ci: binary-compat API baselines, multiplatform matrix CI, module docs

- Commit binary-compatibility-validator .api baselines for core + both modules.
- Replace JVM-only CI with a matrix: Ubuntu runs JVM/JS(node)/Wasm(node)/Native
  + apiCheck; macOS runs the iOS simulator tests.
- README: install + usage for tree-structure-serialization and -coroutines.
- Update kotlin-js-store/yarn.lock for the new modules' JS test deps.

Verified locally: JVM, JS(node), Wasm(node) and iOS-simulator tests pass for
core + both modules; native compiles & links (exec runs on the Linux CI runner).

.github/workflows/publishRelease.yml

@@ -18,21 +18,19 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
-      - name: Set up JDK 11
+      - name: Set up JDK 21
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          distribution: adopt
+          distribution: temurin
-          java-version: 11
+          java-version: '21'
 
         # Runs upload, and then closes & releases the repository
       - name: Publish to MavenCentral
-        run: ./gradlew publish --max-workers 1
+        run: ./gradlew publishToMavenCentral
         env:
-          OSSRH_USERNAME: ${{ secrets.OSSRH_USERNAME }}
+          ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.MAVEN_CENTRAL_USERNAME }}
-          OSSRH_PASSWORD: ${{ secrets.OSSRH_PASSWORD }}
+          ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.MAVEN_CENTRAL_PASSWORD }}
-          SIGNING_KEY_ID: ${{ secrets.SIGNING_KEY_ID }}
+          ORG_GRADLE_PROJECT_signingInMemoryKey: ${{ secrets.SIGNING_KEY }}
-          SIGNING_PASSWORD: ${{ secrets.SIGNING_PASSWORD }}
+          ORG_GRADLE_PROJECT_signingInMemoryKeyPassword: ${{ secrets.SIGNING_PASSWORD }}
-          SIGNING_KEY: ${{ secrets.SIGNING_KEY }}
-          SONATYPE_STAGING_PROFILE_ID: ${{ secrets.SONATYPE_STAGING_PROFILE_ID }}
           SNAPSHOT: false

.github/workflows/publishSnapshot.yml

@@ -1,35 +0,0 @@
-name: Publish Snapshot
-
-on:
-  push:
-    branches: [master, '14-**']
-
-jobs:
-  test:
-    uses: ./.github/workflows/test.yml
-    secrets: inherit
-
-  publish:
-    needs: test
-    name: Publish Snapshot
-    runs-on: ubuntu-latest
-    steps:
-      - name: Check out code
-        uses: actions/checkout@v2
-      - name: Set up JDK 11
-        uses: actions/setup-java@v2
-        with:
-          distribution: adopt
-          java-version: 11
-
-        # Runs upload, and then closes & releases the repository
-      - name: Publish to snapshot to Sonatype
-        run: ./gradlew publish --max-workers 1
-        env:
-          OSSRH_USERNAME: ${{ secrets.OSSRH_USERNAME }}
-          OSSRH_PASSWORD: ${{ secrets.OSSRH_PASSWORD }}
-          SIGNING_KEY_ID: ${{ secrets.SIGNING_KEY_ID }}
-          SIGNING_PASSWORD: ${{ secrets.SIGNING_PASSWORD }}
-          SIGNING_KEY: ${{ secrets.SIGNING_KEY }}
-          SONATYPE_STAGING_PROFILE_ID: ${{ secrets.SONATYPE_STAGING_PROFILE_ID }}
-          SNAPSHOT: true

.github/workflows/test.yml

@@ -6,18 +6,26 @@ on:
   workflow_call:
 
 jobs:
-  build:
+  test:
-    name: Run unit tests
+    name: ${{ matrix.name }}
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: JVM / JS / Wasm / Native + API check
+            os: ubuntu-latest
+            tasks: jvmTest jsNodeTest wasmJsNodeTest nativeTest apiCheck
+          - name: iOS
+            os: macos-latest
+            tasks: iosSimulatorArm64Test
     steps:
       - name: Check out code
-        uses: actions/checkout@v2
+        uses: actions/checkout@v4
-      - name: Set up JDK 11
+      - name: Set up JDK 21
-        uses: actions/setup-java@v2
+        uses: actions/setup-java@v4
         with:
-          distribution: adopt
+          distribution: temurin
-          java-version: 11
+          java-version: '21'
-
-        # Builds the release artifacts of the library
       - name: Test
-        run: ./gradlew test
+        run: ./gradlew ${{ matrix.tasks }} --console=plain

.gitignore

@@ -9,6 +9,7 @@
 /.idea/assetWizardSettings.xml
 .DS_Store
 /build
+build/
 /captures
 .externalNativeBuild
 .cxx
@@ -16,3 +17,4 @@
 /.idea/compiler.xml
 /.idea/jarRepositories.xml
 /.idea/deploymentTargetDropDown.xml
+/.idea/

.idea/.gitignore

@@ -1,4 +0,0 @@
-# Default ignored files
-/shelf/
-/workspace.xml
-artifacts

.idea/codeStyles/Project.xml

@@ -1,10 +0,0 @@
-<component name="ProjectCodeStyleConfiguration">
-  <code_scheme name="Project" version="173">
-    <JetCodeStyleSettings>
-      <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
-    </JetCodeStyleSettings>
-    <codeStyleSettings language="kotlin">
-      <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
-    </codeStyleSettings>
-  </code_scheme>
-</component>

.idea/codeStyles/codeStyleConfig.xml

@@ -1,5 +0,0 @@
-<component name="ProjectCodeStyleConfiguration">
-  <state>
-    <option name="USE_PER_PROJECT_SETTINGS" value="true" />
-  </state>
-</component>

.idea/gradle.xml

@@ -1,17 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="GradleMigrationSettings" migrationVersion="1" />
-  <component name="GradleSettings">
-    <option name="linkedExternalProjectsSettings">
-      <GradleProjectSettings>
-        <option name="distributionType" value="WRAPPED" />
-        <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="modules">
-          <set>
-            <option value="$PROJECT_DIR$" />
-          </set>
-        </option>
-      </GradleProjectSettings>
-    </option>
-  </component>
-</project>

.idea/inspectionProfiles/Project_Default.xml

@@ -1,6 +0,0 @@
-<component name="InspectionProjectProfileManager">
-  <profile version="1.0">
-    <option name="myName" value="Project Default" />
-    <inspection_tool class="ReplaceUntilWithRangeUntil" enabled="true" level="WEAK WARNING" enabled_by_default="true" />
-  </profile>
-</component>

.idea/kotlinScripting.xml

@@ -1,9 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="KotlinScriptingSettings">
-    <scriptDefinition className="org.jetbrains.kotlin.scripting.resolve.KotlinScriptDefinitionFromAnnotatedTemplate" definitionName="KotlinBuildScript">
-      <order>2147483647</order>
-      <autoReloadConfigurations>true</autoReloadConfigurations>
-    </scriptDefinition>
-  </component>
-</project>

.idea/misc.xml

@@ -1,7 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="ExternalStorageConfigurationManager" enabled="true" />
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_11" default="true" project-jdk-name="11" project-jdk-type="JavaSDK">
-    <output url="file://$PROJECT_DIR$/out" />
-  </component>
-</project>

.idea/vcs.xml

@@ -1,6 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<project version="4">
-  <component name="VcsDirectoryMappings">
-    <mapping directory="$PROJECT_DIR$" vcs="Git" />
-  </component>
-</project>

CHANGELOG.md

@@ -0,0 +1,51 @@
+# Changelog
+
+All notable changes to this project are documented here. The format is based on
+[Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and this project adheres to
+[Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+## [3.4.0]
+
+### Added
+- Lazy `Sequence` traversal: `asSequence(order)`, `preOrderSequence()`, `postOrderSequence()`,
+  `levelOrderSequence()` — composes with the Kotlin stdlib and short-circuits.
+- Navigation extensions: `isLeaf`, `degree`, `root()`, `ancestors()`, `siblings()`, `leaves()`,
+  `descendants()`.
+- Functional extensions: `findNode`, `filterNodes`, `anyNode`, `allNodes`, `countNodes`,
+  `foldNodes`, `mapValues`, `deepCopy`, `structurallyEquals` (all stack-safe).
+- New optional modules published as separate artifacts:
+  - `tree-structure-serialization` — `kotlinx.serialization` support via a `TreeNodeDto`.
+  - `tree-structure-coroutines` — `Flow` traversal (`asFlow`, `preOrderFlow`, …).
+- `CHANGELOG.md`, expanded README examples, and class-level KDoc (thread-safety / complexity).
+
+### Changed
+- `nodeCount()`, `height()`, `clear()` and the post-order iterator are now iterative — deep or
+  degenerate (linear) trees no longer throw `StackOverflowError`.
+- Migrated to Kotlin 2.x (K2 compiler) and introduced a Gradle version catalog.
+- Build now uses `binary-compatibility-validator` (committed `.api` baselines) and Kover.
+
+## [3.1.5]
+
+### Fixed
+- Removed a stray `println` in `TreeNode.removeChild()` that printed to stdout on every removal.
+
+### Removed
+- Deleted the `Example.ws.kts` worksheet and the `kotlin("script-runtime")` dependency from the
+  published JVM artifact, plus the leftover `ExampleUnitTest` template test.
+
+### Changed
+- Bumped `actions/checkout` v2 → v4 in CI workflows.
+
+## [3.1.4]
+- Updated Kotlin and JS dependencies; added the `wasmJs` target.
+
+## [3.1.3]
+- iOS targets and Maven Central (Sonatype Central Portal) publishing.
+
+[Unreleased]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.4.0...HEAD
+[3.4.0]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.1.5...v3.4.0
+[3.1.5]: https://github.com/AdrianKuta/Tree-Data-Structure/compare/v3.1.3...v3.1.5
+[3.1.4]: https://github.com/AdrianKuta/Tree-Data-Structure/releases/tag/v3.1.4
+[3.1.3]: https://github.com/AdrianKuta/Tree-Data-Structure/releases/tag/v3.1.3

