WIP full refactor of Meta

dataforge-io/src/commonMain/kotlin/space/kscience/dataforge/io/JsonMetaFormat.kt

@@ -6,11 +6,11 @@ package space.kscience.dataforge.io
 import io.ktor.utils.io.core.Input
 import io.ktor.utils.io.core.Output
 import kotlinx.serialization.json.Json
-import kotlinx.serialization.json.JsonObject
+import kotlinx.serialization.json.JsonElement
 import space.kscience.dataforge.context.Context
 import space.kscience.dataforge.io.IOFormat.Companion.NAME_KEY
 import space.kscience.dataforge.meta.Meta
-import space.kscience.dataforge.meta.descriptors.NodeDescriptor
+import space.kscience.dataforge.meta.descriptors.MetaDescriptor
 import space.kscience.dataforge.meta.toJson
 import space.kscience.dataforge.meta.toMeta
 import kotlin.reflect.KType
@@ -23,20 +23,19 @@ public class JsonMetaFormat(private val json: Json = DEFAULT_JSON) : MetaFormat
 
     override val type: KType get() = typeOf<Meta>()
 
-    override fun writeMeta(output: Output, meta: Meta, descriptor: NodeDescriptor?) {
+    override fun writeMeta(output: Output, meta: Meta, descriptor: MetaDescriptor?) {
         val jsonObject = meta.toJson(descriptor)
-        output.writeUtf8String(json.encodeToString(JsonObject.serializer(), jsonObject))
+        output.writeUtf8String(json.encodeToString(JsonElement.serializer(), jsonObject))
     }
 
     override fun toMeta(): Meta = Meta {
         NAME_KEY put name.toString()
     }
 
-    override fun readMeta(input: Input, descriptor: NodeDescriptor?): Meta {
+    override fun readMeta(input: Input, descriptor: MetaDescriptor?): Meta {
         val str = input.readUtf8String()//readByteArray().decodeToString()
         val jsonElement = json.parseToJsonElement(str)
-        val item = jsonElement.toMeta(descriptor)
+        return jsonElement.toMeta(descriptor)
-        return item.node ?: Meta.EMPTY
     }
 
     public companion object : MetaFormatFactory {
@@ -49,10 +48,10 @@ public class JsonMetaFormat(private val json: Json = DEFAULT_JSON) : MetaFormat
 
         private val default = JsonMetaFormat()
 
-        override fun writeMeta(output: Output, meta: Meta, descriptor: NodeDescriptor?): Unit =
+        override fun writeMeta(output: Output, meta: Meta, descriptor: MetaDescriptor?): Unit =
             default.run { writeMeta(output, meta, descriptor) }
 
-        override fun readMeta(input: Input, descriptor: NodeDescriptor?): Meta =
+        override fun readMeta(input: Input, descriptor: MetaDescriptor?): Meta =
             default.run { readMeta(input, descriptor) }
     }
 }

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

@@ -116,6 +116,10 @@ public class JsonMeta(
         }
     }
 
+    override fun toString(): String = Meta.toString(this)
+    override fun equals(other: Any?): Boolean = Meta.equals(this, other as? Meta)
+    override fun hashCode(): Int = Meta.hashCode(this)
+
     public companion object {
         /**
          * A key representing top-level json array of nodes, which could not be directly represented by a meta node

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

@@ -36,6 +36,10 @@ public class Laminate(layers: List<Meta>) : TypedMeta<SealedMeta> {
         return SealedMeta(value, items)
     }
 
+    override fun toString(): String = Meta.toString(this)
+    override fun equals(other: Any?): Boolean = Meta.equals(this, other as? Meta)
+    override fun hashCode(): Int = Meta.hashCode(this)
+
     public companion object {
 
         /**

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

@@ -63,6 +63,11 @@ public interface Meta : MetaRepr {
     }
 }
 
+/**
+ * True if this [Meta] does not have children
+ */
+public val Meta.isLeaf: Boolean get() = items.isEmpty()
+
 
 public operator fun Meta.get(token: NameToken): Meta? = items[token]
 

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

@@ -17,6 +17,8 @@ import kotlin.jvm.Synchronized
 @Serializable(MutableMetaSerializer::class)
 public interface MutableMeta : Meta {
 
