * FROM cached_file WHERE bookId = :bookId")
+    fun observeByBookId(bookId: Int): Flow<List<CachedFileEntity>>
+
     @Query("SELECT * FROM cached_file WHERE status = :status")
     suspend fun getByStatus(status: String): List<CachedFileEntity>
 

app/src/main/java/org/dueattendant149/bookshelf/data/remote/bookshelfapi/BookshelfApiService.kt

@@ -31,6 +31,10 @@ import retrofit2.http.Streaming
  */
 interface BookshelfApiService {
 
+    // Health
+    @GET("health")
+    suspend fun health(): Response<String>
+
     // Libraries / books
     @GET("api/v1/books/libraries")
     suspend fun getLibraries(): Response<List<LibraryResponse>>

app/src/main/java/org/dueattendant149/bookshelf/data/repository/CacheRepositoryImpl.kt

@@ -0,0 +1,231 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.data.repository
+
+import android.app.Application
+import androidx.work.Constraints
+import androidx.work.Data
+import androidx.work.ExistingWorkPolicy
+import androidx.work.NetworkType
+import androidx.work.OneTimeWorkRequestBuilder
+import androidx.work.WorkManager
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.flow
+import kotlinx.coroutines.flow.flowOn
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.withContext
+import org.dueattendant149.bookshelf.data.local.dto.BookEntity
+import org.dueattendant149.bookshelf.data.local.dto.CachedFileEntity
+import org.dueattendant149.bookshelf.data.local.room.BookDatabase
+import org.dueattendant149.bookshelf.data.mapper.book.BookMapper
+import org.dueattendant149.bookshelf.data.settings.ServerSettings
+import org.dueattendant149.bookshelf.data.worker.CacheDownloadWorker
+import org.dueattendant149.bookshelf.domain.model.cache.CacheState
+import org.dueattendant149.bookshelf.domain.model.cache.CacheStatus
+import org.dueattendant149.bookshelf.domain.model.cache.CachedFile
+import org.dueattendant149.bookshelf.domain.model.library.Book
+import org.dueattendant149.bookshelf.domain.repository.CacheRepository
+import java.io.File
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class CacheRepositoryImpl
+    @Inject
+    constructor(
+        private val database: BookDatabase,
+        private val bookMapper: BookMapper,
+        private val serverSettings: ServerSettings,
+        private val workManager: WorkManager,
+        private val application: Application,
+    ) : CacheRepository {
+        override suspend fun cacheBook(book: Book): Result<Unit> = runCatching {
+            withContext(Dispatchers.IO) {
+                val localBook = findOrInsertBook(book)
+                val bookId = localBook.id
+                val absUrl = serverSettings.getAbsUrl() ?: error("Audiobookshelf URL not configured")
+
+                if (book.coverUrl.isNotBlank()) {
+                    createCacheRecord(bookId, "cover", book.coverUrl)
+                }
+                if (book.hasEbook) {
+                    createCacheRecord(
+                        bookId,
+                        "ebook",
+                        "$absUrl/api/items/${book.remoteId}/download",
+                    )
+                }
+                if (book.hasAudio) {
+                    createCacheRecord(
+                        bookId,
+                        "audio",
+                        "$absUrl/api/items/${book.remoteId}/download",
+                    )
+                }
+
+                val inputData =
+                    Data
+                        .Builder()
+                        .putInt(CacheDownloadWorker.KEY_BOOK_ID, bookId)
+                        .putString(CacheDownloadWorker.KEY_REMOTE_ID, book.remoteId)
+                        .putString(CacheDownloadWorker.KEY_TITLE, book.title)
+                        .putString(CacheDownloadWorker.KEY_MEDIA_TYPE, book.mediaType)
+                        .putBoolean(CacheDownloadWorker.KEY_HAS_AUDIO, book.hasAudio)
+                        .putBoolean(CacheDownloadWorker.KEY_HAS_EBOOK, book.hasEbook)
+                        .putString(CacheDownloadWorker.KEY_COVER_URL, book.coverUrl)
+                        .build()
+
+                val request =
+                    OneTimeWorkRequestBuilder<CacheDownloadWorker>()
+                        .setInputData(inputData)
+                        .setConstraints(
+                            Constraints
+                                .Builder()
+                                .setRequiredNetworkType(NetworkType.CONNECTED)
+                                .build(),
+                        )
+                        .build()
+
+                workManager.enqueueUniqueWork(
+                    CacheDownloadWorker.workName(bookId),
+                    ExistingWorkPolicy.KEEP,
+                    request,
+                )
+            }
+        }
+
+        override suspend fun deleteCache(remoteId: String): Result<Unit> = runCatching {
+            withContext(Dispatchers.IO) {
+                val book = database.bookDao.findBookByRemoteId(remoteId) ?: return@withContext
