[ETCM-331] Separate RateLimit validation in a different trait

src/main/scala/io/iohk/ethereum/jsonrpc/server/http/RateLimit.scala

@@ -0,0 +1,25 @@
+package io.iohk.ethereum.jsonrpc.server.http
+
+import java.time.Clock
+
+import akka.http.scaladsl.model.RemoteAddress
+import com.twitter.util.LruMap
+import io.iohk.ethereum.jsonrpc.server.http.JsonRpcHttpServer.JsonRpcHttpServerConfig
+import io.iohk.ethereum.utils.Logger
+
+trait RateLimitValidator extends Logger {
+
+  val config: JsonRpcHttpServerConfig
+
+  val latestRequestTimestamps = new LruMap[RemoteAddress, Long](config.rateLimit.latestTimestampCacheSize)
+
+  val clock: Clock = Clock.systemUTC()
+
+  def validate(clientAddress: RemoteAddress):Boolean = {
+    val timeMillis = clock.instant().toEpochMilli
+    val latestRequestTimestamp = latestRequestTimestamps.getOrElse(clientAddress, 0L)
+    val response = latestRequestTimestamp + config.rateLimit.minRequestInterval.toMillis < timeMillis
+    if(response) latestRequestTimestamps.put(clientAddress, timeMillis)
+    response
+  }
+}