feat(opds): Enhance KOSync Conflict Handling and Reliability (#1602)

* feat(opds): Enhance KOSync conflict handling and reliability

This commit introduces several improvements to the KOSync integration within the OPDS feed, focusing on fixing bugs, improving network stability, and enhancing user feedback during synchronization conflicts.

- fix(sync): Corrects a KOSync JSON deserialization issue by mapping the `updated_at` field from the server response to the `timestamp` property in the client's data model. This resolves a critical bug where remote progress was being ignored.
- fix(sync): Adds a `Connection: close` header to all KOSync API requests. This prevents `unexpected end of stream` errors by ensuring a fresh connection is used, improving network reliability.
- feat(opds): Resolve sync conflicts by generating separate OPDS entries for local and remote progress. This aligns with the OPDS-PSE specification's implicit design of one stream link per entry. Instead of incorrectly adding multiple links to a single entry, the feed now presents two distinct, clearly labeled entries, allowing users to choose their desired reading position from compatible clients.
- chore(sync): Adds detailed debug logging for KOSync `GET` and `PUT` requests, including request URLs, sent data, and received responses. This improves traceability and makes debugging future issues significantly easier.

* change synced icon

* unnecessary comments removed

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

@@ -110,6 +110,7 @@
     <string name="opds_chapter_status_in_progress">⌛ </string>
     <string name="opds_chapter_status_unread">⭕ </string>
     <string name="opds_chapter_status_downloaded">⬇️ </string>
+    <string name="opds_chapter_status_synced">🌐 </string>
 
     <string name="opds_chapter_details_base">Series: %1$s | %2$s</string>
     <string name="opds_chapter_details_scanlator"> | By %1$s</string>

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

@@ -47,7 +47,7 @@ object KoreaderSyncService {
         val document: String? = null,
         val progress: String? = null,
         val percentage: Float? = null,
-        val timestamp: Long? = null,
+        val updated_at: Long? = null,
         val device: String? = null,
         val device_id: String? = null,
     )
@@ -81,6 +81,7 @@ object KoreaderSyncService {
             .Builder()
             .url(url)
             .addHeader("Accept", "application/vnd.koreader.v1+json")
+            .addHeader("Connection", "close")
             .apply(block)
             .build()
 
@@ -318,7 +319,13 @@ object KoreaderSyncService {
                     addHeader("x-auth-key", userkey)
                 }
 
+            logger.info { "[KOSYNC PUSH] PUT request to URL: ${request.url}" }
+            logger.info { "[KOSYNC PUSH] Sending data: $requestBody" }
+
             network.client.newCall(request).await().use { response ->
+                val responseBody = response.body.string()
+                logger.info { "[KOSYNC PUSH] PUT response status: ${response.code}" }
+                logger.info { "[KOSYNC PUSH] PUT response body: $responseBody" }
                 if (!response.isSuccessful) {
                     logger.warn { "[KOSYNC PUSH] Failed for chapterId=$chapterId: ${response.code}" }
                 } else {
@@ -351,15 +358,19 @@ object KoreaderSyncService {
                     addHeader("x-auth-user", username)
                     addHeader("x-auth-key", userkey)
                 }
+            logger.info { "[KOSYNC PULL] GET request to URL: ${request.url}" }
 
             network.client.newCall(request).await().use { response ->
+                logger.info { "[KOSYNC PULL] GET response status: ${response.code}" }
+
                 if (response.isSuccessful) {
                     val body = response.body.string()
+                    logger.info { "[KOSYNC PULL] GET response body: $body" }
                     if (body.isBlank() || body == "{}") return null
 
                     val progressResponse = json.decodeFromString(KoreaderProgressResponse.serializer(), body)
                     val pageRead = progressResponse.progress?.toIntOrNull()?.minus(1)
-                    val timestamp = progressResponse.timestamp
+                    val timestamp = progressResponse.updated_at
                     val device = progressResponse.device ?: "KOReader"
 
