commonMain.com.caesarealabs.rpc4k.runtime.api.EventClient.kt Maven / Gradle / Ivy
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package com.caesarealabs.rpc4k.runtime.api
import com.caesarealabs.logging.PrintLogging
import com.caesarealabs.rpc4k.runtime.platform.ConcurrentMutableMap
import kotlinx.coroutines.CancellationException
import kotlinx.coroutines.cancel
import kotlinx.coroutines.channels.*
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.buffer
import kotlinx.coroutines.flow.callbackFlow
import kotlinx.coroutines.launch
/**
* Defines how to send messages to the server, and listen to responses.
* Extending [AbstractEventClient] is usually good enough
*/
public interface EventClient {
/**
* Sends arbitrary information to the event accepting server. This is used to set up subscription and unsubscription.
*/
public suspend fun send(message: ByteArray)
/**
* Creates a _cold_ `Flow` that listens to new events
*/
public fun createFlow(subscribeMessage: ByteArray, unsubscribeMessage: ByteArray, listenerId: String): Flow
}
/**
* Utility that handles most of the implementation of a usual [EventClient]
*/
public abstract class AbstractEventClient: EventClient {
/**
* Used in conjunction with [EventClient.createFlowUtil] to manage subscription flows.
* Usually, Values are pushed into the flows in the websocket implementation.
*/
private val activeFlows: MutableMap Unit> = ConcurrentMutableMap()
internal fun handleMessage(message: S2CEventMessage) {
when (message) {
is S2CEventMessage.Emitted -> {
val listener = activeFlows[message.listenerId]
if (listener != null) {
listener(message.payload)
} else {
PrintLogging.logWarn { "Could not find listener for id '${message.listenerId}', the subscription may still open on the server" }
}
}
is S2CEventMessage.SubscriptionError -> {
error("Failed to subscribe to event: ${message.error}")
}
}
}
final override fun createFlow(subscribeMessage: ByteArray, unsubscribeMessage: ByteArray, listenerId: String): Flow {
return callbackFlow {
// Register event for self
activeFlows[listenerId] = {
trySend(it)
.onFailure { e ->
if(e is CancellationException) {
cancel(e)
} else {
if (e != null) throw e
else PrintLogging.logWarn { "Failed to update event listener" }
}
}
}
// Tell the server to start sending events
[email protected](subscribeMessage)
awaitClose {
launch {
// Tell the server to stop sending events
[email protected](unsubscribeMessage)
// Remove event reference from self
activeFlows.remove(listenerId)
}
}
}
}
}