feat(reading-eta): share SeriesReadingEtaCalculator across reader and library

Extract a single ETA estimator, refresh library badges when history changes,
and expose a history revision stream for reactive updates.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/src/main/java/eu/kanade/domain/DomainModule.kt

@@ -67,6 +67,7 @@ import tachiyomi.domain.chapter.interactor.UpdateChapter
 import tachiyomi.domain.chapter.repository.ChapterRepository
 import tachiyomi.domain.history.interactor.GetCrossMangaPageRateHistorySamples
 import tachiyomi.domain.history.interactor.GetHistory
+import tachiyomi.domain.history.interactor.GetHistoryRevision
 import tachiyomi.domain.history.interactor.GetNextChapters
 import tachiyomi.domain.history.interactor.GetReadDurationEntriesByMangaIds
 import tachiyomi.domain.history.interactor.GetTotalReadDuration
@@ -173,6 +174,7 @@ class DomainModule : InjektModule {
 
         addSingletonFactory<HistoryRepository> { HistoryRepositoryImpl(get()) }
         addFactory { GetHistory(get()) }
+        addFactory { GetHistoryRevision(get()) }
         addFactory { UpsertHistory(get()) }
         addFactory { RemoveHistory(get()) }
         addFactory { GetTotalReadDuration(get()) }

app/src/main/java/eu/kanade/tachiyomi/ui/library/LibraryScreenModel.kt

@@ -98,6 +98,9 @@ import tachiyomi.domain.chapter.interactor.GetChaptersByMangaId
 import tachiyomi.domain.chapter.interactor.GetMergedChaptersByMangaId
 import tachiyomi.domain.chapter.model.Chapter
 import tachiyomi.domain.history.interactor.GetNextChapters
+import tachiyomi.domain.chapter.service.getChapterSort
+import tachiyomi.domain.history.interactor.GetCrossMangaPageRateHistorySamples
+import tachiyomi.domain.history.interactor.GetHistoryRevision
 import tachiyomi.domain.history.interactor.GetReadDurationEntriesByMangaIds
 import tachiyomi.domain.history.interactor.GetTotalReadDuration
 import tachiyomi.domain.library.model.LibraryDisplayMode
@@ -107,6 +110,7 @@ import tachiyomi.domain.library.model.LibrarySort
 import tachiyomi.domain.library.model.sort
 import tachiyomi.domain.library.service.LibraryPreferences
 import tachiyomi.domain.reading.ReadingEtaLimits
+import tachiyomi.domain.reading.SeriesReadingEtaCalculator
 import tachiyomi.domain.reading.service.ReadingEtaPreferences
 import tachiyomi.domain.manga.interactor.GetIdsOfFavoriteMangaWithMetadata
 import tachiyomi.domain.manga.interactor.GetLibraryManga
@@ -153,6 +157,8 @@ class LibraryScreenModel(
     private val sourcePreferences: SourcePreferences = Injekt.get(),
     private val getMergedMangaById: GetMergedMangaById = Injekt.get(),
     private val getReadDurationEntriesByMangaIds: GetReadDurationEntriesByMangaIds = Injekt.get(),
+    private val getCrossMangaPageRateHistorySamples: GetCrossMangaPageRateHistorySamples = Injekt.get(),
+    private val getHistoryRevision: GetHistoryRevision = Injekt.get(),
     private val getTotalReadDuration: GetTotalReadDuration = Injekt.get(),
     private val getTracks: GetTracks = Injekt.get(),
     private val getIdsOfFavoriteMangaWithMetadata: GetIdsOfFavoriteMangaWithMetadata = Injekt.get(),
@@ -447,64 +453,57 @@ class LibraryScreenModel(
     ): Map<Long, Long?> {
         if (favorites.isEmpty()) return emptyMap()
 
-        val chapterDurationsByMangaId = favorites.associate { item ->
-            item.id to getReadDurationEntriesByMangaIds.await(item.id).map { it.readDuration }
-        }
-        val globalAverageChapterDurationMs = calculateAverageChapterDurationMs(
-            chapterDurationsByMangaId.values.flatten(),
-            limits,
-        )
-
         return favorites.associate { item ->
-            item.id to calculateEstimatedTimeLeftMs(
-                item = item,
-                chapterDurations = chapterDurationsByMangaId[item.id].orEmpty(),
-                globalAverageChapterDurationMs = globalAverageChapterDurationMs,
-                limits = limits,
-            )
+            item.id to computeEstimatedTimeLeftMs(item, limits)
         }
     }
 
-    private fun calculateEstimatedTimeLeftMs(
+    private suspend fun computeEstimatedTimeLeftMs(
         item: LibraryItem,
-        chapterDurations: List<Long>,
-        globalAverageChapterDurationMs: Long?,
         limits: ReadingEtaLimits,
     ): Long? {
-        val unreadCount = item.libraryManga.unreadCount.coerceAtLeast(0L)
-        if (unreadCount == 0L) return null
+        if (item.libraryManga.unreadCount <= 0L) return null
 
