26-add-ios-target (#28)

* 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
+      - 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]
-
-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
+      - 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 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
 
@@ -25,14 +56,10 @@ 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("USA")
-        }
     child("Europe") {
         child("Poland")
         child("Germany")
@@ -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
 
@@ -99,22 +173,3 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 SOFTWARE.
 
 ---
-
-## Publishing (Maven Central migration)
-
-This project is configured to publish via Sonatype's s01.oss.sonatype.org (Nexus) which is compatible with the new Central (central.sonatype.com). The old oss.sonatype.org host is no longer used.
-
-Environment variables supported by the build:
-- CENTRAL_USERNAME / CENTRAL_PASSWORD — Central Portal user/token (preferred)
-- OSSRH_USERNAME / OSSRH_PASSWORD — legacy credentials (fallback)
-- SIGNING_KEY_ID / SIGNING_KEY / SIGNING_PASSWORD — PGP signing (ASCII-armored key)
-- SNAPSHOT — set to true to append -SNAPSHOT to version
-
-Gradle tasks:
-- Publish all publications to Sonatype: `./gradlew publishAllPublicationsToSonatypeS01Repository`
-- Or, standard publish (selects snapshots vs releases by version): `./gradlew publish`
-
-Notes:
-- Releases are uploaded to: https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/
-- Snapshots are uploaded to: https://s01.oss.sonatype.org/content/repositories/snapshots/
-- Staging/release close and promote are handled by Sonatype. If you use CI, set the env vars in your secrets.

build.gradle.kts

@@ -1,147 +1,88 @@
 import org.jetbrains.kotlin.konan.properties.Properties
 
 plugins {
-    kotlin("multiplatform") version "1.7.20"
+    kotlin("multiplatform") version "1.9.20"
-    id("org.jetbrains.dokka") version "1.7.20"
+    id("org.jetbrains.dokka") version "1.9.20"
-    id("maven-publish")
+    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_ARTIFACT_ID = "tree-structure"    // base artifact; KMP will add -jvm, -ios*, etc.
-val PUBLISH_VERSION = "3.1.0"
+val PUBLISH_VERSION = "3.1.1"
 
-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 {
-    // Prefer Central Portal credentials via environment variables
-    project.ext["centralUsername"] = System.getenv("CENTRAL_USERNAME")
-    project.ext["centralPassword"] = System.getenv("CENTRAL_PASSWORD")
-    // Fallback legacy OSSRH credentials (still supported on s01)
-    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 {
-    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")
+            url.set("https://github.com/AdrianKuta/Tree-Data-Structure")
-                    developerConnection.set("scm:git:ssh://github.com/AdrianKuta/Tree-Data-Structure.git")
+            connection.set("scm:git:https://github.com/AdrianKuta/Tree-Data-Structure.git")
-                    url.set("https://github.com/AdrianKuta/Tree-Data-Structure/tree/master")
+            developerConnection.set("scm:git:ssh://git@github.com/AdrianKuta/Tree-Data-Structure.git")
-                }
         }
     }
 }
 
-    repositories {
+// No legacy publishing {} block or s01 repos — Central Portal handles it.
-        maven {
-            name = "SonatypeS01"
-            // s01 is the supported Nexus host for Central publishing via Maven-compatible uploads
-            val releasesRepoUrl = "https://s01.oss.sonatype.org/service/local/staging/deploy/maven2/"
-            val snapshotsRepoUrl = "https://s01.oss.sonatype.org/content/repositories/snapshots/"
-            url = uri(if (version.toString().endsWith("SNAPSHOT")) snapshotsRepoUrl else releasesRepoUrl)
-            credentials {
-                // Prefer Central Portal credentials when provided, fallback to legacy OSSRH credentials
-                val centralUsername: String? by project
-                val centralPassword: String? by project
-                val CENTRAL_USERNAME: String? by project
-                val CENTRAL_PASSWORD: String? by project
-                val ossrhUsername: String? by project
-                val ossrhPassword: String? by project
-                username = centralUsername
-                    ?: CENTRAL_USERNAME
-                    ?: ossrhUsername
-                    ?: System.getenv("CENTRAL_USERNAME")
-                    ?: System.getenv("OSSRH_USERNAME")
-                password = centralPassword
-                    ?: CENTRAL_PASSWORD
-                    ?: ossrhPassword
-                    ?: System.getenv("CENTRAL_PASSWORD")
-                    ?: System.getenv("OSSRH_PASSWORD")
-            }
-        }
-    }
-}
-
-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()
 }
 
+java {
+    toolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
+}
 kotlin {
+    jvmToolchain(21);
     jvm {
         compilations.all {
-            kotlinOptions.jvmTarget = "1.8"
+            kotlinOptions {
-        }
+                jvmTarget = "21"   // <- was "1.8"
-        withJava()
-        testRuns["test"].executionTask.configure {
-            useJUnitPlatform()
-        }
-    }
-    js(BOTH) {
-        browser {
-            commonWebpackConfig {
-                cssSupport.enabled = true
             }
         }
     }
 
-    // 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 {
@@ -153,16 +94,8 @@ kotlin {
 
     sourceSets {
         val commonMain by getting
-        val commonTest by getting {
+        val commonTest by getting { dependencies { implementation(kotlin("test")) } }
-            dependencies {
+        val jvmMain by getting { dependencies { implementation(kotlin("script-runtime")) } }
-                implementation(kotlin("test"))
-            }
-        }
-        val jvmMain by getting {
-            dependencies {
-                implementation(kotlin("script-runtime"))
-            }
-        }
         val jvmTest by getting
         val jsMain by getting
         val jsTest by getting
@@ -170,12 +103,8 @@ kotlin {
         val nativeTest by getting
 
         // Shared iOS source sets
-        val iosMain by creating {
+        val iosMain by creating { dependsOn(commonMain) }
-            dependsOn(commonMain)
+        val iosTest by creating { dependsOn(commonTest) }
-        }
-        val iosTest by creating {
-            dependsOn(commonTest)
-        }
         val iosX64Main by getting { dependsOn(iosMain) }
         val iosArm64Main by getting { dependsOn(iosMain) }
         val iosSimulatorArm64Main by getting { dependsOn(iosMain) }