Fixed the issue where the Zim File was not displaying in the ZimHostFragment for custom apps.

* In `ZimHostFragment`, we show Zim files that are saved in the database. These files are typically saved when downloading Zim files. In a custom app, where Zim files are already included within the app and not downloaded separately that's why they are not showing on the `ZimHostFragment`, we have addressed this issue by saving the Zim files in the database to ensure they appear in the `ZimHostFragment`.
* Regarding the `FileDescriptor`, there are no file objects available because we read Zim files using `FileDescriptor`. To address this, we have created a `demo.zim` file to save it in the database so that it will be displayed in the `ZimHostFragment`. We handle this file within the `KiwixServer`. When the current Zim file is `demo.zim`, we create an `Archive` object with the `FileDescriptor` to host the Zim file on the `KiwixServer`.

core/src/main/java/org/kiwix/kiwixmobile/core/main/MainRepositoryActions.kt

@@ -24,6 +24,7 @@ import org.kiwix.kiwixmobile.core.di.ActivityScope
 import org.kiwix.kiwixmobile.core.page.bookmark.adapter.BookmarkItem
 import org.kiwix.kiwixmobile.core.page.history.adapter.HistoryListItem.HistoryItem
 import org.kiwix.kiwixmobile.core.page.notes.adapter.NoteListItem
+import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem.BookOnDisk
 import javax.inject.Inject
 
 private const val TAG = "MainPresenter"
@@ -33,6 +34,7 @@ class MainRepositoryActions @Inject constructor(private val dataSource: DataSour
   private var saveHistoryDisposable: Disposable? = null
   private var saveBookmarkDisposable: Disposable? = null
   private var saveNoteDisposable: Disposable? = null
+  private var saveBookDisposable: Disposable? = null
   private var deleteNoteDisposable: Disposable? = null
 
   fun saveHistory(history: HistoryItem) {
@@ -61,10 +63,16 @@ class MainRepositoryActions @Inject constructor(private val dataSource: DataSour
       .subscribe({}, { e -> Log.e(TAG, "Unable to delete note", e) })
   }
 
+  fun saveBook(book: BookOnDisk) {
+    saveBookDisposable = dataSource.saveBook(book)
+      .subscribe({}, { e -> Log.e(TAG, "Unable to save book", e) })
+  }
+
   fun dispose() {
     saveHistoryDisposable?.dispose()
     saveBookmarkDisposable?.dispose()
     saveNoteDisposable?.dispose()
     deleteNoteDisposable?.dispose()
+    saveBookDisposable?.dispose()
   }
 }

core/src/main/java/org/kiwix/kiwixmobile/core/reader/ZimFileReader.kt

@@ -53,7 +53,7 @@ private const val TAG = "ZimFileReader"
 
 class ZimFileReader constructor(
   val zimFile: File?,
-  private val assetFileDescriptor: AssetFileDescriptor? = null,
+  val assetFileDescriptor: AssetFileDescriptor? = null,
   private val jniKiwixReader: Archive,
   private val nightModeConfig: NightModeConfig,
   private val searcher: SuggestionSearcher = SuggestionSearcher(jniKiwixReader)

core/src/main/java/org/kiwix/kiwixmobile/core/utils/files/FileUtils.kt

@@ -29,6 +29,7 @@ import android.provider.DocumentsContract
 import android.util.Log
 import android.webkit.URLUtil
 import android.widget.Toast
+import androidx.core.content.ContextCompat
 import androidx.documentfile.provider.DocumentFile
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Dispatchers
@@ -402,4 +403,8 @@ object FileUtils {
       null
     }
   }
+
+  @JvmStatic
+  fun getDemoFilePathForCustomApp(context: Context) =
+    "${ContextCompat.getExternalFilesDirs(context, null)[0]}/demo.zim"
 }

core/src/main/java/org/kiwix/kiwixmobile/core/webserver/KiwixServer.kt

@@ -18,7 +18,10 @@
 
 package org.kiwix.kiwixmobile.core.webserver
 
+import android.content.Context
 import android.util.Log
+import org.kiwix.kiwixmobile.core.reader.ZimReaderContainer
+import org.kiwix.kiwixmobile.core.utils.files.FileUtils.getDemoFilePathForCustomApp
 import org.kiwix.libkiwix.Book
 import org.kiwix.libkiwix.JNIKiwixException
 import org.kiwix.libkiwix.Library
@@ -36,13 +39,32 @@ class KiwixServer @Inject constructor(
   private val jniKiwixServer: Server
 ) {
 
