Android: recover books and covers when file access is lost

app/src/main/java/com/readarea/core/BookLoader.kt

@@ -227,19 +227,23 @@ object ImageUtil {
 
 object BookLoader {
 
-    private fun metaZip(context: Context, uri: Uri, keep: (String, Long) -> Boolean): MemoryZipAccess {
+    private fun metaZip(context: Context, uri: Uri, maxEntry: Int = MemoryZipAccess.MAX_ENTRY, keep: (String, Long) -> Boolean): MemoryZipAccess {
         val input = if (uri.scheme == "file") File(uri.path!!).inputStream() else context.contentResolver.openInputStream(uri) ?: throw FileNotFoundException("Unable to open file")
-        return input.use { MemoryZipAccess(it, keep) }
+        return input.use { MemoryZipAccess(it, maxEntry, keep) }
     }
 
+    /** Reads one image from a book for its cover; high-resolution covers can be larger than other entries read for details. */
+    private fun coverEntry(context: Context, uri: Uri, ref: String): ByteArray? =
+        metaZip(context, uri, Limits.ENTRY) { name, _ -> name.equals(ref, true) || PathUtil.decode(name).equals(ref, true) }.read(ref)
+
     private fun isImage(name: String): Boolean {
         val l = name.lowercase()
         return l.endsWith(".jpg") || l.endsWith(".jpeg") || l.endsWith(".png") || l.endsWith(".webp") || l.endsWith(".gif") || l.endsWith(".bmp")
     }
 
     private fun withCover(context: Context, uri: Uri, zip: ZipAccess, parsed: ParsedBook): ReflowableBook {
         val ref = parsed.meta.coverRef
-        val bytes = ref?.let { r -> zip.read(r) ?: metaZip(context, uri) { name, _ -> name.equals(r, true) || PathUtil.decode(name).equals(r, true) }.read(r) }
+        val bytes = ref?.let { r -> zip.read(r) ?: coverEntry(context, uri, r) }
         return ReflowableBook(ParsedBook(parsed.meta, emptyList(), emptyList(), ResourceProvider { p -> if (p == ref) bytes else null }))
     }
 
@@ -255,7 +259,7 @@ object BookLoader {
                 val docZip = metaZip(context, uri) { name, _ -> name.equals(doc, true) || PathUtil.decode(name).equals(doc, true) }
                 EpubParser(docZip).firstImageIn(doc)
             }
-            val coverBytes = coverRef?.let { ref -> zip.read(ref) ?: metaZip(context, uri) { name, _ -> name.equals(ref, true) || PathUtil.decode(name).equals(ref, true) }.read(ref) }
+            val coverBytes = coverRef?.let { ref -> zip.read(ref) ?: coverEntry(context, uri, ref) }
             val meta = (if (parsed.meta.title.isBlank()) parsed.meta.copy(title = title) else parsed.meta).copy(coverRef = coverRef)
             ReflowableBook(ParsedBook(meta, emptyList(), emptyList(), ResourceProvider { p -> if (p == coverRef) coverBytes else null }))
         }
@@ -270,7 +274,7 @@ object BookLoader {
         BookFormat.CBZ -> {
             val names = metaZip(context, uri) { _, _ -> false }.entries
             val best = names.filter { isImage(it) && !it.lowercase().startsWith("__macosx") }.minWithOrNull { a, b -> CbzSource.naturalCompare(a, b) }
-            val cover = best?.let { b -> metaZip(context, uri) { name, _ -> name == b }.read(b) }
+            val cover = best?.let { b -> metaZip(context, uri, Limits.ENTRY) { name, _ -> name == b }.read(b) }
             ReflowableBook(ParsedBook(BookMeta(title = title, coverRef = best), emptyList(), emptyList(), ResourceProvider { p -> if (p == best) cover else null }))
         }
         else -> null

app/src/main/java/com/readarea/data/LibraryRepository.kt

@@ -47,6 +47,11 @@ class LibraryRepository(
     private val _scan = MutableStateFlow(ScanState())
     val scan: StateFlow<ScanState> = _scan.asStateFlow()
 