README.md

@@ -1,9 +1,44 @@
 # Tree (Data Structure)
 [![maven](https://img.shields.io/maven-central/v/com.github.adriankuta/tree-structure?style=plastic)](https://mvnrepository.com/artifact/com.github.adriankuta/tree-structure)
 [![License: MIT](https://img.shields.io/github/license/AdrianKuta/Tree-Data-Structure?style=plastic)](https://github.com/AdrianKuta/Tree-Data-Structure/blob/master/LICENSE)
-[![Publish](https://github.com/AdrianKuta/Tree-Data-Structure/actions/workflows/publishRelease.yml/badge.svg)](https://github.com/AdrianKuta/Tree-Data-Structure/actions/workflows/publish.yml)
+[![Publish](https://github.com/AdrianKuta/Tree-Data-Structure/actions/workflows/publishRelease.yml/badge.svg)](https://github.com/AdrianKuta/Tree-Data-Structure/actions/workflows/publishRelease.yml)
 
-Simple implementation to store object in tree structure.
+Lightweight Kotlin Multiplatform tree data structure for Kotlin and Java. Includes a small DSL, multiple traversal iterators, and pretty-print support.
+
+- Kotlin Multiplatform (JVM, JS, Wasm, iOS, and Native host)
+- Pre-order, Post-order, and Level-order iteration
+- Lazy `Sequence` traversal that composes with the Kotlin stdlib (`map`/`filter`/`firstOrNull`…)
+- Navigation helpers: `root()`, `ancestors()`, `siblings()`, `leaves()`, `descendants()`, `isLeaf`, `degree`
+- Functional helpers: `findNode`, `filterNodes`, `anyNode`, `allNodes`, `foldNodes`, `mapValues`, `deepCopy`, `structurallyEquals`
+- Stack-safe: traversal and `height()`/`nodeCount()`/`clear()` handle arbitrarily deep trees without `StackOverflowError`
+- Simple DSL: tree { child(...) }
+- Utilities: nodeCount(), height(), depth(), path(), prettyString(), clear(), removeChild()
+
+## Installation
+
+Gradle (Kotlin DSL):
+```kotlin
+// commonMain for KMP projects, or any sourceSet/module where you need it
+dependencies {
+    implementation("com.github.adriankuta:tree-structure:3.1.5") // see badge above for the latest version
+}
+```
+
+Gradle (Groovy):
+```groovy
+dependencies {
+    implementation "com.github.adriankuta:tree-structure:3.1.5" // see badge above for the latest
+}
+```
+
+Maven:
+```xml
+<dependency>
+  <groupId>com.github.adriankuta</groupId>
+  <artifactId>tree-structure</artifactId>
+  <version>3.1.5</version>
+</dependency>
+```
 
 ## Usage
 
@@ -25,19 +60,15 @@ europe.addChild(france)
 println(root.prettyString())
 ```
 
-**Pretty Kotlin**
+**Pretty Kotlin (DSL)**
-
 ```kotlin
-val root =
+val root = tree("World") {
-    tree("World") {
+    child("North America") { child("USA") }
-        child("North America") {
+    child("Europe") {
-            child("USA")
+        child("Poland")
-        }
+        child("Germany")
-        child("Europe") {
-            child("Poland")
-            child("Germany")
-        }
     }
+}
 ```
 
 **Java**
@@ -58,8 +89,7 @@ europe.addChild(france);
 System.out.println(root.prettyString());
 ```
 
-*Output:*
+Output:
-
 ```
 World
 ├── North America
@@ -69,11 +99,140 @@ World
     └── France
 ```
 
+### Traversal and utilities
+```kotlin
+val root = TreeNode("root")
+// ... build your tree
 
-## Download
+// Choose iteration order (default is PreOrder)
+root.treeIterator = TreeNodeIterators.PostOrder
+for (node in root) println(node.value)
+
+// Utilities
+root.nodeCount()   // number of descendants
+root.height()      // longest path to a leaf (in edges)
+root.depth()       // distance from current node to the root
+val path = root.path(root.children.first()) // nodes from descendant up to root
+
+// Mutations
+val child = root.children.first()
+root.removeChild(child)
+root.clear()       // remove entire subtree
+```
+
+### Lazy traversal with Sequence
+
+Traversal is exposed as a lazy `Sequence`, so it composes with the Kotlin standard library and
+short-circuits (it never materializes the whole tree just to find one node):
+
+```kotlin
+val tree = tree("World") {
+    child("North America") { child("USA") }
+    child("Europe") {
+        child("Poland")
+        child("Germany")
+    }
+}
+
+// Pick an order explicitly — no need to mutate the node's state.
+tree.preOrderSequence().map { it.value }.toList()    // [World, North America, USA, Europe, Poland, Germany]
+tree.levelOrderSequence().first { it.value == "USA" } // stops as soon as it's found
+tree.asSequence(TreeNodeIterators.PostOrder).count()  // 6
+```
+
+### Navigation
+
+```kotlin
+val usa = tree.findNode { it == "USA" }!!
+
+usa.isLeaf           // true
+usa.depth()          // 2
+usa.root().value     // "World"
+usa.ancestors().map { it.value } // [North America, World]
+tree.leaves().map { it.value }   // [USA, Poland, Germany]
+val europe = tree.findNode { it == "Europe" }!!
+europe.children.first().siblings().map { it.value } // [Germany]
+```
+
+### Functional operations
+
+```kotlin
+tree.anyNode { it == "Poland" }            // true
+tree.filterNodes { it.length > 5 }         // nodes whose value is longer than 5 chars
+tree.countNodes { it.startsWith("U") }     // 1
+
+// Transform values into a brand-new tree (the original is untouched); stack-safe.
+val lengths: TreeNode<Int> = tree.mapValues { it.length }
+
+// Deep copy + structural comparison.
+val copy = tree.deepCopy()
+tree.structurallyEquals(copy)              // true (same values, same shape, different nodes)
+```
+
+## Optional modules
+
+The core `tree-structure` artifact has no third-party dependencies. Ecosystem integrations ship as
+separate, opt-in artifacts that depend on the core.
+
+### Serialization — `tree-structure-serialization`
+
+`kotlinx.serialization` support. A `TreeNode` holds a parent back-reference (a cycle), so it cannot
+be `@Serializable` directly — convert to/from the acyclic `TreeNodeDto` instead.
+
+```kotlin
+implementation("com.github.adriankuta:tree-structure-serialization:3.4.0")
+```
+
+```kotlin
+val json = Json.encodeToString(tree.toDto())
+val restored = Json.decodeFromString<TreeNodeDto<String>>(json).toTreeNode()
+```
+
+### Coroutines — `tree-structure-coroutines`
+
+Traverse a tree as a cold `Flow` (handy in coroutine/`ViewModel` pipelines).
+
+```kotlin
+implementation("com.github.adriankuta:tree-structure-coroutines:3.4.0")
+```
+
+```kotlin
+tree.preOrderFlow().collect { println(it.value) }
+tree.asFlow(TreeNodeIterators.LevelOrder).map { it.value }
+```
+
+## Publishing to Maven Central (central.sonatype.com)
+
+This project is configured to publish artifacts to Maven Central via the Sonatype Central Portal.
+
+There are two supported ways to publish:
+
+1) Via GitHub Actions (recommended)
+- Create a GitHub Release (tag) in this repository. When a release is published, the workflow .github/workflows/publishRelease.yml runs automatically.
+- The workflow uses the Gradle task publishToMavenCentral to upload artifacts through the Central Portal.
+- Make sure these repository secrets are configured in GitHub:
+  - MAVEN_CENTRAL_USERNAME — Your Sonatype Central username (not email).
+  - MAVEN_CENTRAL_PASSWORD — Your Sonatype Central password or a token from central.sonatype.com.
+  - SIGNING_KEY — ASCII‑armored GPG private key (exported, single line; for in‑memory signing).
+  - SIGNING_PASSWORD — Passphrase for the key above.
+- The workflow uses JDK 21 and publishes the version defined in build.gradle.kts.
+
+2) Locally via Gradle
+- Ensure you have a Sonatype Central account and that the groupId com.github.adriankuta is verified in central.sonatype.com (Namespace Rules → Verify).
+- Export the same credentials/signing values as environment variables or pass them as Gradle properties:
+  - ORG_GRADLE_PROJECT_mavenCentralUsername
+  - ORG_GRADLE_PROJECT_mavenCentralPassword
+  - ORG_GRADLE_PROJECT_signingInMemoryKey
+  - ORG_GRADLE_PROJECT_signingInMemoryKeyPassword
+- Then run:
+  - ./gradlew publishToMavenCentral
+- For snapshot publishing, set -Psnapshot=true (the version is derived from PUBLISH_VERSION with -SNAPSHOT).
+
+Notes
+- Publishing is powered by the com.vanniktech.maven.publish Gradle plugin and Sonatype Central Portal (no legacy Nexus staging URLs needed).
+- The plugin is configured to sign all publications. Coordinates and POM metadata are defined in build.gradle.kts.
+- If using the combined task is preferred, you can also run publishAndReleaseToMavenCentral when automatic release is enabled; this repository currently uploads with publishToMavenCentral from CI.
 
