adds service name parser (copied from akka-management) (#26132)

* adds service name parser

* Apply suggestions from code review

Co-Authored-By: renatocaval <renato@cavalcanti.be>

* dangling parenthesis on last line

* code formatting

* extended tests for Lookup.isValidSrv

* make it illegal to create Lookups with empty or null service name

* improved tests description

* improved error messages

* formatting

* updated copyright header

* removed weird import

* removes trailing dot

* throw NPE when null is passed

akka-discovery/src/main/scala/akka/discovery/ServiceDiscovery.scala

@@ -128,6 +128,7 @@ object ServiceDiscovery {
  * For example `portName` could be used to distinguish between
  * Akka remoting ports and HTTP ports.
  *
+ * @throws IllegalArgumentException if [[serviceName]] is 'null' or an empty String
  */
 @ApiMayChange
 final class Lookup(
@@ -135,6 +136,9 @@ final class Lookup(
   val portName:    Option[String],
   val protocol:    Option[String]) {
 
+  require(serviceName != null, "'serviceName' cannot be null")
+  require(serviceName.trim.nonEmpty, "'serviceName' cannot be empty")
+
   /**
    * Which port for a service e.g. Akka remoting or HTTP.
    * Maps to "service" for an SRV records.
@@ -194,6 +198,47 @@ case object Lookup {
    * and protocol
    */
   def create(serviceName: String): Lookup = new Lookup(serviceName, None, None)
+
+  private val SrvQuery = """^_(.+?)\._(.+?)\.(.+?)$""".r
+
+  private val DomainName = "^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$".r
+
+  /**
+   * Create a service Lookup from a string with format:
+   * _portName._protocol.serviceName.
+   * (as specified by https://www.ietf.org/rfc/rfc2782.txt)
+   *
+   * If the passed string conforms with this format, a SRV Lookup is returned.
+   * The serviceName part must be a valid domain name.
+   *
+   * The string is parsed and dismembered to build a Lookup as following:
+   * Lookup(serviceName).withPortName(portName).withProtocol(protocol)
+   *
+   *
+   * @throws NullPointerException If the passed string is null
+   * @throws IllegalArgumentException If the string doesn't not conform with the SRV format
+   */
+  def parseSrv(str: String): Lookup =
+    str match {
+      case SrvQuery(portName, protocol, serviceName) if validDomainName(serviceName) ⇒
+        Lookup(serviceName).withPortName(portName).withProtocol(protocol)
+
+      case null ⇒ throw new NullPointerException("Unable to create Lookup from passed SRV string. Passed value is 'null'")
+      case _    ⇒ throw new IllegalArgumentException(s"Unable to create Lookup from passed SRV string, invalid format: $str")
+    }
+
+  /**
+   * Returns true if passed string conforms with SRV format. Otherwise returns false.
+   */
+  def isValidSrv(srv: String): Boolean =
+    srv match {
+      case SrvQuery(_, _, serviceName) ⇒ validDomainName(serviceName)
+      case _                           ⇒ false
+    }
+
+  private def validDomainName(name: String): Boolean =
+    DomainName.pattern.asPredicate().test(name)
+
 }
 
 /**

akka-discovery/src/test/scala/akka/discovery/LookupSpec.scala

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2017-2019 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.discovery
+
+import org.scalatest.{ Matchers, OptionValues, WordSpec }
+
+class LookupSpec extends WordSpec with Matchers with OptionValues {
+
+  // SRV strings with invalid domain names
+  // should fail to build lookups
+  val srvWithInvalidDomainNames = List(
+    "_portName._protocol.service_name.local",
+    "_portName._protocol.servicename,local",
+    "_portName._protocol.servicename.local-",
+    "_portName._protocol.-servicename.local")
+
+  // No SRV that should result in simple A/AAAA lookups
+  val noSrvLookups = List(
+    "portName.protocol.serviceName.local",
+    "serviceName.local",
+    "_portName.serviceName",
+    "_serviceName.local",
+    "_serviceName,local",
+    "-serviceName.local",
+    "serviceName.local-")
+
+  "Lookup.parseSrv" should {
+
+    "generate a SRV Lookup from a SRV String" in {
+      val name = "_portName._protocol.serviceName.local"
+      val lookup = Lookup.parseSrv(name)
+      lookup.serviceName shouldBe "serviceName.local"
+      lookup.portName.value shouldBe "portName"
+      lookup.protocol.value shouldBe "protocol"
+    }
+
+    "throw an IllegalArgumentException when passing a 'null' SRV String" in {
+      assertThrows[NullPointerException] {
+        Lookup.parseSrv(null)
+      }
+    }
+
+    "throw an IllegalArgumentException when passing an empty SRV String" in {
+      assertThrows[IllegalArgumentException] {
+        Lookup.parseSrv("")
+      }
+    }
+
+    "throw an IllegalArgumentException for any non-conforming SRV String" in {
+      noSrvLookups.foreach { str ⇒
+        withClue(s"parsing '$str'") {
+          assertThrows[IllegalArgumentException] {
+            Lookup.parseSrv(str)
+          }
+        }
+      }
+    }
+
+    "throw an IllegalArgumentException for any SRV with invalid domain names" in {
+      srvWithInvalidDomainNames.foreach { str ⇒
+        withClue(s"parsing '$str'") {
+          assertThrows[IllegalArgumentException] {
+            Lookup.parseSrv(str)
+          }
+        }
+      }
+    }
+
+  }
+
+  "Lookup.isValidSrv" should {
+
+    "return true for any conforming SRV String" in {
+      Lookup.isValidSrv("_portName._protocol.serviceName.local") shouldBe true
+    }
+
+    "return false for any non-conforming SRV String" in {
+      noSrvLookups.foreach { str ⇒
+        withClue(s"checking '$str'") {
+          Lookup.isValidSrv(str) shouldBe false
+        }
+      }
+    }
+
+    "return false if domain part in SRV String is an invalid domain name" in {
+      srvWithInvalidDomainNames.foreach { str ⇒
+        withClue(s"checking '$str'") {
+          Lookup.isValidSrv(str) shouldBe false
+        }
+      }
+    }
+
+    "return false for empty SRV String" in {
+      Lookup.isValidSrv("") shouldBe false
+    }
+
+    "return false for 'null' SRV String" in {
+      Lookup.isValidSrv(null) shouldBe false
+    }
+
+    "return true for a SRV with valid domain name" in {
+      Lookup.isValidSrv("_portName._protocol.serviceName.local") shouldBe true
+    }
+
+  }
+}