🛠️ Improve EPUB parser (spine + async)

* Using "content.opf" to get correct chapters and order
* Using manual sorting + getting all chapters if no "content.opf"
* Fixed incorrect order issues
* Fixed missing chapters issues
* Improved parsing time by over 3 times
* Asynchronous chapter parsing

app/src/main/java/ua/acclorite/book_story/data/parser/epub/EpubTextParser.kt

@@ -1,8 +1,14 @@
+@file:OptIn(ExperimentalCoroutinesApi::class)
+
 package ua.acclorite.book_story.data.parser.epub
 
 import android.net.Uri
 import android.util.Log
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.async
+import kotlinx.coroutines.awaitAll
+import kotlinx.coroutines.coroutineScope
 import kotlinx.coroutines.withContext
 import kotlinx.coroutines.yield
 import org.jsoup.Jsoup
@@ -13,13 +19,19 @@ import ua.acclorite.book_story.domain.model.Chapter
 import ua.acclorite.book_story.domain.model.ChapterWithText
 import ua.acclorite.book_story.domain.util.Resource
 import ua.acclorite.book_story.domain.util.UIText
+import ua.acclorite.book_story.presentation.core.util.addAll
 import ua.acclorite.book_story.presentation.core.util.clearMarkdown
 import java.io.File
+import java.util.concurrent.ConcurrentLinkedQueue
 import java.util.zip.ZipEntry
 import java.util.zip.ZipFile
 import javax.inject.Inject
+import kotlin.collections.set
 
 private const val EPUB_TAG = "EPUB Parser"
+private typealias Title = String
+
+private val dispatcher = Dispatchers.IO.limitedParallelism(2)
 
 class EpubTextParser @Inject constructor(
     private val documentParser: DocumentParser
@@ -35,18 +47,30 @@ class EpubTextParser @Inject constructor(
 
             withContext(Dispatchers.IO) {
                 ZipFile(file).use { zip ->
-                    yield()
+                    val tocEntry = zip.entries().toList().find { entry ->
-
-                    zip.entries().asSequence().find { entry ->
                         entry.name.endsWith("toc.ncx", ignoreCase = true)
-                    }.apply {
+                    }
-                        parseEpub(tocEntry = this, zip = zip).let {
+                    val opfEntry = zip.entries().toList().find { entry ->
-                            if (it == null) {
+                        entry.name.endsWith("content.opf", ignoreCase = true)
-                                Log.e(EPUB_TAG, "Could not parse EPUB.")
+                    }
-                                return@withContext
+
-                            }
+                    val chapterEntries = zip.getChapterEntries(opfEntry)
-                            chapters.addAll(it)
+                    val chapterTitleEntries = zip.getChapterTitleMapFromToc(tocEntry)
+
+                    Log.i(EPUB_TAG, "TOC Entry: ${tocEntry?.name ?: "no toc.ncx"}")
+                    Log.i(EPUB_TAG, "OPF Entry: ${opfEntry?.name ?: "no content.opf"}")
+                    Log.i(EPUB_TAG, "Chapter entries, size: ${chapterEntries.size}")
+                    Log.i(EPUB_TAG, "Title entries, size: ${chapterTitleEntries?.size}")
+
+                    zip.parseEpub(
+                        chapterEntries = chapterEntries,
+                        chapterTitleEntries = chapterTitleEntries
+                    ).let {
+                        if (it == null || it.isEmpty()) {
+                            Log.e(EPUB_TAG, "Could not parse EPUB (null or empty).")
+                            return@withContext
                         }
+                        chapters.addAll(it)
                     }
                 }
             }
@@ -74,118 +98,218 @@ class EpubTextParser @Inject constructor(
      * Parses text and chapters from EPUB.
      * Uses toc.ncx(if present) to retrieve titles, otherwise uses first line as title.
      *
+     * @param chapterTitleEntries Titles extracted from toc.ncx.
+     * @param chapterEntries [ZipEntry]s to parse.
+     *
      * @return Null if could not parse.
      */
-    private suspend fun parseEpub(tocEntry: ZipEntry?, zip: ZipFile): List<ChapterWithText>? {
+    @OptIn(ExperimentalCoroutinesApi::class)
-        Log.i(EPUB_TAG, "TOC Entry: ${tocEntry?.name ?: "NO TOC"}")
+    private suspend fun ZipFile.parseEpub(
-
+        chapterEntries: List<ZipEntry>,
-        yield()
+        chapterTitleEntries: Map<Title, List<String>>?
+    ): List<ChapterWithText>? {
 
         val chapters = mutableListOf<ChapterWithText>()
-        var chapterTextIndex = -1
+        coroutineScope {
+            val unformattedChapters = ConcurrentLinkedQueue<ChapterWithText>()
 