-    implementation "com.github.adriankuta:tree-structure:$latest_versions"
-    
 ## License
 
 MIT License
@@ -97,3 +256,5 @@ AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
+
+---

api/tree-structure.api

@@ -0,0 +1,100 @@
+public abstract interface class com/github/adriankuta/datastructure/tree/ChildDeclarationInterface {
+	public abstract synthetic fun child (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+}
+
+public final class com/github/adriankuta/datastructure/tree/ChildDeclarationInterface$DefaultImpls {
+	public static synthetic fun child$default (Lcom/github/adriankuta/datastructure/tree/ChildDeclarationInterface;Ljava/lang/Object;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+}
+
+public class com/github/adriankuta/datastructure/tree/TreeNode : com/github/adriankuta/datastructure/tree/ChildDeclarationInterface, java/lang/Iterable, kotlin/jvm/internal/markers/KMappedMarker {
+	public fun <init> (Ljava/lang/Object;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;)V
+	public synthetic fun <init> (Ljava/lang/Object;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public final fun addChild (Lcom/github/adriankuta/datastructure/tree/TreeNode;)V
+	public synthetic fun child (Ljava/lang/Object;Lkotlin/jvm/functions/Function1;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public final fun clear ()V
+	public final fun depth ()I
+	public final fun getChildren ()Ljava/util/List;
+	public final fun getParent ()Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public final fun getTreeIterator ()Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+	public final fun getValue ()Ljava/lang/Object;
+	public final fun height ()I
+	public final fun isRoot ()Z
+	public fun iterator ()Ljava/util/Iterator;
+	public final fun nodeCount ()I
+	public final fun path (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Ljava/util/List;
+	public final fun prettyString ()Ljava/lang/String;
+	public final fun removeChild (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Z
+	public final fun setTreeIterator (Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;)V
+	public fun toString ()Ljava/lang/String;
+}
+
+public final class com/github/adriankuta/datastructure/tree/TreeNodeFunctionalExtKt {
+	public static final fun allNodes (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)Z
+	public static final fun anyNode (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)Z
+	public static final fun countNodes (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)I
+	public static final fun deepCopy (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public static final fun filterNodes (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)Ljava/util/List;
+	public static final fun findNode (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public static final fun foldNodes (Lcom/github/adriankuta/datastructure/tree/TreeNode;Ljava/lang/Object;Lkotlin/jvm/functions/Function2;)Ljava/lang/Object;
+	public static final fun mapValues (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lkotlin/jvm/functions/Function1;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public static final fun structurallyEquals (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lcom/github/adriankuta/datastructure/tree/TreeNode;)Z
+}
+
+public final class com/github/adriankuta/datastructure/tree/TreeNodeNavigationExtKt {
+	public static final fun ancestors (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Ljava/util/List;
+	public static final fun descendants (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Ljava/util/List;
+	public static final fun getDegree (Lcom/github/adriankuta/datastructure/tree/TreeNode;)I
+	public static final fun isLeaf (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Z
+	public static final fun leaves (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Ljava/util/List;
+	public static final fun root (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public static final fun siblings (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Ljava/util/List;
+}
+
+public final class com/github/adriankuta/datastructure/tree/TreeNodeSequenceExtKt {
+	public static final fun asSequence (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;)Lkotlin/sequences/Sequence;
+	public static synthetic fun asSequence$default (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;ILjava/lang/Object;)Lkotlin/sequences/Sequence;
+	public static final fun levelOrderSequence (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlin/sequences/Sequence;
+	public static final fun postOrderSequence (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlin/sequences/Sequence;
+	public static final fun preOrderSequence (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlin/sequences/Sequence;
+}
+
+public final class com/github/adriankuta/datastructure/tree/exceptions/TreeNodeException : java/lang/RuntimeException {
+	public fun <init> ()V
+	public fun <init> (Ljava/lang/String;)V
+	public fun <init> (Ljava/lang/String;Ljava/lang/Throwable;)V
+	public synthetic fun <init> (Ljava/lang/String;Ljava/lang/Throwable;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+}
+
+public final class com/github/adriankuta/datastructure/tree/iterators/LevelOrderTreeIterator : java/util/Iterator, kotlin/jvm/internal/markers/KMappedMarker {
+	public fun <init> (Lcom/github/adriankuta/datastructure/tree/TreeNode;)V
+	public fun hasNext ()Z
+	public fun next ()Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public synthetic fun next ()Ljava/lang/Object;
+	public fun remove ()V
+}
+
+public final class com/github/adriankuta/datastructure/tree/iterators/PostOrderTreeIterator : java/util/Iterator, kotlin/jvm/internal/markers/KMappedMarker {
+	public fun <init> (Lcom/github/adriankuta/datastructure/tree/TreeNode;)V
+	public fun hasNext ()Z
+	public fun next ()Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public synthetic fun next ()Ljava/lang/Object;
+	public fun remove ()V
+}
+
+public final class com/github/adriankuta/datastructure/tree/iterators/PreOrderTreeIterator : java/util/Iterator, kotlin/jvm/internal/markers/KMappedMarker {
+	public fun <init> (Lcom/github/adriankuta/datastructure/tree/TreeNode;)V
+	public fun hasNext ()Z
+	public fun next ()Lcom/github/adriankuta/datastructure/tree/TreeNode;
+	public synthetic fun next ()Ljava/lang/Object;
+	public fun remove ()V
+}
+
+public final class com/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators : java/lang/Enum {
+	public static final field LevelOrder Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+	public static final field PostOrder Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+	public static final field PreOrder Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+	public static fun getEntries ()Lkotlin/enums/EnumEntries;
+	public static fun valueOf (Ljava/lang/String;)Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+	public static fun values ()[Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;
+}
+

build.gradle.kts

@@ -1,149 +1,98 @@
-import org.jetbrains.kotlin.konan.properties.Properties
+import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
 
 plugins {
-    kotlin("multiplatform") version "1.7.20"
+    alias(libs.plugins.kotlinMultiplatform)
-    id("org.jetbrains.dokka") version "1.7.20"
+    alias(libs.plugins.dokka)
-    id("maven-publish")
+    alias(libs.plugins.mavenPublish)
+    alias(libs.plugins.binaryCompatibilityValidator)
+    alias(libs.plugins.kover)
     signing
 }
 
 val PUBLISH_GROUP_ID = "com.github.adriankuta"
-val PUBLISH_ARTIFACT_ID = "tree-structure"
+val PUBLISH_ARTIFACT_ID = "tree-structure"    // base artifact; KMP will add -jvm, -ios*, etc.
-val PUBLISH_VERSION = "3.0.1"
+val PUBLISH_VERSION = "3.4.0"
 
-val secretFile = File(rootProject.rootDir, "local.properties")
-if (secretFile.exists()) {
-    secretFile.reader().use {
-        Properties().apply {
-            load(it)
-        }
-    }.onEach { (name, value) ->
-        project.ext[name.toString()] = value
-    }
-} else {
-    project.ext["ossrhUsername"] = System.getenv("OSSRH_USERNAME")
-    project.ext["ossrhPassword"] = System.getenv("OSSRH_PASSWORD")
-    project.ext["sonatypeStagingProfileId"] = System.getenv("SONATYPE_STAGING_PROFILE_ID")
-    project.ext["signingKeyId"] = System.getenv("SIGNING_KEY_ID")
-    project.ext["signingPassword"] = System.getenv("SIGNING_PASSWORD")
-    project.ext["signingKey"] = System.getenv("SIGNING_KEY")
-    project.ext["snapshot"] = System.getenv("SNAPSHOT")
-}
 val snapshot: String? by project
 
 group = PUBLISH_GROUP_ID
 version = if (snapshot.toBoolean()) "$PUBLISH_VERSION-SNAPSHOT" else PUBLISH_VERSION
 
-val dokkaHtml by tasks.getting(org.jetbrains.dokka.gradle.DokkaTask::class)
+mavenPublishing {
+    // Central Portal + auto release when we call publishAndReleaseToMavenCentral
+    publishToMavenCentral(automaticRelease = false)
+    signAllPublications()
 
-val javadocJar: TaskProvider<Jar> by tasks.registering(Jar::class) {
+    coordinates(PUBLISH_GROUP_ID, PUBLISH_ARTIFACT_ID, version.toString())
-    dependsOn(dokkaHtml)
-    archiveClassifier.set("javadoc")
-    from(dokkaHtml.outputDirectory)
-}
 
-publishing {
+    pom {
-    publications {
+        name.set("Tree Data Structure")
+        description.set(
+            "Lightweight n-ary tree data structure for Kotlin Multiplatform (JVM, JS, Wasm, iOS, " +
+                "Native). DSL, pre/post/level-order traversal, lazy Sequence traversal, and pretty-print.",
+        )
+        url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
 