+                val records = database.cachedFileDao.getByBookId(book.id)
+                records.forEach { record ->
+                    record.localPath?.let { path ->
+                        File(path).delete()
+                    }
+                    database.cachedFileDao.delete(record)
+                }
+                workManager.cancelUniqueWork(CacheDownloadWorker.workName(book.id))
+            }
+        }
+
+        override fun observeCacheStatus(remoteId: String): Flow<CacheStatus> =
+            flow {
+                val bookId = database.bookDao.findBookByRemoteId(remoteId)?.id
+                if (bookId == null) {
+                    emit(
+                        CacheStatus(
+                            remoteId = remoteId,
+                            state = CacheState.NONE,
+                            progress = 0f,
+                            cachedFiles = emptyList(),
+                        ),
+                    )
+                    return@flow
+                }
+
+                database.cachedFileDao.observeByBookId(bookId).map { records ->
+                    records.toCacheStatus(remoteId)
+                }.collect { emit(it) }
+            }.flowOn(Dispatchers.IO)
+
+        private suspend fun findOrInsertBook(book: Book): BookEntity {
+            val existing = database.bookDao.findBookByRemoteId(book.remoteId)
+            return if (existing != null) {
+                val updated =
+                    existing.copy(
+                        title = book.title,
+                        author = book.author.getAsString() ?: "",
+                        coverUrl = book.coverUrl,
+                        hasAudio = book.hasAudio,
+                        hasEbook = book.hasEbook,
+                        audioDuration = book.audioDuration,
+                        mediaType = book.mediaType,
+                        libraryId = book.libraryId,
+                        lastSyncedAt = System.currentTimeMillis(),
+                    )
+                database.bookDao.updateBook(updated)
+                database.bookDao.findBookByRemoteId(book.remoteId) ?: updated
+            } else {
+                val entity = bookMapper.toBookEntity(book.copy(filePath = ""))
+                database.bookDao.insertBook(entity)
+                database.bookDao.findBookByRemoteId(book.remoteId)
+                    ?: error("Failed to insert book for caching")
+            }
+        }
+
+        private suspend fun createCacheRecord(
+            bookId: Int,
+            type: String,
+            url: String,
+        ) {
+            val existing = database.cachedFileDao.getByBookIdAndTypeSingle(bookId, type)
+            if (existing == null) {
+                database.cachedFileDao.insert(
+                    CachedFileEntity(
+                        bookId = bookId,
+                        type = type,
+                        remoteUrl = url,
+                        status = "pending",
+                        progress = 0f,
+                    ),
+                )
+            } else if (existing.status == "completed" &&
+                existing.localPath != null &&
+                File(existing.localPath).exists()
+            ) {
+                // Already cached locally, leave it alone.
+            } else {
+                database.cachedFileDao.update(
+                    existing.copy(status = "pending", progress = 0f),
+                )
+            }
+        }
+
+        private fun List<CachedFileEntity>.toCacheStatus(remoteId: String): CacheStatus {
+            if (isEmpty()) {
+                return CacheStatus(
+                    remoteId = remoteId,
+                    state = CacheState.NONE,
+                    progress = 0f,
+                    cachedFiles = emptyList(),
+                )
+            }
+
+            val files =
+                map {
+                    CachedFile(
+                        type = it.type,
+                        status = it.status,
+                        progress = it.progress,
+                        localPath = it.localPath,
+                    )
+                }
+
+            val state =
+                when {
+                    files.any { it.status == "failed" } -> CacheState.FAILED
+                    files.any { it.status == "downloading" } -> CacheState.DOWNLOADING
+                    files.all { it.status == "completed" } -> CacheState.COMPLETED
+                    else -> CacheState.PENDING
+                }
+
+            val progress =
+                when (state) {
+                    CacheState.DOWNLOADING -> files.filter { it.status == "downloading" }.map { it.progress }.average().toFloat()
+                    CacheState.COMPLETED -> 1f
+                    else -> 0f
+                }
+
+            return CacheStatus(
+                remoteId = remoteId,
+                state = state,
+                progress = progress,
+                cachedFiles = files,
+            )
+        }
+    }

