core/kotlinx-coroutines-core/src/main/kotlin/kotlinx/coroutines/experimental/scheduling/Tasks.kt

package kotlinx.coroutines.experimental.scheduling

import kotlinx.coroutines.experimental.*
import kotlinx.coroutines.experimental.internal.*
import java.util.concurrent.*


// TODO most of these fields will be moved to 'object ExperimentalDispatcher'

// 100us as default
@JvmField
internal val WORK_STEALING_TIME_RESOLUTION_NS = systemProp(
    "kotlinx.coroutines.scheduler.resolution.ns", 100000L)

@JvmField
internal val QUEUE_SIZE_OFFLOAD_THRESHOLD = systemProp(
    "kotlinx.coroutines.scheduler.offload.threshold", 96, maxValue = BUFFER_CAPACITY)

@JvmField
internal val BLOCKING_DEFAULT_PARALLELISM = systemProp(
    "kotlinx.coroutines.scheduler.blocking.parallelism", 16)

@JvmField
internal val CORE_POOL_SIZE = systemProp("kotlinx.coroutines.scheduler.core.pool.size",
    AVAILABLE_PROCESSORS.coerceAtLeast(2), minValue = 2)

@JvmField
internal val MAX_POOL_SIZE = systemProp("kotlinx.coroutines.scheduler.max.pool.size",
    (AVAILABLE_PROCESSORS * 128).coerceIn(CORE_POOL_SIZE, CoroutineScheduler.MAX_SUPPORTED_POOL_SIZE),
    maxValue = CoroutineScheduler.MAX_SUPPORTED_POOL_SIZE)

@JvmField
internal val IDLE_WORKER_KEEP_ALIVE_NS = TimeUnit.SECONDS.toNanos(
    systemProp("kotlinx.coroutines.scheduler.keep.alive.sec", 5L))

@JvmField
internal var schedulerTimeSource: TimeSource = NanoTimeSource

internal enum class TaskMode {
    // Marker indicating that task is CPU-bound and will not block
    NON_BLOCKING,
    // Marker indicating that task may potentially block, thus giving scheduler a hint that additional thread may be required
    PROBABLY_BLOCKING,
}

internal class Task(
    val block: Runnable,
    val submissionTime: Long,
    val mode: TaskMode
) : LockFreeMPMCQueueNode<Task>() {
    override fun toString(): String =
        "Task[${block.classSimpleName}@${block.hexAddress}, $submissionTime, $mode]"
}

// Open for tests
internal open class GlobalQueue : LockFreeMPMCQueue<Task>() {
    // Open for tests
    public open fun removeFirstBlockingModeOrNull(): Task? =
        removeFistOrNullIf { it.mode == TaskMode.PROBABLY_BLOCKING }
}

internal abstract class TimeSource {
    abstract fun nanoTime(): Long
}

internal object NanoTimeSource : TimeSource() {
    override fun nanoTime() = System.nanoTime()
}