GeneratingTimeLine prototype is working

simulation-kt/src/commonMain/kotlin/GeneratingTimeline.kt

@@ -2,10 +2,9 @@ package space.kscience.simulation
 
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
-import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.channels.BufferOverflow
-import kotlinx.coroutines.flow.asFlow
+import kotlinx.coroutines.channels.Channel
-import kotlinx.coroutines.flow.onEach
+import kotlinx.coroutines.flow.*
-import kotlinx.coroutines.flow.takeWhile
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.sync.Mutex
 import kotlinx.coroutines.sync.withLock
@@ -20,21 +19,49 @@ public class GeneratingTimeline<E : TimelineEvent>(
     private val initialEvent: E,
     private val lookaheadInterval: Duration,
     private val generatorChain: suspend (E) -> E
-) : Timeline<E> {
+) : Timeline<E>, AutoCloseable {
+
+    // push to this channel to trigger event generation
+    private val wakeupChannel = Channel<Unit>(onBufferOverflow = BufferOverflow.DROP_OLDEST)
+
+    private suspend fun kickGenerator() {
+        wakeupChannel.send(Unit)
+    }
 
     private val mutex = Mutex()
 
-    private val events = ArrayDeque<E>()
+    private val history = ArrayDeque<E>()
+
+    private val lastEvent = MutableSharedFlow<E>(replay = Int.MAX_VALUE)
+
+    private val updateHistoryJob = generationScope.launch {
+        lastEvent.onEach {
+            mutex.withLock {
+                history.add(it)
+                //cleanup old events
+                val threshold = observedTime ?: return@withLock
+                while (history.isNotEmpty() && history.last().time > threshold) {
+                    history.removeFirst()
+                }
+
+            }
+        }
+    }
 
     private val observers: MutableSet<TimelineObserver> = mutableSetOf()
 
-    override val lastEventTime: Instant?
+    override val time: Instant
-        get() = events.lastOrNull()?.time
+        get() = history.lastOrNull()?.time ?: initialEvent.time
 
-    override val observedTime: Instant
+    override val observedTime: Instant?
-        get() = observers.minOfOrNull { it.lastCollectedEventTime } ?: Instant.DISTANT_PAST
+        get() = observers.minOfNotNullOrNull { it.time }
 
-    override fun flowUnobservedEvents(): Flow<E> = events.asFlow()
+    override fun flowUnobservedEvents(): Flow<E> = flow {
+        history.forEach { e ->
+            emit(e)
+        }
+        emitAll(lastEvent)
+    }
 
     override suspend fun advance(toTime: Instant) {
         observers.forEach {
@@ -42,51 +69,60 @@ public class GeneratingTimeline<E : TimelineEvent>(
         }
     }
 
-    private var generatorJob: Job = launchGenerateJob(initialEvent)
+    private var generatorJob: Job = launchGenerator(initialEvent)
 
-    private fun launchGenerateJob(event: E): Job = generationScope.launch {
+    private fun launchGenerator(event: E): Job = generationScope.launch {
+        kickGenerator()
         var currentEvent = event
-        while(currentEvent.time < observedTime + lookaheadInterval) {
+        // for each wakeup generate all events in lookaheadInterval
-            val nextEvent = generatorChain(currentEvent)
+        for (u in wakeupChannel) {
-            mutex.withLock {
+            while (currentEvent.time < (observedTime ?: event.time) + lookaheadInterval) {
-                events.add(nextEvent)
+                val nextEvent = generatorChain(currentEvent)
+                lastEvent.emit(nextEvent)
+                currentEvent = nextEvent
             }
-            currentEvent = nextEvent
         }
     }
 
-    private fun regenerate(event: E) {
-        generatorJob.cancel()
-        generatorJob = launchGenerateJob(event)
-    }
 