app/src/main/java/org/dueattendant149/bookshelf/data/settings/ServerSettings.kt

@@ -8,6 +8,8 @@ package org.dueattendant149.bookshelf.data.settings
 
 import androidx.datastore.preferences.core.stringPreferencesKey
 import org.dueattendant149.bookshelf.data.local.data_store.DataStore
+import org.dueattendant149.bookshelf.domain.util.isValidUri
+import org.dueattendant149.bookshelf.domain.util.normalizeUri
 import javax.inject.Inject
 import javax.inject.Singleton
 
@@ -21,23 +23,63 @@ class ServerSettings
         private val absUrlKey = stringPreferencesKey("abs_url")
         private val absTokenKey = stringPreferencesKey("abs_token")
 
-        suspend fun getBookshelfUrl(): String? = dataStore.getNullableData(bookshelfUrlKey)
-        suspend fun setBookshelfUrl(value: String) = dataStore.putData(bookshelfUrlKey, value)
+        suspend fun getBookshelfUrl(): String? =
+            dataStore.getNullableData(bookshelfUrlKey)?.normalizeIfValid()
 
-        suspend fun getAbsUrl(): String? = dataStore.getNullableData(absUrlKey)
-        suspend fun setAbsUrl(value: String) = dataStore.putData(absUrlKey, value)
+        suspend fun setBookshelfUrl(value: String) {
+            dataStore.putData(bookshelfUrlKey, value.normalizeIfValid() ?: value.trim())
+        }
 
-        suspend fun getAbsToken(): String? = dataStore.getNullableData(absTokenKey)
-        suspend fun setAbsToken(value: String) = dataStore.putData(absTokenKey, value)
+        suspend fun getAbsUrl(): String? =
+            dataStore.getNullableData(absUrlKey)?.normalizeIfValid()
 
-        suspend fun hasCredentials(): Boolean =
-            !getBookshelfUrl().isNullOrBlank() &&
-                !getAbsUrl().isNullOrBlank() &&
-                !getAbsToken().isNullOrBlank()
+        suspend fun setAbsUrl(value: String) {
+            dataStore.putData(absUrlKey, value.normalizeIfValid() ?: value.trim())
+        }
+
+        suspend fun getAbsToken(): String? = dataStore.getNullableData(absTokenKey)?.trim()
+        suspend fun setAbsToken(value: String) = dataStore.putData(absTokenKey, value.trim())
+
+        suspend fun hasCredentials(): Boolean = getMissingCredentialsError() == null
+
+        /**
+         * Returns a user-facing error message if any required credential is missing or invalid,
+         * or null when all credentials are present.
+         */
+        suspend fun getMissingCredentialsError(): String? {
+            val bookshelfUrl = dataStore.getNullableData(bookshelfUrlKey)
+            if (bookshelfUrl.isNullOrBlank()) {
+                return "Bookshelf API URL is missing"
+            }
+            if (!bookshelfUrl.isValidUri()) {
+                return "Bookshelf API URL is invalid: $bookshelfUrl"
+            }
+            if (dataStore.getNullableData(absUrlKey).isNullOrBlank()) {
+                return "Audiobookshelf URL is missing"
+            }
+            if (dataStore.getNullableData(absTokenKey).isNullOrBlank()) {
+                return "ABS token is missing"
+            }
+            return null
+        }
+
+        suspend fun validateBookshelfUrl(): Result<String> {
+            val url = dataStore.getNullableData(bookshelfUrlKey)?.trim()
+            return when {
+                url.isNullOrBlank() -> Result.failure(IllegalArgumentException("Bookshelf URL is empty"))
+                !url.isValidUri() -> Result.failure(IllegalArgumentException("Bookshelf URL is invalid: $url"))
+                else -> Result.success(url.normalizeUri())
+            }
+        }
 
         suspend fun clear() {
             setBookshelfUrl("")
             setAbsUrl("")
             setAbsToken("")
         }
+
+        private fun String.normalizeIfValid(): String? {
+            val trimmed = trim()
+            return if (trimmed.isValidUri()) trimmed.normalizeUri() else null
+        }
     }

app/src/main/java/org/dueattendant149/bookshelf/data/worker/CacheDownloadWorker.kt

