Handle 429 TooManyRequests error

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

@@ -0,0 +1,9 @@
+package org.koitharu.kotatsu.core.exceptions
+
+import okio.IOException
+import java.util.Date
+
+class TooManyRequestExceptions(
+	val url: String,
+	val retryAt: Date?,
+) : IOException()

app/src/main/kotlin/org/koitharu/kotatsu/core/network/CommonHeaders.kt

@@ -15,6 +15,7 @@ object CommonHeaders {
 	const val AUTHORIZATION = "Authorization"
 	const val CACHE_CONTROL = "Cache-Control"
 	const val PROXY_AUTHORIZATION = "Proxy-Authorization"
+	const val RETRY_AFTER = "Retry-After"
 
 	val CACHE_CONTROL_NO_STORE: CacheControl
 		get() = CacheControl.Builder().noStore().build()

app/src/main/kotlin/org/koitharu/kotatsu/core/network/NetworkModule.kt

@@ -67,6 +67,7 @@ interface NetworkModule {
 			cache(cache)
 			addInterceptor(GZipInterceptor())
 			addInterceptor(CloudFlareInterceptor())
+			addInterceptor(RateLimitInterceptor())
 			if (BuildConfig.DEBUG) {
 				addInterceptor(CurlLoggingInterceptor())
 			}

app/src/main/kotlin/org/koitharu/kotatsu/core/network/RateLimitInterceptor.kt

@@ -0,0 +1,36 @@
+package org.koitharu.kotatsu.core.network
+
+import okhttp3.Interceptor
+import okhttp3.Response
+import okhttp3.internal.closeQuietly
+import org.koitharu.kotatsu.core.exceptions.TooManyRequestExceptions
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+import java.util.concurrent.TimeUnit
+
+class RateLimitInterceptor : Interceptor {
+
+	private val dateFormat = SimpleDateFormat("EEE, dd MMM yyyy HH:mm:ss ZZZ", Locale.ENGLISH)
+
+	override fun intercept(chain: Interceptor.Chain): Response {
+		val response = chain.proceed(chain.request())
+		if (response.code == 429) {
+			val retryDate = response.header(CommonHeaders.RETRY_AFTER)?.parseRetryDate()
+			val request = response.request
+			response.closeQuietly()
+			throw TooManyRequestExceptions(
+				url = request.url.toString(),
+				retryAt = retryDate,
+			)
+		}
+		return response
+	}
+
+	private fun String.parseRetryDate(): Date? {
+		toIntOrNull()?.let {
+			return Date(System.currentTimeMillis() + TimeUnit.SECONDS.toMillis(it.toLong()))
+		}
+		return dateFormat.parse(this)
+	}
+}