-        val averageChapterDurationMs = calculateAverageChapterDurationMs(chapterDurations, limits)
-            ?: globalAverageChapterDurationMs
-            ?: return null
-
-        val remainingChapterUnits = if (item.libraryManga.totalChapters == 1L) {
-            1L
+        val manga = item.libraryManga.manga
+        val mergedManga = if (manga.source == MERGED_SOURCE_ID) {
+            getMergedMangaById.await(manga.id).associateBy { it.id }
         } else {
-            unreadCount
+            emptyMap()
         }
-        return (averageChapterDurationMs * remainingChapterUnits).coerceAtLeast(0L)
-    }
-
-    private fun calculateAverageChapterDurationMs(
-        chapterDurations: List<Long>,
-        limits: ReadingEtaLimits,
-    ): Long? {
-        val sampledDurations = chapterDurations
-            .filter { it in limits.minTrackedChapterDurationMs..limits.maxTrackedChapterDurationMs }
-            .map { it.coerceAtMost(limits.maxChapterDurationMsForStats) }
-            .takeLast(limits.etaSampleChapterLimit)
-        if (sampledDurations.isEmpty()) return null
-
-        val sortedDurations = sampledDurations.sorted()
-        val trimCount = (sortedDurations.size / 10)
-            .coerceAtMost((sortedDurations.size - 1) / 2)
-        val trimmedDurations = if (trimCount > 0) {
-            sortedDurations.subList(trimCount, sortedDurations.size - trimCount)
+        val rawChapters = if (manga.source == MERGED_SOURCE_ID) {
+            getMergedChaptersByMangaId.await(manga.id, applyFilter = true)
         } else {
-            sortedDurations
+            getChaptersByMangaId.await(manga.id, applyFilter = true)
         }
-        return trimmedDurations.sum() / trimmedDurations.size
+        val orderedChapters = if (manga.source == MERGED_SOURCE_ID) {
+            getMergedChaptersByMangaId.await(manga.id, applyFilter = false)
+        } else {
+            getChaptersByMangaId.await(manga.id, applyFilter = false)
+        }.sortedWith(getChapterSort(manga, sortDescending = false))
+        if (orderedChapters.isEmpty()) return null
+
+        val nextUnread = rawChapters.getNextUnread(manga, downloadManager, mergedManga) ?: return null
+        val histories = getReadDurationEntriesByMangaIds.await(manga.id)
+        val crossMangaSamples = getCrossMangaPageRateHistorySamples.await(manga.id)
+        val currentPage = if (nextUnread.lastPageRead > 0L) {
+            (nextUnread.lastPageRead + 1L).toInt()
+        } else {
+            1
+        }
+
+        return SeriesReadingEtaCalculator.estimate(
+            SeriesReadingEtaCalculator.Input(
+                orderedChapterIds = orderedChapters.map { it.id },
+                chapterReadById = orderedChapters.associate { it.id to it.read },
+                currentChapterId = nextUnread.id,
+                currentPage = currentPage,
+                totalPages = -1,
+                chapterDurations = histories.associate { it.chapterId to it.readDuration },
+                chapterPages = histories.associate { it.chapterId to it.readPages },
+                crossMangaPageRateSamples = crossMangaSamples,
+                limits = limits,
+            ),
+        )?.etaMillis
     }
 
     private fun compareEstimatedTimeLeft(
@@ -906,7 +905,8 @@ class LibraryScreenModel(
             getLibraryManga.subscribe(),
             getLibraryItemPreferencesFlow(),
             downloadCache.changes,
-        ) { libraryManga, preferences, _ ->
+            getHistoryRevision.subscribe(),
+        ) { libraryManga, preferences, _, _ ->
             libraryManga.map { manga ->
                 // Display mode based on user preference: take it from global library setting or category
                 // KMK -->

app/src/main/java/eu/kanade/tachiyomi/ui/reader/ReaderViewModel.kt

@@ -99,9 +99,9 @@ import tachiyomi.domain.history.interactor.UpsertHistory
 import tachiyomi.domain.history.model.HistoryUpdate
 import tachiyomi.domain.library.service.LibraryPreferences
 import tachiyomi.domain.reading.ReadingEtaHistorySample
-import tachiyomi.domain.reading.ReadingEtaPageRateEstimator
 import tachiyomi.domain.reading.ReadingEtaDefaults
 import tachiyomi.domain.reading.ReadingEtaLimits
+import tachiyomi.domain.reading.SeriesReadingEtaCalculator
 import tachiyomi.domain.reading.service.ReadingEtaPreferences
 import tachiyomi.domain.manga.interactor.GetFlatMetadataById
 import tachiyomi.domain.manga.interactor.GetManga
@@ -269,7 +269,6 @@ class ReaderViewModel @JvmOverloads constructor(
     private var crossMangaPageRateSamples: List<ReadingEtaHistorySample> = emptyList()
 
     private var orderedSeriesChapterIds = emptyList<Long>()
-    private var seriesChapterIndexById = emptyMap<Long, Int>()
 
     private var chapterToDownload: Download? = null
 
@@ -972,9 +971,6 @@ class ReaderViewModel @JvmOverloads constructor(
         orderedSeriesChapterIds = unfilteredChapterList
             .sortedWith(getChapterSort(manga, sortDescending = false))
             .mapNotNull { it.id }
-        seriesChapterIndexById = orderedSeriesChapterIds
-            .withIndex()
-            .associate { (index, chapterId) -> chapterId to index }
 
         chapterReadDurationsSession.clear()
         chapterReadDurationsPersistent.clear()
@@ -1000,94 +996,49 @@ class ReaderViewModel @JvmOverloads constructor(
                 return
             }
 