+    private val _lostFolders = MutableStateFlow<List<String>>(emptyList())
+
+    /** Library folders Android no longer lets ReadArea read, whose books are set aside until it's granted again. */
+    val lostFolders: StateFlow<List<String>> = _lostFolders.asStateFlow()
+
     val books = db.books().observeAll()
     val collections = db.collections().observe()
     val highlights = db.notes().allHighlights()
@@ -98,7 +103,17 @@ class LibraryRepository(
         val s = settings.appNow()
         if (!s.reopenLastBook || s.resumeBookId <= 0) return null
         val b = db.books().get(s.resumeBookId) ?: return null
-        return if (b.missing) null else b.id
+        // Starting on an error page instead of the library helps nobody: only reopen a book that can be read.
+        return if (b.missing || !canRead(b.uri)) null else b.id
+    }
+
+    /** Whether a book's file can be opened right now, checked without reading it. */
+    private suspend fun canRead(uri: String): Boolean = withContext(Dispatchers.IO) {
+        val u = uri.toUri()
+        runCatching {
+            if (u.scheme == "file") File(u.path!!).canRead()
+            else context.contentResolver.openFileDescriptor(u, "r")?.use { true } ?: false
+        }.getOrDefault(false)
     }
 
     suspend fun adoptGrantedAccess(): Boolean {
@@ -121,9 +136,19 @@ class LibraryRepository(
             val ignored = app.ignored.toHashSet()
             _scan.value = ScanState(running = true, phase = ScanPhase.FOLDERS)
             var found = 0
+            val lost = ArrayList<String>()
             for (folder in folders) {
                 val tree = folder.toUri()
-                val files = runCatching { walkTree(tree) }.getOrElse { emptyList() }
+                val walked = runCatching { walkTree(tree) }
+                if (walked.exceptionOrNull() is SecurityException) {
+                    // Android took back access to this folder (a reinstall restored from backup, or access withdrawn):
+                    // its books can't be opened, so they are set aside until the folder is chosen again.
+                    lost.add(folder)
+                    val stranded = db.books().all().filter { it.folderUri == folder && !it.missing }.map { it.id }
+                    setMissing(stranded, true)
+                    continue
+                }
+                val files = walked.getOrElse { emptyList() }
                 found += files.size
                 _scan.value = _scan.value.copy(found = found)
                 val all = db.books().all()
@@ -150,7 +175,16 @@ class LibraryRepository(
                 val gone = existing.values.filter { it.uri !in seen && !it.missing }.map { it.id }
                 if (gone.isNotEmpty() && files.isNotEmpty()) db.books().setMissing(gone, true)
             }
-            if (app.deviceScan && DeviceStorage.hasAccess(context)) found += scanDevice(found, ignored)
+            _lostFolders.value = lost
+            if (DeviceStorage.hasAccess(context)) {
+                if (app.deviceScan) found += scanDevice(found, ignored)
+            } else {
+                // Books found on the device can only be read with access to all files; without it they'd fail when opened.
+                val stranded = db.books().all().filter { it.folderUri == DeviceStorage.DEVICE && !it.missing }.map { it.id }
+                setMissing(stranded, true)
+            }
+            checkImportedAccess()
+            forgetLostCovers()
             _scan.value = ScanState(running = true, found = found, phase = ScanPhase.DETAILS)
             metaMutex.withLock { loadPendingMetadata() }
             _scan.value = ScanState(running = false, found = found)
@@ -191,6 +225,32 @@ class LibraryRepository(
         return found.size
     }
 
+    /**
+     * Books added one by one keep a permission per file, which Android can take back (a reinstall, or its limit on
+     * how many it keeps). Those that can't be opened are set aside, and come back once they can be.
+     */
+    private suspend fun checkImportedAccess() = withContext(Dispatchers.IO) {
+        val held = context.contentResolver.persistedUriPermissions.filter { it.isReadPermission }.map { it.uri.toString() }.toHashSet()
+        val imported = db.books().all().filter { it.folderUri == null && it.uri.toUri().scheme == "content" }
+        val lost = ArrayList<Long>()
+        val back = ArrayList<Long>()
+        for (b in imported) {
+            val readable = b.uri in held || canRead(b.uri)
+            if (!readable && !b.missing) lost.add(b.id) else if (readable && b.missing) back.add(b.id)
+        }
+        setMissing(lost, true)
+        setMissing(back, false)
+    }
+
+    /** Covers live in app storage, which a restore from backup doesn't bring back: read the ones that are gone again. */
+    private suspend fun forgetLostCovers() = withContext(Dispatchers.IO) {
+        val gone = db.books().all().filter { b -> b.coverPath?.let { !File(it).exists() } == true }.map { it.id }
+        gone.chunked(500).forEach { db.books().forgetCovers(it) }
+    }
+
+    /** Android's SQLite takes at most 999 values in one statement, and these lists can be a whole library. */
+    private suspend fun setMissing(ids: List<Long>, missing: Boolean) = ids.chunked(500).forEach { db.books().setMissing(it, missing) }
+
     private data class FoundFile(val uri: String, val name: String, val size: Long, val modified: Long, val format: BookFormat)
 
