Allow configuring clients from application.conf (#254)

runtime/src/main/resources/reference.conf

@@ -0,0 +1,8 @@
+akka.grpc.client."*" {
+  host = ""
+  port = 0
+  deadline = infinite
+  override-authority = ""
+  trusted-ca-certificate = ""
+  user-agent = ""
+}

runtime/src/main/scala/akka/grpc/GrpcClientSettings.scala

@@ -4,15 +4,58 @@
 
 package akka.grpc
 
-import scala.concurrent.duration.Duration
+import akka.actor.ActorSystem
+import akka.util.Helpers
+import com.typesafe.config.Config
 
+import scala.concurrent.duration.Duration
 import io.grpc.CallCredentials
 
 object GrpcClientSettings {
   /** Scala API */
   def apply(host: String, port: Int): GrpcClientSettings =
     new GrpcClientSettings(host, port)
 
+  /** Scala API */
+  def apply(serviceName: String, sys: ActorSystem): GrpcClientSettings = {
+    val akkaGrpcClientConfig = sys.settings.config.getConfig("akka.grpc.client")
+
+    val serviceConfig =
+      if (akkaGrpcClientConfig.hasPath('"' + serviceName + '"'))
+        akkaGrpcClientConfig.getConfig('"' + serviceName + '"').withFallback(akkaGrpcClientConfig.getConfig("\"*\""))
+      else
+        akkaGrpcClientConfig.getConfig("\"*\"")
+
+    GrpcClientSettings(serviceConfig)
+  }
+
+  /** Scala API */
+  def apply(config: Config): GrpcClientSettings =
+    GrpcClientSettings(config getString "host", config getInt "port")
+      .copy(
+        overrideAuthority = getOptionalString(config, "override-authority"),
+        deadline = getPotentiallyInfiniteDuration(config, "deadline"),
+        trustedCaCertificate = getOptionalString(config, "trusted-ca-certificate"),
+        userAgent = getOptionalString(config, "user-agent"))
+
+  private def getOptionalString(config: Config, path: String): Option[String] = config.getString(path) match {
+    case "" => None
+    case other => Some(other)
+  }
+
+  private def getPotentiallyInfiniteDuration(underlying: Config, path: String): Duration = Helpers.toRootLowerCase(underlying.getString(path)) match {
+    case "infinite" ⇒ Duration.Inf
+    case _ ⇒ Duration.fromNanos(underlying.getDuration(path).toNanos)
+  }
+
+  /** Java API */
+  def create(serviceName: String, sys: ActorSystem): GrpcClientSettings =
+    GrpcClientSettings(serviceName, sys)
+
+  /** Java API */
+  def create(config: Config): GrpcClientSettings =
+    GrpcClientSettings(config)
+
   /** Java API */
   def create(host: String, port: Int): GrpcClientSettings = apply(host, port)
 }
@@ -64,4 +107,3 @@ final class GrpcClientSettings private (
     userAgent = userAgent)
 
 }
-

runtime/src/test/scala/akka/grpc/GrpcClientSettingsSpec.scala

@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2018 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package akka.grpc
+
+import com.typesafe.config.ConfigFactory
+
+import scala.concurrent.duration._
+
+import akka.actor.ActorSystem
+
+import org.scalatest.{ Matchers, WordSpec }
+
+class GrpcClientSettingsSpec extends WordSpec with Matchers {
+  "The gRPC client settings spec" should {
+    val sys = ActorSystem("test", ConfigFactory.parseString(
+      """
+        |akka.grpc.client {
+        |  "project.WithSpecificConfiguration" {
+        |    host = "myhost"
+        |    port = 42
+        |    override-authority = "google.fr"
+        |    trusted-ca-certificate = "ca.pem"
+        |    deadline = 10m
+        |    user-agent = "Akka-gRPC"
+        |  }
+        |}
+      """.stripMargin).withFallback(ConfigFactory.load()))
+
+    "fall back to the default configuration if no specific configuration is found" in {
+      // Should not crash:
+      GrpcClientSettings("project.WithoutSpecificConfiguration", sys)
+    }
+
+    "parse configuration values" in {
+      val parsed = GrpcClientSettings("project.WithSpecificConfiguration", sys)
+      parsed.host should be("myhost")
+      parsed.port should be(42)
+      parsed.overrideAuthority should be(Some("google.fr"))
+      parsed.trustedCaCertificate should be(Some("ca.pem"))
+      parsed.deadline should be(10.minutes)
+      parsed.userAgent should be(Some("Akka-gRPC"))
+    }
+  }
+}