-    /**
+    public suspend fun interrupt(newStart: E) {
-     * Discard unconsumed events after [atTime].
+        check(newStart.time > (observedTime ?: Instant.DISTANT_FUTURE)) {
-     */
+            "Can't interrupt generating timeline after observed event"
-    override suspend fun interrupt(atTime: Instant): Unit {
+        }
-        if (atTime < observedTime)
-            error("Timeline interrupt at time $atTime is not possible because there are observed events before $observedTime")
         mutex.withLock {
-            while (events.isNotEmpty() && events.last().time > atTime) {
+            while (history.isNotEmpty() && history.last().time > newStart.time) {
-                events.removeLast()
+                history.removeLast()
             }
+            generatorJob.cancel()
+            generatorJob = launchGenerator(newStart)
+
         }
+        kickGenerator()
+    }
+
+    override fun close() {
+        updateHistoryJob.cancel()
+        generatorJob.cancel()
     }
 
     override suspend fun observe(collector: suspend Flow<E>.() -> Unit): TimelineObserver {
         val observer = object : TimelineObserver {
-            val observerMutex = Mutex()
+            override var time: Instant = this@GeneratingTimeline.time
-            override var lastCollectedEventTime: Instant = Instant.DISTANT_PAST
 
-            override suspend fun collect(upTo: Instant) = observerMutex.withLock {
+            override suspend fun collect(upTo: Instant) {
-                flowUnobservedEvents().takeWhile { it.time <= upTo }.onEach {
+                flowUnobservedEvents().takeWhile {
-                    lastCollectedEventTime = it.time
+                    it.time <= upTo
+                }.onEach {
+                    time = it.time
+                    kickGenerator()
                 }.collector()
-                //cleanup()
             }
 
             override fun close() {
                 observers.remove(this)
+                if(observers.isEmpty()){
+                    this@GeneratingTimeline.close()
+                }
             }
 
         }

simulation-kt/src/commonMain/kotlin/MergedTimeline.kt

@@ -6,13 +6,15 @@ import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.flow.takeWhile
 import kotlinx.datetime.Instant
 
+
 public class MergedTimeline<E : TimelineEvent>(
     private val timelines: List<Timeline<E>>
 ) : Timeline<E> {
-    override val lastEventTime: Instant?
+    override val time: Instant
-        get() = timelines.minOfOrNull { it.lastEventTime ?: Instant.DISTANT_PAST }
+        get() = timelines.minOfNotNullOrNull { it.time } ?: Instant.DISTANT_PAST
-    override val observedTime: Instant
+
-        get() = timelines.maxOfOrNull { it.observedTime } ?: Instant.DISTANT_FUTURE
+    override val observedTime: Instant?
+        get() = timelines.maxOfNotNullOrNull { it.observedTime }
 
     override fun flowUnobservedEvents(): Flow<E> = timelines.map { flowUnobservedEvents() }.merge()
 
@@ -20,21 +22,21 @@ public class MergedTimeline<E : TimelineEvent>(
         timelines.forEach { it.advance(toTime) }
     }
 
-    override suspend fun interrupt(atTime: Instant) {
+//    override suspend fun interrupt(atTime: Instant) {
-        timelines.forEach { it.interrupt(atTime) }
+//        timelines.forEach { it.interrupt(atTime) }
-    }
+//    }
 
     private val observers: MutableSet<TimelineObserver> = mutableSetOf()
 
     override suspend fun observe(collector: suspend Flow<E>.() -> Unit): TimelineObserver {
         val observer = object : TimelineObserver {
-            override var lastCollectedEventTime: Instant = Instant.DISTANT_PAST
+            override var time: Instant = this@MergedTimeline.time
 
             override suspend fun collect(upTo: Instant) = timelines
                 .map { flowUnobservedEvents() }
                 .merge()
                 .takeWhile { it.time <= upTo }.onEach {
-                    lastCollectedEventTime = it.time
+                    time = it.time
                 }.collector()
 
 

simulation-kt/src/commonMain/kotlin/SharedTimeline.kt

@@ -19,11 +19,11 @@ public class SharedTimeline<E : TimelineEvent> : Timeline<E> {
 
     private val observers: MutableSet<TimelineObserver> = mutableSetOf()
 
-    override val lastEventTime: Instant?
+    override val time: Instant
-        get() = events.lastOrNull()?.time
+        get() = events.lastOrNull()?.time ?: Instant.DISTANT_PAST
 
