/*                     __                                               *\
**     ________ ___   / /  ___     Scala API                            **
**    / __/ __// _ | / /  / _ |    (c) 2003-2013, LAMP/EPFL             **
**  __\ \/ /__/ __ |/ /__/ __ |    http://scala-lang.org/               **
** /____/\___/_/ |_/____/_/ | |                                         **
**                          |/                                          **
\*                                                                      */

package scala.concurrent.impl



import java.util.concurrent.{ LinkedBlockingQueue, Callable, Executor, ExecutorService, Executors, ThreadFactory, TimeUnit, ThreadPoolExecutor }
import java.util.Collection
import scala.concurrent.forkjoin._
import scala.concurrent.{ BlockContext, ExecutionContext, Awaitable, CanAwait, ExecutionContextExecutor, ExecutionContextExecutorService }
import scala.util.control.NonFatal



private[scala] class ExecutionContextImpl private[impl] (es: Executor, reporter: Throwable => Unit) extends ExecutionContextExecutor {

  val executor: Executor = es match {
    case null => createExecutorService
    case some => some
  }

  // Implement BlockContext on FJP threads
  class DefaultThreadFactory(daemonic: Boolean) extends ThreadFactory with ForkJoinPool.ForkJoinWorkerThreadFactory { 
    def wire[T <: Thread](thread: T): T = {
      thread.setDaemon(daemonic)
      //Potentially set things like uncaught exception handler, name etc
      thread
    }

    def newThread(runnable: Runnable): Thread = wire(new Thread(runnable))

    def newThread(fjp: ForkJoinPool): ForkJoinWorkerThread = wire(new ForkJoinWorkerThread(fjp) with BlockContext {
      override def blockOn[T](thunk: =>T)(implicit permission: CanAwait): T = {
        var result: T = null.asInstanceOf[T]
        ForkJoinPool.managedBlock(new ForkJoinPool.ManagedBlocker {
          @volatile var isdone = false
          override def block(): Boolean = {
            result = try thunk finally { isdone = true }
            true
          }
          override def isReleasable = isdone
        })
        result
      }
    })
  }

  def createExecutorService: ExecutorService = {

    def getInt(name: String, f: String => Int): Int =
        try f(System.getProperty(name)) catch { case e: Exception => Runtime.getRuntime.availableProcessors }
    def range(floor: Int, desired: Int, ceiling: Int): Int =
      if (ceiling < floor) range(ceiling, desired, floor) else scala.math.min(scala.math.max(desired, floor), ceiling)

    val desiredParallelism = range(
      getInt("scala.concurrent.context.minThreads", _.toInt),
      getInt("scala.concurrent.context.numThreads", {
        case null | "" => Runtime.getRuntime.availableProcessors
        case s if s.charAt(0) == 'x' => (Runtime.getRuntime.availableProcessors * s.substring(1).toDouble).ceil.toInt
        case other => other.toInt
      }),
      getInt("scala.concurrent.context.maxThreads", _.toInt))

    val threadFactory = new DefaultThreadFactory(daemonic = true)
    
    try {
      new ForkJoinPool(
        desiredParallelism,
        threadFactory,
        null, //FIXME we should have an UncaughtExceptionHandler, see what Akka does
        true) // Async all the way baby
    } catch {
      case NonFatal(t) =>
        System.err.println("Failed to create ForkJoinPool for the default ExecutionContext, falling back to ThreadPoolExecutor")
        t.printStackTrace(System.err)
        val exec = new ThreadPoolExecutor(
          desiredParallelism,
          desiredParallelism,
          5L,
          TimeUnit.MINUTES,
          new LinkedBlockingQueue[Runnable],
          threadFactory
        )
        exec.allowCoreThreadTimeOut(true)
        exec
    }
  }

  def execute(runnable: Runnable): Unit = executor match {
    case fj: ForkJoinPool =>
      Thread.currentThread match {
        case fjw: ForkJoinWorkerThread if fjw.getPool eq fj =>
          (runnable match {
            case fjt: ForkJoinTask[_] => fjt
            case _ => ForkJoinTask.adapt(runnable)
          }).fork
        case _ => fj.execute(runnable)
      }
    case generic => generic execute runnable
  }

  def reportFailure(t: Throwable) = reporter(t)
}


private[concurrent] object ExecutionContextImpl {

  def fromExecutor(e: Executor, reporter: Throwable => Unit = ExecutionContext.defaultReporter): ExecutionContextImpl = new ExecutionContextImpl(e, reporter)
  def fromExecutorService(es: ExecutorService, reporter: Throwable => Unit = ExecutionContext.defaultReporter): ExecutionContextImpl with ExecutionContextExecutorService =
    new ExecutionContextImpl(es, reporter) with ExecutionContextExecutorService {
      final def asExecutorService: ExecutorService = executor.asInstanceOf[ExecutorService]
      override def execute(command: Runnable) = executor.execute(command)
      override def shutdown() { asExecutorService.shutdown() }
      override def shutdownNow() = asExecutorService.shutdownNow()
      override def isShutdown = asExecutorService.isShutdown
      override def isTerminated = asExecutorService.isTerminated
      override def awaitTermination(l: Long, timeUnit: TimeUnit) = asExecutorService.awaitTermination(l, timeUnit)
      override def submit[T](callable: Callable[T]) = asExecutorService.submit(callable)
      override def submit[T](runnable: Runnable, t: T) = asExecutorService.submit(runnable, t)
      override def submit(runnable: Runnable) = asExecutorService.submit(runnable)
      override def invokeAll[T](callables: Collection[_ <: Callable[T]]) = asExecutorService.invokeAll(callables)
      override def invokeAll[T](callables: Collection[_ <: Callable[T]], l: Long, timeUnit: TimeUnit) = asExecutorService.invokeAll(callables, l, timeUnit)
      override def invokeAny[T](callables: Collection[_ <: Callable[T]]) = asExecutorService.invokeAny(callables)
      override def invokeAny[T](callables: Collection[_ <: Callable[T]], l: Long, timeUnit: TimeUnit) = asExecutorService.invokeAny(callables, l, timeUnit)
    }
}