Replace properties with flows

dataforge-context/src/commonMain/kotlin/space/kscience/dataforge/properties/metaAsFlow.kt

@@ -0,0 +1,51 @@
+package space.kscience.dataforge.properties
+
+
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Job
+import kotlinx.coroutines.channels.awaitClose
+import kotlinx.coroutines.flow.*
+import kotlinx.coroutines.launch
+import space.kscience.dataforge.meta.*
+import space.kscience.dataforge.misc.DFExperimental
+
+@DFExperimental
+public fun <T> ObservableMeta.asFlow(converter: MetaSpec<T>): Flow<T> = callbackFlow {
+    onChange(this){
+        trySend(converter.read(this))
+    }
+
+    awaitClose{
+        removeListener(this)
+    }
+}
+
+@DFExperimental
+public fun <T> MutableMeta.listenTo(
+    scope: CoroutineScope,
+    converter: MetaConverter<T>,
+    flow: Flow<T>,
+): Job = flow.onEach {
+    update(converter.convert(it))
+}.launchIn(scope)
+
+@DFExperimental
+public fun <T> ObservableMutableMeta.bind(
+    scope: CoroutineScope,
+    converter: MetaConverter<T>,
+    flow: MutableSharedFlow<T>,
+): Job = scope.launch{
+    listenTo(this, converter,flow)
+    onChange(flow){
+        launch {
+            flow.emit(converter.read(this@onChange))
+        }
+    }
+    flow.onCompletion {
+        removeListener(flow)
+    }
+}.also {
+    it.invokeOnCompletion {
+        removeListener(flow)
+    }
+}

dataforge-meta/src/commonMain/kotlin/space/kscience/dataforge/meta/ObservableMeta.kt

@@ -17,12 +17,15 @@ internal data class MetaListener(
  */
 public interface ObservableMeta : Meta {
     /**
-     * Add change listener to this meta. Owner is declared to be able to remove listeners later. Listener without owner could not be removed
+     * Add change listener to this meta. The Owner is declared to be able to remove listeners later.
+     * Listeners without an owner could be only removed all together.
+     *
+     * `this` object in the listener represents the current state of this meta. The name points to a changed node
      */
     public fun onChange(owner: Any?, callback: Meta.(name: Name) -> Unit)
 
     /**
-     * Remove all listeners belonging to given owner
+     * Remove all listeners belonging to the given [owner]. Passing null removes all listeners.
      */
     public fun removeListener(owner: Any?)