Simple related manga search implementation

src/main/kotlin/org/koitharu/kotatsu/parsers/MangaParser.kt

@@ -8,6 +8,7 @@ import org.koitharu.kotatsu.parsers.network.OkHttpWebClient
 import org.koitharu.kotatsu.parsers.network.UserAgents
 import org.koitharu.kotatsu.parsers.network.WebClient
 import org.koitharu.kotatsu.parsers.util.FaviconParser
+import org.koitharu.kotatsu.parsers.util.RelatedMangaFinder
 import org.koitharu.kotatsu.parsers.util.domain
 import org.koitharu.kotatsu.parsers.util.toAbsoluteUrl
 import java.util.*
@@ -127,4 +128,14 @@ abstract class MangaParser @InternalParsersApi constructor(
 	open fun onCreateConfig(keys: MutableCollection<ConfigKey<*>>) {
 		keys.add(configKeyDomain)
 	}
+
+	open suspend fun getRelatedManga(seed: Manga): List<Manga> {
+		return RelatedMangaFinder(listOf(this)).invoke(seed)
+	}
+
+	protected fun getParser(source: MangaSource) = if (this.source == source) {
+		this
+	} else {
+		context.newParserInstance(source)
+	}
 }

src/main/kotlin/org/koitharu/kotatsu/parsers/site/grouple/GroupleParser.kt

@@ -76,6 +76,7 @@ internal abstract class GroupleParser(
 				mapOf(
 					"q" to query.urlEncoded(),
 					"offset" to (offset upBy PAGE_SIZE_SEARCH).toString(),
+					"fast-filter" to "CREATION",
 				),
 			)
 
@@ -321,6 +322,15 @@ internal abstract class GroupleParser(
 		keys.add(userAgentKey)
 	}
 
+	override suspend fun getRelatedManga(seed: Manga): List<Manga> {
+		val parsers = listOf(
+			getParser(MangaSource.READMANGA_RU),
+			getParser(MangaSource.MINTMANGA),
+			getParser(MangaSource.SELFMANGA),
+		)
+		return RelatedMangaFinder(parsers).invoke(seed)
+	}
+
 	private fun getSortKey(sortOrder: SortOrder) =
 		when (sortOrder) {
 			SortOrder.ALPHABETICAL -> "name"

src/main/kotlin/org/koitharu/kotatsu/parsers/site/madara/pt/Atlantisscan.kt

@@ -8,7 +8,7 @@ import org.koitharu.kotatsu.parsers.site.madara.MadaraParser
 
 @MangaSourceParser("ATLANTISSCAN", "Atlantisscan", "pt")
 internal class Atlantisscan(context: MangaLoaderContext) :
-	MadaraParser(context, MangaSource.ATLANTISSCAN, "atlantisscan.com") {
+	MadaraParser(context, MangaSource.ATLANTISSCAN, "br.atlantisscan.com", pageSize = 10) {
 
 	override val datePattern = "dd/MM/yyyy"
 

src/main/kotlin/org/koitharu/kotatsu/parsers/util/RelatedMangaFinder.kt

@@ -0,0 +1,47 @@
+package org.koitharu.kotatsu.parsers.util
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.async
+import kotlinx.coroutines.awaitAll
+import kotlinx.coroutines.coroutineScope
+import org.koitharu.kotatsu.parsers.MangaParser
+import org.koitharu.kotatsu.parsers.model.Manga
+
+class RelatedMangaFinder(
+	private val parsers: Collection<MangaParser>,
+) {
+
+	private val regexWhitespace = Regex("\\s+")
+
+	suspend operator fun invoke(seed: Manga): List<Manga> = coroutineScope {
+		parsers.singleOrNull()?.let { parser ->
+			findRelatedImpl(this, parser, seed)
+		} ?: parsers.map { parser ->
+			async {
+				findRelatedImpl(this, parser, seed)
+			}
+		}.awaitAll().flatten()
+	}
+
+	private suspend fun findRelatedImpl(scope: CoroutineScope, parser: MangaParser, seed: Manga): List<Manga> {
+		val words = HashSet<String>()
+		words += seed.title.split(regexWhitespace)
+		seed.altTitle?.let {
+			words += it.split(regexWhitespace)
+		}
+		if (words.isEmpty()) {
+			return emptyList()
+		}
+		val results = words.map { keyword ->
+			scope.async {
+				val result = parser.getList(0, keyword)
+				result.filter { it.id != seed.id && it.containKeyword(keyword) }
+			}
+		}.awaitAll()
+		return results.minBy { if (it.isEmpty()) Int.MAX_VALUE else it.size }
+	}
+
+	private fun Manga.containKeyword(keyword: String): Boolean {
+		return title.contains(keyword, ignoreCase = true) || altTitle?.contains(keyword, ignoreCase = true) == true
+	}
+}

src/main/kotlin/org/koitharu/kotatsu/parsers/util/String.kt

@@ -2,6 +2,7 @@
 
 package org.koitharu.kotatsu.parsers.util
 
+import androidx.annotation.FloatRange
 import androidx.collection.arraySetOf
 import java.math.BigInteger
 import java.net.URLEncoder
@@ -209,6 +210,18 @@ fun String.levenshteinDistance(other: String): Int {
 	return cost[lhsLength - 1]
 }
 
+/**
+ * @param threshold 0 = exact match
+ */
+fun String.almostEquals(other: String, @FloatRange(from = 0.0) threshold: Float): Boolean {
+	if (threshold <= 0f) {
+		return equals(other, ignoreCase = true)
+	}
+	val diff = lowercase().levenshteinDistance(other.lowercase()) / ((length + other.length) / 2f)
+	return diff < threshold
+}
+
+
 inline fun <T> Appendable.appendAll(
 	items: Iterable<T>,
 	separator: CharSequence,

src/test/kotlin/org/koitharu/kotatsu/parsers/MangaParserTest.kt

@@ -3,6 +3,7 @@ package org.koitharu.kotatsu.parsers
 import kotlinx.coroutines.test.runTest
 import okhttp3.HttpUrl
 import org.junit.jupiter.api.Disabled
+import org.junit.jupiter.api.Test
 import org.junit.jupiter.api.extension.ExtendWith
 import org.junit.jupiter.params.ParameterizedTest
 import org.koitharu.kotatsu.parsers.model.Manga
@@ -22,6 +23,14 @@ internal class MangaParserTest {
 
 	private val context = MangaLoaderContextMock
 
+	@Test
+	fun related() = runTest {
+		val parser = context.newParserInstance(MangaSource.READMANGA_RU)
+		val seed = parser.getList(0, "emanon").first()
+		val related = parser.getRelatedManga(seed)
+		assert(related.isNotEmpty() && seed !in related)
+	}
+
 	@ParameterizedTest(name = "{index}|list|{0}")
 	@MangaSources
 	fun list(source: MangaSource) = runTest {