-    override val observedTime: Instant
+    override val observedTime: Instant?
-        get() = observers.minOfOrNull { it.lastCollectedEventTime } ?: Instant.DISTANT_PAST
+        get() = observers.minOfNotNullOrNull { it.time }
 
     override fun flowUnobservedEvents(): Flow<E> = events.asFlow()
 
@@ -31,7 +31,9 @@ public class SharedTimeline<E : TimelineEvent> : Timeline<E> {
      * Emit new event to the timeline
      */
     public suspend fun emit(event: E): Boolean = mutex.withLock {
-        if (event.time < observedTime) error("Can't emit event $event because there are observed events after $observedTime")
+        if (event.time < (observedTime ?: Instant.DISTANT_PAST)) {
+            error("Can't emit event $event because there are observed events after $observedTime")
+        }
         events.add(event)
     }
 
@@ -44,33 +46,33 @@ public class SharedTimeline<E : TimelineEvent> : Timeline<E> {
     /**
      * Discard all events before [observedTime]
      */
-    private suspend fun cleanup(): Unit {
+    private suspend fun cleanup(): Unit = mutex.withLock {
-        val threshold = observedTime
+        val threshold = observedTime ?: return@withLock
         while (events.isNotEmpty() && events.last().time > threshold) {
             events.removeFirst()
         }
     }
 
-    /**
+//    /**
-     * Discard unconsumed events after [atTime].
+//     * Discard unconsumed events after [atTime].
-     */
+//     */
-    override suspend fun interrupt(atTime: Instant): Unit = mutex.withLock {
+//    override suspend fun interrupt(atTime: Instant): Unit = mutex.withLock {
-        val threshold = observedTime
+//        val threshold = observedTime
-        if (atTime < threshold)
+//        if (atTime < threshold)
-            error("Timeline interrupt at time $atTime is not possible because there are observed events before $threshold")
+//            error("Timeline interrupt at time $atTime is not possible because there are observed events before $threshold")
-        while (events.isNotEmpty() && events.last().time > atTime) {
+//        while (events.isNotEmpty() && events.last().time > atTime) {
-            events.removeLast()
+//            events.removeLast()
-        }
+//        }
-    }
+//    }
 
     override suspend fun observe(collector: suspend Flow<E>.() -> Unit): TimelineObserver {
         val observer = object : TimelineObserver {
             val observerMutex = Mutex()
-            override var lastCollectedEventTime: Instant = Instant.DISTANT_PAST
+            override var time: Instant = this@SharedTimeline.time
 
             override suspend fun collect(upTo: Instant) = observerMutex.withLock {
                 flowUnobservedEvents().takeWhile { it.time <= upTo }.onEach {
-                    lastCollectedEventTime = it.time
+                    time = it.time
                 }.collector()
                 cleanup()
             }

simulation-kt/src/commonMain/kotlin/Timeline.kt

@@ -2,20 +2,31 @@ package space.kscience.simulation
 
 import kotlinx.coroutines.flow.Flow
 import kotlinx.datetime.Instant
+import kotlin.time.Duration
 
 
 public interface TimelineEvent {
     public val time: Instant
 }
 
-public interface TimelineObserver: AutoCloseable {
+public interface TimelineInterval : TimelineEvent {
+    public val startTime: Instant
+    public val duration: Duration
+
+    override val time: Instant
+        get() = startTime + duration
+}
+
+public data class SimpleTimelineEvent<T>(override val time: Instant, val value: T) : TimelineEvent
+
+public interface TimelineObserver : AutoCloseable {
     /**
-     * The time of the last event collected by this collector
+     * The subjective time of this observer
      */
-    public val lastCollectedEventTime: Instant
+    public val time: Instant
 
     /**
-     * Collect all uncollected events from [lastCollectedEventTime] to [upTo].
+     * Collect all uncollected events from [time] to [upTo].
      *
      * By default, collects all events.
      */
@@ -32,17 +43,17 @@ public interface TimelineObserver: AutoCloseable {
  */
 public interface Timeline<E : TimelineEvent> {
     /**
-     * The timestamp of the last event in a timeline
+     * A subjective time of this timeline. The time could advance without events being produced.
      */
-    public val lastEventTime: Instant?
+    public val time: Instant
 
     /**
      * The time of the last event that was observed by all observers
      */
-    public val observedTime: Instant
+    public val observedTime: Instant?
 