                     val localProgress =

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

@@ -209,40 +209,122 @@ object OpdsEntryBuilder {
     }
 
     /**
-     * Creates an OPDS entry for a chapter's metadata, used when page count is not initially available.
+     * Creates one or two OPDS entries for a chapter, handling synchronization conflicts internally.
+     *
      * @param chapter The chapter metadata object.
      * @param manga The parent manga's details.
      * @param baseUrl The base URL for constructing links.
      * @param locale The locale for localization.
-     * @return An [OpdsEntryXml] object for the chapter's metadata.
+     * @return A `Pair` where the first element is the primary entry (always present) and the
+     * second is an optional entry representing the remote progress in case of a conflict.
      */
-    suspend fun createChapterMetadataEntry(
+    suspend fun createChapterMetadataEntries(
         chapter: OpdsChapterMetadataAcqEntry,
         manga: OpdsMangaDetails,
         baseUrl: String,
         locale: Locale,
-    ): OpdsEntryXml {
+    ): Pair<OpdsEntryXml, OpdsEntryXml?> {
         // Check remote progress before building the entry
         val syncResult = KoreaderSyncService.checkAndPullProgress(chapter.id)
 
-        val localLastPageRead = chapter.lastPageRead
-        val remoteLastPageRead = syncResult?.pageRead
-        val remoteLastReadAt = syncResult?.timestamp
+        // Exists a conflict if the sync service reports a conflict and the page numbers differ.
+        val hasConflict = syncResult?.isConflict == true && syncResult.pageRead != chapter.lastPageRead
 
-        val showConflict = syncResult?.isConflict == true && remoteLastPageRead != null && localLastPageRead != remoteLastPageRead
+        if (hasConflict) {
+            // Generate two entries: one for local progress and another for remote.
+            val localEntry =
+                buildSingleChapterMetadataEntry(
+                    chapter,
+                    manga,
+                    baseUrl,
+                    locale,
+                    progressSource = ProgressSource.Local(chapter.lastPageRead, chapter.lastReadAt),
+                    isConflict = true,
+                )
 
-        val finalLastPageRead = if (syncResult?.shouldUpdate == true) remoteLastPageRead ?: localLastPageRead else localLastPageRead
-        val finalLastReadAt = if (syncResult?.shouldUpdate == true) remoteLastReadAt ?: chapter.lastReadAt else chapter.lastReadAt
+            val remoteEntry =
+                buildSingleChapterMetadataEntry(
+                    chapter,
+                    manga,
+                    baseUrl,
+                    locale,
+                    progressSource = ProgressSource.Remote(syncResult!!.pageRead, syncResult.timestamp, syncResult.device),
+                    isConflict = true,
+                )
+            return Pair(localEntry, remoteEntry)
+        } else {
+            // No conflict, generate a single entry. Use remote progress if a silent update occurred.
+            val progressSource =
+                if (syncResult?.shouldUpdate == true) {
+                    ProgressSource.Remote(syncResult.pageRead, syncResult.timestamp, syncResult.device)
+                } else {
+                    ProgressSource.Local(chapter.lastPageRead, chapter.lastReadAt)
+                }
 