-        withType<MavenPublication> {
+        licenses {
-            artifact(javadocJar)
+            license {
-            pom {
+                name.set("MIT License")
-                name.set("Tree Data Structure")
+                url.set("https://opensource.org/licenses/MIT")
-                description.set("Simple implementation to store object in tree structure.")
+                distribution.set("repo")
-                url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
-                licenses {
-                    license {
-                        name.set("MIT License")
-                        url.set("https://www.mit.edu/~amini/LICENSE.md")
-                    }
-                }
-                developers {
-                    developer {
-                        name.set("Adrian Kuta")
-                        email.set("adrian.kuta93@gmail.com")
-                    }
-                }
-                scm {
-                    connection.set("scm:git:github.com/AdrianKuta/Tree-Data-Structure.git")
-                    developerConnection.set("scm:git:ssh://github.com/AdrianKuta/Tree-Data-Structure.git")
-                    url.set("https://github.com/AdrianKuta/Tree-Data-Structure/tree/master")
-                }
             }
         }
-    }
+        developers {
-
+            developer {
-    repositories {
+                id.set("AdrianKuta")
-        maven {
+                name.set("Adrian Kuta")
-            name = "Sonatype"
+                email.set("adrian.kuta93@gmail.com")
-            val releasesRepoUrl = "https://oss.sonatype.org/service/local/staging/deploy/maven2"
-            val snapshotsRepoUrl = "https://oss.sonatype.org/content/repositories/snapshots"
-            url = uri(if (version.toString().endsWith("SNAPSHOT")) snapshotsRepoUrl else releasesRepoUrl)
-            credentials {
-                val ossrhUsername: String? by project
-                val ossrhPassword: String? by project
-                username = ossrhUsername
-                password = ossrhPassword
             }
         }
+        scm {
+            url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+            connection.set("scm:git:https://github.com/AdrianKuta/Tree-Data-Structure.git")
+            developerConnection.set("scm:git:ssh://git@github.com/AdrianKuta/Tree-Data-Structure.git")
+        }
     }
 }
 
-signing {
-    val signingKeyId: String? by project
-    val signingPassword: String? by project
-    val signingKey: String? by project
-    useInMemoryPgpKeys(signingKeyId, signingKey, signingPassword)
-
-    sign(publishing.publications)
-}
-
 repositories {
     mavenCentral()
 }
 
 kotlin {
-    jvm {
+    jvmToolchain(21)
-        compilations.all {
+
-            kotlinOptions.jvmTarget = "1.8"
+    jvm()
-        }
+
-        withJava()
+    js(IR) {
-        testRuns["test"].executionTask.configure {
+        browser()
-            useJUnitPlatform()
+        nodejs()
-        }
     }
-    js(BOTH) {
+
-        browser {
+    @OptIn(ExperimentalWasmDsl::class)
-            commonWebpackConfig {
+    wasmJs {
-                cssSupport.enabled = true
+        browser()
-            }
+        nodejs()
-        }
     }
+
+    // Apple targets
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+
+    // Native host target
     val hostOs = System.getProperty("os.name")
     val isMingwX64 = hostOs.startsWith("Windows")
-    val nativeTarget = when {
+    when {
         hostOs == "Mac OS X" -> macosX64("native")
         hostOs == "Linux" -> linuxX64("native")
         isMingwX64 -> mingwX64("native")
         else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
     }
 
-
     sourceSets {
-        val commonMain by getting
+        commonTest.dependencies {
-        val commonTest by getting {
+            implementation(kotlin("test"))
-            dependencies {
-                implementation(kotlin("test"))
-            }
         }
-        val jvmMain by getting {
-            dependencies {
-                implementation(kotlin("script-runtime"))
-            }
-        }
-        val jvmTest by getting
-        val jsMain by getting
-        val jsTest by getting
-        val nativeMain by getting
-        val nativeTest by getting
     }
 }

gradle.properties

@@ -1,2 +1 @@
 kotlin.code.style=official
-kotlin.js.compiler=ir

gradle/libs.versions.toml

@@ -0,0 +1,21 @@
+[versions]
+kotlin = "2.1.0"
+dokka = "1.9.20"
+mavenPublish = "0.34.0"
+binaryCompatibilityValidator = "0.16.3"
+kover = "0.8.3"
+coroutines = "1.9.0"
+kotlinxSerialization = "1.7.3"
+
+[plugins]
+kotlinMultiplatform = { id = "org.jetbrains.kotlin.multiplatform", version.ref = "kotlin" }
+kotlinSerialization = { id = "org.jetbrains.kotlin.plugin.serialization", version.ref = "kotlin" }
+dokka = { id = "org.jetbrains.dokka", version.ref = "dokka" }
+mavenPublish = { id = "com.vanniktech.maven.publish", version.ref = "mavenPublish" }
+binaryCompatibilityValidator = { id = "org.jetbrains.kotlinx.binary-compatibility-validator", version.ref = "binaryCompatibilityValidator" }
+kover = { id = "org.jetbrains.kotlinx.kover", version.ref = "kover" }
+
+[libraries]
+kotlinx-coroutines-core = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-core", version.ref = "coroutines" }
+kotlinx-coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", version.ref = "coroutines" }
+kotlinx-serialization-json = { module = "org.jetbrains.kotlinx:kotlinx-serialization-json", version.ref = "kotlinxSerialization" }

gradle/wrapper/gradle-wrapper.properties

@@ -1,5 +1,7 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.4.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

gradlew

@@ -55,7 +55,7 @@
 #       Darwin, MinGW, and NonStop.
 #
 #   (3) This script is generated from the Groovy template
-#       https://github.com/gradle/gradle/blob/master/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       https://github.com/gradle/gradle/blob/HEAD/subprojects/plugins/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
 #       within the Gradle project.
 #
 #       You can find Gradle at https://github.com/gradle/gradle/.
@@ -80,13 +80,11 @@ do
     esac
 done
 
-APP_HOME=$( cd "${APP_HOME:-./}" && pwd -P ) || exit
+# This is normally unused
-
+# shellcheck disable=SC2034
-APP_NAME="Gradle"
 APP_BASE_NAME=${0##*/}
-
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
-# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+APP_HOME=$( cd "${APP_HOME:-./}" > /dev/null && pwd -P ) || exit
-DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
 
 # Use the maximum available, or set MAX_FD != -1 to use that value.
 MAX_FD=maximum
@@ -133,22 +131,29 @@ location of your Java installation."
     fi
 else
     JAVACMD=java
-    which java >/dev/null 2>&1 || die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
 
 Please set the JAVA_HOME variable in your environment to match the
 location of your Java installation."
+    fi
 fi
 
 # Increase the maximum file descriptors if we can.
 if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
     case $MAX_FD in #(
       max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         MAX_FD=$( ulimit -H -n ) ||
             warn "Could not query maximum file descriptor limit"
     esac
     case $MAX_FD in  #(
       '' | soft) :;; #(
       *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
         ulimit -n "$MAX_FD" ||
             warn "Could not set maximum file descriptor limit to $MAX_FD"
     esac
@@ -193,11 +198,15 @@ if "$cygwin" || "$msys" ; then
     done
 fi
 
-# Collect all arguments for the java command;
+
-#   * $DEFAULT_JVM_OPTS, $JAVA_OPTS, and $GRADLE_OPTS can contain fragments of
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
-#     shell script including quotes and variable substitutions, so put them in
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
-#     double quotes to make sure that they get re-expanded; and
+
-#   * put everything else in single quotes, so that it's not re-expanded.
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
 
 set -- \
         "-Dorg.gradle.appname=$APP_BASE_NAME" \
@@ -205,6 +214,12 @@ set -- \
         org.gradle.wrapper.GradleWrapperMain \
         "$@"
 
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
 # Use "xargs" to parse quoted args.
 #
 # With -n1 it outputs one arg per line, with the quotes and backslashes removed.

gradlew.bat

@@ -14,7 +14,7 @@
 @rem limitations under the License.
 @rem
 
-@if "%DEBUG%" == "" @echo off
+@if "%DEBUG%"=="" @echo off
 @rem ##########################################################################
 @rem
 @rem  Gradle startup script for Windows
@@ -25,7 +25,8 @@
 if "%OS%"=="Windows_NT" setlocal
 
 set DIRNAME=%~dp0
-if "%DIRNAME%" == "" set DIRNAME=.
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
 set APP_BASE_NAME=%~n0
 set APP_HOME=%DIRNAME%
 
@@ -40,7 +41,7 @@ if defined JAVA_HOME goto findJavaFromJavaHome
 
 set JAVA_EXE=java.exe
 %JAVA_EXE% -version >NUL 2>&1
-if "%ERRORLEVEL%" == "0" goto execute
+if %ERRORLEVEL% equ 0 goto execute
 
 echo.
 echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
@@ -75,13 +76,15 @@ set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
 
 :end
 @rem End local scope for the variables with windows NT shell
-if "%ERRORLEVEL%"=="0" goto mainEnd
+if %ERRORLEVEL% equ 0 goto mainEnd
 
 :fail
 rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
 rem the _cmd.exe /c_ return code!
-if  not "" == "%GRADLE_EXIT_CONSOLE%" exit 1
+set EXIT_CODE=%ERRORLEVEL%
-exit /b 1
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
 
 :mainEnd
 if "%OS%"=="Windows_NT" endlocal

settings.gradle.kts

@@ -1,3 +1,4 @@
-
 rootProject.name = "tree-structure"
 
+include(":tree-structure-serialization")
+include(":tree-structure-coroutines")

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNode.kt

@@ -8,7 +8,26 @@ import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators.*
 import kotlin.jvm.JvmSynthetic
 
