From 28ec2bc8b8135072ddb154abbaf17325f667cc41 Mon Sep 17 00:00:00 2001
From: Alexander Nozik <altavir@gmail.com>
Date: Mon, 4 Mar 2024 11:12:16 +0300
Subject: [PATCH] Add PropertyHistory API

---
 .../kscience/controls/misc/PropertyHistory.kt | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 controls-core/src/commonMain/kotlin/space/kscience/controls/misc/PropertyHistory.kt

diff --git a/controls-core/src/commonMain/kotlin/space/kscience/controls/misc/PropertyHistory.kt b/controls-core/src/commonMain/kotlin/space/kscience/controls/misc/PropertyHistory.kt
new file mode 100644
index 0000000..5b58321
--- /dev/null
+++ b/controls-core/src/commonMain/kotlin/space/kscience/controls/misc/PropertyHistory.kt
@@ -0,0 +1,66 @@
+package space.kscience.controls.misc
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.*
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+import space.kscience.controls.api.Device
+import space.kscience.controls.api.DeviceMessage
+import space.kscience.controls.api.PropertyChangedMessage
+import space.kscience.controls.spec.DevicePropertySpec
+import space.kscience.controls.spec.name
+import space.kscience.dataforge.meta.transformations.MetaConverter
+
+/**
+ * An interface for device property history.
+ */
+public interface PropertyHistory<T> {
+    /**
+     * Flow property values filtered by a time range. The implementation could flow it as a chunk or provide paging.
+     * So the resulting flow is allowed to suspend.
+     *
+     * If [until] is in the future, the resulting flow is potentially unlimited.
+     * Theoretically, it could be also unlimited if the event source keeps producing new event with timestamp in a given range.
+     */
+    public fun flowHistory(
+        from: Instant = Instant.DISTANT_PAST,
+        until: Instant = Clock.System.now(),
+    ): Flow<ValueWithTime<T>>
+}
+
+/**
+ * An in-memory property values history collector
+ */
+public class CollectedPropertyHistory<T>(
+    public val scope: CoroutineScope,
+    eventFlow: Flow<DeviceMessage>,
+    public val propertyName: String,
+    public val converter: MetaConverter<T>,
+    maxSize: Int = 1000,
+) : PropertyHistory<T> {
+
+    private val store: SharedFlow<ValueWithTime<T>> = eventFlow
+        .filterIsInstance<PropertyChangedMessage>()
+        .filter { it.property == propertyName }
+        .map { ValueWithTime(converter.metaToObject(it.value), it.time) }
+        .shareIn(scope, started = SharingStarted.Eagerly, replay = maxSize)
+
+    override fun flowHistory(from: Instant, until: Instant): Flow<ValueWithTime<T>> =
+        store.filter { it.time in from..until }
+}
+
+/**
+ * Collect and store in memory device property changes for a given property
+ */
+public fun <T> Device.collectPropertyHistory(
+    scope: CoroutineScope = this,
+    propertyName: String,
+    converter: MetaConverter<T>,
+    maxSize: Int = 1000,
+): PropertyHistory<T> = CollectedPropertyHistory(scope, messageFlow, propertyName, converter, maxSize)
+
+public fun <D : Device, T> D.collectPropertyHistory(
+    scope: CoroutineScope = this,
+    spec: DevicePropertySpec<D, T>,
+    maxSize: Int = 1000,
+): PropertyHistory<T> = collectPropertyHistory(scope, spec.name, spec.converter, maxSize)
\ No newline at end of file