@@ -0,0 +1,194 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.data.worker
+
+import android.content.Context
+import android.util.Log
+import androidx.work.CoroutineWorker
+import androidx.work.WorkerParameters
+import dagger.hilt.EntryPoint
+import dagger.hilt.InstallIn
+import dagger.hilt.android.EntryPointAccessors
+import dagger.hilt.components.SingletonComponent
+import okhttp3.ResponseBody
+import org.dueattendant149.bookshelf.data.local.dto.CachedFileEntity
+import org.dueattendant149.bookshelf.data.local.room.BookDatabase
+import org.dueattendant149.bookshelf.data.remote.audiobookshelf.AudiobookshelfApiClientFactory
+import org.dueattendant149.bookshelf.data.settings.ServerSettings
+import retrofit2.Response
+import java.io.File
+import java.io.IOException
+
+class CacheDownloadWorker(
+    context: Context,
+    params: WorkerParameters,
+) : CoroutineWorker(context, params) {
+    companion object {
+        const val KEY_BOOK_ID = "book_id"
+        const val KEY_REMOTE_ID = "remote_id"
+        const val KEY_TITLE = "title"
+        const val KEY_MEDIA_TYPE = "media_type"
+        const val KEY_HAS_AUDIO = "has_audio"
+        const val KEY_HAS_EBOOK = "has_ebook"
+        const val KEY_COVER_URL = "cover_url"
+
+        fun workName(bookId: Int) = "cache-download-$bookId"
+    }
+
+    private val entryPoint: CacheWorkerEntryPoint by lazy {
+        EntryPointAccessors.fromApplication(applicationContext, CacheWorkerEntryPoint::class.java)
+    }
+
+    override suspend fun doWork(): Result {
+        val bookId = inputData.getInt(KEY_BOOK_ID, -1)
+        val remoteId = inputData.getString(KEY_REMOTE_ID) ?: return Result.failure()
+        val title = inputData.getString(KEY_TITLE) ?: remoteId
+        val hasAudio = inputData.getBoolean(KEY_HAS_AUDIO, false)
+        val hasEbook = inputData.getBoolean(KEY_HAS_EBOOK, false)
+        val coverUrl = inputData.getString(KEY_COVER_URL) ?: ""
+
+        if (bookId < 0) {
+            return Result.failure()
+        }
+
+        val database = entryPoint.database()
+        val serverSettings = entryPoint.serverSettings()
+        val clientFactory = entryPoint.audiobookshelfFactory()
+
+        val absUrl = serverSettings.getAbsUrl()
+        val token = serverSettings.getAbsToken()
+        if (absUrl.isNullOrBlank() || token.isNullOrBlank()) {
+            Log.e(TAG, "ABS credentials not configured")
+            return Result.failure()
+        }
+
+        val client = clientFactory.provideClient(absUrl, token)
+        if (client == null) {
+            Log.e(TAG, "Failed to create ABS client")
+            return Result.failure()
+        }
+
+        val bookDir = File(applicationContext.filesDir, "bookshelf-cache/$bookId").apply { mkdirs() }
+
+        return try {
+            if (coverUrl.isNotBlank()) {
+                downloadFile(
+                    database = database,
+                    bookId = bookId,
+                    type = "cover",
+                    remoteUrl = coverUrl,
+                    localFile = File(bookDir, "cover"),
+                ) { client.getCover(remoteId) }
+            }
+
+            if (hasEbook) {
+                downloadFile(
+                    database = database,
+                    bookId = bookId,
+                    type = "ebook",
+                    remoteUrl = "$absUrl/api/items/$remoteId/download",
+                    localFile = File(bookDir, "ebook"),
+                ) { client.downloadBook(remoteId) }
+            }
+
+            if (hasAudio) {
+                downloadFile(
+                    database = database,
+                    bookId = bookId,
+                    type = "audio",
+                    remoteUrl = "$absUrl/api/items/$remoteId/download",
+                    localFile = File(bookDir, "audio"),
+                ) { client.downloadBook(remoteId) }
+            }
+
+            Result.success()
+        } catch (e: Exception) {
+            Log.e(TAG, "Cache download failed for book $bookId ($title)", e)
+            Result.retry()
+        }
+    }
+
+    private suspend fun downloadFile(
+        database: BookDatabase,
+        bookId: Int,
+        type: String,
+        remoteUrl: String,
+        localFile: File,
+        download: suspend () -> Response<ResponseBody>,
+    ) {
+        val record = getOrCreateRecord(database, bookId, type, remoteUrl)
+
+        if (record.status == "completed" && record.localPath != null && File(record.localPath).exists()) {
+            return
+        }
+
+        database.cachedFileDao.update(record.copy(status = "downloading", progress = 0f))
+
+        try {
+            val response = download()
+            if (!response.isSuccessful) {
+                throw IOException("Download failed: ${response.code()}")
+            }
+
+            val body = response.body() ?: throw IOException("Empty response body")
+            val totalBytes = body.contentLength().takeIf { it > 0 } ?: -1L
+
+            body.byteStream().use { input ->
+                localFile.outputStream().use { output ->
+                    val buffer = ByteArray(8192)
+                    var read: Int
+                    var totalRead = 0L
+                    while (input.read(buffer).also { read = it } != -1) {
+                        output.write(buffer, 0, read)
+                        totalRead += read
+                        if (totalBytes > 0) {
+                            val progress = totalRead / totalBytes.toFloat()
+                            database.cachedFileDao.update(
+                                record.copy(status = "downloading", progress = progress),
+                            )
+                        }
+                    }
+                }
+            }
+
+            database.cachedFileDao.update(
+                record.copy(
+                    status = "completed",
+                    progress = 1f,
+                    localPath = localFile.absolutePath,
+                ),
+            )
+        } catch (e: Exception) {
+            database.cachedFileDao.update(record.copy(status = "failed", progress = 0f))
+            throw e
+        }
+    }
+
+    private suspend fun getOrCreateRecord(
+        database: BookDatabase,
+        bookId: Int,
+        type: String,
+        remoteUrl: String,
+    ): CachedFileEntity {
+        return database.cachedFileDao.getByBookIdAndTypeSingle(bookId, type)
+            ?: CachedFileEntity(
+                bookId = bookId,
+                type = type,
+                remoteUrl = remoteUrl,
+            ).also { database.cachedFileDao.insert(it) }
+    }
+
+    @EntryPoint
+    @InstallIn(SingletonComponent::class)
+    interface CacheWorkerEntryPoint {
+        fun database(): BookDatabase
+        fun serverSettings(): ServerSettings
+        fun audiobookshelfFactory(): AudiobookshelfApiClientFactory
+    }
+}
+
+private const val TAG = "CacheDownloadWorker"

app/src/main/java/org/dueattendant149/bookshelf/domain/model/cache/CacheStatus.kt