-open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationInterface<T> {
+/**
+ * A node in a generic, mutable n-ary tree. Each node holds a [value], a reference to its [parent]
+ * and an ordered list of [children].
+ *
+ * Iterating a node (via [iterator], or the lazy [asSequence]/[preOrderSequence] extensions) visits
+ * the node and all of its descendants. Traversal and the [height]/[nodeCount]/[clear] helpers are
+ * implemented iteratively, so they are safe on arbitrarily deep trees.
+ *
+ * **Not thread-safe.** Nodes are mutable ([addChild]/[removeChild]/[clear] mutate the structure and
+ * parent pointers). Sharing a tree across threads requires external synchronization, and the tree
+ * must not be modified while it is being iterated.
+ *
+ * Equality is by reference (identity); use the `structurallyEquals` extension to compare two trees
+ * by value and shape.
+ *
+ * @param value the value stored in this node.
+ * @param treeIterator the default traversal order used by [iterator]. Prefer the
+ *   `asSequence(order)` / `preOrderSequence()` extensions to choose an order without mutating state.
+ */
+open class TreeNode<T>(val value: T, var treeIterator: TreeNodeIterators = PreOrder) : Iterable<TreeNode<T>>, ChildDeclarationInterface<T> {
 
     private var _parent: TreeNode<T>? = null
 
@@ -33,11 +52,6 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
     val isRoot: Boolean
         get() = _parent == null
 
-    /**
-     * Choose one of available iterators from [TreeNodeIterators]
-     */
-    var defaultIterator: TreeNodeIterators = PreOrder
-
     /**
      * Add new child to current node or root.
      *
@@ -64,7 +78,6 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
      * @return `true` if the node has been successfully removed; `false` if it was not present in the tree.
      */
     fun removeChild(child: TreeNode<T>): Boolean {
-        println(child.value)
         val removed = child._parent?._children?.remove(child)
         child._parent = null
         return removed ?: false
@@ -75,20 +88,30 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
      * @return All child and nested child count.
      */
     fun nodeCount(): Int {
-        if (_children.isEmpty())
+        var count = 0
-            return 0
+        val stack = ArrayDeque<TreeNode<T>>()
-        return _children.size +
+        stack.addAll(_children)
-                _children.sumOf { it.nodeCount() }
+        while (stack.isNotEmpty()) {
+            val node = stack.removeLast()
+            count++
+            stack.addAll(node._children)
+        }
+        return count
     }
 
     /**
      * @return The number of edges on the longest path between current node and a descendant leaf.
      */
     fun height(): Int {
-        val childrenMaxDepth = _children.map { it.height() }
+        var maxDepth = 0
-            .maxOrNull()
+        val stack = ArrayDeque<Pair<TreeNode<T>, Int>>()
-            ?: -1 // -1 because this method counts nodes, and edges are always one less then nodes.
+        stack.addLast(this to 0)
-        return childrenMaxDepth + 1
+        while (stack.isNotEmpty()) {
+            val (node, depthSoFar) = stack.removeLast()
+            if (depthSoFar > maxDepth) maxDepth = depthSoFar
+            node._children.forEach { stack.addLast(it to depthSoFar + 1) }
+        }
+        return maxDepth
     }
 
     /**
@@ -135,9 +158,18 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
      * Remove all children from root and every node in tree.
      */
     fun clear() {
-        _parent = null
+        val all = ArrayDeque<TreeNode<T>>()
-        _children.forEach { it.clear() }
+        val stack = ArrayDeque<TreeNode<T>>()
-        _children.clear()
+        stack.addLast(this)
+        while (stack.isNotEmpty()) {
+            val node = stack.removeLast()
+            all.addLast(node)
+            stack.addAll(node._children)
+        }
+        all.forEach { node ->
+            node._parent = null
+            node._children.clear()
+        }
     }
 
     override fun toString(): String {
@@ -166,9 +198,9 @@ open class TreeNode<T>(val value: T) : Iterable<TreeNode<T>>, ChildDeclarationIn
     }
 
     /**
-     * You can change default iterator by changing [defaultIterator] property.
+     * You can change default iterator by changing [treeIterator] property.
      */
-    override fun iterator(): Iterator<TreeNode<T>> = when (defaultIterator) {
+    override fun iterator(): Iterator<TreeNode<T>> = when (treeIterator) {
         PreOrder -> PreOrderTreeIterator(this)
         PostOrder -> PostOrderTreeIterator(this)
         LevelOrder -> LevelOrderTreeIterator(this)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeExt.kt

@@ -19,8 +19,7 @@ inline fun <reified T> tree(
     defaultIterator: TreeNodeIterators = TreeNodeIterators.PreOrder,
     childDeclaration: ChildDeclaration<T>
 ): TreeNode<T> {
-    val treeNode = TreeNode(root)
+    val treeNode = TreeNode(root, defaultIterator)
-    treeNode.defaultIterator = defaultIterator
     treeNode.childDeclaration()
     return treeNode
 }

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeFunctionalExt.kt

@@ -0,0 +1,65 @@
+package com.github.adriankuta.datastructure.tree
+
+/** Returns the first node (pre-order) whose value matches [predicate], or `null`. Short-circuits. */
+fun <T> TreeNode<T>.findNode(predicate: (T) -> Boolean): TreeNode<T>? =
+    preOrderSequence().firstOrNull { predicate(it.value) }
+
+/** All nodes (pre-order) whose value matches [predicate]. */
+fun <T> TreeNode<T>.filterNodes(predicate: (T) -> Boolean): List<TreeNode<T>> =
+    preOrderSequence().filter { predicate(it.value) }.toList()
+
+/** `true` if any node's value matches [predicate]. Short-circuits. */
+fun <T> TreeNode<T>.anyNode(predicate: (T) -> Boolean): Boolean =
+    preOrderSequence().any { predicate(it.value) }
+
+/** `true` if every node's value matches [predicate]. Short-circuits. */
+fun <T> TreeNode<T>.allNodes(predicate: (T) -> Boolean): Boolean =
+    preOrderSequence().all { predicate(it.value) }
+
+/** Counts nodes whose value matches [predicate]. */
+fun <T> TreeNode<T>.countNodes(predicate: (T) -> Boolean): Int =
+    preOrderSequence().count { predicate(it.value) }
+
+/** Folds [operation] over all nodes in pre-order, starting from [initial]. */
+fun <T, R> TreeNode<T>.foldNodes(initial: R, operation: (acc: R, node: TreeNode<T>) -> R): R =
+    preOrderSequence().fold(initial) { acc, node -> operation(acc, node) }
+
+/**
+ * Returns a new tree with the same shape whose values are produced by [transform]. The original is
+ * left untouched. Stack-safe (iterative), so it handles arbitrarily deep trees.
+ */
+fun <T, R> TreeNode<T>.mapValues(transform: (T) -> R): TreeNode<R> {
+    val newRoot = TreeNode(transform(value), treeIterator)
+    val stack = ArrayDeque<Pair<TreeNode<T>, TreeNode<R>>>()
+    stack.addLast(this to newRoot)
+    while (stack.isNotEmpty()) {
+        val (source, target) = stack.removeLast()
+        source.children.forEach { child ->
+            val mappedChild = TreeNode(transform(child.value), child.treeIterator)
+            target.addChild(mappedChild)
+            stack.addLast(child to mappedChild)
+        }
+    }
+    return newRoot
+}
+
+/** Returns an independent deep copy of this subtree (same values, same shape, new nodes). */
+fun <T> TreeNode<T>.deepCopy(): TreeNode<T> = mapValues { it }
+
+/**
+ * Structural equality: `true` when [other] holds the same values in the same shape. Unlike
+ * [TreeNode]'s reference equality, this compares the entire subtree. Stack-safe.
+ */
+fun <T> TreeNode<T>.structurallyEquals(other: TreeNode<T>): Boolean {
+    val stack = ArrayDeque<Pair<TreeNode<T>, TreeNode<T>>>()
+    stack.addLast(this to other)
+    while (stack.isNotEmpty()) {
+        val (a, b) = stack.removeLast()
+        if (a.value != b.value) return false
+        if (a.children.size != b.children.size) return false
+        for (i in a.children.indices) {
+            stack.addLast(a.children[i] to b.children[i])
+        }
+    }
+    return true
+}

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeNavigationExt.kt

@@ -0,0 +1,41 @@
+package com.github.adriankuta.datastructure.tree
+
+/** `true` when this node has no children. */
+val <T> TreeNode<T>.isLeaf: Boolean get() = children.isEmpty()
+
+/** The number of direct children of this node. */
+val <T> TreeNode<T>.degree: Int get() = children.size
+
+/** Walks up the parent chain and returns the topmost ancestor (the tree root). */
+fun <T> TreeNode<T>.root(): TreeNode<T> {
+    var node = this
+    var parent = node.parent
+    while (parent != null) {
+        node = parent
+        parent = node.parent
+    }
+    return node
+}
+
+/** The chain of ancestors from the immediate [parent] up to (and including) the root. */
+fun <T> TreeNode<T>.ancestors(): List<TreeNode<T>> {
+    val result = mutableListOf<TreeNode<T>>()
+    var parent = this.parent
+    while (parent != null) {
+        result.add(parent)
+        parent = parent.parent
+    }
+    return result
+}
+
+/** The other children of this node's parent (excludes this node). Empty for the root. */
+fun <T> TreeNode<T>.siblings(): List<TreeNode<T>> =
+    parent?.children?.filter { it !== this } ?: emptyList()
+
+/** All leaf nodes in this subtree, in pre-order. */
+fun <T> TreeNode<T>.leaves(): List<TreeNode<T>> =
+    preOrderSequence().filter { it.isLeaf }.toList()
+
+/** All nodes in this subtree except this node, in pre-order. */
+fun <T> TreeNode<T>.descendants(): List<TreeNode<T>> =
+    preOrderSequence().filter { it !== this }.toList()

