1 files changed, 90 insertions, 0 deletions
diff --git a/core/src/test/kotlin/NodeSelect.kt b/core/src/test/kotlin/NodeSelect.kt
new file mode 100644
index 00000000..fe0394f9
--- /dev/null
+++ b/core/src/test/kotlin/NodeSelect.kt
@@ -0,0 +1,90 @@
+package org.jetbrains.dokka.tests
+
+import org.jetbrains.dokka.DocumentationNode
+import org.jetbrains.dokka.NodeKind
+import org.jetbrains.dokka.RefKind
+
+class SelectBuilder {
+    private val root = ChainFilterNode(SubgraphTraverseFilter(), null)
+    private var activeNode = root
+    private val chainEnds = mutableListOf<SelectFilter>()
+
+    fun withName(name: String) = matching { it.name == name }
+
+    fun withKind(kind: NodeKind) = matching{ it.kind == kind }
+
+    fun matching(block: (DocumentationNode) -> Boolean) {
+        attachFilterAndMakeActive(PredicateFilter(block))
+    }
+
+    fun subgraph() {
+        attachFilterAndMakeActive(SubgraphTraverseFilter())
+    }
+
+    fun subgraphOf(kind: RefKind) {
+        attachFilterAndMakeActive(DirectEdgeFilter(kind))
+    }
+
+    private fun attachFilterAndMakeActive(next: SelectFilter) {
+        activeNode = ChainFilterNode(next, activeNode)
+    }
+
+    private fun endChain() {
+        chainEnds += activeNode
+    }
+
+    fun build(): SelectFilter {
+        endChain()
+        return CombineFilterNode(chainEnds)
+    }
+}
+
+private class ChainFilterNode(val filter: SelectFilter, val previous: SelectFilter?): SelectFilter() {
+    override fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode> {
+        return filter.select(previous?.select(roots) ?: roots)
+    }
+}
+
+private class CombineFilterNode(val previous: List<SelectFilter>): SelectFilter() {
+    override fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode> {
+        return previous.asSequence().flatMap { it.select(roots) }
+    }
+}
+
+abstract class SelectFilter {
+    abstract fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode>
+}
+
+private class SubgraphTraverseFilter: SelectFilter() {
+    override fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode> {
+        val visited = mutableSetOf<DocumentationNode>()
+        return roots.flatMap {
+            generateSequence(listOf(it)) { nodes ->
+                nodes.flatMap { it.allReferences() }
+                    .map { it.to }
+                    .filter { visited.add(it) }
+                    .takeUnless { it.isEmpty() }
+            }
+        }.flatten()
+    }
+
+}
+
+private class PredicateFilter(val condition: (DocumentationNode) -> Boolean): SelectFilter() {
+    override fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode> {
+        return roots.filter(condition)
+    }
+}
+
+private class DirectEdgeFilter(val kind: RefKind): SelectFilter() {
+    override fun select(roots: Sequence<DocumentationNode>): Sequence<DocumentationNode> {
+        return roots.flatMap { it.references(kind).asSequence() }.map { it.to }
+    }
+}
+
+
+fun selectNodes(root: DocumentationNode, block: SelectBuilder.() -> Unit): List<DocumentationNode> {
+    val builder = SelectBuilder()
+    builder.apply(block)
+    return builder.build().select(sequenceOf(root)).toMutableSet().toList()
+}
+\ No newline at end of file