-        val tocContent = tocEntry?.let {
+            // Asynchronously getting all chapters with text
-            withContext(Dispatchers.IO) {
+            val jobs = chapterEntries.mapIndexed { index, entry ->
-                zip.getInputStream(it)
+                async(dispatcher) {
-            }.bufferedReader().use { it.readText() }
+                    yield()
-        }
-        val tocDocument = tocContent?.let { Jsoup.parse(it) }
-        val chaptersTitles = tocDocument.run {
-            if (this == null) return@run null
-            var titles = mutableMapOf<String, List<String>>()
 
-            select("navPoint").forEach { navPoint ->
+                    unformattedChapters.parseZipEntry(
-                val title = navPoint.selectFirst("navLabel > text")?.text()?.trim()
+                        zip = this@parseEpub,
-                    ?: return@forEach
+                        index = index,
-                val source = navPoint.selectFirst("content")?.attr("src")?.trim().let {
+                        entry = entry,
-                    if (it == null) return@forEach
+                        chapterTitleMap = chapterTitleEntries
-                    Uri.parse(it).path ?: it
+                    )
-                }.substringAfterLast("/")
 
-                titles[source] = (titles[source] ?: emptyList()) + title
+                    yield()
-            }
-
-            titles
-        }
-
-        yield()
-
-        zip.entries().asSequence().sortedBy {
-            it.name.filter { it.isDigit() }.toIntOrNull()
-        }.forEach { entry ->
-            yield()
-
-            if (
-                !entry.name.endsWith(".xhtml")
-                && !entry.name.endsWith(".html")
-                && !entry.name.endsWith(".htm")
-            ) return@forEach
-
-            yield()
-
-            val content = zip.getInputStream(entry).bufferedReader().use { it.readText() }
-            var chapter = documentParser.run {
-                Jsoup.parse(content).parseDocument()
-            }
-
-            if (chapter.isEmpty()) {
-                Log.w(EPUB_TAG, "Chapter ${entry.name} is empty.")
-                return@forEach
-            }
-
-            val chapterTitle = getChapterTitleFromToc(
-                chapterSource = entry.name,
-                chaptersTitles = chaptersTitles
-            ).run {
-                if (this != null) {
-                    return@run this
                 }
-                chapter.first().clearMarkdown()
             }
+            jobs.awaitAll()
 
-            chapter = chapter.dropWhile {
+            // Sorting chapters in correct order
-                it.clearMarkdown().lowercase() == chapterTitle.lowercase()
+            chapters.addAll {
+                var textIndex = -1
+                unformattedChapters.toList()
+                    .sortedBy { it.chapter.index }
+                    .mapIndexed { index, item ->
+                        item.copy(
+                            chapter = item.chapter.copy(
+                                index = index,
+                                startIndex = textIndex + 1,
+                                endIndex = textIndex + item.text.size
+                            )
+                        ).also { textIndex += item.text.size }
+                    }
             }
-            
-            if (chapter.isEmpty()) {
-                Log.w(EPUB_TAG, "Chapter ${entry.name} is empty.")
-                return@forEach
-            }
-
-            yield()
-
-            chapters.add(
-                ChapterWithText(
-                    chapter = Chapter(
-                        index = chapters.size,
-                        title = chapterTitle,
-                        startIndex = chapterTextIndex + 1,
-                        endIndex = chapterTextIndex + chapter.size
-                    ),
-                    text = chapter
-                )
-            )
-            chapterTextIndex += chapter.size
         }
 
-        yield()
-
         if (chapters.isEmpty()) {
-            Log.e(EPUB_TAG, "Could not parse file without toc.ncx")
             return null
         }
 
