refactor: clean up comparison.

Signed-off-by: KaiserBh <kaiserbh@proton.me>

app/src/main/java/eu/kanade/tachiyomi/data/sync/SyncManager.kt

@@ -22,6 +22,7 @@ import tachiyomi.data.Chapters
 import tachiyomi.data.DatabaseHandler
 import tachiyomi.data.manga.MangaMapper.mapManga
 import tachiyomi.domain.category.interactor.GetCategories
+import tachiyomi.domain.chapter.model.Chapter
 import tachiyomi.domain.manga.interactor.GetFavorites
 import tachiyomi.domain.manga.model.Manga
 import tachiyomi.domain.sync.SyncPreferences
@@ -169,58 +170,73 @@ class SyncManager(
     }
 
     /**
-     * Compares two Manga objects (one from the local database and one from the backup) to check if they are different.
-     * @param localManga the Manga object from the local database.
-     * @param remoteManga the BackupManga object from the backup.
-     * @return true if the Manga objects are different, otherwise false.
+     * Determines if there are differences between the local manga details and categories and their corresponding
+     * remote backup versions. This is used to identify changes or updates that might have occurred.
+     *
+     * @param localManga The manga object from the local database of type [Manga].
+     * @param backupManga The manga object from the remote backup of type [BackupManga].
+     *
+     * @return Boolean indicating whether there are differences. Returns true if any of the following is true:
+     * - The local manga details differ from the remote backup manga details.
+     * - The chapters of the local manga differ from the chapters of the remote backup manga.
+     * - The categories of the local manga differ from the categories of the remote backup manga.
+     *
+     * This function uses a combination of direct property comparisons and delegated comparison functions
+     * to assess differences across manga details, chapters, and categories. It relies on proper conversion
+     * of remote manga and chapters to the local format for accurate comparison.
      */
-    private suspend fun isMangaDifferent(localManga: Manga, remoteManga: BackupManga): Boolean {
+    private suspend fun isMangaDifferent(localManga: Manga, backupManga: BackupManga): Boolean {
+        val remoteManga = backupManga.getMangaImpl()
         val localChapters = handler.await { chaptersQueries.getChaptersByMangaId(localManga.id, 0).executeAsList() }
         val localCategories = getCategories.await(localManga.id).map { it.order }
 
-        return localManga.source != remoteManga.source ||
-            localManga.url != remoteManga.url ||
-            localManga.title != remoteManga.title ||
-            localManga.artist != remoteManga.artist ||
-            localManga.author != remoteManga.author ||
-            localManga.description != remoteManga.description ||
-            localManga.genre != remoteManga.genre ||
-            localManga.status.toInt() != remoteManga.status ||
-            localManga.thumbnailUrl != remoteManga.thumbnailUrl ||
-            localManga.dateAdded != remoteManga.dateAdded ||
-            localManga.chapterFlags.toInt() != remoteManga.chapterFlags ||
-            localManga.favorite != remoteManga.favorite ||
-            localManga.viewerFlags.toInt() != remoteManga.viewer_flags ||
-            localManga.updateStrategy != remoteManga.updateStrategy ||
-            areChaptersDifferent(localChapters, remoteManga.chapters) ||
-            localCategories != remoteManga.categories
+        return localManga != remoteManga || areChaptersDifferent(localChapters, backupManga.chapters) || localCategories != backupManga.categories
     }
 
     /**
-     * Compares two lists of chapters (one from the local database and one from the backup) to check if they are different.
-     * @param localChapters the list of chapters from the local database.
-     * @param remoteChapters the list of BackupChapter objects from the backup.
-     * @return true if the lists of chapters are different, otherwise false.
+     * Checks if there are any differences between a list of local chapters and a list of backup chapters.
+     * This function is used to determine if updates or changes have occurred between the two sets of chapters.
+     *
+     * @param localChapters The list of chapters from the local source, of type [Chapters].
+     * @param remoteChapters The list of chapters from the remote backup source, of type [BackupChapter].
+     *
+     * @return Boolean indicating whether there are differences. Returns true if any of the following is true:
+     * - The count of local and remote chapters differs.
+     * - Any corresponding chapters (matched by URL) have differing attributes including name, scanlator,
+     *   read status, bookmark status, last page read, chapter number, source order, fetch date, upload date,
+     *   or last modified date.
+     *
+     * Each chapter is compared based on a set of fields that define its content and state. If any of these fields
+     * differ between the local chapter and its corresponding remote chapter, it is considered a difference.
+     *
      */
     private fun areChaptersDifferent(localChapters: List<Chapters>, remoteChapters: List<BackupChapter>): Boolean {
+        // Early return if the sizes are different
         if (localChapters.size != remoteChapters.size) {
             return true
         }
 
+        // Convert all remote chapters to Chapter instances
+        val convertedRemoteChapters = remoteChapters.map { it.toChapterImpl() }
+
+        // Create a map for the local chapters for efficient comparison
         val localChapterMap = localChapters.associateBy { it.url }
 
-        return remoteChapters.any { remoteChapter ->
-            localChapterMap[remoteChapter.url]?.let { localChapter ->
+        // Check for any differences
+        return convertedRemoteChapters.any { remoteChapter ->
+            val localChapter = localChapterMap[remoteChapter.url]
+            localChapter == null || // No corresponding local chapter
+                localChapter.url != remoteChapter.url ||
                 localChapter.name != remoteChapter.name ||
-                    localChapter.scanlator != remoteChapter.scanlator ||
-                    localChapter.read != remoteChapter.read ||
-                    localChapter.bookmark != remoteChapter.bookmark ||
-                    localChapter.last_page_read != remoteChapter.lastPageRead ||
-                    localChapter.date_fetch != remoteChapter.dateFetch ||
-                    localChapter.date_upload != remoteChapter.dateUpload ||
-                    localChapter.chapter_number.toFloat() != remoteChapter.chapterNumber ||
-                    localChapter.source_order != remoteChapter.sourceOrder
-            } ?: true
+                localChapter.scanlator != remoteChapter.scanlator ||
+                localChapter.read != remoteChapter.read ||
+                localChapter.bookmark != remoteChapter.bookmark ||
+                localChapter.last_page_read != remoteChapter.lastPageRead ||
+                localChapter.chapter_number != remoteChapter.chapterNumber ||
+                localChapter.source_order != remoteChapter.sourceOrder ||
+                localChapter.date_fetch != remoteChapter.dateFetch ||
+                localChapter.date_upload != remoteChapter.dateUpload ||
+                localChapter.last_modified_at != remoteChapter.lastModifiedAt
         }
     }