First commit

.gitignore

@@ -0,0 +1,25 @@
+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+
+target/
+bin/
+
+*.iml
+.idea
+
+dependency-reduced-pom.xml

.mvn/wrapper/MavenWrapperDownloader.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2007-present the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+import java.net.*;
+import java.io.*;
+import java.nio.channels.*;
+import java.util.Properties;
+
+public class MavenWrapperDownloader {
+
+    private static final String WRAPPER_VERSION = "0.5.6";
+    /**
+     * Default URL to download the maven-wrapper.jar from, if no 'downloadUrl' is provided.
+     */
+    private static final String DEFAULT_DOWNLOAD_URL = "https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/"
+        + WRAPPER_VERSION + "/maven-wrapper-" + WRAPPER_VERSION + ".jar";
+
+    /**
+     * Path to the maven-wrapper.properties file, which might contain a downloadUrl property to
+     * use instead of the default one.
+     */
+    private static final String MAVEN_WRAPPER_PROPERTIES_PATH =
+            ".mvn/wrapper/maven-wrapper.properties";
+
+    /**
+     * Path where the maven-wrapper.jar will be saved to.
+     */
+    private static final String MAVEN_WRAPPER_JAR_PATH =
+            ".mvn/wrapper/maven-wrapper.jar";
+
+    /**
+     * Name of the property which should be used to override the default download url for the wrapper.
+     */
+    private static final String PROPERTY_NAME_WRAPPER_URL = "wrapperUrl";
+
+    public static void main(String args[]) {
+        System.out.println("- Downloader started");
+        File baseDirectory = new File(args[0]);
+        System.out.println("- Using base directory: " + baseDirectory.getAbsolutePath());
+
+        // If the maven-wrapper.properties exists, read it and check if it contains a custom
+        // wrapperUrl parameter.
+        File mavenWrapperPropertyFile = new File(baseDirectory, MAVEN_WRAPPER_PROPERTIES_PATH);
+        String url = DEFAULT_DOWNLOAD_URL;
+        if(mavenWrapperPropertyFile.exists()) {
+            FileInputStream mavenWrapperPropertyFileInputStream = null;
+            try {
+                mavenWrapperPropertyFileInputStream = new FileInputStream(mavenWrapperPropertyFile);
+                Properties mavenWrapperProperties = new Properties();
+                mavenWrapperProperties.load(mavenWrapperPropertyFileInputStream);
+                url = mavenWrapperProperties.getProperty(PROPERTY_NAME_WRAPPER_URL, url);
+            } catch (IOException e) {
+                System.out.println("- ERROR loading '" + MAVEN_WRAPPER_PROPERTIES_PATH + "'");
+            } finally {
+                try {
+                    if(mavenWrapperPropertyFileInputStream != null) {
+                        mavenWrapperPropertyFileInputStream.close();
+                    }
+                } catch (IOException e) {
+                    // Ignore ...
+                }
+            }
+        }
+        System.out.println("- Downloading from: " + url);
+
+        File outputFile = new File(baseDirectory.getAbsolutePath(), MAVEN_WRAPPER_JAR_PATH);
+        if(!outputFile.getParentFile().exists()) {
+            if(!outputFile.getParentFile().mkdirs()) {
+                System.out.println(
+                        "- ERROR creating output directory '" + outputFile.getParentFile().getAbsolutePath() + "'");
+            }
+        }
+        System.out.println("- Downloading to: " + outputFile.getAbsolutePath());
+        try {
+            downloadFileFromURL(url, outputFile);
+            System.out.println("Done");
+            System.exit(0);
+        } catch (Throwable e) {
+            System.out.println("- Error downloading");
+            e.printStackTrace();
+            System.exit(1);
+        }
+    }
+
+    private static void downloadFileFromURL(String urlString, File destination) throws Exception {
+        if (System.getenv("MVNW_USERNAME") != null && System.getenv("MVNW_PASSWORD") != null) {
+            String username = System.getenv("MVNW_USERNAME");
+            char[] password = System.getenv("MVNW_PASSWORD").toCharArray();
+            Authenticator.setDefault(new Authenticator() {
+                @Override
+                protected PasswordAuthentication getPasswordAuthentication() {
+                    return new PasswordAuthentication(username, password);
+                }
+            });
+        }
+        URL website = new URL(urlString);
+        ReadableByteChannel rbc;
+        rbc = Channels.newChannel(website.openStream());
+        FileOutputStream fos = new FileOutputStream(destination);
+        fos.getChannel().transferFrom(rbc, 0, Long.MAX_VALUE);
+        fos.close();
+        rbc.close();
+    }
+
+}

