js/kotlinx-coroutines-core-js/src/CoroutineContext.kt

/*
 * Copyright 2016-2017 JetBrains s.r.o.
 *
 * 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 kotlinx.coroutines.experimental

import kotlin.browser.*
import kotlin.coroutines.experimental.*

private external val navigator: dynamic
private const val UNDEFINED = "undefined"

/**
 * This is the default [CoroutineDispatcher] that is used by all standard builders like
 * [launch], [async], etc if no dispatcher nor any other [ContinuationInterceptor] is specified in their context.
 */
@Suppress("PropertyName", "UnsafeCastFromDynamic")
public actual val DefaultDispatcher: CoroutineDispatcher = when {
    // Check if we are running under ReactNative. We have to use NodeDispatcher under it.
    // The problem is that ReactNative has a `window` object with `addEventListener`, but it does not  really work.
    // For details see https://github.com/Kotlin/kotlinx.coroutines/issues/236
    // The check for ReactNative is based on https://github.com/facebook/react-native/commit/3c65e62183ce05893be0822da217cb803b121c61
    jsTypeOf(navigator) != UNDEFINED && navigator != null && navigator.product == "ReactNative" ->
        NodeDispatcher()
    // Check if we are in the browser and must use window.postMessage to avoid setTimeout throttling
    jsTypeOf(window) != UNDEFINED && window.asDynamic() != null && jsTypeOf(window.asDynamic().addEventListener) != UNDEFINED ->
        window.asCoroutineDispatcher()
    // Fallback to NodeDispatcher when browser environment is not detected
    else -> NodeDispatcher()
}

internal actual val DefaultDelay: Delay = DefaultDispatcher as Delay

/**
 * Creates context for the new coroutine. It installs [DefaultDispatcher] when no other dispatcher nor
 * [ContinuationInterceptor] is specified, and adds optional support for debugging facilities (when turned on).
 */
@Suppress("ACTUAL_FUNCTION_WITH_DEFAULT_ARGUMENTS")
public actual fun newCoroutineContext(context: CoroutineContext, parent: Job? = null): CoroutineContext {
    val wp = if (parent == null) context else context + parent
    return if (context !== DefaultDispatcher && context[ContinuationInterceptor] == null)
        wp + DefaultDispatcher else wp
}

// No debugging facilities on JS
internal actual inline fun <T> withCoroutineContext(context: CoroutineContext, block: () -> T): T = block()
internal actual fun Continuation<*>.toDebugString(): String = toString()
internal actual val CoroutineContext.coroutineName: String? get() = null // not supported on JS