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/TreeNodeSequenceExt.kt

@@ -0,0 +1,31 @@
+package com.github.adriankuta.datastructure.tree
+
+import com.github.adriankuta.datastructure.tree.iterators.LevelOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PostOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.PreOrderTreeIterator
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+
+/**
+ * Lazily traverses this subtree in the given [order] as a [Sequence], without forcing the whole
+ * traversal up front. Pairs with the Kotlin stdlib, e.g.
+ * `root.asSequence().map { it.value }.firstOrNull { it == target }`.
+ */
+fun <T> TreeNode<T>.asSequence(
+    order: TreeNodeIterators = TreeNodeIterators.PreOrder,
+): Sequence<TreeNode<T>> {
+    val self = this
+    return when (order) {
+        TreeNodeIterators.PreOrder -> Sequence { PreOrderTreeIterator(self) }
+        TreeNodeIterators.PostOrder -> Sequence { PostOrderTreeIterator(self) }
+        TreeNodeIterators.LevelOrder -> Sequence { LevelOrderTreeIterator(self) }
+    }
+}
+
+/** Lazy pre-order traversal as a [Sequence]. */
+fun <T> TreeNode<T>.preOrderSequence(): Sequence<TreeNode<T>> = asSequence(TreeNodeIterators.PreOrder)
+
+/** Lazy post-order traversal as a [Sequence]. */
+fun <T> TreeNode<T>.postOrderSequence(): Sequence<TreeNode<T>> = asSequence(TreeNodeIterators.PostOrder)
+
+/** Lazy level-order (breadth-first) traversal as a [Sequence]. */
+fun <T> TreeNode<T>.levelOrderSequence(): Sequence<TreeNode<T>> = asSequence(TreeNodeIterators.LevelOrder)

src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/iterators/PostOrderTreeIterator.kt

@@ -22,27 +22,22 @@ import com.github.adriankuta.datastructure.tree.TreeNode
  */
 class PostOrderTreeIterator<T>(root: TreeNode<T>) : Iterator<TreeNode<T>> {
 
-    private val stack = ArrayDeque<TreeNode<T>>()
+    private val result = ArrayDeque<TreeNode<T>>()
 
     init {
-        stack.addAll(getChildrenStack(root))
+        // Iterative post-order: pop a node, prepend it to `result`, then push its children
-    }
+        // left-to-right. Reading `result` front-to-back yields post-order — without the deep
-
+        // recursion that overflowed the stack on degenerate (linear) trees.
-    override fun hasNext(): Boolean = stack.isNotEmpty()
-
-    override fun next(): TreeNode<T> {
-        return stack.removeFirst()
-    }
-
-    private fun getChildrenStack(node: TreeNode<T>): ArrayDeque<TreeNode<T>> {
         val stack = ArrayDeque<TreeNode<T>>()
-        if(node.children.isEmpty()) {
+        stack.addLast(root)
-            return ArrayDeque(listOf(node))
+        while (stack.isNotEmpty()) {
+            val node = stack.removeLast()
+            result.addFirst(node)
+            node.children.forEach { stack.addLast(it) }
         }
-        node.children.forEach {
-            stack.addAll(getChildrenStack(it))
-        }
-        stack.addLast(node)
-        return stack
     }
+
+    override fun hasNext(): Boolean = result.isNotEmpty()
+
+    override fun next(): TreeNode<T> = result.removeFirst()
 }

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/ExampleUnitTest.kt

@@ -1,16 +0,0 @@
-package com.github.adriankuta.datastructure.tree
-
-import kotlin.test.Test
-import kotlin.test.assertEquals
-
-/**
- * Example local unit test, which will execute on the development machine (host).
- *
- * See [testing documentation](http://d.android.com/tools/testing).
- */
-class ExampleUnitTest {
-    @Test
-    fun addition_isCorrect() {
-        assertEquals(4, 2 + 2)
-    }
-}

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeFunctionalTest.kt

@@ -0,0 +1,78 @@
+package com.github.adriankuta.datastructure.tree
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertNotSame
+import kotlin.test.assertNull
+import kotlin.test.assertSame
+import kotlin.test.assertTrue
+
+class TreeNodeFunctionalTest {
+
+    private fun sample() = tree(1) {
+        child(2) {
+            child(4)
+            child(5)
+        }
+        child(3) {
+            child(6)
+        }
+    }
+
+    @Test
+    fun findNode() {
+        assertEquals(6, sample().findNode { it == 6 }?.value)
+        assertNull(sample().findNode { it == 99 })
+    }
+
+    @Test
+    fun filterNodes() =
+        assertContentEquals(listOf(2, 4, 6), sample().filterNodes { it % 2 == 0 }.map { it.value })
+
+    @Test
+    fun anyNode() {
+        assertTrue(sample().anyNode { it == 6 })
+        assertFalse(sample().anyNode { it == 99 })
+    }
+
+    @Test
+    fun allNodes() {
+        assertTrue(sample().allNodes { it > 0 })
+        assertFalse(sample().allNodes { it < 5 })
+    }
+
+    @Test
+    fun countNodes() = assertEquals(3, sample().countNodes { it > 3 })
+
+    @Test
+    fun foldNodes() = assertEquals(21, sample().foldNodes(0) { acc, node -> acc + node.value })
+
+    @Test
+    fun mapPreservesStructureAndTransformsValues() {
+        val mapped = sample().mapValues { it * 10 }
+        assertContentEquals(
+            listOf(10, 20, 40, 50, 30, 60),
+            mapped.preOrderSequence().map { it.value }.toList(),
+        )
+    }
+
+    @Test
+    fun deepCopyIsStructurallyEqualButDistinct() {
+        val original = sample()
+        val copy = original.deepCopy()
+        assertNotSame(original, copy)
+        assertTrue(original.structurallyEquals(copy))
+    }
+
+    @Test
+    fun structurallyEqualsDistinguishesByValueAndShape() {
+        assertTrue(sample().structurallyEquals(sample()))
+        val different = tree(1) {
+            child(2) { child(4) }
+            child(3) { child(6) }
+        }
+        assertFalse(sample().structurallyEquals(different))
+    }
+}

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeNavigationTest.kt

@@ -0,0 +1,66 @@
+package com.github.adriankuta.datastructure.tree
+
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFalse
+import kotlin.test.assertSame
+import kotlin.test.assertTrue
+
+class TreeNodeNavigationTest {
+
+    private val root = TreeNode(1)
+    private val n2 = TreeNode(2)
+    private val n3 = TreeNode(3)
+    private val n4 = TreeNode(4)
+    private val n5 = TreeNode(5)
+    private val n6 = TreeNode(6)
+
+    init {
+        root.addChild(n2)
+        root.addChild(n3)
+        n2.addChild(n4)
+        n2.addChild(n5)
+        n3.addChild(n6)
+    }
+
+    @Test
+    fun isLeaf() {
+        assertTrue(n4.isLeaf)
+        assertFalse(root.isLeaf)
+    }
+
+    @Test
+    fun degree() {
+        assertEquals(2, root.degree)
+        assertEquals(0, n4.degree)
+    }
+
+    @Test
+    fun root() {
+        assertSame(root, n6.root())
+        assertSame(root, root.root())
+    }
+
+    @Test
+    fun ancestors() {
+        assertContentEquals(listOf(n2, root), n4.ancestors())
+        assertContentEquals(emptyList(), root.ancestors())
+    }
+
+    @Test
+    fun siblings() {
+        assertContentEquals(listOf(n5), n4.siblings())
+        assertContentEquals(emptyList(), root.siblings())
+    }
+
+    @Test
+    fun leaves() {
+        assertContentEquals(listOf(n4, n5, n6), root.leaves())
+    }
+
+    @Test
+    fun descendants() {
+        assertContentEquals(listOf(n2, n4, n5, n3, n6), root.descendants())
+    }
+}

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeSequenceTest.kt

@@ -0,0 +1,46 @@
+package com.github.adriankuta.datastructure.tree
+
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+
+class TreeNodeSequenceTest {
+
+    private fun sample() = tree(1) {
+        child(2) {
+            child(4)
+            child(5)
+        }
+        child(3) {
+            child(6)
+        }
+    }
+
+    @Test
+    fun preOrderSequence() =
+        assertContentEquals(listOf(1, 2, 4, 5, 3, 6), sample().preOrderSequence().map { it.value }.toList())
+
+    @Test
+    fun postOrderSequence() =
+        assertContentEquals(listOf(4, 5, 2, 6, 3, 1), sample().postOrderSequence().map { it.value }.toList())
+
+    @Test
+    fun levelOrderSequence() =
+        assertContentEquals(listOf(1, 2, 3, 4, 5, 6), sample().levelOrderSequence().map { it.value }.toList())
+
+    @Test
+    fun asSequenceDefaultsToPreOrder() =
+        assertContentEquals(listOf(1, 2, 4, 5, 3, 6), sample().asSequence().map { it.value }.toList())
+
+    @Test
+    fun asSequenceHonorsExplicitOrder() =
+        assertContentEquals(
+            listOf(1, 2, 3, 4, 5, 6),
+            sample().asSequence(TreeNodeIterators.LevelOrder).map { it.value }.toList(),
+        )
+
+    @Test
+    fun sequenceShortCircuitsLazily() =
+        assertEquals(4, sample().preOrderSequence().map { it.value }.first { it == 4 })
+}