.mvn/wrapper/maven-wrapper.properties

@@ -0,0 +1,2 @@
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.3/apache-maven-3.6.3-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar

mvnw

@@ -0,0 +1,310 @@
+#!/bin/sh
+# ----------------------------------------------------------------------------
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+# ----------------------------------------------------------------------------
+
+# ----------------------------------------------------------------------------
+# Maven Start Up Batch script
+#
+# Required ENV vars:
+# ------------------
+#   JAVA_HOME - location of a JDK home dir
+#
+# Optional ENV vars
+# -----------------
+#   M2_HOME - location of maven2's installed home dir
+#   MAVEN_OPTS - parameters passed to the Java VM when running Maven
+#     e.g. to debug Maven itself, use
+#       set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+#   MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+# ----------------------------------------------------------------------------
+
+if [ -z "$MAVEN_SKIP_RC" ] ; then
+
+  if [ -f /etc/mavenrc ] ; then
+    . /etc/mavenrc
+  fi
+
+  if [ -f "$HOME/.mavenrc" ] ; then
+    . "$HOME/.mavenrc"
+  fi
+
+fi
+
+# OS specific support.  $var _must_ be set to either true or false.
+cygwin=false;
+darwin=false;
+mingw=false
+case "`uname`" in
+  CYGWIN*) cygwin=true ;;
+  MINGW*) mingw=true;;
+  Darwin*) darwin=true
+    # Use /usr/libexec/java_home if available, otherwise fall back to /Library/Java/Home
+    # See https://developer.apple.com/library/mac/qa/qa1170/_index.html
+    if [ -z "$JAVA_HOME" ]; then
+      if [ -x "/usr/libexec/java_home" ]; then
+        export JAVA_HOME="`/usr/libexec/java_home`"
+      else
+        export JAVA_HOME="/Library/Java/Home"
+      fi
+    fi
+    ;;
+esac
+
+if [ -z "$JAVA_HOME" ] ; then
+  if [ -r /etc/gentoo-release ] ; then
+    JAVA_HOME=`java-config --jre-home`
+  fi
+fi
+
+if [ -z "$M2_HOME" ] ; then
+  ## resolve links - $0 may be a link to maven's home
+  PRG="$0"
+
+  # need this for relative symlinks
+  while [ -h "$PRG" ] ; do
+    ls=`ls -ld "$PRG"`
+    link=`expr "$ls" : '.*-> \(.*\)$'`
+    if expr "$link" : '/.*' > /dev/null; then
+      PRG="$link"
+    else
+      PRG="`dirname "$PRG"`/$link"
+    fi
+  done
+
+  saveddir=`pwd`
+
+  M2_HOME=`dirname "$PRG"`/..
+
+  # make it fully qualified
+  M2_HOME=`cd "$M2_HOME" && pwd`
+
+  cd "$saveddir"
+  # echo Using m2 at $M2_HOME
+fi
+
+# For Cygwin, ensure paths are in UNIX format before anything is touched
+if $cygwin ; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME=`cygpath --unix "$M2_HOME"`
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=`cygpath --unix "$JAVA_HOME"`
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=`cygpath --path --unix "$CLASSPATH"`
+fi
+
+# For Mingw, ensure paths are in UNIX format before anything is touched
+if $mingw ; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME="`(cd "$M2_HOME"; pwd)`"
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME="`(cd "$JAVA_HOME"; pwd)`"
+fi
+
+if [ -z "$JAVA_HOME" ]; then
+  javaExecutable="`which javac`"
+  if [ -n "$javaExecutable" ] && ! [ "`expr \"$javaExecutable\" : '\([^ ]*\)'`" = "no" ]; then
+    # readlink(1) is not available as standard on Solaris 10.
+    readLink=`which readlink`
+    if [ ! `expr "$readLink" : '\([^ ]*\)'` = "no" ]; then
+      if $darwin ; then
+        javaHome="`dirname \"$javaExecutable\"`"
+        javaExecutable="`cd \"$javaHome\" && pwd -P`/javac"
+      else
+        javaExecutable="`readlink -f \"$javaExecutable\"`"
+      fi
+      javaHome="`dirname \"$javaExecutable\"`"
+      javaHome=`expr "$javaHome" : '\(.*\)/bin'`
+      JAVA_HOME="$javaHome"
+      export JAVA_HOME
+    fi
+  fi
+fi
+
+if [ -z "$JAVACMD" ] ; then
+  if [ -n "$JAVA_HOME"  ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+      # IBM's JDK on AIX uses strange locations for the executables
+      JAVACMD="$JAVA_HOME/jre/sh/java"
+    else
+      JAVACMD="$JAVA_HOME/bin/java"
+    fi
+  else
+    JAVACMD="`which java`"
+  fi
+fi
+
+if [ ! -x "$JAVACMD" ] ; then
+  echo "Error: JAVA_HOME is not defined correctly." >&2
+  echo "  We cannot execute $JAVACMD" >&2
+  exit 1
+fi
+
+if [ -z "$JAVA_HOME" ] ; then
+  echo "Warning: JAVA_HOME environment variable is not set."
+fi
+
+CLASSWORLDS_LAUNCHER=org.codehaus.plexus.classworlds.launcher.Launcher
+
+# traverses directory structure from process work directory to filesystem root
+# first directory with .mvn subdirectory is considered project base directory
+find_maven_basedir() {
+
+  if [ -z "$1" ]
+  then
+    echo "Path not specified to find_maven_basedir"
+    return 1
+  fi
+
+  basedir="$1"
+  wdir="$1"
+  while [ "$wdir" != '/' ] ; do
+    if [ -d "$wdir"/.mvn ] ; then
+      basedir=$wdir
+      break
+    fi
