Bump version to 3.1.2

* Refactor: Modernize build and publishing workflow

- Upgraded Kotlin from 1.7.20 to 1.9.20.
- Upgraded JDK from 11 to 21 across all GitHub Actions workflows.
- Replaced the legacy `maven-publish` plugin with `com.vanniktech.maven.publish` for simplified publishing to Maven Central.
- Removed the `publishSnapshot.yml` workflow, as snapshot publishing is now managed by the new plugin.
- Updated `publishRelease.yml` to use the `publishToMavenCentral` task and new secrets (`MAVEN_CENTRAL_USERNAME`, `MAVEN_CENTRAL_PASSWORD`).
- Simplified `build.gradle.kts` by removing manual publishing and signing logic.
- Set the JVM target to "21".
- Bumped the project version to `3.1.1`.
- Removed `js` targets and related configurations.
- Added a new code style configuration file for the project (`.idea/codeStyles/Project.xml`).

* fix: Add JavaScript targets

- Added JS (IR) targets (`browser` and `nodejs`) to the Kotlin Multiplatform configuration for publishing.

* Improve README and document new publishing workflow

- Expanded the project description to highlight key features like Kotlin Multiplatform support, traversal iterators, DSL, and utility functions.
- Added a new "Installation" section with instructions for Gradle (Kotlin/Groovy) and Maven.
- Added a "Traversal and utilities" section to demonstrate usage of iterators and helper functions.
- Replaced the old publishing documentation with updated instructions for publishing to Maven Central via the Central Portal.
- Detailed the two publishing methods: automatically via GitHub Actions on release and manually via local Gradle commands.
- Clarified required secrets and environment variables for the new publishing process.

.github/workflows/publishRelease.yml

@@ -19,20 +19,18 @@ jobs:
     steps:
       - name: Check out code
         uses: actions/checkout@v2
-      - name: Set up JDK 11
-        uses: actions/setup-java@v2
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
         with:
-          distribution: adopt
-          java-version: 11
+          distribution: temurin
+          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 }}
-          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 }}
+          ORG_GRADLE_PROJECT_mavenCentralUsername: ${{ secrets.MAVEN_CENTRAL_USERNAME }}
+          ORG_GRADLE_PROJECT_mavenCentralPassword: ${{ secrets.MAVEN_CENTRAL_PASSWORD }}
+          ORG_GRADLE_PROJECT_signingInMemoryKey: ${{ secrets.SIGNING_KEY }}
+          ORG_GRADLE_PROJECT_signingInMemoryKeyPassword: ${{ secrets.SIGNING_PASSWORD }}
           SNAPSHOT: false

.github/workflows/publishSnapshot.yml

@@ -1,35 +0,0 @@
-name: Publish Snapshot
-
-on:
-  push:
-    branches: [master]
-
-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

@@ -12,12 +12,12 @@ jobs:
     steps:
       - name: Check out code
         uses: actions/checkout@v2
-      - name: Set up JDK 11
-        uses: actions/setup-java@v2
+      - name: Set up JDK 21
+        uses: actions/setup-java@v4
         with:
-          distribution: adopt
-          java-version: 11
+          distribution: temurin
+          java-version: '21'
 
         # Builds the release artifacts of the library
       - name: Test
-        run: ./gradlew test
+        run: ./gradlew cleanJvmTest jvmTest

.idea/codeStyles/Project.xml

@@ -1,5 +1,40 @@
 <component name="ProjectCodeStyleConfiguration">
   <code_scheme name="Project" version="173">
+    <JavaCodeStyleSettings>
+      <option name="IMPORT_LAYOUT_TABLE">
+        <value>
+          <package name="" withSubpackages="true" static="false" module="true" />
+          <package name="android" withSubpackages="true" static="true" />
+          <package name="androidx" withSubpackages="true" static="true" />
+          <package name="com" withSubpackages="true" static="true" />
+          <package name="junit" withSubpackages="true" static="true" />
+          <package name="net" withSubpackages="true" static="true" />
+          <package name="org" withSubpackages="true" static="true" />
+          <package name="java" withSubpackages="true" static="true" />
+          <package name="javax" withSubpackages="true" static="true" />
+          <package name="" withSubpackages="true" static="true" />
+          <emptyLine />
+          <package name="android" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="androidx" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="com" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="junit" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="net" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="org" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="java" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="javax" withSubpackages="true" static="false" />
+          <emptyLine />
+          <package name="" withSubpackages="true" static="false" />
+          <emptyLine />
+        </value>
+      </option>
+    </JavaCodeStyleSettings>
     <JetCodeStyleSettings>
       <option name="CODE_STYLE_DEFAULTS" value="KOTLIN_OFFICIAL" />
     </JetCodeStyleSettings>

.idea/studiobot.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="StudioBotProjectSettings">
+    <option name="shareContext" value="OptedIn" />
+  </component>
+</project>

