/* =========================================================================================
 * Copyright © 2013-2018 the kamon project <http://kamon.io/>
 *
 * Licensed 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 kamon.bench

import java.util.concurrent.TimeUnit

import kamon.context.Storage.Scope
import kamon.context.{Context, Storage}
import org.openjdk.jmh.annotations._

@State(Scope.Benchmark)
class ThreadLocalStorageBenchmark {

  val TestKey: Context.Key[Int] = Context.key("test-key", 0)
  val ContextWithKey: Context = Context.of(TestKey, 43)

  val TLS: Storage =  new OldThreadLocal
  val FTLS: Storage =  new Storage.ThreadLocal


  @Benchmark
  @BenchmarkMode(Array(Mode.AverageTime))
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  @Fork
  def currentThreadLocal: Context = {
    val scope = TLS.store(ContextWithKey)
    TLS.current()
    scope.close()
    TLS.current()
  }

  @Benchmark
  @BenchmarkMode(Array(Mode.AverageTime))
  @OutputTimeUnit(TimeUnit.NANOSECONDS)
  @Fork
  def fastThreadLocal: Context = {
    val scope = FTLS.store(ContextWithKey)
    FTLS.current()
    scope.close()
    FTLS.current()
  }
}


class OldThreadLocal extends Storage {
  private val tls = new java.lang.ThreadLocal[Context]() {
    override def initialValue(): Context = Context.Empty
  }

  override def current(): Context =
    tls.get()

  override def store(context: Context): Scope = {
    val newContext = context
    val previousContext = tls.get()
    tls.set(newContext)

    new Scope {
      override def context: Context = newContext
      override def close(): Unit = tls.set(previousContext)
    }
  }
}

object OldThreadLocal {
  def apply(): OldThreadLocal = new OldThreadLocal()
}