TransformedStateFlow.kt

private class TransformedStateFlow<T>(
    private val getValue: () -> T,
    private val flow: Flow<T>
) : StateFlow<T> {
    
    override val replayCache: List<T> get() = listOf(value)
    override val value: T get() = getValue()

    override suspend fun collect(collector: FlowCollector<T>): Nothing =
        coroutineScope { flow.stateIn(this).collect(collector) }
}

/**
 * Returns [StateFlow] from [flow] having initial value from calculation of [getValue]
 */
fun <T> stateFlow(
    getValue: () -> T,
    flow: Flow<T>
): StateFlow<T> = TransformedStateFlow(getValue, flow)

/**
 * Combines all [stateFlows] and transforms them into another [StateFlow] with [transform]
 */
inline fun <reified T, R> combineStates(
    vararg stateFlows: StateFlow<T>,
    crossinline transform: (Array<T>) -> R
): StateFlow<R> = stateFlow(
    getValue = { transform(stateFlows.map { it.value }.toTypedArray()) },
    flow = combine(*stateFlows) { transform(it) }
)