-        val statusKey =
-            when {
-                chapter.downloaded -> MR.strings.opds_chapter_status_downloaded
-                chapter.read -> MR.strings.opds_chapter_status_read
-                finalLastPageRead > 0 -> MR.strings.opds_chapter_status_in_progress
-                else -> MR.strings.opds_chapter_status_unread
+            val mainEntry =
+                buildSingleChapterMetadataEntry(
+                    chapter,
+                    manga,
+                    baseUrl,
+                    locale,
+                    progressSource = progressSource,
+                    isConflict = false,
+                )
+            return Pair(mainEntry, null)
+        }
+    }
+
+    /**
+     * Represents the source of progress information for a chapter.
+     */
+    private sealed class ProgressSource {
+        abstract val lastPageRead: Int
+        abstract val lastReadAt: Long
+
+        data class Local(
+            override val lastPageRead: Int,
+            override val lastReadAt: Long,
+        ) : ProgressSource()
+
+        data class Remote(
+            override val lastPageRead: Int,
+            override val lastReadAt: Long,
+            val device: String,
+        ) : ProgressSource()
+    }
+
+    /**
+     * Helper function to build a single OpdsEntryXml for a chapter.
+     */
+    private suspend fun buildSingleChapterMetadataEntry(
+        chapter: OpdsChapterMetadataAcqEntry,
+        manga: OpdsMangaDetails,
+        baseUrl: String,
+        locale: Locale,
+        progressSource: ProgressSource,
+        isConflict: Boolean,
+    ): OpdsEntryXml {
+        val idSuffix: String
+        val titlePrefix: String
+
+        when (progressSource) {
+            is ProgressSource.Local -> {
+                idSuffix = "" // No suffix for the primary/local entry
+                val statusKey =
+                    when {
+                        chapter.downloaded -> MR.strings.opds_chapter_status_downloaded
+                        chapter.read -> MR.strings.opds_chapter_status_read
+                        progressSource.lastPageRead > 0 -> MR.strings.opds_chapter_status_in_progress
+                        else -> MR.strings.opds_chapter_status_unread
+                    }
+                titlePrefix = statusKey.localized(locale)
             }
-        val titlePrefix = statusKey.localized(locale)
-        val entryTitle = "$titlePrefix ${chapter.name}"
+            is ProgressSource.Remote -> {
+                idSuffix = ":remote"
+                titlePrefix = MR.strings.opds_chapter_status_synced.localized(locale, progressSource.device)
+            }
+        }
+
         val details =
             buildString {
                 append(MR.strings.opds_chapter_details_base.localized(locale, manga.title, chapter.name))
@@ -250,105 +332,75 @@ object OpdsEntryBuilder {
                     append(MR.strings.opds_chapter_details_scanlator.localized(locale, it))
                 }
                 val pageCountDisplay = chapter.pageCount.takeIf { it > 0 } ?: "?"
-                append(MR.strings.opds_chapter_details_progress.localized(locale, finalLastPageRead, pageCountDisplay))
+                append(MR.strings.opds_chapter_details_progress.localized(locale, progressSource.lastPageRead, pageCountDisplay))
             }
+
+        val entryTitle = "$titlePrefix ${chapter.name}"
+
         val links = mutableListOf<OpdsLinkXml>()
-        var cbzFileSize: Long? = null
         chapter.url?.let {
             links.add(
-                OpdsLinkXml(
-                    OpdsConstants.LINK_REL_ALTERNATE,
-                    it,
-                    "text/html",
-                    MR.strings.opds_linktitle_view_on_web.localized(locale),
-                ),
+                OpdsLinkXml(OpdsConstants.LINK_REL_ALTERNATE, it, "text/html", MR.strings.opds_linktitle_view_on_web.localized(locale)),
             )
         }
         if (chapter.downloaded) {
-            val cbzStreamPair =
-                withContext(
-                    Dispatchers.IO,
-                ) { runCatching { ChapterDownloadHelper.getArchiveStreamWithSize(manga.id, chapter.id) }.getOrNull() }
-            cbzFileSize = cbzStreamPair?.second
-            cbzStreamPair?.let {
-                links.add(
-                    OpdsLinkXml(
-                        OpdsConstants.LINK_REL_ACQUISITION_OPEN_ACCESS,
-                        "/api/v1/chapter/${chapter.id}/download?markAsRead=${serverConfig.opdsMarkAsReadOnDownload.value}",
-                        OpdsConstants.TYPE_CBZ,
-                        MR.strings.opds_linktitle_download_cbz.localized(locale),
-                    ),
-                )
-            }
+            links.add(
+                OpdsLinkXml(
+                    OpdsConstants.LINK_REL_ACQUISITION_OPEN_ACCESS,
+                    "/api/v1/chapter/${chapter.id}/download?markAsRead=${serverConfig.opdsMarkAsReadOnDownload.value}",
+                    OpdsConstants.TYPE_CBZ,
+                    MR.strings.opds_linktitle_download_cbz.localized(locale),
+                ),
+            )
         }
         if (chapter.pageCount > 0) {
             val basePageHref =
                 "/api/v1/manga/${manga.id}/chapter/${chapter.sourceOrder}/page/{pageNumber}" +
                     "?updateProgress=${serverConfig.opdsEnablePageReadProgress.value}"
 
