Working on meta transformations

build.gradle.kts

@@ -1,4 +1,4 @@
-val dataforgeVersion by extra("0.1.2")
+val dataforgeVersion by extra("0.1.3-dev-1")
 
 allprojects {
     repositories {

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/Meta.kt

@@ -94,16 +94,31 @@ fun Meta.getAll(name: String): Map<String, MetaItem<out Meta>> = getAll(name.toN
  * Get a sequence of [Name]-[Value] pairs
  */
 fun Meta.values(): Sequence<Pair<Name, Value>> {
-    return items.asSequence().flatMap { entry ->
-        val item = entry.value
+    return items.asSequence().flatMap { (key, item) ->
         when (item) {
-            is ValueItem -> sequenceOf(entry.key.asName() to item.value)
-            is NodeItem -> item.node.values().map { pair -> (entry.key.asName() + pair.first) to pair.second }
+            is ValueItem -> sequenceOf(key.asName() to item.value)
+            is NodeItem -> item.node.values().map { pair -> (key.asName() + pair.first) to pair.second }
         }
     }
 }
 
-operator fun Meta.iterator(): Iterator<Pair<Name, Value>> = values().iterator()
+/**
+ * Get a sequence of all [Name]-[MetaItem] pairs for all items including nodes
+ */
+fun Meta.sequence(): Sequence<Pair<Name, MetaItem<*>>> {
+    return sequence {
+        items.forEach { (key, item) ->
+            yield(key.asName() to item)
+            if(item is NodeItem<*>) {
+                yieldAll(item.node.sequence().map { (innerKey, innerItem)->
+                    (key + innerKey) to innerItem
+                })
+            }
+        }
+    }
+}
+
+operator fun Meta.iterator(): Iterator<Pair<Name, MetaItem<*>>> = sequence().iterator()
 
 /**
  * A meta node that ensures that all of its descendants has at least the same type

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaBuilder.kt

@@ -46,4 +46,12 @@ fun Meta.builder(): MetaBuilder {
     }
 }
 
-fun buildMeta(builder: MetaBuilder.() -> Unit): MetaBuilder = MetaBuilder().apply(builder)
+/**
+ * Build a [MetaBuilder] using given transformation
+ */
+fun buildMeta(builder: MetaBuilder.() -> Unit): MetaBuilder = MetaBuilder().apply(builder)
+
+/**
+ * Build meta using given source meta as a base
+ */
+fun buildMeta(source: Meta, builder: MetaBuilder.() -> Unit): MetaBuilder = source.builder().apply(builder)

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MetaTransformation.kt

@@ -0,0 +1,72 @@
+package hep.dataforge.meta
+
+import hep.dataforge.names.Name
+
+/**
+ * A transformation for meta item or a group of items
+ */
+interface TransformationRule {
+
+    /**
+     * Check if this transformation
+     */
+    fun matches(name: Name, item: MetaItem<*>?): Boolean
+
+    /**
+     * Select all items to be transformed. Item could be a value as well as node
+     *
+     * @return a sequence of item paths to be transformed
+     */
+    fun selectItems(meta: Meta): Sequence<Name> =
+        meta.sequence().filter { matches(it.first, it.second) }.map { it.first }
+
+    /**
+     * Apply transformation for a single item (Node or Value) and return resulting tree with absolute path
+     */
+    fun <M : MutableMetaNode<M>> transformItem(name: Name, item: MetaItem<*>?, target: M): Unit
+}
+
+data class SelfTransformationRule(val name: Name) : TransformationRule {
+    override fun matches(name: Name, item: MetaItem<*>?): Boolean {
+        return name == name
+    }
+
+    override fun selectItems(meta: Meta): Sequence<Name> = sequenceOf(name)
+
+    override fun <M : MutableMetaNode<M>> transformItem(name: Name, item: MetaItem<*>?, target: M) {
+        if (name == this.name) target[name] = item
+    }
+}
+
+data class SingleItemTransformationRule(
+    val from: Name,
+    val to: Name,
+    val transform: MutableMetaNode<*>.(MetaItem<*>?) -> Unit
+) : TransformationRule {
+    override fun matches(name: Name, item: MetaItem<*>?): Boolean {
+        return name == from
+    }
+
+    override fun selectItems(meta: Meta): Sequence<Name> = sequenceOf(from)
+
+    override fun <M : MutableMetaNode<M>> transformItem(name: Name, item: MetaItem<*>?, target: M) {
+        if (name == this.from) {
+            target.transform(item)
+        }
+    }
+}
+
+class MetaTransformation {
+    private val transformations = HashSet<TransformationRule>()
+
+    /**
+     * Produce new meta using only those items that match transformation rules
+     */
+    fun produce(source: Meta): Meta = buildMeta {
+        transformations.forEach { rule ->
+            rule.selectItems(source).forEach { name ->
+                rule.transformItem(name, source[name], this)
+            }
+        }
+    }
+}

dataforge-meta/src/commonMain/kotlin/hep/dataforge/meta/MutableMeta.kt

@@ -96,11 +96,20 @@ fun <M : MutableMeta<M>> MutableMeta<M>.remove(name: Name) = set(name, null)
 fun <M : MutableMeta<M>> MutableMeta<M>.remove(name: String) = remove(name.toName())
 
 fun <M : MutableMeta<M>> MutableMeta<M>.setValue(name: Name, value: Value) = set(name, MetaItem.ValueItem(value))
-fun <M : MutableMeta<M>> MutableMeta<M>.setItem(name: String, item: MetaItem<M>) = set(name.toName(), item)
+//fun <M : MutableMeta<M>> MutableMeta<M>.setItem(name: String, item: MetaItem<M>) = set(name.toName(), item)
 fun <M : MutableMeta<M>> MutableMeta<M>.setValue(name: String, value: Value) =
     set(name.toName(), MetaItem.ValueItem(value))
 
-fun <M : MutableMeta<M>> MutableMeta<M>.setItem(token: NameToken, item: MetaItem<M>?) = set(token.asName(), item)
+//fun <M : MutableMeta<M>> MutableMeta<M>.setItem(token: NameToken, item: MetaItem<M>?) = set(token.asName(), item)
+
+fun <M : MutableMetaNode<M>> MutableMetaNode<M>.setItem(name: Name, item: MetaItem<*>) {
+    when (item) {
+        is MetaItem.ValueItem<*> -> setValue(name, item.value)
+        is MetaItem.NodeItem<*> -> setNode(name, item.node)
+    }
+}
+
+fun <M : MutableMetaNode<M>> MutableMetaNode<M>.setItem(name: String, item: MetaItem<*>) = setItem(name.toName(), item)
 
 fun <M : MutableMetaNode<M>> MutableMetaNode<M>.setNode(name: Name, node: Meta) =
     set(name, MetaItem.NodeItem(wrap(name, node)))
@@ -110,13 +119,10 @@ fun <M : MutableMetaNode<M>> MutableMetaNode<M>.setNode(name: String, node: Meta
 /**
  * Universal set method
  */
-operator fun <M : MutableMetaNode<M>> M.set(name: Name, value: Any?) {
+operator fun <M : MutableMetaNode<M>> MutableMetaNode<M>.set(name: Name, value: Any?) {
     when (value) {
         null -> remove(name)
-        is MetaItem<*> -> when (value) {
-            is MetaItem.ValueItem<*> -> setValue(name, value.value)
-            is MetaItem.NodeItem<*> -> setNode(name, value.node)
-        }
+        is MetaItem<*> -> setItem(name, value)
         is Meta -> setNode(name, value)
         is Specific -> setNode(name, value.config)
         else -> setValue(name, Value.of(value))