     private fun walkTree(tree: Uri): List<FoundFile> {
@@ -357,13 +417,18 @@ class LibraryRepository(
             } finally {
                 opened.close()
             }
-        }.getOrElse { book.copy(metaLoaded = true) }
+        }
+        // A file that can't be opened right now (not reachable, or access not granted yet) is tried again on the next
+        // scan; only one that opened but couldn't be read is settled without details.
+        val error = updated.exceptionOrNull()
+        if (error is java.io.FileNotFoundException || error is SecurityException) return
+        val details = updated.getOrElse { book.copy(metaLoaded = true) }
         val current = db.books().get(book.id) ?: return
         db.books().update(
             current.copy(
-                title = updated.title, author = updated.author, description = updated.description, language = updated.language,
-                series = updated.series, seriesIndex = updated.seriesIndex, publisher = updated.publisher, coverPath = updated.coverPath,
-                metaLoaded = true, pageCount = updated.pageCount,
+                title = details.title, author = details.author, description = details.description, language = details.language,
+                series = details.series, seriesIndex = details.seriesIndex, publisher = details.publisher, coverPath = details.coverPath,
+                metaLoaded = true, pageCount = details.pageCount,
             ),
         )
     }

app/src/main/java/com/readarea/data/db/Daos.kt

@@ -60,6 +60,10 @@ interface BookDao {
     @Query("UPDATE books SET missing = :missing WHERE id IN (:ids)")
     suspend fun setMissing(ids: List<Long>, missing: Boolean)
 
+    /** Forgets covers whose image is gone, so their details are read again. */
+    @Query("UPDATE books SET coverPath = NULL, metaLoaded = 0 WHERE id IN (:ids)")
+    suspend fun forgetCovers(ids: List<Long>)
+
     @Query("DELETE FROM books WHERE id IN (:ids)")
     suspend fun delete(ids: List<Long>)
 

app/src/main/java/com/readarea/ui/LibraryViewModel.kt

@@ -154,11 +154,14 @@ class LibraryViewModel(application: Application) : AndroidViewModel(application)
 
     suspend fun resumeTarget(): Long? = repo.resumeTarget()
 
-    suspend fun shouldOfferDeviceScan(): Boolean {
+    /** Whether to offer finding books on the device: the first time, or when it's on but Android took back the access it needs. */
+    suspend fun shouldOfferDeviceScan(hasAccess: Boolean): Boolean {
         val s = settingsRepo.appNow()
-        return !s.askedDeviceScan && !s.deviceScan
+        return (!s.askedDeviceScan && !s.deviceScan) || (s.deviceScan && !hasAccess)
     }
 
+    val lostFolders = repo.lostFolders
+
     fun importFiles(uris: List<Uri>, onDone: (List<Long>) -> Unit = {}) {
         viewModelScope.launch { onDone(repo.importFiles(uris)) }
     }