@@ -0,0 +1,29 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.model.cache
+
+data class CacheStatus(
+    val remoteId: String,
+    val state: CacheState,
+    val progress: Float,
+    val cachedFiles: List<CachedFile>,
+)
+
+enum class CacheState {
+    NONE,
+    PENDING,
+    DOWNLOADING,
+    COMPLETED,
+    FAILED,
+}
+
+data class CachedFile(
+    val type: String,
+    val status: String,
+    val progress: Float,
+    val localPath: String?,
+)

app/src/main/java/org/dueattendant149/bookshelf/domain/repository/CacheRepository.kt

@@ -0,0 +1,17 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.repository
+
+import kotlinx.coroutines.flow.Flow
+import org.dueattendant149.bookshelf.domain.model.cache.CacheStatus
+import org.dueattendant149.bookshelf.domain.model.library.Book
+
+interface CacheRepository {
+    suspend fun cacheBook(book: Book): Result<Unit>
+    suspend fun deleteCache(remoteId: String): Result<Unit>
+    fun observeCacheStatus(remoteId: String): Flow<CacheStatus>
+}

app/src/main/java/org/dueattendant149/bookshelf/domain/use_case/cache/CacheBookUseCase.kt

@@ -0,0 +1,19 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.use_case.cache
+
+import org.dueattendant149.bookshelf.domain.model.library.Book
+import org.dueattendant149.bookshelf.domain.repository.CacheRepository
+import javax.inject.Inject
+
+class CacheBookUseCase
+    @Inject
+    constructor(
+        private val repository: CacheRepository,
+    ) {
+        suspend operator fun invoke(book: Book): Result<Unit> = repository.cacheBook(book)
+    }

app/src/main/java/org/dueattendant149/bookshelf/domain/use_case/cache/DeleteCacheUseCase.kt

@@ -0,0 +1,18 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.use_case.cache
+
+import org.dueattendant149.bookshelf.domain.repository.CacheRepository
+import javax.inject.Inject
+
+class DeleteCacheUseCase
+    @Inject
+    constructor(
+        private val repository: CacheRepository,
+    ) {
+        suspend operator fun invoke(remoteId: String): Result<Unit> = repository.deleteCache(remoteId)
+    }

app/src/main/java/org/dueattendant149/bookshelf/domain/use_case/cache/GetCacheStatusUseCase.kt

@@ -0,0 +1,20 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.use_case.cache
+
+import kotlinx.coroutines.flow.Flow
+import org.dueattendant149.bookshelf.domain.model.cache.CacheStatus
+import org.dueattendant149.bookshelf.domain.repository.CacheRepository
+import javax.inject.Inject
+
+class GetCacheStatusUseCase
+    @Inject
+    constructor(
+        private val repository: CacheRepository,
+    ) {
+        operator fun invoke(remoteId: String): Flow<CacheStatus> = repository.observeCacheStatus(remoteId)
+    }

app/src/main/java/org/dueattendant149/bookshelf/domain/use_case/remote/CheckHealthUseCase.kt

@@ -0,0 +1,39 @@
+/*
+ * Book's Story — free and open-source Material You eBook reader.
+ * Copyright (C) 2024-2026 Acclorite
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package org.dueattendant149.bookshelf.domain.use_case.remote
+
+import org.dueattendant149.bookshelf.data.remote.bookshelfapi.BookshelfApiClientFactory
+import org.dueattendant149.bookshelf.domain.util.isValidUri
+import org.dueattendant149.bookshelf.domain.util.normalizeUri
+import javax.inject.Inject
+
+class CheckHealthUseCase
+    @Inject
+    constructor(
+        private val clientFactory: BookshelfApiClientFactory,
+    ) {
+        suspend operator fun invoke(url: String): Result<Unit> {
+            val trimmed = url.trim()
+            if (trimmed.isBlank()) {
+                return Result.failure(IllegalArgumentException("Bookshelf URL is empty"))
+            }
+            if (!trimmed.isValidUri()) {
+                return Result.failure(IllegalArgumentException("Bookshelf URL is invalid: $trimmed"))
+            }
+
+            val normalized = trimmed.normalizeUri()
+            val client = clientFactory.provideClient(normalized)
+                ?: return Result.failure(IllegalStateException("Could not create API client for $normalized"))
+
+            return runCatching {
+                val response = client.health()
+                if (!response.isSuccessful) {
+                    throw IllegalStateException("Server returned HTTP ${response.code()}")
+                }
+            }
+        }
+    }