-            if (showConflict) {
-                // Option 1: Local progress
-                val localTitleRes =
-                    if (localLastPageRead >
-                        0
-                    ) {
-                        MR.strings.opds_linktitle_stream_pages_continue_local
-                    } else {
-                        MR.strings.opds_linktitle_stream_pages_start_local
+            val title: String =
+                when {
+                    !isConflict -> {
+                        val titleRes =
+                            if (progressSource.lastPageRead > 0) {
+                                MR.strings.opds_linktitle_stream_pages_continue
+                            } else {
+                                MR.strings.opds_linktitle_stream_pages_start
+                            }
+                        titleRes.localized(locale)
                     }
-                links.add(
-                    OpdsLinkXml(
-                        rel = OpdsConstants.LINK_REL_PSE_STREAM,
-                        href = basePageHref,
-                        type = OpdsConstants.TYPE_IMAGE_JPEG,
-                        title = localTitleRes.localized(locale),
-                        pseCount = chapter.pageCount,
-                        pseLastRead = localLastPageRead.takeIf { it >= 0 },
-                        pseLastReadDate = chapter.lastReadAt.takeIf { it > 0 }?.let { OpdsDateUtil.formatEpochMillisForOpds(it * 1000) },
-                    ),
-                )
-                // Option 2: Remote progress
-                val remoteTitleRes =
-                    if (remoteLastPageRead >
-                        0
-                    ) {
-                        MR.strings.opds_linktitle_stream_pages_continue_remote
-                    } else {
-                        MR.strings.opds_linktitle_stream_pages_start_remote
+                    progressSource is ProgressSource.Local -> {
+                        val titleRes =
+                            if (progressSource.lastPageRead > 0) {
+                                MR.strings.opds_linktitle_stream_pages_continue_local
+                            } else {
+                                MR.strings.opds_linktitle_stream_pages_start_local
+                            }
+                        titleRes.localized(locale)
                     }
-                links.add(
-                    OpdsLinkXml(
-                        rel = OpdsConstants.LINK_REL_PSE_STREAM,
-                        href = basePageHref,
-                        type = OpdsConstants.TYPE_IMAGE_JPEG,
-                        title = remoteTitleRes.localized(locale, syncResult.device),
-                        pseCount = chapter.pageCount,
-                        pseLastRead = remoteLastPageRead,
-                        pseLastReadDate = remoteLastReadAt?.takeIf { it > 0 }?.let { OpdsDateUtil.formatEpochMillisForOpds(it * 1000) },
-                    ),
-                )
-            } else {
-                // Normal behavior: single progress link
-                val titleRes =
-                    if (finalLastPageRead >
-                        0
-                    ) {
-                        MR.strings.opds_linktitle_stream_pages_continue
-                    } else {
-                        MR.strings.opds_linktitle_stream_pages_start
+                    progressSource is ProgressSource.Remote -> {
+                        val titleRes =
+                            if (progressSource.lastPageRead > 0) {
+                                MR.strings.opds_linktitle_stream_pages_continue_remote
+                            } else {
+                                MR.strings.opds_linktitle_stream_pages_start_remote
+                            }
+                        titleRes.localized(locale, progressSource.device)
                     }
-                links.add(
-                    OpdsLinkXml(
-                        rel = OpdsConstants.LINK_REL_PSE_STREAM,
-                        href = basePageHref,
-                        type = OpdsConstants.TYPE_IMAGE_JPEG,
-                        title = titleRes.localized(locale),
-                        pseCount = chapter.pageCount,
-                        pseLastRead = finalLastPageRead.takeIf { it > 0 },
-                        pseLastReadDate = finalLastReadAt.takeIf { it > 0 }?.let { OpdsDateUtil.formatEpochMillisForOpds(it * 1000) },
-                    ),
-                )
-            }
+                    else -> "" // Should not happen
+                }
+
+            links.add(
+                OpdsLinkXml(
+                    rel = OpdsConstants.LINK_REL_PSE_STREAM,
+                    href = basePageHref,
+                    type = OpdsConstants.TYPE_IMAGE_JPEG,
+                    title = title,
+                    pseCount = chapter.pageCount,
+                    pseLastRead = progressSource.lastPageRead.takeIf { it > 0 },
+                    pseLastReadDate = progressSource.lastReadAt.takeIf { it > 0 }?.let { OpdsDateUtil.formatEpochMillisForOpds(it * 1000) },
+                ),
+            )
             links.add(
                 OpdsLinkXml(
                     rel = OpdsConstants.LINK_REL_IMAGE,
@@ -358,8 +410,18 @@ object OpdsEntryBuilder {
                 ),
             )
         }
+
+        val cbzFileSize =
+            if (chapter.downloaded) {
+                withContext(Dispatchers.IO) {
+                    runCatching { ChapterDownloadHelper.getArchiveStreamWithSize(manga.id, chapter.id).second }.getOrNull()
+                }
+            } else {
+                null
+            }
+
         return OpdsEntryXml(
-            id = "urn:suwayomi:chapter:${chapter.id}:metadata",
+            id = "urn:suwayomi:chapter:${chapter.id}:metadata$idSuffix",
             title = entryTitle,
             updated = OpdsDateUtil.formatEpochMillisForOpds(chapter.uploadDate),
             authors =