-            val currentChapterIndex = seriesChapterIndexById[currentChapterId]
-            if (currentChapterIndex == null) {
+            val limits = readingEtaPreferences.currentLimits()
+            val chapterDurations = getEtaChapterDurations(currentChapterId, limits)
+            val chapterPages = getEtaChapterPages(currentChapterId, limits)
+            val activeSession = chapterReadStartTime?.let { startTime ->
+                chapterReadStartPageIndex?.let { startPageIndex ->
+                    val totalPages = state.value.totalPages
+                    if (totalPages <= 1) {
+                        null
+                    } else {
+                        SeriesReadingEtaCalculator.ActiveSession(
+                            sessionDurationMs = SystemClock.elapsedRealtime() - startTime,
+                            startPageIndex = startPageIndex,
+                            currentPageIndex = (state.value.currentPage - 1).coerceAtLeast(startPageIndex),
+                            totalPages = totalPages,
+                        )
+                    }
+                }
+            }
+            val result = SeriesReadingEtaCalculator.estimate(
+                SeriesReadingEtaCalculator.Input(
+                    orderedChapterIds = orderedSeriesChapterIds,
+                    chapterReadById = unfilteredChapterList.associate { it.id to it.read },
+                    currentChapterId = currentChapterId,
+                    currentPage = state.value.currentPage,
+                    totalPages = state.value.totalPages,
+                    chapterDurations = chapterDurations,
+                    chapterPages = chapterPages,
+                    crossMangaPageRateSamples = crossMangaPageRateSamples,
+                    limits = limits,
+                    activeSession = activeSession,
+                ),
+            ) ?: run {
                 mutableState.update { it.copy(seriesReadingProgress = null) }
                 return
             }
 
-            val totalChapters = orderedSeriesChapterIds.size
-            val isCurrentChapterRead = state.value.currentChapter?.chapter?.read == true
-            val remainingChapters = (
-                totalChapters - currentChapterIndex - if (isCurrentChapterRead) 1 else 0
-                ).coerceAtLeast(0)
-            val limits = readingEtaPreferences.currentLimits()
-            val chapterDurations = getEtaChapterDurations(currentChapterId, limits)
-            val chapterPages = getEtaChapterPages(currentChapterId, limits)
-            val currentChapterProgress = calculateChapterProgress(
-                currentPage = state.value.currentPage,
-                totalPages = state.value.totalPages,
-            )
-            val projectedCurrentChapterDuration =
-                estimateFullChapterMsFromActiveSession(limits)
-                    ?.coerceAtMost(limits.maxChapterDurationMsForStats)
-                    ?: calculateProjectedChapterDurationMs(
-                        chapterDuration = chapterDurations[currentChapterId] ?: 0L,
-                        chapterProgress = currentChapterProgress,
-                        limits = limits,
-                    )
-            val averageChapterDuration = calculateAverageChapterDurationMs(
-                chapterDurations = chapterDurations,
-                currentChapterId = currentChapterId,
-                currentChapterIndex = currentChapterIndex,
-                isCurrentChapterRead = isCurrentChapterRead,
-                currentChapterProgress = currentChapterProgress,
-                limits = limits,
-            )
-            val pageBasedEta = calculatePageBasedEtaMillis(
-                chapterDurations = chapterDurations,
-                chapterPages = chapterPages,
-                currentChapterId = currentChapterId,
-                currentChapterIndex = currentChapterIndex,
-                isCurrentChapterRead = isCurrentChapterRead,
-                currentChapterProgress = currentChapterProgress,
-                totalPages = state.value.totalPages,
-                currentPage = state.value.currentPage,
-                remainingChapters = remainingChapters,
-                limits = limits,
-            )
-            val chapterDurationForWholeChapters = averageChapterDuration ?: projectedCurrentChapterDuration
-            val chapterDurationForCurrentChapter = projectedCurrentChapterDuration ?: chapterDurationForWholeChapters
-            val chapterBasedEta = when {
-                totalChapters == 1 -> {
-                    if (isCurrentChapterRead) {
-                        0L
-                    } else {
-                        calculateRemainingChapterTimeMs(
-                            chapterDuration = chapterDurationForCurrentChapter,
-                            chapterProgress = currentChapterProgress,
-                        ) ?: chapterDurationForCurrentChapter
-                    }
-                }
-                else -> {
-                    when {
-                        remainingChapters == 0 -> 0L
-                        else -> chapterDurationForWholeChapters?.let { chapterDurationMs ->
-                            val currentChapterRemainingMs = if (isCurrentChapterRead) {
-                                0L
-                            } else {
-                                calculateRemainingChapterTimeMs(
-                                    chapterDuration = chapterDurationForCurrentChapter,
-                                    chapterProgress = currentChapterProgress,
-                                ) ?: chapterDurationForCurrentChapter ?: 0L
-                            }
-                            val remainingWholeChapters = (
-                                remainingChapters - if (isCurrentChapterRead) 0 else 1
-                                ).coerceAtLeast(0)
-                            currentChapterRemainingMs + (chapterDurationMs * remainingWholeChapters)
-                        }
-                    }
-                }
-            }
-            val etaMillis = (pageBasedEta ?: chapterBasedEta)?.coerceAtLeast(0L)
-
             mutableState.update {
                 it.copy(
                     seriesReadingProgress = SeriesReadingProgress(
-                        currentChapter = currentChapterIndex + 1,
-                        totalChapters = totalChapters,
-                        remainingChapters = remainingChapters,
-                        etaMillis = etaMillis,
+                        currentChapter = result.currentChapter,
+                        totalChapters = result.totalChapters,
+                        remainingChapters = result.remainingChapters,
+                        etaMillis = result.etaMillis,
                     ),
                 )
             }
@@ -1133,157 +1084,6 @@ class ReaderViewModel @JvmOverloads constructor(
         return trackedPages
     }
 
