/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License
 */
package org.apache.toree.kernel.interpreter.sparkr

/**
 * Provides reflective access into the backend R component that is not
 * publicly accessible.
 */
class ReflectiveRBackend {
  private val rBackendClass = Class.forName("org.apache.spark.api.r.RBackend")
  private val rBackendInstance = rBackendClass.newInstance()

  /**
   * Initializes the underlying RBackend service.
   *
   * @return The port used by the service
   */
  def init(cl: ClassLoader): Int = {
    val runMethod = rBackendClass.getDeclaredMethod("init")
    Thread.currentThread().setContextClassLoader(cl)
    runMethod.invoke(rBackendInstance).asInstanceOf[Int]
  }

  /** Blocks until the service has finished. */
  def run(): Unit = {
    val runMethod = rBackendClass.getDeclaredMethod("run")

    runMethod.invoke(rBackendInstance)
  }

  /** Closes the underlying RBackend service. */
  def close(): Unit = {
    val runMethod = rBackendClass.getDeclaredMethod("close")

    runMethod.invoke(rBackendInstance)
  }
}