Await.kt

/*
 * Copyright 2016-2020 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
 */

package kotlinx.coroutines.jdk9

import java.util.concurrent.*
import org.reactivestreams.FlowAdapters
import kotlinx.coroutines.reactive.*

/**
 * Awaits for the first value from the given publisher without blocking a thread and
 * returns the resulting value or throws the corresponding exception if this publisher had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 *
 * @throws NoSuchElementException if publisher does not emit any value
 */
public suspend fun <T> Flow.Publisher<T>.awaitFirst(): T = FlowAdapters.toPublisher(this).awaitFirst()

/**
 * Awaits for the first value from the given observable or the [default] value if none is emitted without blocking a
 * thread and returns the resulting value or throws the corresponding exception if this observable had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 */
public suspend fun <T> Flow.Publisher<T>.awaitFirstOrDefault(default: T): T =
        FlowAdapters.toPublisher(this).awaitFirstOrDefault(default)

/**
 * Awaits for the first value from the given observable or `null` value if none is emitted without blocking a
 * thread and returns the resulting value or throws the corresponding exception if this observable had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 */
public suspend fun <T> Flow.Publisher<T>.awaitFirstOrNull(): T? =
        FlowAdapters.toPublisher(this).awaitFirstOrNull()

/**
 * Awaits for the first value from the given observable or call [defaultValue] to get a value if none is emitted without blocking a
 * thread and returns the resulting value or throws the corresponding exception if this observable had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 */
public suspend fun <T> Flow.Publisher<T>.awaitFirstOrElse(defaultValue: () -> T): T =
        FlowAdapters.toPublisher(this).awaitFirstOrElse(defaultValue)

/**
 * Awaits for the last value from the given publisher without blocking a thread and
 * returns the resulting value or throws the corresponding exception if this publisher had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 *
 * @throws NoSuchElementException if publisher does not emit any value
 */
public suspend fun <T> Flow.Publisher<T>.awaitLast(): T =
        FlowAdapters.toPublisher(this).awaitLast()

/**
 * Awaits for the single value from the given publisher without blocking a thread and
 * returns the resulting value or throws the corresponding exception if this publisher had produced error.
 *
 * This suspending function is cancellable.
 * If the [Job] of the current coroutine is cancelled or completed while this suspending function is waiting, this function
 * immediately resumes with [CancellationException].
 *
 * @throws NoSuchElementException if publisher does not emit any value
 * @throws IllegalArgumentException if publisher emits more than one value
 */
public suspend fun <T> Flow.Publisher<T>.awaitSingle(): T =
        FlowAdapters.toPublisher(this).awaitSingle()