-    private fun calculatePageBasedEtaMillis(
-        chapterDurations: Map<Long, Long>,
-        chapterPages: Map<Long, Long>,
-        currentChapterId: Long,
-        currentChapterIndex: Int,
-        isCurrentChapterRead: Boolean,
-        currentChapterProgress: Double?,
-        totalPages: Int,
-        currentPage: Int,
-        remainingChapters: Int,
-        limits: ReadingEtaLimits,
-    ): Long? {
-        val seriesPageRatesMsPerPage = orderedSeriesChapterIds
-            .take(currentChapterIndex + 1)
-            .mapNotNull { chapterId ->
-                val duration = chapterDurations[chapterId]?.sanitizeTrackedDuration(limits) ?: return@mapNotNull null
-                val pages = chapterPages[chapterId]?.sanitizeTrackedPages(limits) ?: return@mapNotNull null
-                if (duration <= 0L || pages <= 0L) return@mapNotNull null
-                duration.toDouble() / pages.toDouble()
-            }
-            .takeLast(limits.etaSampleChapterLimit)
-
-        val sampledPages = orderedSeriesChapterIds
-            .take(currentChapterIndex + 1)
-            .mapNotNull { chapterPages[it]?.sanitizeTrackedPages(limits) }
-            .takeLast(limits.etaSampleChapterLimit)
-        if (sampledPages.isEmpty()) return null
-        val avgPagesPerChapter = (sampledPages.sum() / sampledPages.size).coerceAtLeast(1L)
-
-        if (seriesPageRatesMsPerPage.isEmpty() && crossMangaPageRateSamples.isEmpty()) return null
-
-        val targetChapterPages = if (totalPages > 0) {
-            totalPages
-        } else {
-            avgPagesPerChapter.toInt().coerceAtLeast(1)
-        }
-
-        val avgMsPerPage = ReadingEtaPageRateEstimator.estimateBlendedMsPerPage(
-            targetChapterPages = targetChapterPages,
-            seriesPageRatesMsPerPage = seriesPageRatesMsPerPage,
-            crossMangaSamples = crossMangaPageRateSamples,
-            limits = limits,
-        ) ?: return null
-
-        val currentRemainingPages = if (isCurrentChapterRead) {
-            0L
-        } else if (totalPages > 0 && currentPage > 0) {
-            (totalPages - currentPage).toLong().coerceAtLeast(0L)
-        } else {
-            val progress = (currentChapterProgress ?: 0.0).coerceIn(0.0, 1.0)
-            ((1.0 - progress) * avgPagesPerChapter.toDouble()).toLong().coerceAtLeast(0L)
-        }
-        val remainingWholeChapters = (remainingChapters - if (isCurrentChapterRead) 0 else 1).coerceAtLeast(0)
-        return currentRemainingPages * avgMsPerPage + remainingWholeChapters * avgPagesPerChapter * avgMsPerPage
-    }
-
-    private fun calculateAverageChapterDurationMs(
-        chapterDurations: Map<Long, Long>,
-        currentChapterId: Long,
-        currentChapterIndex: Int,
-        isCurrentChapterRead: Boolean,
-        currentChapterProgress: Double?,
-        limits: ReadingEtaLimits,
-    ): Long? {
-        if (currentChapterIndex < 0) return null
-        val sampledDurations = orderedSeriesChapterIds
-            .take(currentChapterIndex + 1)
-            .mapNotNull { chapterId ->
-                val chapterDuration = chapterDurations[chapterId] ?: return@mapNotNull null
-                val normalizedDuration = when {
-                    chapterId == currentChapterId && !isCurrentChapterRead -> {
-                        calculateProjectedChapterDurationMs(
-                            chapterDuration = chapterDuration,
-                            chapterProgress = currentChapterProgress,
-                            limits = limits,
-                        )
-                    }
-                    else -> chapterDuration
-                } ?: return@mapNotNull null
-                normalizedDuration
-            }
-            .filter { it in limits.minTrackedChapterDurationMs..limits.maxTrackedChapterDurationMs }
-            .map { it.coerceAtMost(limits.maxChapterDurationMsForStats) }
-            .takeLast(limits.etaSampleChapterLimit)
-        if (sampledDurations.isEmpty()) return null
-
-        val sortedDurations = sampledDurations.sorted()
-        val trimCount = (sortedDurations.size / 10)
-            .coerceAtMost((sortedDurations.size - 1) / 2)
-        val trimmedDurations = if (trimCount > 0) {
-            sortedDurations.subList(trimCount, sortedDurations.size - trimCount)
-        } else {
-            sortedDurations
-        }
-        return trimmedDurations.sum() / trimmedDurations.size
-    }
-
-    private fun calculateChapterProgress(
-        currentPage: Int,
-        totalPages: Int,
-    ): Double? {
-        if (currentPage <= 0 || totalPages <= 1) return null
-        return (currentPage.toDouble() / totalPages.toDouble()).coerceIn(0.0, 1.0)
-    }
-
-    private fun calculateProjectedChapterDurationMs(
-        chapterDuration: Long,
-        chapterProgress: Double?,
-        limits: ReadingEtaLimits,
-    ): Long? {
-        if (chapterDuration <= 0L) return null
-        val progress = chapterProgress
-            ?.takeIf { it >= MIN_PROGRESS_FOR_DURATION_PROJECTION }
-            ?.coerceIn(0.0, 1.0)
-            ?: return null
-        if (progress == 0.0) return null
-        return (chapterDuration.toDouble() / progress).toLong()
-            .coerceAtLeast(0L)
-            .coerceAtMost(limits.maxChapterDurationMsForStats)
-    }
-
-    /**
-     * Estimates full-chapter duration from the current session's ms/page rate.
-     * Prefer over scaling cumulative DB read time by absolute chapter progress — history times are
-     * summed across revisits, which inflates `duration / progress` for rereads.
-     */
-    private fun estimateFullChapterMsFromActiveSession(limits: ReadingEtaLimits): Long? {
-        val totalPages = state.value.totalPages
-        val startPageIndex = chapterReadStartPageIndex ?: return null
-        val startTime = chapterReadStartTime ?: return null
-        if (totalPages <= 1) return null
-
-        val sessionMs = (SystemClock.elapsedRealtime() - startTime).sanitizeTrackedDuration(limits)
-        if (sessionMs < limits.minTrackedChapterDurationMs) return null
-
-        val currentPageIndex = (state.value.currentPage - 1).coerceAtLeast(startPageIndex)
-        val pagesThisSession = (currentPageIndex - startPageIndex + 1).coerceAtLeast(1)
-        val msPerPage = sessionMs.toDouble() / pagesThisSession.toDouble()
-        val estimated = (msPerPage * totalPages.toDouble()).toLong()
-        return estimated.takeIf { it > 0L }
-    }
-
-    private fun calculateRemainingChapterTimeMs(
-        chapterDuration: Long?,
-        chapterProgress: Double?,
-    ): Long? {
-        val duration = chapterDuration?.takeIf { it > 0L } ?: return null
-        val remainingProgress = 1.0 - (chapterProgress ?: 0.0).coerceIn(0.0, 1.0)
-        return (duration.toDouble() * remainingProgress).toLong().coerceAtLeast(0L)
-    }
-
     private fun Long.sanitizeTrackedDuration(limits: ReadingEtaLimits): Long {
         return if (this in limits.minTrackedChapterDurationMs..limits.maxTrackedChapterDurationMs) this else 0L
     }
@@ -1842,10 +1642,6 @@ class ReaderViewModel @JvmOverloads constructor(
         }
     }
 