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeStackSafetyTest.kt

@@ -0,0 +1,49 @@
+package com.github.adriankuta.datastructure.tree
+
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+/**
+ * A deep, degenerate (linear) tree must not overflow the call stack. These tests build a chain
+ * thousands of nodes deep — recursive implementations of [TreeNode.height], [TreeNode.nodeCount]
+ * and the post-order iterator blow the stack here, so they pin the iterative rewrites.
+ */
+class TreeNodeStackSafetyTest {
+
+    private val depth = 50_000
+
+    private fun deepChain(): TreeNode<Int> {
+        val root = TreeNode(0)
+        var current = root
+        for (i in 1..depth) {
+            val child = TreeNode(i)
+            current.addChild(child)
+            current = child
+        }
+        return root
+    }
+
+    @Test
+    fun heightDoesNotOverflowOnDeepTree() {
+        assertEquals(depth, deepChain().height())
+    }
+
+    @Test
+    fun nodeCountDoesNotOverflowOnDeepTree() {
+        // nodeCount() excludes the root, so a chain of `depth` extra nodes counts as `depth`.
+        assertEquals(depth, deepChain().nodeCount())
+    }
+
+    @Test
+    fun postOrderIterationDoesNotOverflowOnDeepTree() {
+        val tree = deepChain().apply { treeIterator = TreeNodeIterators.PostOrder }
+        assertEquals(depth + 1, tree.toList().size)
+    }
+
+    @Test
+    fun preOrderIterationDoesNotOverflowOnDeepTree() {
+        val tree = deepChain().apply { treeIterator = TreeNodeIterators.PreOrder }
+        assertEquals(depth + 1, tree.toList().size)
+    }
+}

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeTest.kt

@@ -4,7 +4,9 @@ import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
 import kotlin.test.Test
 import kotlin.test.assertContentEquals
 import kotlin.test.assertEquals
+import kotlin.test.assertFalse
 import kotlin.test.assertNull
+import kotlin.test.assertTrue
 
 class TreeNodeTest {
 
@@ -62,6 +64,18 @@ class TreeNodeTest {
         )
     }
 
+    @Test
+    fun removeChildReturnsTrueWhenPresentFalseOtherwise() {
+        val root = TreeNode("Root")
+        val child = TreeNode("Child")
+        root.addChild(child)
+
+        assertTrue(root.removeChild(child), "Removing a present child returns true")
+        assertFalse(root.removeChild(child), "Removing an already-removed child returns false")
+        assertNull(child.parent, "Removed child is detached from its parent")
+        assertEquals(emptyList(), root.children)
+    }
+
     @Test
     fun clearTest() {
         val root = TreeNode("Root")

src/commonTest/kotlin/com.github.adriankuta/datastructure.tree/TreeNodeUtilitiesTest.kt

@@ -0,0 +1,54 @@
+package com.github.adriankuta.datastructure.tree
+
+import com.github.adriankuta.datastructure.tree.exceptions.TreeNodeException
+import kotlin.test.Test
+import kotlin.test.assertContentEquals
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+
+class TreeNodeUtilitiesTest {
+
+    private val root = TreeNode(1)
+    private val a = TreeNode(2)
+    private val b = TreeNode(3)
+
+    init {
+        root.addChild(a)
+        a.addChild(b)
+    }
+
+    @Test
+    fun nodeCountCountsDescendantsExcludingRoot() {
+        assertEquals(0, TreeNode("solo").nodeCount())
+        assertEquals(2, root.nodeCount())
+    }
+
+    @Test
+    fun heightIsLongestEdgePathToLeaf() {
+        assertEquals(0, TreeNode("solo").height())
+        assertEquals(2, root.height())
+        assertEquals(1, a.height())
+    }
+
+    @Test
+    fun depthIsDistanceToRoot() {
+        assertEquals(0, root.depth())
+        assertEquals(1, a.depth())
+        assertEquals(2, b.depth())
+    }
+
+    @Test
+    fun pathReturnsDescendantToReceiverChain() {
+        assertContentEquals(listOf(b, a, root), root.path(b))
+    }
+
+    @Test
+    fun pathThrowsWhenNotADescendant() {
+        assertFailsWith<TreeNodeException> { root.path(TreeNode(99)) }
+    }
+
+    @Test
+    fun pathThrowsWhenDescendantIsRootItself() {
+        assertFailsWith<TreeNodeException> { root.path(root) }
+    }
+}

src/jvmMain/kotlin/Example.ws.kts

@@ -1,14 +0,0 @@
-import com.github.adriankuta.datastructure.tree.tree
-
-val root =
-    tree("World") {
-        child("North America") {
-            child("USA")
-        }
-        child("Europe") {
-            child("Poland")
-            child("Germany")
-        }
-    }
-
-print(root.prettyString())

tree-structure-coroutines/api/tree-structure-coroutines.api

@@ -0,0 +1,8 @@
+public final class com/github/adriankuta/datastructure/tree/coroutines/TreeNodeFlowExtKt {
+	public static final fun asFlow (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;)Lkotlinx/coroutines/flow/Flow;
+	public static synthetic fun asFlow$default (Lcom/github/adriankuta/datastructure/tree/TreeNode;Lcom/github/adriankuta/datastructure/tree/iterators/TreeNodeIterators;ILjava/lang/Object;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun levelOrderFlow (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun postOrderFlow (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlinx/coroutines/flow/Flow;
+	public static final fun preOrderFlow (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lkotlinx/coroutines/flow/Flow;
+}
+

tree-structure-coroutines/build.gradle.kts

@@ -0,0 +1,88 @@
+import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
+
+plugins {
+    alias(libs.plugins.kotlinMultiplatform)
+    alias(libs.plugins.dokka)
+    alias(libs.plugins.mavenPublish)
+    signing
+}
+
+group = "com.github.adriankuta"
+version = rootProject.version
+
+mavenPublishing {
+    publishToMavenCentral(automaticRelease = false)
+    signAllPublications()
+
+    coordinates("com.github.adriankuta", "tree-structure-coroutines", version.toString())
+
+    pom {
+        name.set("Tree Data Structure — coroutines")
+        description.set("kotlinx.coroutines Flow traversal for the tree-structure library.")
+        url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+        licenses {
+            license {
+                name.set("MIT License")
+                url.set("https://opensource.org/licenses/MIT")
+                distribution.set("repo")
+            }
+        }
+        developers {
+            developer {
+                id.set("AdrianKuta")
+                name.set("Adrian Kuta")
+                email.set("adrian.kuta93@gmail.com")
+            }
+        }
+        scm {
+            url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+            connection.set("scm:git:https://github.com/AdrianKuta/Tree-Data-Structure.git")
+            developerConnection.set("scm:git:ssh://git@github.com/AdrianKuta/Tree-Data-Structure.git")
+        }
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+kotlin {
+    jvmToolchain(21)
+
+    jvm()
+
+    js(IR) {
+        browser()
+        nodejs()
+    }
+
+    @OptIn(ExperimentalWasmDsl::class)
+    wasmJs {
+        browser()
+        nodejs()
+    }
+
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+
+    val hostOs = System.getProperty("os.name")
+    val isMingwX64 = hostOs.startsWith("Windows")
+    when {
+        hostOs == "Mac OS X" -> macosX64("native")
+        hostOs == "Linux" -> linuxX64("native")
+        isMingwX64 -> mingwX64("native")
+        else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
+    }
+
+    sourceSets {
+        commonMain.dependencies {
+            api(project(":"))
+            api(libs.kotlinx.coroutines.core)
+        }
+        commonTest.dependencies {
+            implementation(kotlin("test"))
+            implementation(libs.kotlinx.coroutines.test)
+        }
+    }
+}

tree-structure-coroutines/src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/coroutines/TreeNodeFlowExt.kt

@@ -0,0 +1,24 @@
+package com.github.adriankuta.datastructure.tree.coroutines
+
+import com.github.adriankuta.datastructure.tree.TreeNode
+import com.github.adriankuta.datastructure.tree.asSequence
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import kotlinx.coroutines.flow.Flow
+import kotlinx.coroutines.flow.asFlow
+
+/**
+ * Emits this node and all of its descendants as a cold [Flow], traversed in the given [order].
+ * Useful for plugging tree traversal into coroutine/Flow pipelines (e.g. in a ViewModel).
+ */
+public fun <T> TreeNode<T>.asFlow(
+    order: TreeNodeIterators = TreeNodeIterators.PreOrder,
+): Flow<TreeNode<T>> = asSequence(order).asFlow()
+
+/** Pre-order traversal as a cold [Flow]. */
+public fun <T> TreeNode<T>.preOrderFlow(): Flow<TreeNode<T>> = asFlow(TreeNodeIterators.PreOrder)
+
+/** Post-order traversal as a cold [Flow]. */
+public fun <T> TreeNode<T>.postOrderFlow(): Flow<TreeNode<T>> = asFlow(TreeNodeIterators.PostOrder)
+
+/** Level-order (breadth-first) traversal as a cold [Flow]. */
+public fun <T> TreeNode<T>.levelOrderFlow(): Flow<TreeNode<T>> = asFlow(TreeNodeIterators.LevelOrder)

tree-structure-coroutines/src/commonTest/kotlin/com.github.adriankuta/datastructure/tree/coroutines/TreeNodeFlowTest.kt

