fix(opds): handle dead sources and prevent kosync binary hash crashes (#2116)

server/i18n/src/commonMain/moko-resources/values/base/strings.xml

@@ -50,6 +50,7 @@
     <!-- OPDS errors -->
     <string name="opds_error_manga_not_found">Series with ID %1$d not found.</string>
     <string name="opds_error_chapter_not_found">Chapter with index %1$d not found.</string>
+    <string name="opds_error_chapters_not_found">No chapters found or the source is unreachable on page %1$d.</string>
 
     <!-- OPDS facets (Filters and Sorting) -->
     <string name="opds_facetgroup_sort_order">Sort Order</string>

server/src/main/kotlin/suwayomi/tachidesk/manga/impl/sync/KoreaderSyncService.kt

@@ -127,11 +127,14 @@ object KoreaderSyncService {
             }
 
             val mangaId = chapterRow[ChapterTable.manga].value
+            val isDownloaded = chapterRow[ChapterTable.isDownloaded]
             val checksumMethod = serverConfig.koreaderSyncChecksumMethod.value
 
             val newHash =
                 when (checksumMethod) {
                     KoreaderSyncChecksumMethod.BINARY -> {
+                        // Only generate binary hash if the chapter is downloaded to avoid fetching missing files
+                        if (isDownloaded) {
                             logger.debug { "[KOSYNC HASH] No hash for chapterId=$chapterId. Generating from downloaded content." }
                             try {
                                 // Always create a CBZ in memory if it doesn't exist
@@ -152,6 +155,10 @@ object KoreaderSyncService {
                                 logger.warn(e) { "[KOSYNC HASH] Failed to generate archive stream for chapterId=$chapterId." }
                                 null
                             }
+                        } else {
+                            logger.debug { "[KOSYNC HASH] Skipping binary hash for chapterId=$chapterId because it is not downloaded." }
+                            null
+                        }
                     }
 
                     KoreaderSyncChecksumMethod.FILENAME -> {
@@ -175,7 +182,7 @@ object KoreaderSyncService {
                 }
                 logger.info { "[KOSYNC HASH] Generated and saved new hash for chapterId=$chapterId" }
             } else {
-                logger.warn { "[KOSYNC HASH] Hashing failed for chapterId=$chapterId." }
+                logger.warn { "[KOSYNC HASH] Hashing failed or skipped for chapterId=$chapterId." }
             }
             newHash
         }

server/src/main/kotlin/suwayomi/tachidesk/opds/impl/OpdsFeedBuilder.kt

@@ -644,6 +644,16 @@ object OpdsFeedBuilder {
                 skipMetadata,
             )
 
+        // Return a not-found feed if all available chapters are filtered out as unreachable
+        if (skipMetadata && chapterEntries.isEmpty() && totalChapters > 0L) {
+            return buildNotFoundFeed(
+                baseUrl = baseUrl,
+                locale = locale,
+                idPath = "series/$mangaId/chapters",
+                title = MR.strings.opds_error_chapters_not_found.localized(locale, pageNum),
+            )
+        }
+
         // If no chapters are found in the database, attempt to fetch them from the source.
         if (chapterEntries.isEmpty() && totalChapters == 0L) {
             try {

server/src/main/kotlin/suwayomi/tachidesk/opds/repository/ChapterRepository.kt

@@ -169,6 +169,8 @@ object ChapterRepository {
                     }
                 }
             }.awaitAll()
+                // Exclude unreachable chapters that are not downloaded and have no page count
+                .filter { it.downloaded || it.pageCount > 0 }
 
         return Pair(enrichedChapters, totalCount)
     }