README.md

@@ -1,9 +1,40 @@
 # 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, iOS, and Native host)
+- Pre-order, Post-order, and Level-order iteration
+- 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:3.1.1") // see badge above for the latest version
+}
+```
+
+Gradle (Groovy):
+```groovy
+dependencies {
+    implementation "com.github.adriankuta:tree-structure:3.1.1" // see badge above for the latest
+}
+```
+
+Maven:
+```xml
+<dependency>
+  <groupId>com.github.adriankuta</groupId>
+  <artifactId>tree-structure</artifactId>
+  <version>3.1.1</version>
+</dependency>
+```
 
 ## Usage
 
@@ -25,19 +56,15 @@ europe.addChild(france)
 println(root.prettyString())
 ```
 
-**Pretty Kotlin**
-
+**Pretty Kotlin (DSL)**
 ```kotlin
-val root =
-    tree("World") {
-        child("North America") {
-            child("USA")
-        }
+val root = tree("World") {
+    child("North America") { child("USA") }
     child("Europe") {
         child("Poland")
         child("Germany")
     }
-    }
+}
 ```
 
 **Java**
@@ -58,8 +85,7 @@ europe.addChild(france);
 System.out.println(root.prettyString());
 ```
 
-*Output:*
-
+Output:
 ```
 World
 ├── North America
@@ -69,10 +95,58 @@ 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)
 
-    implementation "com.github.adriankuta:tree-structure:$latest_versions"
+// 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
+```
+
+## 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.
 
 ## License
 
@@ -97,3 +171,5 @@ 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.
+
+---

build.gradle.kts

@@ -1,129 +1,88 @@
 import org.jetbrains.kotlin.konan.properties.Properties
 
 plugins {
-    kotlin("multiplatform") version "1.7.20"
-    id("org.jetbrains.dokka") version "1.7.20"
-    id("maven-publish")
+    kotlin("multiplatform") version "1.9.20"
+    id("org.jetbrains.dokka") version "1.9.20"
+    id("com.vanniktech.maven.publish") version "0.34.0"
     signing
 }
 
 val PUBLISH_GROUP_ID = "com.github.adriankuta"
-val PUBLISH_ARTIFACT_ID = "tree-structure"
-val PUBLISH_VERSION = "3.1.0"
+val PUBLISH_ARTIFACT_ID = "tree-structure"    // base artifact; KMP will add -jvm, -ios*, etc.
+val PUBLISH_VERSION = "3.1.2"
 
-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) {
-    dependsOn(dokkaHtml)
-    archiveClassifier.set("javadoc")
-    from(dokkaHtml.outputDirectory)
-}
+    coordinates(PUBLISH_GROUP_ID, PUBLISH_ARTIFACT_ID, version.toString())
 
-publishing {
-    publications {
-
-        withType<MavenPublication> {
-            artifact(javadocJar)
     pom {
         name.set("Tree Data Structure")
         description.set("Simple implementation to store object in tree structure.")
         url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
+
         licenses {
             license {
                 name.set("MIT License")
-                        url.set("https://www.mit.edu/~amini/LICENSE.md")
+                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 {
-                    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")
-                }
-            }
-        }
-    }
-
-    repositories {
-        maven {
-            name = "Sonatype"
-            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
-            }
+            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)
-}
+// No legacy publishing {} block or s01 repos — Central Portal handles it.
 
 repositories {
     mavenCentral()
 }
 
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+}
 kotlin {
+    jvmToolchain(21);
     jvm {
         compilations.all {
-            kotlinOptions.jvmTarget = "1.8"
-        }
-        withJava()
-        testRuns["test"].executionTask.configure {
-            useJUnitPlatform()
-        }
-    }
-    js(BOTH) {
-        browser {
-            commonWebpackConfig {
-                cssSupport.enabled = true
+            kotlinOptions {
+                jvmTarget = "21"   // <- was "1.8"
             }
         }
     }
 
-    // Add iOS targets
+    // JS targets (IR) for publishing
+    js(IR) {
+        browser()
+        nodejs()
+    }
+
+    // iOS targets
     iosX64()
     iosArm64()
     iosSimulatorArm64()
 
+    // Native host target
     val hostOs = System.getProperty("os.name")
     val isMingwX64 = hostOs.startsWith("Windows")
     val nativeTarget = when {
@@ -135,16 +94,8 @@ kotlin {
 
     sourceSets {
         val commonMain by getting
-        val commonTest by getting {
-            dependencies {
-                implementation(kotlin("test"))
-            }
-        }
-        val jvmMain by getting {
-            dependencies {
-                implementation(kotlin("script-runtime"))
-            }
-        }
+        val commonTest by getting { 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
@@ -152,12 +103,8 @@ kotlin {
         val nativeTest by getting
 
         // Shared iOS source sets
-        val iosMain by creating {
-            dependsOn(commonMain)
-        }
-        val iosTest by creating {
-            dependsOn(commonTest)
-        }
+        val iosMain by creating { dependsOn(commonMain) }
+        val iosTest by creating { dependsOn(commonTest) }
         val iosX64Main by getting { dependsOn(iosMain) }
         val iosArm64Main by getting { dependsOn(iosMain) }
         val iosSimulatorArm64Main by getting { dependsOn(iosMain) }