app/src/main/java/com/readarea/ui/ReadAreaRoot.kt

@@ -26,6 +26,8 @@ import androidx.compose.material3.adaptive.navigationsuite.NavigationSuiteScaffo
 import androidx.compose.material3.adaptive.navigationsuite.NavigationSuiteType
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.getValue
+import androidx.core.net.toUri
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.compose.runtime.mutableStateOf
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.saveable.rememberSaveable
@@ -108,14 +110,31 @@ fun ReadAreaRoot(vm: LibraryViewModel) {
         if (granted) vm.setDeviceScan(true) else vm.markDeviceScanAsked()
     }
     LaunchedEffect(Unit) {
-        if (vm.shouldOfferDeviceScan()) {
+        if (vm.shouldOfferDeviceScan(DeviceStorage.hasAccess(context))) {
             if (DeviceStorage.hasAccess(context)) vm.setDeviceScan(true) else findDialog = true
         }
     }
     LifecycleResumeEffect(Unit) {
         vm.adoptGrantedAccess()
         onPauseOrDispose {}
     }
+    val lostFolders by vm.lostFolders.collectAsStateWithLifecycle()
+    var dismissedFolders by rememberSaveable { mutableStateOf(listOf<String>()) }
+    lostFolders.firstOrNull { it !in dismissedFolders }?.let { folder ->
+        AlertDialog(
+            onDismissRequest = { dismissedFolders = dismissedFolders + folder },
+            icon = { Icon(Icons.Rounded.TravelExplore, null) },
+            title = { Text(stringResource(R.string.folder_access_lost_title)) },
+            text = { Text(stringResource(R.string.folder_access_lost_body, folderLabel(context, folder))) },
+            confirmButton = {
+                Button(onClick = {
+                    dismissedFolders = dismissedFolders + folder
+                    runCatching { folderPicker.launch(folder.toUri()) }
+                }) { Text(stringResource(R.string.choose_folder_again)) }
+            },
+            dismissButton = { TextButton(onClick = { dismissedFolders = dismissedFolders + folder }) { Text(stringResource(R.string.not_now)) } },
+        )
+    }
     if (findDialog) {
         AlertDialog(
             onDismissRequest = { findDialog = false; vm.markDeviceScanAsked() },
@@ -191,3 +210,11 @@ fun ReadAreaRoot(vm: LibraryViewModel) {
     }
     details?.let { id -> BookDetailsSheet(vm, actions, id) { details = null } }
 }
+
+/** A library folder as people know it, e.g. "Internal storage › Books", from its tree address. */
+private fun folderLabel(context: android.content.Context, uri: String): String = runCatching {
+    val id = android.provider.DocumentsContract.getTreeDocumentId(uri.toUri())
+    val path = id.substringAfter(':', id)
+    val root = id.substringBefore(':')
+    (if (root.equals("primary", true)) context.getString(R.string.internal_storage) else root) + if (path.isNotEmpty()) " › " + path.replace("/", " › ") else ""
+}.getOrElse { Uri.decode(uri) }

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

@@ -444,4 +444,7 @@
         <item quantity="many">تم تحديد %d عنصرًا</item>
         <item quantity="other">تم تحديد %d عنصر</item>
     </plurals>
+    <string name="choose_folder_again">اختيار المجلد</string>
+    <string name="folder_access_lost_body">لم يعد بإمكان ReadArea فتح الكتب في «%s». اختر ذلك المجلد مجددًا لاستعادتها.</string>
+    <string name="folder_access_lost_title">هل تسمح بالوصول مجددًا؟</string>
 </resources>

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

@@ -404,4 +404,7 @@
         <item quantity="one">%d ausgewählt</item>
         <item quantity="other">%d ausgewählt</item>
     </plurals>
+    <string name="choose_folder_again">Ordner wählen</string>
+    <string name="folder_access_lost_body">ReadArea kann die Bücher in „%s“ nicht mehr öffnen. Wähle diesen Ordner erneut aus, um sie zurückzuholen.</string>
+    <string name="folder_access_lost_title">Zugriff erneut erlauben?</string>
 </resources>

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

@@ -414,4 +414,7 @@
         <item quantity="many">%d seleccionados</item>
         <item quantity="other">%d seleccionados</item>
     </plurals>
+    <string name="choose_folder_again">Elegir carpeta</string>
+    <string name="folder_access_lost_body">ReadArea ya no puede abrir los libros de «%s». Vuelve a elegir esa carpeta para recuperarlos.</string>
+    <string name="folder_access_lost_title">¿Permitir el acceso de nuevo?</string>
 </resources>

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

@@ -414,4 +414,7 @@
         <item quantity="many">%d sélectionnés</item>
         <item quantity="other">%d sélectionnés</item>
     </plurals>
+    <string name="choose_folder_again">Choisir le dossier</string>
+    <string name="folder_access_lost_body">ReadArea ne peut plus ouvrir les livres de « %s ». Choisissez de nouveau ce dossier pour les retrouver.</string>
+    <string name="folder_access_lost_title">Autoriser l\'accès à nouveau ?</string>
 </resources>