+    override val items: Map<NameToken, MutableMeta>
+
     /**
      * Get or set value of this node
      */
@@ -241,12 +243,12 @@ private class MutableMetaImpl(
     children: Map<NameToken, Meta> = emptyMap()
 ) : ObservableMutableMeta {
 
-    private val children: LinkedHashMap<NameToken, ObservableMutableMeta> =
+    private val children: LinkedHashMap<NameToken, MutableMetaImpl> =
         LinkedHashMap(children.mapValues { (key, meta) ->
             MutableMetaImpl(meta.value, meta.items).apply { adoptBy(this, key) }
         })
 
-    override val items: Map<NameToken, ObservableMutableMeta> get() = children
+    override val items: Map<NameToken, MutableMetaImpl> get() = children
 
     private val listeners = HashSet<MetaListener>()
 
@@ -271,21 +273,37 @@ private class MutableMetaImpl(
         }
     }
 
-    override fun attach(name: Name, node: ObservableMutableMeta) {
+
+//    fun attach(name: Name, node: MutableMetaImpl) {
+//        when (name.length) {
+//            0 -> error("Can't set a meta with empty name")
+//            1 -> {
+//                val key = name.firstOrNull()!!
+//                children[key] = node
+//                adoptBy(this, key)
+//                changed(name)
+//            }
+//            else -> get(name.cutLast())?.attach(name.lastOrNull()!!.asName(), node)
+//        }
+//    }
+
+    /**
+     * Create and attach empty node
+     */
+    private fun createNode(name: Name): ObservableMutableMeta {
+        val newNode = MutableMetaImpl(null)
         when (name.length) {
-            0 -> error("Can't set a meta with empty name")
+            0 -> throw IllegalArgumentException("Can't create a node with empty name")
             1 -> {
-                val key = name.firstOrNull()!!
+                children[name.first()] = newNode
-                children[key] = node
+                newNode.adoptBy(this, name.first())
-                adoptBy(this, key)
+            } //do not notify, no value changed
-                changed(name)
+            else -> getOrCreate(name.first().asName()).getOrCreate(name.cutFirst())
-            }
-            else -> get(name.cutLast())?.attach(name.lastOrNull()!!.asName(), node)
         }
+        return newNode
     }
 
-    override fun getOrCreate(name: Name): ObservableMutableMeta =
+    override fun getOrCreate(name: Name): ObservableMutableMeta = get(name) ?: createNode(name)
-        get(name) ?: MutableMetaImpl(null).also { attach(name, it) }
 
     override fun removeNode(name: Name) {
         when (name.length) {

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

@@ -25,7 +25,7 @@ public fun MutableMeta.item(key: Name? = null): MutableMetaDelegate = object : M
 /* Mutable converters */
 
 /**
- * A type converter for a mutable [TypedMetaItem] delegate
+ * A type converter for a [MutableMetaDelegate]
  */
 public fun <R : Any> MutableMetaDelegate.convert(
     converter: MetaConverter<R>,

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

@@ -32,11 +32,11 @@ public interface ObservableMeta : Meta {
 /**
  * A [Meta] which is both observable and mutable
  */
-public interface ObservableMutableMeta : ObservableMeta, MutableTypedMeta<ObservableMutableMeta>
+public interface ObservableMutableMeta : ObservableMeta, MutableMeta, TypedMeta<ObservableMutableMeta>
 
-private class ObservableMetaWrapper<M : MutableTypedMeta<M>>(
+private class ObservableMetaWrapper(
-    val origin: M,
+    val origin: MutableMeta,
-) : ObservableMutableMeta,  Meta by origin {
+) : ObservableMutableMeta, Meta by origin {
 
     private val listeners = HashSet<MetaListener>()
 
@@ -54,7 +54,7 @@ private class ObservableMetaWrapper<M : MutableTypedMeta<M>>(
         listeners.removeAll { it.owner === owner }
     }
 
-    override val items: Map<NameToken, ObservableMetaWrapper<M>>
+    override val items: Map<NameToken, ObservableMetaWrapper>
         get() = origin.items.mapValues { ObservableMetaWrapper(it.value) }
 
     override var value: Value?
@@ -64,11 +64,6 @@ private class ObservableMetaWrapper<M : MutableTypedMeta<M>>(
             changed(Name.EMPTY)
         }
 