app/src/main/java/org/dueattendant149/bookshelf/domain/util/UriUtils.kt

@@ -1,16 +1,71 @@
 package org.dueattendant149.bookshelf.domain.util
 
+import android.net.Uri
+
+private val URL_SCHEME_REGEX = Regex("^[hH][tT][tT][pP][sS]?://")
+
 /**
- * Ensures the URL ends with a trailing slash so Retrofit can append relative paths.
- * Also adds a default scheme if missing.
+ * Returns true if the string is non-blank, has an http/https scheme,
+ * and can be parsed by [Uri.parse] into a host-bearing URI.
  */
-fun String.fixUriScheme(): String {
-    var url = this.trim()
-    if (!url.startsWith("http://") && !url.startsWith("https://")) {
-        url = "https://$url"
+fun String.isValidUri(): Boolean {
+    val trimmed = trim()
+    if (trimmed.isBlank()) return false
+    if (!trimmed.hasUriScheme()) return false
+
+    val uri = runCatching { Uri.parse(trimmed) }.getOrNull() ?: return false
+    return !uri.host.isNullOrBlank()
 }
-    if (!url.endsWith("/")) {
-        url = "$url/"
+
+/**
+ * Returns true if the string starts with http:// or https:// (case-insensitive).
+ */
+fun String.hasUriScheme(): Boolean = matches(URL_SCHEME_REGEX)
+
+/**
+ * Adds https:// if the string has no http/https scheme.
+ */
+fun String.ensureUriScheme(): String {
+    val trimmed = trim()
+    return if (trimmed.hasUriScheme()) trimmed else "https://$trimmed"
 }
-    return url
+
+/**
+ * Adds a trailing slash if missing.
+ */
+fun String.ensureTrailingSlash(): String {
+    val trimmed = trim()
+    return if (trimmed.endsWith("/")) trimmed else "$trimmed/"
+}
+
+/**
+ * Normalizes a URL for Retrofit: trims whitespace, adds a scheme if missing,
+ * and ensures a trailing slash.
+ */
+fun String.normalizeUri(): String = ensureUriScheme().ensureTrailingSlash()
+
+/**
+ * Legacy alias for [normalizeUri].
+ */
+fun String.fixUriScheme(): String = normalizeUri()
+
+/**
+ * Derives a likely Audiobookshelf URL from a Bookshelf API URL.
+ * Replaces a known bookshelf-api port (8073) with the default ABS port (13378),
+ * or appends :13378 when no port is present. Returns null if the input is invalid.
+ */
+fun String.deriveAbsUrl(): String? {
+    if (!isValidUri()) return null
+    val normalized = normalizeUri()
+    val uri = Uri.parse(normalized)
+    val host = uri.host ?: return null
+    val port = uri.port
+    val scheme = uri.scheme?.lowercase() ?: "https"
+
+    val derivedPort = when (port) {
+        8073 -> 13378
+        -1 -> 13378
+        else -> port
+    }
+    return "$scheme://$host:$derivedPort/"
 }

app/src/main/java/org/dueattendant149/bookshelf/presentation/bookshelf/RemoteLibraryModel.kt

@@ -9,13 +9,20 @@ package org.dueattendant149.bookshelf.presentation.bookshelf
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.Job
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.combine
+import kotlinx.coroutines.flow.flowOf
 import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import org.dueattendant149.bookshelf.data.settings.ServerSettings
+import org.dueattendant149.bookshelf.domain.model.cache.CacheStatus
 import org.dueattendant149.bookshelf.domain.model.library.Book
 import org.dueattendant149.bookshelf.domain.model.remote.RemoteLibrary
+import org.dueattendant149.bookshelf.domain.use_case.cache.CacheBookUseCase
+import org.dueattendant149.bookshelf.domain.use_case.cache.DeleteCacheUseCase
+import org.dueattendant149.bookshelf.domain.use_case.cache.GetCacheStatusUseCase
 import org.dueattendant149.bookshelf.domain.use_case.remote.FetchBooksUseCase
 import org.dueattendant149.bookshelf.domain.use_case.remote.FetchLibrariesUseCase
 import javax.inject.Inject
@@ -26,6 +33,8 @@ data class RemoteLibraryState(
     val selectedLibrary: RemoteLibrary? = null,
     val isLoading: Boolean = false,
     val error: String? = null,
+    val cacheStatuses: Map<String, CacheStatus> = emptyMap(),
+    val offlineOnly: Boolean = false,
 )
 
 @HiltViewModel
@@ -34,10 +43,14 @@ class RemoteLibraryModel
     constructor(
         private val fetchLibrariesUseCase: FetchLibrariesUseCase,
         private val fetchBooksUseCase: FetchBooksUseCase,
+        private val cacheBookUseCase: CacheBookUseCase,
+        private val deleteCacheUseCase: DeleteCacheUseCase,
+        private val getCacheStatusUseCase: GetCacheStatusUseCase,
         private val serverSettings: ServerSettings,
     ) : ViewModel() {
         private val _state = MutableStateFlow(RemoteLibraryState())
         val state = _state.asStateFlow()
+        private var cacheStatusJob: Job? = null
 
