Handle TooManyRequestsException during downloading

app/src/main/kotlin/org/koitharu/kotatsu/core/exceptions/TooManyRequestExceptions.kt

@@ -6,4 +6,8 @@ import java.util.Date
 class TooManyRequestExceptions(
 	val url: String,
 	val retryAt: Date?,
-) : IOException()
+) : IOException() {
+
+	val retryAfter: Long
+		get() = if (retryAt == null) 0 else (retryAt.time - System.currentTimeMillis()).coerceAtLeast(0)
+}

app/src/main/kotlin/org/koitharu/kotatsu/download/ui/worker/DownloadWorker.kt

@@ -37,6 +37,7 @@ import okio.IOException
 import okio.buffer
 import okio.sink
 import org.koitharu.kotatsu.R
+import org.koitharu.kotatsu.core.exceptions.TooManyRequestExceptions
 import org.koitharu.kotatsu.core.network.CommonHeaders
 import org.koitharu.kotatsu.core.network.MangaHttpClient
 import org.koitharu.kotatsu.core.parser.MangaDataRepository
@@ -277,7 +278,12 @@ class DownloadWorker @AssistedInject constructor(
 					publishState(currentState.copy(isPaused = false, error = null))
 				} else {
 					countDown--
-					delay(DOWNLOAD_ERROR_DELAY)
+					val retryDelay = if (e is TooManyRequestExceptions) {
+						e.retryAfter + DOWNLOAD_ERROR_DELAY
+					} else {
+						DOWNLOAD_ERROR_DELAY
+					}
+					delay(retryDelay)
 				}
 			}
 		}