-    override fun attach(name: Name, node: ObservableMutableMeta) {
-        origin.attach(name, node.origin)
-        changed(name)
-    }
-
     override fun getOrCreate(name: Name): ObservableMutableMeta =
         get(name) ?: ObservableMetaWrapper(origin.getOrCreate(name))
 
@@ -91,8 +86,8 @@ private class ObservableMetaWrapper<M : MutableTypedMeta<M>>(
     }
 }
 
-public fun <M : MutableTypedMeta<M>> MutableTypedMeta<M>.asObservable(): ObservableMeta =
+public fun MutableMeta.asObservable(): ObservableMeta =
-    (this as? ObservableMeta) ?: ObservableMetaWrapper(self)
+    (this as? ObservableMeta) ?: ObservableMetaWrapper(this)
 
 
 /**

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

@@ -1,6 +1,7 @@
 package space.kscience.dataforge.meta
 
 import space.kscience.dataforge.meta.descriptors.MetaDescriptor
+import space.kscience.dataforge.meta.descriptors.get
 import space.kscience.dataforge.misc.DFExperimental
 import space.kscience.dataforge.names.toName
 import space.kscience.dataforge.values.ListValue
@@ -9,39 +10,45 @@ import space.kscience.dataforge.values.Value
 /**
  * Convert meta to map of maps
  */
-public fun Meta.toMap(descriptor: MetaDescriptor? = null): Map<String, Any?> {
+public fun Meta.toMap(descriptor: MetaDescriptor? = null): Map<String, Any?> = buildMap {
-    return items.entries.associate { (token, item) ->
+    items.forEach { (key, child) ->
-        token.toString() to when (item) {
+        if (child.items.isEmpty()) {
-            is MetaItemNode -> item.node.toMap()
+            //single-value meta is considered a leaf
-            is MetaItemValue -> item.value.value
+            put(key.toString(), child.value)
+        } else {
+            //if child contains both children and value, then value will be placed into `@value` key
+            put(key.toString(), child.toMap(descriptor?.get(key.body)))
         }
     }
+    if (value != null) {
+        put(Meta.VALUE_KEY, value)
+    }
 }
 
+
 /**
- * Convert map of maps to meta. This method will recognize [TypedMetaItem], [Map]<String,Any?> and [List] of all mentioned above as value.
+ * Convert map of maps to meta. This method will recognize [Meta], [Map]<String,Any?> and [List] of all mentioned above as value.
  * All other values will be converted to values.
  */
 @DFExperimental
 public fun Map<String, Any?>.toMeta(descriptor: MetaDescriptor? = null): Meta = Meta {
     @Suppress("UNCHECKED_CAST")
-    fun toItem(value: Any?): MetaItem = when (value) {
+    fun toMeta(value: Any?): Meta = when (value) {
-        is MetaItem -> value
+        is Meta -> value
-        is Meta -> MetaItemNode(value)
+        is Map<*, *> -> (value as Map<String, Any?>).toMeta()
-        is Map<*, *> -> MetaItemNode((value as Map<String, Any?>).toMeta())
+        else -> Meta(Value.of(value))
-        else -> MetaItemValue(Value.of(value))
     }
 
     entries.forEach { (key, value) ->
         if (value is List<*>) {
-            val items = value.map { toItem(it) }
+            val items = value.map { toMeta(it) }
-            if (items.all { it is MetaItemValue }) {
+            if (items.all { it.isLeaf }) {
                 set(key, ListValue(items.map { it.value!! }))
             } else {
-                setIndexedItems(key.toName(), value.map { toItem(it) })
+                setIndexedItems(key.toName(), value.map { toMeta(it) })
             }
         } else {
-            set(key, toItem(value))
+            set(key, toMeta(value))
         }
     }
 }

dataforge-meta/src/commonMain/kotlin/space/kscience/dataforge/names/Name.kt

@@ -74,6 +74,11 @@ public fun Name.lastOrNull(): NameToken? = tokens.lastOrNull()
  */
 public fun Name.firstOrNull(): NameToken? = tokens.firstOrNull()
 
+/**
+ * First token or throw exception
+ */
+public fun Name.first(): NameToken = tokens.first()
+
 
 /**
  * Convert a [String] to name parsing it and extracting name tokens and index syntax.