fix: create process instance with message/timer start event

Change the API to create a new process instance to support not only none start events but also message and timer events.

This change is a short-term solution to enable the Web-Modeler.

src/main/kotlin/org/camunda/community/zeebe/play/rest/ProcessesResource.kt

@@ -1,28 +1,172 @@
 package org.camunda.community.zeebe.play.rest
 
 import io.camunda.zeebe.client.ZeebeClient
+import io.camunda.zeebe.model.bpmn.Bpmn
+import io.camunda.zeebe.model.bpmn.instance.MessageEventDefinition
+import io.camunda.zeebe.model.bpmn.instance.Process
+import io.camunda.zeebe.model.bpmn.instance.StartEvent
+import io.camunda.zeebe.model.bpmn.instance.TimerEventDefinition
+import io.zeebe.zeeqs.data.entity.TimerState
+import io.zeebe.zeeqs.data.repository.MessageCorrelationRepository
+import io.zeebe.zeeqs.data.repository.MessageSubscriptionRepository
+import io.zeebe.zeeqs.data.repository.ProcessRepository
+import io.zeebe.zeeqs.data.repository.TimerRepository
 import org.camunda.community.zeebe.play.connectors.ConnectorService
+import org.camunda.community.zeebe.play.services.ZeebeClockService
+import org.springframework.data.repository.findByIdOrNull
 import org.springframework.web.bind.annotation.*
+import java.io.ByteArrayInputStream
+import java.time.Duration
+import java.time.Instant
+import java.util.concurrent.Callable
+import java.util.concurrent.Executors
+
+private val RETRY_INTERVAL = Duration.ofMillis(100)
 
 @RestController
 @RequestMapping("/rest/processes")
 class ProcessesResource(
     private val zeebeClient: ZeebeClient,
-    private val connectorService: ConnectorService
+    private val connectorService: ConnectorService,
+    private val processRepository: ProcessRepository,
+    private val messageSubscriptionRepository: MessageSubscriptionRepository,
+    private val messageCorrelationRepository: MessageCorrelationRepository,
+    private val timerRepository: TimerRepository,
+    private val clockService: ZeebeClockService
 ) {
 
+    private val executor = Executors.newSingleThreadExecutor()
+
     @RequestMapping(path = ["/{processKey}"], method = [RequestMethod.POST])
     fun createInstance(
         @PathVariable("processKey") processKey: Long,
         @RequestBody variables: String
     ): Long {
+        // hack for the web-modeler to deal with not none start events
+        val process = processRepository.findByIdOrNull(processKey)
+            ?.let { Bpmn.readModelFromStream(ByteArrayInputStream(it.bpmnXML.toByteArray())) }
+            ?: throw RuntimeException("No process found with key '$processKey'")
+
+        val startEvents = process.getModelElementsByType(StartEvent::class.java)
+            .filter { it.scope is Process }
+
+        if (startEvents.isEmpty()) {
+            throw RuntimeException("No start event found.")
+        }
+
+        val noneStartEvent = startEvents.find { it.eventDefinitions.isEmpty() }
+
+        return noneStartEvent?.let {
+            createProcessInstanceWithNoneStartEvent(processKey, variables)
+        }
+            ?: if (startEvents.size > 1) {
+                throw RuntimeException("More than one start event found but none of them is a none start event.")
+            } else {
+                return createProcessInstanceWithStartEvent(
+                    processKey = processKey,
+                    startEvent = startEvents.first(),
+                    variables = variables
+                )
+            }
+    }
 
-        return zeebeClient.newCreateInstanceCommand()
+    private fun createProcessInstanceWithNoneStartEvent(processKey: Long, variables: String) =
+        zeebeClient.newCreateInstanceCommand()
             .processDefinitionKey(processKey)
             .variables(variables)
             .send()
             .join()
             .processInstanceKey
+
+    private fun createProcessInstanceWithStartEvent(
+        processKey: Long,
+        startEvent: StartEvent,
+        variables: String
+    ): Long {
+
+        if (startEvent.eventDefinitions.any { it is MessageEventDefinition }) {
+            return createProcessInstanceWithMessageStartEvent(processKey, variables)
+        } else if (startEvent.eventDefinitions.any { it is TimerEventDefinition }) {
+            return createProcessInstanceWithTimerStartEvent(processKey)
+        } else {
+            val type = startEvent.eventDefinitions.first().elementType.typeName
+            throw RuntimeException("Can't start process instance with start event of type '$type'")
+        }
+    }
+
+    private fun createProcessInstanceWithMessageStartEvent(
+        processKey: Long,
+        variables: String
+    ): Long {
+        val messageSubscription = messageSubscriptionRepository
+            .findByProcessDefinitionKeyAndElementInstanceKeyIsNull(processKey)
+            .firstOrNull()
+            ?: throw RuntimeException("No message subscription found for process '$processKey'")
+
+        val messageKey = zeebeClient.newPublishMessageCommand()
+            .messageName(messageSubscription.messageName)
+            .correlationKey("")
+            .variables(variables)
+            .timeToLive(Duration.ZERO)
+            .send()
+            .join()
+            .messageKey
+
+        return executor.submit(Callable {
+            getProcessInstanceKeyForMessage(
+                processKey = processKey,
+                messageKey = messageKey
+            )
+        }).get()
+    }
+
+    private fun getProcessInstanceKeyForMessage(processKey: Long, messageKey: Long): Long {
+        var processInstanceKey = -1L
+        while (processInstanceKey < 0) {
+            processInstanceKey =
+                messageCorrelationRepository.findByMessageKey(messageKey = messageKey)
+                    .firstOrNull { it.processDefinitionKey == processKey }
+                    ?.processInstanceKey
+                    ?: run {
+                        // wait and retry
+                        Thread.sleep(RETRY_INTERVAL.toMillis())
+                        -1L
+                    }
+        }
+        return processInstanceKey
+    }
+
+    private fun createProcessInstanceWithTimerStartEvent(processKey: Long): Long {
+        val timer =
+            (timerRepository.findByProcessDefinitionKeyAndElementInstanceKeyIsNull(processKey)
+                .firstOrNull { it.state == TimerState.CREATED }
+                ?: throw RuntimeException("No timer found for process '$processKey'"))
+
+        val currentTime = clockService.getCurrentTime()
+        val duration = Duration.between(currentTime, Instant.ofEpochMilli(timer.dueDate))
+        clockService.increaseTime(duration)
+
+        return executor.submit(Callable {
+            getProcessInstanceForTimer(
+                timerKey = timer.key
+            )
+        }).get()
+    }
+
+    private fun getProcessInstanceForTimer(timerKey: Long): Long {
+        var processInstanceKey = -1L
+        while (processInstanceKey < 0) {
+            processInstanceKey =
+                timerRepository.findByIdOrNull(timerKey)
+                    ?.takeIf { it.state == TimerState.TRIGGERED }
+                    ?.processInstanceKey
+                    ?: run {
+                        // wait and retry
+                        Thread.sleep(RETRY_INTERVAL.toMillis())
+                        -1L
+                    }
+        }
+        return processInstanceKey
     }
 
     @RequestMapping(