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

@@ -699,6 +699,7 @@ object OpdsFeedBuilder {
                     MR.strings.opds_error_chapter_not_found.localized(locale, chapterSourceOrder),
                     locale,
                 )
+
         val builder =
             FeedBuilderInternal(
                 baseUrl,
@@ -708,13 +709,29 @@ object OpdsFeedBuilder {
                 OpdsConstants.TYPE_ATOM_XML_FEED_ACQUISITION,
                 null,
             )
-        builder.totalResults = 1
+
         mangaDetails.thumbnailUrl?.let { proxyThumbnailUrl(mangaDetails.id) }?.also {
             builder.icon = it
             builder.links.add(OpdsLinkXml(OpdsConstants.LINK_REL_IMAGE, it, OpdsConstants.TYPE_IMAGE_JPEG))
             builder.links.add(OpdsLinkXml(OpdsConstants.LINK_REL_IMAGE_THUMBNAIL, it, OpdsConstants.TYPE_IMAGE_JPEG))
         }
-        builder.entries.add(OpdsEntryBuilder.createChapterMetadataEntry(chapterMetadata, mangaDetails, baseUrl, locale))
+
+        val (primaryEntry, conflictEntry) =
+            OpdsEntryBuilder.createChapterMetadataEntries(
+                chapter = chapterMetadata,
+                manga = mangaDetails,
+                baseUrl = baseUrl,
+                locale = locale,
+            )
+
+        builder.entries.add(primaryEntry)
+        if (conflictEntry != null) {
+            builder.entries.add(conflictEntry)
+            builder.totalResults = 2
+        } else {
+            builder.totalResults = 1
+        }
+
         return OpdsXmlUtil.serializeFeedToString(builder.build())
     }