+    # workaround for JBEAP-8937 (on Solaris 10/Sparc)
+    if [ -d "${wdir}" ]; then
+      wdir=`cd "$wdir/.."; pwd`
+    fi
+    # end of workaround
+  done
+  echo "${basedir}"
+}
+
+# concatenates all lines of a file
+concat_lines() {
+  if [ -f "$1" ]; then
+    echo "$(tr -s '\n' ' ' < "$1")"
+  fi
+}
+
+BASE_DIR=`find_maven_basedir "$(pwd)"`
+if [ -z "$BASE_DIR" ]; then
+  exit 1;
+fi
+
+##########################################################################################
+# Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+# This allows using the maven wrapper in projects that prohibit checking in binary data.
+##########################################################################################
+if [ -r "$BASE_DIR/.mvn/wrapper/maven-wrapper.jar" ]; then
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Found .mvn/wrapper/maven-wrapper.jar"
+    fi
+else
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Couldn't find .mvn/wrapper/maven-wrapper.jar, downloading it ..."
+    fi
+    if [ -n "$MVNW_REPOURL" ]; then
+      jarUrl="$MVNW_REPOURL/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    else
+      jarUrl="https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    fi
+    while IFS="=" read key value; do
+      case "$key" in (wrapperUrl) jarUrl="$value"; break ;;
+      esac
+    done < "$BASE_DIR/.mvn/wrapper/maven-wrapper.properties"
+    if [ "$MVNW_VERBOSE" = true ]; then
+      echo "Downloading from: $jarUrl"
+    fi
+    wrapperJarPath="$BASE_DIR/.mvn/wrapper/maven-wrapper.jar"
+    if $cygwin; then
+      wrapperJarPath=`cygpath --path --windows "$wrapperJarPath"`
+    fi
+
+    if command -v wget > /dev/null; then
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Found wget ... using wget"
+        fi
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            wget "$jarUrl" -O "$wrapperJarPath"
+        else
+            wget --http-user=$MVNW_USERNAME --http-password=$MVNW_PASSWORD "$jarUrl" -O "$wrapperJarPath"
+        fi
+    elif command -v curl > /dev/null; then
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Found curl ... using curl"
+        fi
+        if [ -z "$MVNW_USERNAME" ] || [ -z "$MVNW_PASSWORD" ]; then
+            curl -o "$wrapperJarPath" "$jarUrl" -f
+        else
+            curl --user $MVNW_USERNAME:$MVNW_PASSWORD -o "$wrapperJarPath" "$jarUrl" -f
+        fi
+
+    else
+        if [ "$MVNW_VERBOSE" = true ]; then
+          echo "Falling back to using Java to download"
+        fi
+        javaClass="$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.java"
+        # For Cygwin, switch paths to Windows format before running javac
+        if $cygwin; then
+          javaClass=`cygpath --path --windows "$javaClass"`
+        fi
+        if [ -e "$javaClass" ]; then
+            if [ ! -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
+                if [ "$MVNW_VERBOSE" = true ]; then
+                  echo " - Compiling MavenWrapperDownloader.java ..."
+                fi
+                # Compiling the Java class
+                ("$JAVA_HOME/bin/javac" "$javaClass")
+            fi
+            if [ -e "$BASE_DIR/.mvn/wrapper/MavenWrapperDownloader.class" ]; then
+                # Running the downloader
+                if [ "$MVNW_VERBOSE" = true ]; then
+                  echo " - Running MavenWrapperDownloader.java ..."
+                fi
+                ("$JAVA_HOME/bin/java" -cp .mvn/wrapper MavenWrapperDownloader "$MAVEN_PROJECTBASEDIR")
+            fi
+        fi
+    fi
+fi
+##########################################################################################
+# End of extension
+##########################################################################################
+
+export MAVEN_PROJECTBASEDIR=${MAVEN_BASEDIR:-"$BASE_DIR"}
+if [ "$MVNW_VERBOSE" = true ]; then
+  echo $MAVEN_PROJECTBASEDIR
+fi
+MAVEN_OPTS="$(concat_lines "$MAVEN_PROJECTBASEDIR/.mvn/jvm.config") $MAVEN_OPTS"
+
+# For Cygwin, switch paths to Windows format before running java
+if $cygwin; then
+  [ -n "$M2_HOME" ] &&
+    M2_HOME=`cygpath --path --windows "$M2_HOME"`
+  [ -n "$JAVA_HOME" ] &&
+    JAVA_HOME=`cygpath --path --windows "$JAVA_HOME"`
+  [ -n "$CLASSPATH" ] &&
+    CLASSPATH=`cygpath --path --windows "$CLASSPATH"`
+  [ -n "$MAVEN_PROJECTBASEDIR" ] &&
+    MAVEN_PROJECTBASEDIR=`cygpath --path --windows "$MAVEN_PROJECTBASEDIR"`
+fi
+
+# Provide a "standardized" way to retrieve the CLI args that will
+# work with both Windows and non-Windows executions.
+MAVEN_CMD_LINE_ARGS="$MAVEN_CONFIG $@"
+export MAVEN_CMD_LINE_ARGS
+
+WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+exec "$JAVACMD" \
+  $MAVEN_OPTS \
+  -classpath "$MAVEN_PROJECTBASEDIR/.mvn/wrapper/maven-wrapper.jar" \
+  "-Dmaven.home=${M2_HOME}" "-Dmaven.multiModuleProjectDirectory=${MAVEN_PROJECTBASEDIR}" \
+  ${WRAPPER_LAUNCHER} $MAVEN_CONFIG "$@"