-    private companion object {
-        const val MIN_PROGRESS_FOR_DURATION_PROJECTION = 0.05
-    }
-
     @Immutable
     data class State(
         val manga: Manga? = null,

data/src/main/java/tachiyomi/data/history/HistoryRepositoryImpl.kt

@@ -57,6 +57,10 @@ class HistoryRepositoryImpl(
         return handler.awaitList { historyQueries.getHistoryByMangaId(mangaId, HistoryMapper::mapHistory) }
     }
 
+    override fun subscribeToRevision(): Flow<Long> {
+        return handler.subscribeToOne { historyQueries.historyRevision() }
+    }
+
     override suspend fun getCrossMangaPageRateHistorySamples(
         excludeMangaId: Long,
         minDurationMs: Long,

data/src/main/sqldelight/tachiyomi/data/history.sq

@@ -83,6 +83,10 @@ getReadDuration:
 SELECT coalesce(sum(time_read), 0)
 FROM history;
 
+historyRevision:
+SELECT coalesce(sum(time_read), 0) + coalesce(sum(pages_read), 0) + count(*)
+FROM history;
+
 -- Recent completed-chapter history from other series, for data-driven ms/page ETA priors.
 getCrossMangaPageRateHistorySamples:
 SELECT

domain/src/main/java/tachiyomi/domain/history/interactor/GetHistoryRevision.kt

@@ -0,0 +1,10 @@
+package tachiyomi.domain.history.interactor
+
+import kotlinx.coroutines.flow.Flow
+import tachiyomi.domain.history.repository.HistoryRepository
+
+class GetHistoryRevision(
+    private val repository: HistoryRepository,
+) {
+    fun subscribe(): Flow<Long> = repository.subscribeToRevision()
+}

domain/src/main/java/tachiyomi/domain/history/repository/HistoryRepository.kt

@@ -23,6 +23,8 @@ interface HistoryRepository {
 
     suspend fun getHistoryByMangaId(mangaId: Long): List<History>
 
+    fun subscribeToRevision(): Flow<Long>
+
     suspend fun getCrossMangaPageRateHistorySamples(
         excludeMangaId: Long,
         minDurationMs: Long,