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

@@ -404,4 +404,7 @@
         <item quantity="one">%d चुनी गई</item>
         <item quantity="other">%d चुनी गईं</item>
     </plurals>
+    <string name="choose_folder_again">फ़ोल्डर चुनें</string>
+    <string name="folder_access_lost_body">ReadArea अब “%s” में मौजूद किताबें नहीं खोल सकता। उन्हें वापस पाने के लिए वह फ़ोल्डर फिर से चुनें।</string>
+    <string name="folder_access_lost_title">फिर से एक्सेस की अनुमति दें?</string>
 </resources>

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

@@ -394,4 +394,7 @@
     <plurals name="selected_count">
         <item quantity="other">%d dipilih</item>
     </plurals>
+    <string name="choose_folder_again">Pilih folder</string>
+    <string name="folder_access_lost_body">ReadArea tidak bisa lagi membuka buku di “%s”. Pilih folder itu lagi untuk mengembalikannya.</string>
+    <string name="folder_access_lost_title">Izinkan akses lagi?</string>
 </resources>

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

@@ -414,4 +414,7 @@
         <item quantity="many">%d selezionati</item>
         <item quantity="other">%d selezionati</item>
     </plurals>
+    <string name="choose_folder_again">Scegli cartella</string>
+    <string name="folder_access_lost_body">ReadArea non può più aprire i libri in “%s”. Scegli di nuovo quella cartella per riaverli.</string>
+    <string name="folder_access_lost_title">Consentire di nuovo l\'accesso?</string>
 </resources>

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

@@ -394,4 +394,7 @@
     <plurals name="selected_count">
         <item quantity="other">%d件選択</item>
     </plurals>
+    <string name="choose_folder_again">フォルダを選択</string>
+    <string name="folder_access_lost_body">ReadArea は「%s」の本を開けなくなりました。そのフォルダをもう一度選ぶと元に戻ります。</string>
+    <string name="folder_access_lost_title">もう一度アクセスを許可しますか？</string>
 </resources>

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

@@ -394,4 +394,7 @@
     <plurals name="selected_count">
         <item quantity="other">%d개 선택됨</item>
     </plurals>
+    <string name="choose_folder_again">폴더 선택</string>
+    <string name="folder_access_lost_body">ReadArea에서 더 이상 “%s”의 책을 열 수 없습니다. 해당 폴더를 다시 선택하면 책이 돌아옵니다.</string>
+    <string name="folder_access_lost_title">다시 접근을 허용할까요?</string>
 </resources>

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

@@ -404,4 +404,7 @@
         <item quantity="one">%d geselecteerd</item>
         <item quantity="other">%d geselecteerd</item>
     </plurals>
+    <string name="choose_folder_again">Map kiezen</string>
+    <string name="folder_access_lost_body">ReadArea kan de boeken in ‘%s’ niet meer openen. Kies die map opnieuw om ze terug te halen.</string>
+    <string name="folder_access_lost_title">Opnieuw toegang geven?</string>
 </resources>

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

@@ -424,4 +424,7 @@
         <item quantity="many">Zaznaczono %d</item>
         <item quantity="other">Zaznaczono %d</item>
     </plurals>
+    <string name="choose_folder_again">Wybierz folder</string>
+    <string name="folder_access_lost_body">ReadArea nie może już otworzyć książek w „%s”. Wybierz ten folder ponownie, aby je odzyskać.</string>
+    <string name="folder_access_lost_title">Zezwolić ponownie na dostęp?</string>
 </resources>

app/src/main/res/values-pt-rBR/strings.xml

@@ -414,4 +414,7 @@
         <item quantity="many">%d selecionados</item>
         <item quantity="other">%d selecionados</item>
     </plurals>
+    <string name="choose_folder_again">Escolher pasta</string>
+    <string name="folder_access_lost_body">O ReadArea não consegue mais abrir os livros em “%s”. Escolha essa pasta de novo para recuperá-los.</string>
+    <string name="folder_access_lost_title">Permitir o acesso de novo?</string>
 </resources>