Try to launch ENSIME server

.gitignore

@@ -75,11 +75,14 @@ workingDir/
 .idea/
 .idea_modules/
 src/main/main.iml
-lib/
 *.pem
 
 .tags*
 .ensime*
 .classpath*
 .atom*
 .imdone*
+
+# APM
+lib/
+package.json

apm.sbt

@@ -69,6 +69,23 @@ apmPackage := {
       "outline-view" -> Json.obj(
         "versions" -> Json.obj("0.1.0" -> "provideOutlines")
       )
+    ),
+    "configSchema" -> Json.obj(
+      "server" -> Json.obj(
+        "type" -> "string",
+        "title" -> "Language server",
+        "default" -> "scalameta",
+        "enum" -> Json.arr(
+          Json.obj(
+            "value" -> "scalameta",
+            "description" -> "Scalameta"
+          ),
+          Json.obj(
+            "value" -> "ensime",
+            "description" -> "ENSIME"
+          )
+        )
+      )
     )
   )
 

src/main/scala/ScalaLanguageClient.scala

@@ -9,37 +9,33 @@ import facade.atom_ide.busy_signal._
 
 class ScalaLanguageClient extends AutoLanguageClient { client =>
 
+  private lazy val server: ServerType = ServerType.fromConfig
+
   override def getGrammarScopes(): js.Array[String] = js.Array("source.scala")
   override def getLanguageName(): String = "Scala"
-  override def getServerName(): String = "Scalameta"
+  override def getServerName(): String = server.name
 
   override def startServerProcess(projectPath: String): ChildProcess = {
-    global.console.log(s"startServerProcess(${projectPath})")
-
     // FIXME: use more civilized way of detecting JAVA_HOME
     val javaHome = ChildProcess.asInstanceOf[js.Dynamic].execSync("/usr/libexec/java_home").toString.trim
     val toolsJar = Path.join(javaHome, "lib", "tools.jar")
 
-    // TODO: try to use coursier directly
+    // TODO: try to use coursier directly or download it on the first run
     val coursierJar = Path.join(OS.homedir, "bin", "coursier")
-    val coursierArgs = js.Array(
-      "launch", "--quiet",
-      "--repository", "bintray:dhpcs/maven",
-      "--repository", "sonatype:releases",
-      "--extra-jars", toolsJar,
-      "org.scalameta:metaserver_2.12:0.1-SNAPSHOT",
-      "--main", "scala.meta.languageserver.Main"
-    )
 
     val javaBin = Path.join(javaHome, "bin", "java")
-    val javaArgs = js.Array(
-      s"-Dvscode.workspace=${projectPath}",
-      "-jar", coursierJar
-    ).concat(coursierArgs)
+    val javaArgs =
+      server.javaArgs(projectPath) ++
+      Seq(
+        "-jar", coursierJar,
+        "launch", "--quiet",
+        "--extra-jars", toolsJar
+      ) ++
+      server.coursierArgs
 
-    global.console.log(javaArgs.mkString(javaBin, "\n", ""))
+    println((javaBin +: javaArgs).mkString("\n"))
 
-    val serverProcess = ChildProcess.spawn(javaBin, javaArgs)
+    val serverProcess = ChildProcess.spawn(javaBin, js.Array(javaArgs: _*))
     client.captureServerErrors(serverProcess)
     serverProcess.on("exit", { err: js.Any =>
       busySignal.clear()
@@ -49,8 +45,7 @@ class ScalaLanguageClient extends AutoLanguageClient { client =>
   }
 
   override def filterChangeWatchedFiles(filePath: String): Boolean = {
-    filePath.endsWith(".semanticdb") ||
-    filePath.endsWith(".compilerconfig")
+    server.watchFilter(filePath)
   }
 
   override def preInitialization(connection: js.Any): Unit = {

src/main/scala/ServerType.scala

@@ -0,0 +1,69 @@
+package laughedelic.atom.ide.scala
+
+import scala.scalajs.js, js.annotation._, js.Dynamic.global
+
+sealed trait ServerType {
+
+  val name: String
+
+  def javaArgs(projectPath: String): Seq[String]
+  val coursierArgs: Seq[String]
+
+  def watchFilter(filePath: String): Boolean
+}
+
+case object ServerType {
+
+  case object Scalameta extends ServerType {
+    val name: String = "Scalameta"
+
+    def javaArgs(projectPath: String): Seq[String] = Seq(
+      s"-Dvscode.workspace=${projectPath}"
+    )
+
+    val coursierArgs: Seq[String] = Seq(
+      "--repository", "bintray:dhpcs/maven",
+      "--repository", "sonatype:releases",
+      "org.scalameta:metaserver_2.12:0.1-SNAPSHOT",
+      "--main", "scala.meta.languageserver.Main"
+    )
+
+    def watchFilter(filePath: String): Boolean = {
+      filePath.endsWith(".semanticdb") ||
+      filePath.endsWith(".compilerconfig")
+    }
+  }
+
+  case object Ensime extends ServerType {
+    val name: String = "ENSIME"
+
+    def javaArgs(projectPath: String): Seq[String] = Seq(
+      "-Xmx4G", // heap size
+      // FIXME: how to setup classpath properly without parsing .ensime config?
+      // "-classpath", classpath,
+      s"-Dlsp.workspace=${projectPath}",
+      // TODO: add log level to the plugin settings
+      s"-Dlsp.logLevel=DEBUG",
+    )
+
+    val coursierArgs: Seq[String] = Seq(
+      "--repository", "bintray:dhpcs/maven",
+      "--repository", "sonatype:snapshots",
+      "org.ensime:server_2.12:3.0.0-SNAPSHOT",
+      "--main", "org.ensime.server.Server",
+      "--", "--lsp"
+    )
+
+    def watchFilter(filePath: String): Boolean = {
+      // TODO: should be more precise:
+      filePath.contains(".ensime")
+    }
+  }
+
+  def fromConfig: ServerType = {
+    global.atom.config.get("ide-scala.server").toString match {
+      case "scalameta" => Scalameta
+      case "ensime" => Ensime
+    }
+  }
+}