domain/src/main/java/tachiyomi/domain/reading/SeriesReadingEtaCalculator.kt

@@ -0,0 +1,311 @@
+package tachiyomi.domain.reading
+
+/**
+ * Shared series reading-time estimate used by the reader overlay and library badges.
+ */
+object SeriesReadingEtaCalculator {
+
+    const val MIN_PROGRESS_FOR_DURATION_PROJECTION = 0.05
+
+    data class ActiveSession(
+        val sessionDurationMs: Long,
+        val startPageIndex: Int,
+        val currentPageIndex: Int,
+        val totalPages: Int,
+    )
+
+    data class Input(
+        val orderedChapterIds: List<Long>,
+        val chapterReadById: Map<Long, Boolean>,
+        val currentChapterId: Long,
+        val currentPage: Int,
+        val totalPages: Int,
+        val chapterDurations: Map<Long, Long>,
+        val chapterPages: Map<Long, Long>,
+        val crossMangaPageRateSamples: List<ReadingEtaHistorySample>,
+        val limits: ReadingEtaLimits,
+        val activeSession: ActiveSession? = null,
+    )
+
+    data class Result(
+        val currentChapter: Int,
+        val totalChapters: Int,
+        val remainingChapters: Int,
+        val etaMillis: Long?,
+    )
+
+    fun estimate(input: Input): Result? {
+        if (input.orderedChapterIds.isEmpty()) return null
+
+        val chapterIndexById = input.orderedChapterIds
+            .withIndex()
+            .associate { (index, chapterId) -> chapterId to index }
+        val currentChapterIndex = chapterIndexById[input.currentChapterId] ?: return null
+
+        val totalChapters = input.orderedChapterIds.size
+        val isCurrentChapterRead = input.chapterReadById[input.currentChapterId] == true
+        val remainingChapters = (
+            totalChapters - currentChapterIndex - if (isCurrentChapterRead) 1 else 0
+            ).coerceAtLeast(0)
+
+        val chapterDurations = buildChapterDurations(input)
+        val chapterPages = buildChapterPages(input)
+        val currentChapterProgress = calculateChapterProgress(
+            currentPage = input.currentPage,
+            totalPages = input.totalPages,
+        )
+        val projectedCurrentChapterDuration =
+            estimateFullChapterMsFromActiveSession(input)
+                ?.coerceAtMost(input.limits.maxChapterDurationMsForStats)
+                ?: calculateProjectedChapterDurationMs(
+                    chapterDuration = chapterDurations[input.currentChapterId] ?: 0L,
+                    chapterProgress = currentChapterProgress,
+                    limits = input.limits,
+                )
+        val averageChapterDuration = calculateAverageChapterDurationMs(
+            orderedChapterIds = input.orderedChapterIds,
+            chapterDurations = chapterDurations,
+            currentChapterId = input.currentChapterId,
+            currentChapterIndex = currentChapterIndex,
+            isCurrentChapterRead = isCurrentChapterRead,
+            currentChapterProgress = currentChapterProgress,
+            limits = input.limits,
+        )
+        val pageBasedEta = calculatePageBasedEtaMillis(
+            orderedChapterIds = input.orderedChapterIds,
+            chapterDurations = chapterDurations,
+            chapterPages = chapterPages,
+            currentChapterId = input.currentChapterId,
+            currentChapterIndex = currentChapterIndex,
+            isCurrentChapterRead = isCurrentChapterRead,
+            currentChapterProgress = currentChapterProgress,
+            totalPages = input.totalPages,
+            currentPage = input.currentPage,
+            remainingChapters = remainingChapters,
+            crossMangaPageRateSamples = input.crossMangaPageRateSamples,
+            limits = input.limits,
+        )
+        val chapterDurationForWholeChapters = averageChapterDuration ?: projectedCurrentChapterDuration
+        val chapterDurationForCurrentChapter = projectedCurrentChapterDuration ?: chapterDurationForWholeChapters
+        val chapterBasedEta = when {
+            totalChapters == 1 -> {
+                if (isCurrentChapterRead) {
+                    0L
+                } else {
+                    calculateRemainingChapterTimeMs(
+                        chapterDuration = chapterDurationForCurrentChapter,
+                        chapterProgress = currentChapterProgress,
+                    ) ?: chapterDurationForCurrentChapter
+                }
+            }
+            else -> {
+                when {
+                    remainingChapters == 0 -> 0L
+                    else -> chapterDurationForWholeChapters?.let { chapterDurationMs ->