         init {
             loadLibraries()
@@ -77,6 +90,56 @@ class RemoteLibraryModel
                         error = result.exceptionOrNull()?.message,
                     )
                 }
+                observeCacheStatuses()
+            }
+        }
+
+        fun cacheBook(book: Book) {
+            viewModelScope.launch {
+                val result = cacheBookUseCase(book)
+                if (result.isFailure) {
+                    _state.update {
+                        it.copy(error = result.exceptionOrNull()?.message ?: "Cache failed")
+                    }
+                }
+                observeCacheStatuses()
+            }
+        }
+
+        fun deleteCache(book: Book) {
+            viewModelScope.launch {
+                val result = deleteCacheUseCase(book.remoteId)
+                if (result.isFailure) {
+                    _state.update {
+                        it.copy(error = result.exceptionOrNull()?.message ?: "Delete cache failed")
+                    }
+                }
+            }
+        }
+
+        fun toggleOfflineOnly() {
+            _state.update { it.copy(offlineOnly = !it.offlineOnly) }
+        }
+
+        private fun observeCacheStatuses() {
+            cacheStatusJob?.cancel()
+            val remoteIds = state.value.books.map { it.remoteId }.filter { it.isNotBlank() }
+            if (remoteIds.isEmpty()) {
+                _state.update { it.copy(cacheStatuses = emptyMap()) }
+                return
+            }
+
+            cacheStatusJob =
+                viewModelScope.launch {
+                    combine(
+                        remoteIds.map { remoteId ->
+                            getCacheStatusUseCase(remoteId)
+                        },
+                    ) { statuses ->
+                        statuses.toList().associateBy { it.remoteId }
+                    }.collect { statuses ->
+                        _state.update { it.copy(cacheStatuses = statuses) }
+                    }
                 }
         }
     }

app/src/main/java/org/dueattendant149/bookshelf/presentation/settings/BookshelfSettingsModel.kt

@@ -15,7 +15,9 @@ import kotlinx.coroutines.flow.update
 import kotlinx.coroutines.launch
 import org.dueattendant149.bookshelf.data.settings.ServerSettings
 import org.dueattendant149.bookshelf.domain.model.remote.RemoteLibrary
+import org.dueattendant149.bookshelf.domain.use_case.remote.CheckHealthUseCase
 import org.dueattendant149.bookshelf.domain.use_case.remote.FetchLibrariesUseCase
+import org.dueattendant149.bookshelf.domain.util.deriveAbsUrl
 import javax.inject.Inject
 
 data class BookshelfSettingsState(
@@ -24,6 +26,9 @@ data class BookshelfSettingsState(
     val absToken: String = "",
     val libraries: List<RemoteLibrary> = emptyList(),
     val isLoading: Boolean = false,
+    val isCheckingConnection: Boolean = false,
+    val connectionError: String? = null,
+    val connectionSuccess: Boolean = false,
     val error: String? = null,
     val librariesSuccess: Boolean = false,
 )
@@ -34,6 +39,7 @@ class BookshelfSettingsModel
     constructor(
         private val serverSettings: ServerSettings,
         private val fetchLibrariesUseCase: FetchLibrariesUseCase,
+        private val checkHealthUseCase: CheckHealthUseCase,
     ) : ViewModel() {
         private val _state = MutableStateFlow(BookshelfSettingsState())
         val state = _state.asStateFlow()
@@ -58,6 +64,8 @@ class BookshelfSettingsModel
             it.copy(
                 bookshelfUrl = value,
                 librariesSuccess = false,
+                connectionSuccess = false,
+                connectionError = null,
                 error = null,
             )
         }
@@ -66,6 +74,8 @@ class BookshelfSettingsModel
             it.copy(
                 absUrl = value,
                 librariesSuccess = false,
+                connectionSuccess = false,
+                connectionError = null,
                 error = null,
             )
         }
@@ -74,10 +84,27 @@ class BookshelfSettingsModel
             it.copy(
                 absToken = value,
                 librariesSuccess = false,
+                connectionSuccess = false,
+                connectionError = null,
                 error = null,
             )
         }
 
+        fun deriveAbsUrlFromBookshelf() {
+            viewModelScope.launch {
+                val derived = _state.value.bookshelfUrl.deriveAbsUrl()
+                if (derived != null) {
+                    _state.update {
+                        it.copy(
+                            absUrl = derived,
+                            librariesSuccess = false,
+                            error = null,
+                        )
+                    }
+                }
+            }
+        }
+
         fun save() {
             viewModelScope.launch {
                 val current = _state.value
@@ -87,6 +114,29 @@ class BookshelfSettingsModel
             }
         }
 
+        fun checkConnection() {
+            viewModelScope.launch {
+                _state.update {
+                    it.copy(
+                        isCheckingConnection = true,
+                        connectionError = null,
+                        connectionSuccess = false,
+                    )
+                }
+                save()
+
+                val url = _state.value.bookshelfUrl
+                val result = checkHealthUseCase(url)
+                _state.update {
+                    it.copy(
+                        isCheckingConnection = false,
+                        connectionSuccess = result.isSuccess,
+                        connectionError = result.exceptionOrNull()?.message,
+                    )
+                }
+            }
+        }
+
         fun testLibraries() {
             viewModelScope.launch {
                 _state.update {
@@ -98,6 +148,18 @@ class BookshelfSettingsModel
                 }
                 save()
 