         return chapters
     }
 
+    /**
+     * Parses [entry] to get it's text and chapter.
+     * Adds parsed entry in [ConcurrentLinkedQueue].
+     *
+     * @param zip [ZipFile] of the [entry].
+     * @param index Index of the [entry].
+     * @param entry [ZipEntry].
+     * @param chapterTitleMap Titles from [getChapterTitleMapFromToc].
+     */
+    private suspend fun ConcurrentLinkedQueue<ChapterWithText>.parseZipEntry(
+        zip: ZipFile,
+        index: Int,
+        entry: ZipEntry,
+        chapterTitleMap: Map<Title, List<String>>?
+    ) {
+        // Getting all text
+        val content = zip.getInputStream(entry).bufferedReader().use { it.readText() }
+        var chapter = documentParser.run {
+            Jsoup.parse(content).parseDocument()
+        }
+
+        if (chapter.isEmpty()) {
+            Log.w(EPUB_TAG, "Chapter ${entry.name} is empty.")
+            return
+        }
+
+        // Getting title and removing first line (if matches title)
+        val chapterTitle = getChapterTitleFromToc(
+            chapterSource = entry.name,
+            chapterTitleMap = chapterTitleMap
+        ).run {
+            if (this != null) {
+                return@run this
+            }
+            chapter.first().clearMarkdown()
+        }.also { title ->
+            chapter = chapter.dropWhile { line ->
+                line.clearMarkdown().lowercase() == title.lowercase()
+            }
+        }
+
+        if (chapter.isEmpty()) {
+            Log.w(EPUB_TAG, "Chapter ${entry.name} is empty.")
+            return
+        }
+
+        add(
+            ChapterWithText(
+                Chapter(
+                    index = index,
+                    title = chapterTitle,
+                    startIndex = 0,
+                    endIndex = 0
+                ),
+                text = chapter
+            )
+        )
+    }
+
+    /**
+     * Getting all titles from [tocEntry].
+     *
+     * @return null if [tocEntry] is null.
+     */
+    private suspend fun ZipFile.getChapterTitleMapFromToc(
+        tocEntry: ZipEntry?
+    ): Map<Title, List<String>>? {
+        val tocContent = tocEntry?.let {
+            withContext(Dispatchers.IO) {
+                getInputStream(it)
+            }.bufferedReader().use { it.readText() }
+        }
+        val tocDocument = tocContent?.let { Jsoup.parse(it) }
+
+        if (tocDocument == null) return null
+        var titleMap = mutableMapOf<Title, List<String>>()
+
+        tocDocument.select("navPoint").forEach { navPoint ->
+            val title = navPoint.selectFirst("navLabel > text")?.text()?.trim()
+                ?: return@forEach
+            val source = navPoint.selectFirst("content")?.attr("src")?.trim()
+                .let {
+                    if (it == null) return@forEach
+                    Uri.parse(it).path ?: it
+                }.substringAfterLast("/")
+
+            titleMap[source] = (titleMap[source] ?: emptyList()) + title
+        }
+
+        return titleMap
+    }
+
+    /**
+     * Getting title from [chapterTitleMap].
+     *
+     * @return Null if did not find matching chapters to the [chapterSource].
+     */
     private fun getChapterTitleFromToc(
         chapterSource: String,
-        chaptersTitles: Map<String, List<String>>?
+        chapterTitleMap: Map<String, List<String>>?
     ): String? {
-        if (chaptersTitles.isNullOrEmpty()) return null
+        if (chapterTitleMap.isNullOrEmpty()) return null
-        return chaptersTitles
+        return chapterTitleMap
             .getOrElse(chapterSource.substringAfterLast("/")) { null }
             ?.joinToString(separator = " / ")
             ?.ifBlank { null }
     }
+
+    /**
+     * Getting all chapter entries.
+     * If [opfEntry] is not null, then getting chapters from Spine.
+     * If [opfEntry] is null, then getting chapters from the whole [ZipFile] and manually sorting them.
+     *
+     * @param opfEntry OPF entry. May be null.
+     *
+     * @return List of chapter entries in correct order (do not reorder).
+     */
+    private fun ZipFile.getChapterEntries(opfEntry: ZipEntry?): List<ZipEntry> {
+        opfEntry.let { opfEntry ->
+            if (opfEntry == null) {
+                return@let
+            }
+
+            val opfContent = getInputStream(opfEntry).bufferedReader().use {
+                it.readText()
+            }
+            val document = Jsoup.parse(opfContent)
+            val zipEntries = entries().toList()
+
+            val manifestItems = document.select("manifest > item").associate {
+                it.attr("id") to it.attr("href")
+            }
+
+            document.select("spine > itemref").mapNotNull { itemRef ->
+                val spineId = itemRef.attr("idref")
+                val chapterSource = manifestItems[spineId]?.substringAfterLast('/')?.lowercase()
+                    ?: return@mapNotNull null
+
+                zipEntries.find { entry ->
+                    entry.name.substringAfterLast('/').lowercase() == chapterSource
+                }
+            }.also { entries ->
+                if (entries.isEmpty()) return@let
+
+                Log.i(EPUB_TAG, "Successfully parsed OPF to get entries from spine.")
+                return entries
+            }
+        }
+
+        Log.w(EPUB_TAG, "Could not parse OPF, manual filtering.")
+        return entries().toList().filter { entry ->
+            listOf(".html", ".htm", ".xhtml").any {
+                entry.name.endsWith(it, ignoreCase = true)
+            }
+        }.sortedBy {
+            it.name.filter { char -> char.isDigit() }.toBigIntegerOrNull()
+        }
+    }
 }

app/src/main/java/ua/acclorite/book_story/presentation/core/util/Extensions.kt

@@ -72,3 +72,7 @@ fun Modifier.noRippleClickable(
 fun String.clearMarkdown(): String {
     return replace(Regex("_|\\*\\*"), "")
 }
+
+fun <T> MutableList<T>.addAll(calculation: () -> List<T>) {
+    addAll(calculation())
+}