Automaticaly switch mirrors on network errors

app/src/main/java/org/koitharu/kotatsu/core/AppModule.kt

@@ -86,6 +86,7 @@ interface AppModule {
 		fun provideOkHttpClient(
 			localStorageManager: LocalStorageManager,
 			commonHeadersInterceptor: CommonHeadersInterceptor,
+			mirrorSwitchInterceptor: MirrorSwitchInterceptor,
 			cookieJar: CookieJar,
 			settings: AppSettings,
 		): OkHttpClient {
@@ -103,6 +104,7 @@ interface AppModule {
 				addInterceptor(GZipInterceptor())
 				addInterceptor(commonHeadersInterceptor)
 				addInterceptor(CloudFlareInterceptor())
+				addInterceptor(mirrorSwitchInterceptor)
 				if (BuildConfig.DEBUG) {
 					addInterceptor(CurlLoggingInterceptor())
 				}

app/src/main/java/org/koitharu/kotatsu/core/network/MirrorSwitchInterceptor.kt

@@ -0,0 +1,88 @@
+package org.koitharu.kotatsu.core.network
+
+import dagger.Lazy
+import okhttp3.Interceptor
+import okhttp3.Request
+import okhttp3.Response
+import okhttp3.internal.canParseAsIpAddress
+import okhttp3.internal.closeQuietly
+import okhttp3.internal.publicsuffix.PublicSuffixDatabase
+import org.koitharu.kotatsu.core.parser.MangaRepository
+import org.koitharu.kotatsu.core.parser.RemoteMangaRepository
+import org.koitharu.kotatsu.parsers.model.MangaSource
+import javax.inject.Inject
+import javax.inject.Singleton
+
+@Singleton
+class MirrorSwitchInterceptor @Inject constructor(
+	private val mangaRepositoryFactoryLazy: Lazy<MangaRepository.Factory>,
+) : Interceptor {
+
+	override fun intercept(chain: Interceptor.Chain): Response {
+		val request = chain.request()
+		return try {
+			val response = chain.proceed(request)
+			if (response.isFailed) {
+				val responseCopy = response.newBuilder().build()
+				response.close()
+				trySwitchMirror(request, chain) ?: responseCopy
+			} else {
+				response
+			}
+		} catch (e: Exception) {
+			trySwitchMirror(request, chain) ?: throw e
+		}
+	}
+
+	private fun trySwitchMirror(request: Request, chain: Interceptor.Chain): Response? {
+		val source = request.tag(MangaSource::class.java) ?: return null
+		val repository = mangaRepositoryFactoryLazy.get().create(source) as? RemoteMangaRepository ?: return null
+		val mirrors = repository.getAvailableMirrors()
+		if (mirrors.isEmpty()) {
+			return null
+		}
+		return tryMirrors(repository, mirrors, chain, request)
+	}
+
+	private fun tryMirrors(
+		repository: RemoteMangaRepository,
+		mirrors: List<String>,
+		chain: Interceptor.Chain,
+		request: Request,
+	): Response? {
+		val url = request.url
+		val currentDomain = url.topPrivateDomain()
+		if (currentDomain !in mirrors) {
+			return null
+		}
+		val urlBuilder = url.newBuilder()
+		for (mirror in mirrors) {
+			if (mirror == currentDomain) {
+				continue
+			}
+			val newHost = hostOf(url.host, mirror) ?: continue
+			val newRequest = request.newBuilder()
+				.url(urlBuilder.host(newHost).build())
+				.build()
+			val response = chain.proceed(newRequest)
+			if (response.isFailed) {
+				response.closeQuietly()
+			} else {
+				repository.domain = mirror
+				return response
+			}
+		}
+		return null
+	}
+
+	private val Response.isFailed: Boolean
+		get() = code in 400..599
+
+	private fun hostOf(host: String, newDomain: String): String? {
+		if (newDomain.canParseAsIpAddress()) {
+			return newDomain
+		}
+		val domain = PublicSuffixDatabase.get().getEffectiveTldPlusOne(host) ?: return null
+		return host.removeSuffix(domain) + newDomain
+	}
+}

app/src/main/java/org/koitharu/kotatsu/core/parser/RemoteMangaRepository.kt

@@ -43,8 +43,11 @@ class RemoteMangaRepository(
 			getConfig().defaultSortOrder = value
 		}
 
-	val domain: String
+	var domain: String
 		get() = parser.domain
+		set(value) {
+			getConfig()[parser.configKeyDomain] = value
+		}
 
 	val headers: Headers?
 		get() = parser.headers
@@ -95,6 +98,10 @@ class RemoteMangaRepository(
 		parser.onCreateConfig(it)
 	}
 
+	fun getAvailableMirrors(): List<String> {
+		return parser.configKeyDomain.presetValues?.toList().orEmpty()
+	}
+
 	private fun getConfig() = parser.config as SourceSettings
 
 	private suspend fun <T> asyncSafe(block: suspend CoroutineScope.() -> T): SafeDeferred<T> {

app/src/main/java/org/koitharu/kotatsu/core/prefs/SourceSettings.kt

@@ -28,4 +28,12 @@ class SourceSettings(context: Context, source: MangaSource) : MangaSourceConfig
 			is ConfigKey.ShowSuspiciousContent -> prefs.getBoolean(key.key, key.defaultValue)
 		} as T
 	}
+
+	operator fun <T> set(key: ConfigKey<T>, value: T) = prefs.edit {
+		when (key) {
+			is ConfigKey.Domain -> putString(key.key, value as String?)
+			is ConfigKey.ShowSuspiciousContent -> putBoolean(key.key, value as Boolean)
+			is ConfigKey.UserAgent -> putString(key.key, value as String?)
+		}
+	}
 }