BehaviorSubjectChannel - assuming that means buffering the last element in a broadcast channel for new subscriptions

BehaviorSubjectChannel.kt

import kotlinx.coroutines.*
import kotlinx.coroutines.channels.*
import kotlin.coroutines.CoroutineContext
import kotlin.coroutines.EmptyCoroutineContext

class BehaviorSubjectChannel<E>(val del: BroadcastChannel<E>, context: CoroutineContext? = null) : BroadcastChannel<E> by del {
    @Volatile
    private var hasElem: Boolean = false
    @Volatile
    private var lastElem: E? = null
    
    private val scope = CoroutineScope((context ?: EmptyCoroutineContext) + SupervisorJob(context?.get(Job)))

    init {
        scope.createBufferJob()
    }

    override fun openSubscription(): ReceiveChannel<E> {
        val result = del.openSubscription()
        if (hasElem) {
            scope.launch(start = CoroutineStart.UNDISPATCHED) {
                @Suppress("UNCHECKED_CAST")
                (result as SendChannel<E>).send(lastElem as E)
            }
        }
        return result
    }

    private fun CoroutineScope.createBufferJob() {
        launch {
            val channel = del.openSubscription()
            try {
                lastElem = channel.receive()
                hasElem = true
                for (elem in channel) {
                    lastElem = elem
                }
            } catch (e: ClosedReceiveChannelException) {
            } finally {
                channel.cancel()
            }
        }
    }

}