+                        val currentChapterRemainingMs = if (isCurrentChapterRead) {
+                            0L
+                        } else {
+                            calculateRemainingChapterTimeMs(
+                                chapterDuration = chapterDurationForCurrentChapter,
+                                chapterProgress = currentChapterProgress,
+                            ) ?: chapterDurationForCurrentChapter ?: 0L
+                        }
+                        val remainingWholeChapters = (
+                            remainingChapters - if (isCurrentChapterRead) 0 else 1
+                            ).coerceAtLeast(0)
+                        currentChapterRemainingMs + (chapterDurationMs * remainingWholeChapters)
+                    }
+                }
+            }
+        }
+        val etaMillis = (pageBasedEta ?: chapterBasedEta)?.coerceAtLeast(0L)
+
+        return Result(
+            currentChapter = currentChapterIndex + 1,
+            totalChapters = totalChapters,
+            remainingChapters = remainingChapters,
+            etaMillis = etaMillis,
+        )
+    }
+
+    private fun buildChapterDurations(input: Input): Map<Long, Long> {
+        val trackedDurations = input.chapterDurations.toMutableMap()
+        val activeSession = input.activeSession ?: return trackedDurations
+
+        val inProgressDuration = activeSession.sessionDurationMs
+            .sanitizeTrackedDuration(input.limits)
+        if (inProgressDuration > 0L) {
+            trackedDurations.merge(input.currentChapterId, inProgressDuration, Long::plus)
+        }
+        return trackedDurations
+    }
+
+    private fun buildChapterPages(input: Input): Map<Long, Long> {
+        val trackedPages = input.chapterPages.toMutableMap()
+        val activeSession = input.activeSession ?: return trackedPages
+
+        val inProgressPages = (
+            activeSession.currentPageIndex - activeSession.startPageIndex + 1L
+            ).sanitizeTrackedPages(input.limits)
+        if (inProgressPages > 0L) {
+            trackedPages.merge(input.currentChapterId, inProgressPages, Long::plus)
+        }
+        return trackedPages
+    }
+
+    private fun estimateFullChapterMsFromActiveSession(input: Input): Long? {
+        val activeSession = input.activeSession ?: return null
+        if (activeSession.totalPages <= 1) return null
+
+        val sessionMs = activeSession.sessionDurationMs.sanitizeTrackedDuration(input.limits)
+        if (sessionMs < input.limits.minTrackedChapterDurationMs) return null
+
+        val pagesThisSession = (
+            activeSession.currentPageIndex - activeSession.startPageIndex + 1
+            ).coerceAtLeast(1)
+        val msPerPage = sessionMs.toDouble() / pagesThisSession.toDouble()
+        val estimated = (msPerPage * activeSession.totalPages.toDouble()).toLong()
+        return estimated.takeIf { it > 0L }
+    }
+
+    private fun calculatePageBasedEtaMillis(
+        orderedChapterIds: List<Long>,
+        chapterDurations: Map<Long, Long>,
+        chapterPages: Map<Long, Long>,
+        currentChapterId: Long,
+        currentChapterIndex: Int,
+        isCurrentChapterRead: Boolean,
+        currentChapterProgress: Double?,
+        totalPages: Int,
+        currentPage: Int,
+        remainingChapters: Int,
+        crossMangaPageRateSamples: List<ReadingEtaHistorySample>,
+        limits: ReadingEtaLimits,
+    ): Long? {
+        val seriesPageRatesMsPerPage = orderedChapterIds
+            .take(currentChapterIndex + 1)
+            .mapNotNull { chapterId ->
+                val duration = chapterDurations[chapterId]?.sanitizeTrackedDuration(limits) ?: return@mapNotNull null
+                val pages = chapterPages[chapterId]?.sanitizeTrackedPages(limits) ?: return@mapNotNull null
+                if (duration <= 0L || pages <= 0L) return@mapNotNull null
+                duration.toDouble() / pages.toDouble()
+            }
+            .takeLast(limits.etaSampleChapterLimit)
+
+        val sampledPages = orderedChapterIds
+            .take(currentChapterIndex + 1)
+            .mapNotNull { chapterPages[it]?.sanitizeTrackedPages(limits) }
+            .takeLast(limits.etaSampleChapterLimit)
+        if (sampledPages.isEmpty()) return null
+        val avgPagesPerChapter = (sampledPages.sum() / sampledPages.size).coerceAtLeast(1L)
+
+        if (seriesPageRatesMsPerPage.isEmpty() && crossMangaPageRateSamples.isEmpty()) return null
+
+        val targetChapterPages = if (totalPages > 0) {
+            totalPages
+        } else {