@@ -0,0 +1,35 @@
+package com.github.adriankuta.datastructure.tree.coroutines
+
+import com.github.adriankuta.datastructure.tree.iterators.TreeNodeIterators
+import com.github.adriankuta.datastructure.tree.tree
+import kotlinx.coroutines.flow.map
+import kotlinx.coroutines.flow.toList
+import kotlinx.coroutines.test.runTest
+import kotlin.test.Test
+import kotlin.test.assertEquals
+
+class TreeNodeFlowTest {
+
+    private fun sample() = tree(1) {
+        child(2) {
+            child(4)
+            child(5)
+        }
+        child(3) {
+            child(6)
+        }
+    }
+
+    @Test
+    fun preOrderFlowEmitsInPreOrder() = runTest {
+        assertEquals(listOf(1, 2, 4, 5, 3, 6), sample().preOrderFlow().map { it.value }.toList())
+    }
+
+    @Test
+    fun levelOrderFlowEmitsInLevelOrder() = runTest {
+        assertEquals(
+            listOf(1, 2, 3, 4, 5, 6),
+            sample().asFlow(TreeNodeIterators.LevelOrder).map { it.value }.toList(),
+        )
+    }
+}

tree-structure-serialization/api/tree-structure-serialization.api

@@ -0,0 +1,35 @@
+public final class com/github/adriankuta/datastructure/tree/serialization/TreeNodeDto {
+	public static final field Companion Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto$Companion;
+	public fun <init> (Ljava/lang/Object;Ljava/util/List;)V
+	public synthetic fun <init> (Ljava/lang/Object;Ljava/util/List;ILkotlin/jvm/internal/DefaultConstructorMarker;)V
+	public final fun component1 ()Ljava/lang/Object;
+	public final fun component2 ()Ljava/util/List;
+	public final fun copy (Ljava/lang/Object;Ljava/util/List;)Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;
+	public static synthetic fun copy$default (Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;Ljava/lang/Object;Ljava/util/List;ILjava/lang/Object;)Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;
+	public fun equals (Ljava/lang/Object;)Z
+	public final fun getChildren ()Ljava/util/List;
+	public final fun getValue ()Ljava/lang/Object;
+	public fun hashCode ()I
+	public fun toString ()Ljava/lang/String;
+}
+
+public synthetic class com/github/adriankuta/datastructure/tree/serialization/TreeNodeDto$$serializer : kotlinx/serialization/internal/GeneratedSerializer {
+	public fun <init> (Lkotlinx/serialization/KSerializer;)V
+	public final fun childSerializers ()[Lkotlinx/serialization/KSerializer;
+	public final fun deserialize (Lkotlinx/serialization/encoding/Decoder;)Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;
+	public synthetic fun deserialize (Lkotlinx/serialization/encoding/Decoder;)Ljava/lang/Object;
+	public final fun getDescriptor ()Lkotlinx/serialization/descriptors/SerialDescriptor;
+	public final fun serialize (Lkotlinx/serialization/encoding/Encoder;Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;)V
+	public synthetic fun serialize (Lkotlinx/serialization/encoding/Encoder;Ljava/lang/Object;)V
+	public final fun typeParametersSerializers ()[Lkotlinx/serialization/KSerializer;
+}
+
+public final class com/github/adriankuta/datastructure/tree/serialization/TreeNodeDto$Companion {
+	public final fun serializer (Lkotlinx/serialization/KSerializer;)Lkotlinx/serialization/KSerializer;
+}
+
+public final class com/github/adriankuta/datastructure/tree/serialization/TreeNodeDtoKt {
+	public static final fun toDto (Lcom/github/adriankuta/datastructure/tree/TreeNode;)Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;
+	public static final fun toTreeNode (Lcom/github/adriankuta/datastructure/tree/serialization/TreeNodeDto;)Lcom/github/adriankuta/datastructure/tree/TreeNode;
+}
+

tree-structure-serialization/build.gradle.kts

@@ -0,0 +1,88 @@
+import org.jetbrains.kotlin.gradle.ExperimentalWasmDsl
+
+plugins {
+    alias(libs.plugins.kotlinMultiplatform)
+    alias(libs.plugins.kotlinSerialization)
+    alias(libs.plugins.dokka)
+    alias(libs.plugins.mavenPublish)
+    signing
+}
+
+group = "com.github.adriankuta"
+version = rootProject.version
+
+mavenPublishing {
+    publishToMavenCentral(automaticRelease = false)
+    signAllPublications()
+
+    coordinates("com.github.adriankuta", "tree-structure-serialization", version.toString())
+
+    pom {
+        name.set("Tree Data Structure — kotlinx.serialization")
+        description.set("kotlinx.serialization support (TreeNodeDto round-trip) for the tree-structure library.")
+        url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+        licenses {
+            license {
+                name.set("MIT License")
+                url.set("https://opensource.org/licenses/MIT")
+                distribution.set("repo")
+            }
+        }
+        developers {
+            developer {
+                id.set("AdrianKuta")
+                name.set("Adrian Kuta")
+                email.set("adrian.kuta93@gmail.com")
+            }
+        }
+        scm {
+            url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+            connection.set("scm:git:https://github.com/AdrianKuta/Tree-Data-Structure.git")
+            developerConnection.set("scm:git:ssh://git@github.com/AdrianKuta/Tree-Data-Structure.git")
+        }
+    }
+}
+
+repositories {
+    mavenCentral()
+}
+
+kotlin {
+    jvmToolchain(21)
+
+    jvm()
+
+    js(IR) {
+        browser()
+        nodejs()
+    }
+
+    @OptIn(ExperimentalWasmDsl::class)
+    wasmJs {
+        browser()
+        nodejs()
+    }
+
+    iosX64()
+    iosArm64()
+    iosSimulatorArm64()
+
+    val hostOs = System.getProperty("os.name")
+    val isMingwX64 = hostOs.startsWith("Windows")
+    when {
+        hostOs == "Mac OS X" -> macosX64("native")
+        hostOs == "Linux" -> linuxX64("native")
+        isMingwX64 -> mingwX64("native")
+        else -> throw GradleException("Host OS is not supported in Kotlin/Native.")
+    }
+
+    sourceSets {
+        commonMain.dependencies {
+            api(project(":"))
+            api(libs.kotlinx.serialization.json)
+        }
+        commonTest.dependencies {
+            implementation(kotlin("test"))
+        }
+    }
+}

tree-structure-serialization/src/commonMain/kotlin/com.github.adriankuta/datastructure/tree/serialization/TreeNodeDto.kt

@@ -0,0 +1,30 @@
+package com.github.adriankuta.datastructure.tree.serialization
+
+import com.github.adriankuta.datastructure.tree.TreeNode
+import kotlinx.serialization.Serializable
+
+/**
+ * A serializable, acyclic view of a [TreeNode] subtree. [TreeNode] itself holds a back-reference to
+ * its parent (a cycle), so it cannot be `@Serializable` directly — convert to/from this DTO instead.
+ *
+ * ```
+ * val json = Json.encodeToString(tree.toDto())
+ * val restored = Json.decodeFromString<TreeNodeDto<String>>(json).toTreeNode()
+ * ```
+ */
+@Serializable
+public data class TreeNodeDto<T>(
+    val value: T,
+    val children: List<TreeNodeDto<T>> = emptyList(),
+)
+
+/** Converts this subtree into a serializable [TreeNodeDto], preserving values and shape. */
+public fun <T> TreeNode<T>.toDto(): TreeNodeDto<T> =
+    TreeNodeDto(value, children.map { it.toDto() })
+
+/** Rebuilds a mutable [TreeNode] tree from this DTO. */
+public fun <T> TreeNodeDto<T>.toTreeNode(): TreeNode<T> {
+    val node = TreeNode(value)
+    children.forEach { node.addChild(it.toTreeNode()) }
+    return node
+}

tree-structure-serialization/src/commonTest/kotlin/com.github.adriankuta/datastructure/tree/serialization/TreeNodeSerializationTest.kt

@@ -0,0 +1,40 @@
+package com.github.adriankuta.datastructure.tree.serialization
+
+import com.github.adriankuta.datastructure.tree.structurallyEquals
+import com.github.adriankuta.datastructure.tree.tree
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertTrue
+
+class TreeNodeSerializationTest {
+
+    @Test
+    fun roundTripsThroughJson() {
+        val original = tree("World") {
+            child("North America") { child("USA") }
+            child("Europe") {
+                child("Poland")
+                child("Germany")
+            }
+        }
+
+        val json = Json.encodeToString(original.toDto())
+        val restored = Json.decodeFromString<TreeNodeDto<String>>(json).toTreeNode()
+
+        assertTrue(original.structurallyEquals(restored))
+    }
+
+    @Test
+    fun dtoMirrorsTreeShape() {
+        val dto = tree(1) {
+            child(2)
+            child(3) { child(4) }
+        }.toDto()
+
+        assertEquals(1, dto.value)
+        assertEquals(2, dto.children.size)
+        assertEquals(4, dto.children[1].children[0].value)
+    }
+}