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Extensions for the Kotlin standard library and third-party libraries.
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package com.bselzer.ktx.datetime.timer
import kotlinx.coroutines.delay
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.conflate
import kotlinx.coroutines.flow.flow
import kotlinx.datetime.Clock
import kotlinx.datetime.Instant
import kotlin.time.Duration
import kotlin.time.Duration.Companion.seconds
/**
* Creates a flow that emits the remaining amount of time every [delay].
* Emitting ceases when the remaining amount of time reaches zero.
*
* @param startTime the start time
* @param duration the amount of time since the [startTime] the countdown should last for
* @param delay the amount of time to wait before emitting a new value
* @return the flow of remaining amount of time
*/
fun Clock.countdown(startTime: Instant, duration: Duration, delay: Duration = 1.seconds): Flow = flow {
while (true) {
val remaining = duration - now().minus(startTime)
// Stop emitting values once the timer has reached zero.
if (remaining <= Duration.ZERO) {
emit(Duration.ZERO)
break
}
emit(remaining)
delay(delay)
}
}.conflate() // Only need to care about the latest value so use conflation to ignore slow collection.