     /**
-     * Flow events from [observedTime] to [lastEventTime].
+     * Flow events from [observedTime] to [time].
      *
      * The resulting flow is finite and should not suspend.
      *
@@ -53,8 +64,8 @@ public interface Timeline<E : TimelineEvent> {
     /**
      * Attach observer to this [Timeline]. The observer collection is not triggered right away, but only on demand.
      *
-     * Each collection shifts [TimelineObserver.lastCollectedEventTime] for this observer.
+     * Each collection shifts [TimelineObserver.time] for this observer.
-     * The value of [observedTime] is the least of all observers [TimelineObserver.lastCollectedEventTime].
+     * The value of [observedTime] is the least of all observers [TimelineObserver.time].
      */
     public suspend fun observe(
         collector: suspend Flow<E>.() -> Unit
@@ -67,10 +78,10 @@ public interface Timeline<E : TimelineEvent> {
      */
     public suspend fun advance(toTime: Instant)
 
-    /**
+//    /**
-     * Interrupt generation of this timeline and discard unconsumed events after [atTime].
+//     * Interrupt generation of this timeline and discard unconsumed events after [atTime].
-     *
+//     *
-     * Throw exception if at least one observer advanced
+//     * Throw exception if at least one observer advanced
-     */
+//     */
-    public suspend fun interrupt(atTime: Instant): Unit
+//    public suspend fun interrupt(atTime: Instant): Unit
 }

simulation-kt/src/commonMain/kotlin/notNullUtils.kt

@@ -0,0 +1,35 @@
+package space.kscience.simulation
+
+internal inline fun <T, R : Comparable<R>> Iterable<T>.minOfNotNullOrNull(selector: (T) -> R?): R? {
+    val iterator = iterator()
+    if (!iterator.hasNext()) return null
+    var minValue = selector(iterator.next())
+    while (iterator.hasNext()) {
+        val v = selector(iterator.next())
+        when {
+            minValue == null -> minValue = v
+            v == null -> {/*do nothing*/}
+            minValue > v -> {
+                minValue = v
+            }
+        }
+    }
+    return minValue
+}
+
+internal inline fun <T, R : Comparable<R>> Iterable<T>.maxOfNotNullOrNull(selector: (T) -> R?): R? {
+    val iterator = iterator()
+    if (!iterator.hasNext()) return null
+    var maxValue = selector(iterator.next())
+    while (iterator.hasNext()) {
+        val v = selector(iterator.next())
+        when {
+            maxValue == null -> maxValue = v
+            v == null -> {/*do nothing*/}
+            maxValue < v -> {
+                maxValue = v
+            }
+        }
+    }
+    return maxValue
+}

simulation-kt/src/commonTest/kotlin/TimelineTests.kt

@@ -0,0 +1,34 @@
+package space.kscience.simulation
+
+import kotlinx.coroutines.test.runTest
+import kotlinx.datetime.Instant
+import kotlin.test.Test
+import kotlin.time.Duration.Companion.seconds
+
+class TimelineTests {
+
+
+    @Test
+    fun testGeneration() = runTest(timeout = 5.seconds) {
+        val startTime = Instant.parse("2020-01-01T00:00:00.000Z")
+
+        val generation = GeneratingTimeline<SimpleTimelineEvent<DoubleArray>>(
+            this,
+            initialEvent = SimpleTimelineEvent(startTime, List(10) { it.toDouble() }.toDoubleArray()),
+            lookaheadInterval = 1.seconds
+        ) { event ->
+            val time = event.time + 0.1.seconds
+            println("Emit: $time")
+            SimpleTimelineEvent(time, event.value.map { it + 1.0 }.toDoubleArray())
+        }
+
+        val collector = generation.observe {
+            collect {
+                println("Consume: ${it.time}")
+            }
+        }
+
+        collector.collect(startTime + 2.seconds)
+        collector.close()
+    }
+}