mvnw.cmd

@@ -0,0 +1,182 @@
+@REM ----------------------------------------------------------------------------
+@REM Licensed to the Apache Software Foundation (ASF) under one
+@REM or more contributor license agreements.  See the NOTICE file
+@REM distributed with this work for additional information
+@REM regarding copyright ownership.  The ASF licenses this file
+@REM to you under the Apache License, Version 2.0 (the
+@REM "License"); you may not use this file except in compliance
+@REM with the License.  You may obtain a copy of the License at
+@REM
+@REM    http://www.apache.org/licenses/LICENSE-2.0
+@REM
+@REM Unless required by applicable law or agreed to in writing,
+@REM software distributed under the License is distributed on an
+@REM "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+@REM KIND, either express or implied.  See the License for the
+@REM specific language governing permissions and limitations
+@REM under the License.
+@REM ----------------------------------------------------------------------------
+
+@REM ----------------------------------------------------------------------------
+@REM Maven Start Up Batch script
+@REM
+@REM Required ENV vars:
+@REM JAVA_HOME - location of a JDK home dir
+@REM
+@REM Optional ENV vars
+@REM M2_HOME - location of maven2's installed home dir
+@REM MAVEN_BATCH_ECHO - set to 'on' to enable the echoing of the batch commands
+@REM MAVEN_BATCH_PAUSE - set to 'on' to wait for a keystroke before ending
+@REM MAVEN_OPTS - parameters passed to the Java VM when running Maven
+@REM     e.g. to debug Maven itself, use
+@REM set MAVEN_OPTS=-Xdebug -Xrunjdwp:transport=dt_socket,server=y,suspend=y,address=8000
+@REM MAVEN_SKIP_RC - flag to disable loading of mavenrc files
+@REM ----------------------------------------------------------------------------
+
+@REM Begin all REM lines with '@' in case MAVEN_BATCH_ECHO is 'on'
+@echo off
+@REM set title of command window
+title %0
+@REM enable echoing by setting MAVEN_BATCH_ECHO to 'on'
+@if "%MAVEN_BATCH_ECHO%" == "on"  echo %MAVEN_BATCH_ECHO%
+
+@REM set %HOME% to equivalent of $HOME
+if "%HOME%" == "" (set "HOME=%HOMEDRIVE%%HOMEPATH%")
+
+@REM Execute a user defined script before this one
+if not "%MAVEN_SKIP_RC%" == "" goto skipRcPre
+@REM check for pre script, once with legacy .bat ending and once with .cmd ending
+if exist "%HOME%\mavenrc_pre.bat" call "%HOME%\mavenrc_pre.bat"
+if exist "%HOME%\mavenrc_pre.cmd" call "%HOME%\mavenrc_pre.cmd"
+:skipRcPre
+
+@setlocal
+
+set ERROR_CODE=0
+
+@REM To isolate internal variables from possible post scripts, we use another setlocal
+@setlocal
+
+@REM ==== START VALIDATION ====
+if not "%JAVA_HOME%" == "" goto OkJHome
+
+echo.
+echo Error: JAVA_HOME not found in your environment. >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+:OkJHome
+if exist "%JAVA_HOME%\bin\java.exe" goto init
+
+echo.
+echo Error: JAVA_HOME is set to an invalid directory. >&2
+echo JAVA_HOME = "%JAVA_HOME%" >&2
+echo Please set the JAVA_HOME variable in your environment to match the >&2
+echo location of your Java installation. >&2
+echo.
+goto error
+
+@REM ==== END VALIDATION ====
+
+:init
+
+@REM Find the project base dir, i.e. the directory that contains the folder ".mvn".
+@REM Fallback to current working directory if not found.
+
+set MAVEN_PROJECTBASEDIR=%MAVEN_BASEDIR%