+            avgPagesPerChapter.toInt().coerceAtLeast(1)
+        }
+
+        val avgMsPerPage = ReadingEtaPageRateEstimator.estimateBlendedMsPerPage(
+            targetChapterPages = targetChapterPages,
+            seriesPageRatesMsPerPage = seriesPageRatesMsPerPage,
+            crossMangaSamples = crossMangaPageRateSamples,
+            limits = limits,
+        ) ?: return null
+
+        val currentRemainingPages = if (isCurrentChapterRead) {
+            0L
+        } else if (totalPages > 0 && currentPage > 0) {
+            (totalPages - currentPage).toLong().coerceAtLeast(0L)
+        } else {
+            val progress = (currentChapterProgress ?: 0.0).coerceIn(0.0, 1.0)
+            ((1.0 - progress) * avgPagesPerChapter.toDouble()).toLong().coerceAtLeast(0L)
+        }
+        val remainingWholeChapters = (remainingChapters - if (isCurrentChapterRead) 0 else 1).coerceAtLeast(0)
+        return currentRemainingPages * avgMsPerPage + remainingWholeChapters * avgPagesPerChapter * avgMsPerPage
+    }
+
+    private fun calculateAverageChapterDurationMs(
+        orderedChapterIds: List<Long>,
+        chapterDurations: Map<Long, Long>,
+        currentChapterId: Long,
+        currentChapterIndex: Int,
+        isCurrentChapterRead: Boolean,
+        currentChapterProgress: Double?,
+        limits: ReadingEtaLimits,
+    ): Long? {
+        if (currentChapterIndex < 0) return null
+        val sampledDurations = orderedChapterIds
+            .take(currentChapterIndex + 1)
+            .mapNotNull { chapterId ->
+                val chapterDuration = chapterDurations[chapterId] ?: return@mapNotNull null
+                val normalizedDuration = when {
+                    chapterId == currentChapterId && !isCurrentChapterRead -> {
+                        calculateProjectedChapterDurationMs(
+                            chapterDuration = chapterDuration,
+                            chapterProgress = currentChapterProgress,
+                            limits = limits,
+                        )
+                    }
+                    else -> chapterDuration
+                } ?: return@mapNotNull null
+                normalizedDuration
+            }
+            .filter { it in limits.minTrackedChapterDurationMs..limits.maxTrackedChapterDurationMs }
+            .map { it.coerceAtMost(limits.maxChapterDurationMsForStats) }
+            .takeLast(limits.etaSampleChapterLimit)
+        if (sampledDurations.isEmpty()) return null
+
+        val sortedDurations = sampledDurations.sorted()
+        val trimCount = (sortedDurations.size / 10)
+            .coerceAtMost((sortedDurations.size - 1) / 2)
+        val trimmedDurations = if (trimCount > 0) {
+            sortedDurations.subList(trimCount, sortedDurations.size - trimCount)
+        } else {
+            sortedDurations
+        }
+        return trimmedDurations.sum() / trimmedDurations.size
+    }
+
+    private fun calculateChapterProgress(
+        currentPage: Int,
+        totalPages: Int,
+    ): Double? {
+        if (currentPage <= 0 || totalPages <= 1) return null
+        return (currentPage.toDouble() / totalPages.toDouble()).coerceIn(0.0, 1.0)
+    }
+
+    private fun calculateProjectedChapterDurationMs(
+        chapterDuration: Long,
+        chapterProgress: Double?,
+        limits: ReadingEtaLimits,
+    ): Long? {
+        if (chapterDuration <= 0L) return null
+        val progress = chapterProgress
+            ?.takeIf { it >= MIN_PROGRESS_FOR_DURATION_PROJECTION }
+            ?.coerceIn(0.0, 1.0)
+            ?: return null
+        if (progress == 0.0) return null
+        return (chapterDuration.toDouble() / progress).toLong()
+            .coerceAtLeast(0L)
+            .coerceAtMost(limits.maxChapterDurationMsForStats)
+    }
+
+    private fun calculateRemainingChapterTimeMs(
+        chapterDuration: Long?,
+        chapterProgress: Double?,
+    ): Long? {
+        val duration = chapterDuration?.takeIf { it > 0L } ?: return null
+        val remainingProgress = 1.0 - (chapterProgress ?: 0.0).coerceIn(0.0, 1.0)
+        return (duration.toDouble() * remainingProgress).toLong().coerceAtLeast(0L)
+    }
+
+    private fun Long.sanitizeTrackedDuration(limits: ReadingEtaLimits): Long {
+        return if (this in limits.minTrackedChapterDurationMs..limits.maxTrackedChapterDurationMs) this else 0L
+    }
+
+    private fun Long.sanitizeTrackedPages(limits: ReadingEtaLimits): Long {
+        return if (this in ReadingEtaDefaults.MIN_PAGES_READ_FOR_PAGE_RATE..limits.maxPagesReadForPageRate) this else 0L
+    }
+}