+                val missingError = serverSettings.getMissingCredentialsError()
+                if (missingError != null) {
+                    _state.update {
+                        it.copy(
+                            isLoading = false,
+                            libraries = emptyList(),
+                            error = missingError,
+                        )
+                    }
+                    return@launch
+                }
+
                 val result = fetchLibrariesUseCase()
                 val libraries = result.getOrDefault(emptyList())
                 _state.update {

app/src/main/java/org/dueattendant149/bookshelf/ui/settings/bookshelf/BookshelfSettingsContent.kt

@@ -104,14 +104,39 @@ fun BookshelfSettingsContent(
                 ) {
                     Button(
                         onClick = model::save,
-                        enabled = !state.isLoading,
+                        enabled = !state.isLoading && !state.isCheckingConnection,
                         modifier = Modifier.weight(1f)
                     ) {
                         Text(stringResource(R.string.save_button))
                     }
+                    Button(
+                        onClick = model::checkConnection,
+                        enabled = !state.isLoading && !state.isCheckingConnection,
+                        modifier = Modifier.weight(1f)
+                    ) {
+                        if (state.isCheckingConnection) {
+                            CircularProgressIndicator()
+                        } else {
+                            Text(stringResource(R.string.check_connection_button))
+                        }
+                    }
+                }
+            }
+            item {
+                Row(
+                    modifier = Modifier.fillMaxWidth(),
+                    horizontalArrangement = Arrangement.spacedBy(8.dp)
+                ) {
+                    OutlinedButton(
+                        onClick = model::deriveAbsUrlFromBookshelf,
+                        enabled = state.bookshelfUrl.isNotBlank() && !state.isLoading,
+                        modifier = Modifier.weight(1f)
+                    ) {
+                        Text(stringResource(R.string.derive_abs_url_button))
+                    }
                     OutlinedButton(
                         onClick = model::testLibraries,
-                        enabled = !state.isLoading,
+                        enabled = !state.isLoading && !state.isCheckingConnection,
                         modifier = Modifier.weight(1f)
                     ) {
                         if (state.isLoading) {
@@ -122,6 +147,22 @@ fun BookshelfSettingsContent(
                     }
                 }
             }
+            state.connectionSuccess.takeIf { it }?.let {
+                item {
+                    Text(
+                        text = stringResource(R.string.connection_successful),
+                        color = MaterialTheme.colorScheme.primary,
+                    )
+                }
+            }
+            state.connectionError?.let { error ->
+                item {
+                    Text(
+                        text = error,
+                        color = MaterialTheme.colorScheme.error,
+                    )
+                }
+            }
             state.librariesSuccess.takeIf { it }?.let {
                 item {
                     Row(

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

@@ -137,6 +137,18 @@
     <string name="bookshelf_settings">Bookshelf</string>
     <string name="bookshelf_settings_desc">Server, ABS, TTS</string>
 
+    <!-- TTS -->
+    <string name="tts_screen">TTS</string>
+    <string name="tts_engine">Engine</string>
+    <string name="tts_voice">Voice</string>
+    <string name="tts_book_id">Book ID</string>
+    <string name="tts_speed">Speed</string>
+    <string name="tts_create_job">Create job</string>
+    <string name="tts_refresh_jobs">Refresh jobs</string>
+    <string name="tts_jobs">Jobs</string>
+    <string name="tts_jobs_button">TTS jobs</string>
+    <string name="tts_button">TTS</string>
+
     <!-- Bookshelf server settings -->
     <string name="bookshelf_settings_screen_title">Bookshelf server</string>
     <string name="bookshelf_url_option">Bookshelf API URL</string>
@@ -146,7 +158,10 @@
     <string name="abs_token_option">ABS token</string>
     <string name="abs_token_option_desc">API token from Audiobookshelf settings</string>
     <string name="save_button">Save</string>
+    <string name="check_connection_button">Check connection</string>
+    <string name="derive_abs_url_button">Derive ABS URL</string>
     <string name="fetch_libraries_button">Fetch libraries</string>
+    <string name="connection_successful">Connection successful</string>
     <string name="libraries_fetched_successful">Connected to %1$d libraries</string>
     <string name="bookshelf_libraries_header">Libraries</string>
     <string name="bookshelf_library_subtitle">%1$s • %2$d items</string>
@@ -510,6 +525,13 @@
     <string name="browse_content_desc">Add books</string>
     <string name="bookshelf_screen">Bookshelf</string>
     <string name="bookshelf_content_desc">Remote bookshelf</string>
+    <string name="bookshelf_offline_only_label">Offline only</string>
+    <string name="bookshelf_cache_pending">Pending</string>
+    <string name="bookshelf_cache_downloading">Downloading</string>
+    <string name="bookshelf_cache_completed">Cached</string>
+    <string name="bookshelf_cache_failed">Failed</string>
+    <string name="bookshelf_download_action">Download</string>
+    <string name="bookshelf_delete_cache_action">Delete</string>
     <string name="arrow_content_desc">Arrow</string>
     <string name="reset_start_content_desc">Reset start guide</string>
     <string name="open_in_web_content_desc">Open in web</string>