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

@@ -0,0 +1,202 @@
+package space.kscience.dataforge.meta
+
+import kotlinx.serialization.json.Json
+import space.kscience.dataforge.meta.descriptors.Described
+import space.kscience.dataforge.meta.descriptors.MetaDescriptor
+import space.kscience.dataforge.meta.descriptors.MetaDescriptorBuilder
+import space.kscience.dataforge.misc.DFExperimental
+import space.kscience.dataforge.names.Name
+import space.kscience.dataforge.names.asName
+import kotlin.properties.PropertyDelegateProvider
+import kotlin.properties.ReadOnlyProperty
+
+
+/**
+ * A reference to a read-only value of type [T] inside [MetaProvider] or writable value in [MutableMetaProvider]
+ */
+@DFExperimental
+public data class MetaRef<T>(
+    public val name: Name,
+    public val converter: MetaConverter<T>,
+    override val descriptor: MetaDescriptor? = converter.descriptor,
+) : Described
+
+/**
+ * Get a value from provider by [ref] or return null if node with given name is missing
+ */
+@DFExperimental
+public operator fun <T> MetaProvider.get(ref: MetaRef<T>): T? = get(ref.name)?.let { ref.converter.readOrNull(it) }
+
+/**
+ * Set a value in a mutable provider by [ref]
+ */
+@DFExperimental
+public operator fun <T> MutableMetaProvider.set(ref: MetaRef<T>, value: T) {
+    set(ref.name, ref.converter.convert(value))
+}
+
+/**
+ * Remove a node corresponding to [ref] from a mutable provider if it exists
+ */
+@DFExperimental
+public fun MutableMetaProvider.remove(ref: MetaRef<*>) {
+    remove(ref.name)
+}
+
+/**
+ * Base storage of [MetaRef]
+ */
+@OptIn(DFExperimental::class)
+public interface MetaRefStore : Described {
+    public val refs: List<MetaRef<*>>
+}
+
+/**
+ * A base class for [Meta] specification that stores references to meta nodes.
+ */
+@DFExperimental
+public abstract class MetaSpec : MetaRefStore {
+    private val _refs: MutableList<MetaRef<*>> = mutableListOf()
+    override val refs: List<MetaRef<*>> get() = _refs
+
+    /**
+     * Register a ref in this specification
+     */
+    protected fun registerRef(ref: MetaRef<*>) {
+        _refs.add(ref)
+    }
+
+    /**
+     * Create and register a ref by property name and provided converter.
+     * By default, uses descriptor from the converter
+     */
+    public fun <T> item(
+        converter: MetaConverter<T>,
+        key: Name? = null,
+        descriptor: MetaDescriptor? = converter.descriptor,
+    ): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<T>>> =
+        PropertyDelegateProvider { _, property ->
+            val ref = MetaRef(key ?: property.name.asName(), converter, descriptor)
+            registerRef(ref)
+            ReadOnlyProperty { _, _ ->
+                ref
+            }
+        }
+
+    /**
+     * Override to provide custom [MetaDescriptor]
+     */
+    protected open fun MetaDescriptorBuilder.buildDescriptor(): Unit = Unit
+
+    override val descriptor: MetaDescriptor by lazy {
+        MetaDescriptor {
+            refs.forEach { ref ->
+                ref.descriptor?.let {
+                    node(ref.name, ref.descriptor)
+                }
+            }
+            buildDescriptor()
+        }
+    }
+}
+
+/**
+ * Register an item using a [descriptorBuilder] to customize descriptor
+ */
+@DFExperimental
+public fun <T> MetaSpec.item(
+    converter: MetaConverter<T>,
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<T>>> = item(converter, key, MetaDescriptor {
+    converter.descriptor?.let { from(it) }
+    descriptorBuilder()
+})
+
+//utility methods to add different nodes
+
+@DFExperimental
+public fun MetaSpec.metaItem(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Meta>>> =
+    item(MetaConverter.meta, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.string(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<String>>> =
+    item(MetaConverter.string, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.boolean(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Boolean>>> =
+    item(MetaConverter.boolean, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.stringList(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<List<String>>>> =
+    item(MetaConverter.stringList, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.float(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Float>>> =
+    item(MetaConverter.float, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.double(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Double>>> =
+    item(MetaConverter.double, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.int(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Int>>> =
+    item(MetaConverter.int, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.long(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<Long>>> =
+    item(MetaConverter.long, key, descriptorBuilder)
+
+
+@DFExperimental
+public fun MetaSpec.doubleArray(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<DoubleArray>>> =
+    item(MetaConverter.doubleArray, key, descriptorBuilder)
+
+@DFExperimental
+public fun MetaSpec.byteArray(
+    key: Name? = null,
+    descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<ByteArray>>> =
+    item(MetaConverter.byteArray, key, descriptorBuilder)
+
+@DFExperimental
+public inline fun <reified E : Enum<E>> MetaSpec.enum(
+    key: Name? = null,
+    noinline descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<E>>> =
+    item(MetaConverter.enum(), key, descriptorBuilder)
+
+@DFExperimental
+public inline fun <reified T> MetaSpec.serializable(
+    key: Name? = null,
+    jsonEncoder: Json = Json,
+    noinline descriptorBuilder: MetaDescriptorBuilder.() -> Unit = {},
+): PropertyDelegateProvider<MetaSpec, ReadOnlyProperty<MetaSpec, MetaRef<T>>> =
+    item(MetaConverter.serializable(jsonEncoder = jsonEncoder), key, descriptorBuilder)

dataforge-meta/src/commonTest/kotlin/space/kscience/dataforge/meta/MetaRefTest.kt

@@ -0,0 +1,35 @@
+package space.kscience.dataforge.meta
+
+import kotlinx.serialization.Serializable
+import space.kscience.dataforge.misc.DFExperimental
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+@DFExperimental
+internal class MetaRefTest {
+
+    @Serializable
+    data class XY(val x: Double, val y: Double)
+
+    object TestMetaSpec : MetaSpec() {
+        val integer by int { description = "Integer value" }
+        val string by string { description = "String value" }
+        val custom by item(MetaConverter.serializable<XY>()) { description = "custom value" }
+    }
+
+    @Test
+    fun specWriteRead()  = with(TestMetaSpec){
+        val meta = MutableMeta()
+
+        meta[integer] = 22
+        meta[string] = "33"
+        val xy = XY(33.0, -33.0)
+        meta[custom] = xy
+
+        val sealed = meta.seal()
+
+        assertEquals(22, sealed[integer])
+        assertEquals("33", sealed[string])
+        assertEquals(xy, sealed[custom])
+    }
+}