commonMain.progressive.Accumulators.kt Maven / Gradle / Ivy
package opensavvy.state.progressive
/**
* Replaces incomplete outcomes by the previous completed outcome, with the updated progress information.
*
* For example, if the incoming iterable contains:
* ```
* [Incomplete(loading(0.23%)), Success(5, Done), Incomplete(loading(0.5%))]
* ```
* then this method returns:
* ```
* [Incomplete(loading(0.23%)), Success(5, Done), Success(5, loading(0.5%))]
* ```
* You can see how the last incomplete value has been transformed into a loading success.
* The same transformation is applied to failures.
*
* This operator is useful when the iterable represents changes to a single value over time: when we receive an
* incomplete event, we merge it with the previous complete event to still display a value.
* For example, in a UI, this would allow displaying old values while refresh requests are ongoing.
*/
fun Iterable>.combineCompleted(): Iterable> {
var lastComplete: ProgressiveOutcome? = null
return map {
when (it) {
is ProgressiveOutcome.Success -> {
lastComplete = it
it
}
is ProgressiveOutcome.Failure -> {
lastComplete = it
it
}
is ProgressiveOutcome.Incomplete -> {
when (val lastCompleteCopy = lastComplete) {
// No previous completed elements has been stored, just return the incomplete state
null -> it
// A previous completed element is stored, return it with the new progress
is ProgressiveOutcome.Success -> lastCompleteCopy.copy(progress = it.progress)
is ProgressiveOutcome.Failure -> lastCompleteCopy.copy(progress = it.progress)
is ProgressiveOutcome.Incomplete -> error("Impossible case: stored an incomplete value in the complete accumulator: $lastCompleteCopy")
}
}
}
}
}
/**
* Replaces incomplete outcomes by the previous completed outcome, with the updated progress information.
*
* For example, if the incoming sequence contains:
* ```
* [Incomplete(loading(0.23%)), Success(5, Done), Incomplete(loading(0.5%))]
* ```
* then this method returns:
* ```
* [Incomplete(loading(0.23%)), Success(5, Done), Success(5, loading(0.5%))]
* ```
* You can see how the last incomplete value has been transformed into a loading success.
* The same transformation is applied to failures.
*
* This operator is useful when the iterable represents changes to a single value over time: when we receive an
* incomplete event, we merge it with the previous complete event to still display a value.
* For example, in a UI, this would allow displaying old values while refresh requests are ongoing.
*/
fun Sequence>.combineCompleted(): Sequence> = this
.asIterable()
.combineCompleted()
.asSequence()