+IF NOT "%MAVEN_PROJECTBASEDIR%"=="" goto endDetectBaseDir
+
+set EXEC_DIR=%CD%
+set WDIR=%EXEC_DIR%
+:findBaseDir
+IF EXIST "%WDIR%"\.mvn goto baseDirFound
+cd ..
+IF "%WDIR%"=="%CD%" goto baseDirNotFound
+set WDIR=%CD%
+goto findBaseDir
+
+:baseDirFound
+set MAVEN_PROJECTBASEDIR=%WDIR%
+cd "%EXEC_DIR%"
+goto endDetectBaseDir
+
+:baseDirNotFound
+set MAVEN_PROJECTBASEDIR=%EXEC_DIR%
+cd "%EXEC_DIR%"
+
+:endDetectBaseDir
+
+IF NOT EXIST "%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config" goto endReadAdditionalConfig
+
+@setlocal EnableExtensions EnableDelayedExpansion
+for /F "usebackq delims=" %%a in ("%MAVEN_PROJECTBASEDIR%\.mvn\jvm.config") do set JVM_CONFIG_MAVEN_PROPS=!JVM_CONFIG_MAVEN_PROPS! %%a
+@endlocal & set JVM_CONFIG_MAVEN_PROPS=%JVM_CONFIG_MAVEN_PROPS%
+
+:endReadAdditionalConfig
+
+SET MAVEN_JAVA_EXE="%JAVA_HOME%\bin\java.exe"
+set WRAPPER_JAR="%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.jar"
+set WRAPPER_LAUNCHER=org.apache.maven.wrapper.MavenWrapperMain
+
+set DOWNLOAD_URL="https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+
+FOR /F "tokens=1,2 delims==" %%A IN ("%MAVEN_PROJECTBASEDIR%\.mvn\wrapper\maven-wrapper.properties") DO (
+    IF "%%A"=="wrapperUrl" SET DOWNLOAD_URL=%%B
+)
+
+@REM Extension to allow automatically downloading the maven-wrapper.jar from Maven-central
+@REM This allows using the maven wrapper in projects that prohibit checking in binary data.
+if exist %WRAPPER_JAR% (
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Found %WRAPPER_JAR%
+    )
+) else (
+    if not "%MVNW_REPOURL%" == "" (
+        SET DOWNLOAD_URL="%MVNW_REPOURL%/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar"
+    )
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Couldn't find %WRAPPER_JAR%, downloading it ...
+        echo Downloading from: %DOWNLOAD_URL%
+    )
+
+    powershell -Command "&{"^
+		"$webclient = new-object System.Net.WebClient;"^
+		"if (-not ([string]::IsNullOrEmpty('%MVNW_USERNAME%') -and [string]::IsNullOrEmpty('%MVNW_PASSWORD%'))) {"^
+		"$webclient.Credentials = new-object System.Net.NetworkCredential('%MVNW_USERNAME%', '%MVNW_PASSWORD%');"^
+		"}"^
+		"[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12; $webclient.DownloadFile('%DOWNLOAD_URL%', '%WRAPPER_JAR%')"^
+		"}"
+    if "%MVNW_VERBOSE%" == "true" (
+        echo Finished downloading %WRAPPER_JAR%
+    )
+)
+@REM End of extension
+
+@REM Provide a "standardized" way to retrieve the CLI args that will
+@REM work with both Windows and non-Windows executions.
+set MAVEN_CMD_LINE_ARGS=%*
+
+%MAVEN_JAVA_EXE% %JVM_CONFIG_MAVEN_PROPS% %MAVEN_OPTS% %MAVEN_DEBUG_OPTS% -classpath %WRAPPER_JAR% "-Dmaven.multiModuleProjectDirectory=%MAVEN_PROJECTBASEDIR%" %WRAPPER_LAUNCHER% %MAVEN_CONFIG% %*
+if ERRORLEVEL 1 goto error
+goto end
+
+:error
+set ERROR_CODE=1
+
+:end
+@endlocal & set ERROR_CODE=%ERROR_CODE%
+
+if not "%MAVEN_SKIP_RC%" == "" goto skipRcPost
+@REM check for post script, once with legacy .bat ending and once with .cmd ending
+if exist "%HOME%\mavenrc_post.bat" call "%HOME%\mavenrc_post.bat"
+if exist "%HOME%\mavenrc_post.cmd" call "%HOME%\mavenrc_post.cmd"
+:skipRcPost
+
+@REM pause the script if MAVEN_BATCH_PAUSE is set to 'on'
+if "%MAVEN_BATCH_PAUSE%" == "on" pause
+
+if "%MAVEN_TERMINATE_CMD%" == "on" exit %ERROR_CODE%
+
+exit /B %ERROR_CODE%