-  class Factory @Inject constructor() {
+  class Factory @Inject constructor(
+    private val context: Context,
+    private val zimReaderContainer: ZimReaderContainer
+  ) {
+    @Suppress("NestedBlockDepth")
     fun createKiwixServer(selectedBooksPath: ArrayList<String>): KiwixServer {
       val kiwixLibrary = Library()
       selectedBooksPath.forEach { path ->
         try {
           val book = Book().apply {
-            update(Archive(path))
+            // Determine whether to create an Archive from an asset or a file path
+            val archive = if (path == getDemoFilePathForCustomApp(context)) {
+              // For custom apps using a demo file, create an Archive with FileDescriptor
+              val assetFileDescriptor = zimReaderContainer.zimFileReader?.assetFileDescriptor
+              val startOffset = assetFileDescriptor?.startOffset ?: 0L
+              val size = assetFileDescriptor?.length ?: 0L
+              Archive(
+                assetFileDescriptor?.parcelFileDescriptor?.dup()?.fileDescriptor,
+                startOffset,
+                size
+              )
+            } else {
+              // For regular files, create an Archive from the file path
+              Archive(path)
+            }
+            update(archive)
           }
           kiwixLibrary.addBook(book)
         } catch (e: JNIKiwixException) {

core/src/main/java/org/kiwix/kiwixmobile/core/webserver/ZimHostFragment.kt

@@ -53,6 +53,7 @@ import org.kiwix.kiwixmobile.core.extensions.ActivityExtensions.requestNotificat
 import org.kiwix.kiwixmobile.core.extensions.toast
 import org.kiwix.kiwixmobile.core.navigateToAppSettings
 import org.kiwix.kiwixmobile.core.reader.ZimFileReader
+import org.kiwix.kiwixmobile.core.reader.ZimReaderContainer
 import org.kiwix.kiwixmobile.core.utils.ConnectivityReporter
 import org.kiwix.kiwixmobile.core.utils.REQUEST_POST_NOTIFICATION_PERMISSION
 import org.kiwix.kiwixmobile.core.utils.ServerUtils
@@ -60,15 +61,15 @@ import org.kiwix.kiwixmobile.core.utils.SharedPreferenceUtil
 import org.kiwix.kiwixmobile.core.utils.dialog.AlertDialogShower
 import org.kiwix.kiwixmobile.core.utils.dialog.KiwixDialog
 import org.kiwix.kiwixmobile.core.utils.dialog.KiwixDialog.StartServer
+import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService
+import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_CHECK_IP_ADDRESS
+import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_START_SERVER
+import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_STOP_SERVER
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.SelectionMode
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BookOnDiskDelegate
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskAdapter
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem
 import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem.BookOnDisk
-import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService
-import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_CHECK_IP_ADDRESS
-import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_START_SERVER
-import org.kiwix.kiwixmobile.core.webserver.wifi_hotspot.HotspotService.Companion.ACTION_STOP_SERVER
 import javax.inject.Inject
 
 class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
@@ -87,6 +88,9 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
   @Inject
   lateinit var zimReaderFactory: ZimFileReader.Factory
 
+  @Inject
+  lateinit var zimReaderContainer: ZimReaderContainer
+
   private lateinit var booksAdapter: BooksOnDiskAdapter
   private lateinit var bookDelegate: BookOnDiskDelegate.BookDelegate
   private var hotspotService: HotspotService? = null
@@ -485,19 +489,14 @@ class ZimHostFragment : BaseFragment(), ZimHostCallbacks, ZimHostContract.View {
       val updatedBooksList: MutableList<BooksOnDiskListItem> = arrayListOf()
       books.forEach {
         if (it is BookOnDisk) {
-          zimReaderFactory.create(it.file)?.let { zimFileReader ->
+          zimReaderContainer.zimFileReader?.let { zimFileReader ->
             val booksOnDiskListItem =
-              zimFileReader.zimFile?.let { file ->
+              (BookOnDisk(it.file, zimFileReader) as BooksOnDiskListItem)
-                (BookOnDisk(file, zimFileReader) as BooksOnDiskListItem)
                 .apply {
                   isSelected = true
                 }
-              }
-            if (booksOnDiskListItem != null) {
             updatedBooksList.add(booksOnDiskListItem)
           }
-            zimFileReader.dispose()
-          }
         } else {
           updatedBooksList.add(it)
         }

custom/src/main/java/org/kiwix/kiwixmobile/custom/main/CustomReaderFragment.kt

@@ -32,6 +32,7 @@ import org.kiwix.kiwixmobile.core.base.BaseActivity
 import org.kiwix.kiwixmobile.core.base.FragmentActivityExtensions
 import org.kiwix.kiwixmobile.core.extensions.ActivityExtensions.observeNavigationResult
 import org.kiwix.kiwixmobile.core.extensions.ActivityExtensions.setupDrawerToggle
+import org.kiwix.kiwixmobile.core.extensions.isFileExist
 import org.kiwix.kiwixmobile.core.main.CoreReaderFragment
 import org.kiwix.kiwixmobile.core.main.FIND_IN_PAGE_SEARCH_STRING
 import org.kiwix.kiwixmobile.core.main.MainMenu
@@ -39,11 +40,14 @@ import org.kiwix.kiwixmobile.core.search.viewmodel.effects.SearchItemToOpen
 import org.kiwix.kiwixmobile.core.utils.LanguageUtils
 import org.kiwix.kiwixmobile.core.utils.TAG_FILE_SEARCHED
 import org.kiwix.kiwixmobile.core.utils.dialog.DialogShower
+import org.kiwix.kiwixmobile.core.utils.files.FileUtils.getDemoFilePathForCustomApp
 import org.kiwix.kiwixmobile.core.utils.titleToUrl
 import org.kiwix.kiwixmobile.core.utils.urlSuffixToParsableUrl
+import org.kiwix.kiwixmobile.core.zim_manager.fileselect_view.adapter.BooksOnDiskListItem.BookOnDisk
 import org.kiwix.kiwixmobile.custom.BuildConfig
 import org.kiwix.kiwixmobile.custom.R
 import org.kiwix.kiwixmobile.custom.customActivityComponent
+import java.io.File
 import java.util.Locale
 import javax.inject.Inject
 
@@ -149,6 +153,15 @@ class CustomReaderFragment : CoreReaderFragment() {
             } else {
               openZimFile(it.file, true)
             }
+            // Save book in the database to display it in `ZimHostFragment`.
+            zimReaderContainer?.zimFileReader?.let { zimFileReader ->
+              // Check if the file is not null. If the file is null,
+              // it means we have created zimFileReader with a fileDescriptor,
+              // so we create a demo file to save it in the database for display on the `ZimHostFragment`.
+              val file = it.file ?: createDemoFile()
+              val bookOnDisk = BookOnDisk(file, zimFileReader)
+              repositoryActions?.saveBook(bookOnDisk)
+            }
           }
           is ValidationState.HasBothFiles -> {
             it.zimFile.delete()
@@ -163,6 +176,11 @@ class CustomReaderFragment : CoreReaderFragment() {
     )
   }
 
+  private fun createDemoFile() =
+    File(getDemoFilePathForCustomApp(requireActivity())).also {
+      if (!it.isFileExist()) it.createNewFile()
+    }
+
   @Suppress("DEPRECATION")
   override fun onCreateOptionsMenu(menu: Menu, inflater: MenuInflater) {
     super.onCreateOptionsMenu(menu, inflater)