pom.xml

@@ -0,0 +1,99 @@
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+  <modelVersion>4.0.0</modelVersion>
+
+  <groupId>com.albertoventurini.parsley</groupId>
+  <artifactId>parsley</artifactId>
+  <packaging>jar</packaging>
+  <version>0.1.0-SNAPSHOT</version>
+
+  <name>graphino</name>
+
+  <url>https://github.com/albertoventurini/parsley</url>
+
+  <properties>
+    <antlr.version>4.7.1</antlr.version>
+    <junit.version>5.6.1</junit.version>
+    <maven-compiler-plugin.version>3.8.1</maven-compiler-plugin.version>
+    <maven-surefire-plugin.version>3.0.0-M5</maven-surefire-plugin.version>
+    <maven-jar-plugin.version>3.2.0</maven-jar-plugin.version>
+    <maven-shade.plugin.version>3.2.2</maven-shade.plugin.version>
+    <mainClass>com.albertoventurini.parsley.Main</mainClass>
+  </properties>
+
+  <dependencyManagement>
+
+    <dependencies>
+
+      <dependency>
+        <groupId>org.junit.jupiter</groupId>
+        <artifactId>junit-jupiter</artifactId>
+        <version>${junit.version}</version>
+        <scope>test</scope>
+      </dependency>
+
+      <dependency>
+        <groupId>org.junit.jupiter</groupId>
+        <artifactId>junit-jupiter-engine</artifactId>
+        <version>${junit.version}</version>
+        <scope>test</scope>
+      </dependency>
+
+    </dependencies>
+
+  </dependencyManagement>
+
+  <dependencies>
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter</artifactId>
+      <scope>test</scope>
+    </dependency>
+
+    <dependency>
+      <groupId>org.junit.jupiter</groupId>
+      <artifactId>junit-jupiter-engine</artifactId>
+      <scope>test</scope>
+    </dependency>
+  </dependencies>
+
+
+  <build>
+
+    <plugins>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <version>${maven-compiler-plugin.version}</version>
+        <configuration>
+          <source>11</source>
+          <target>11</target>
+          <release>11</release>
+        </configuration>
+      </plugin>
+
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-surefire-plugin</artifactId>
+        <version>${maven-surefire-plugin.version}</version>
+        <configuration>
+          <argLine>--enable-preview</argLine>
+        </configuration>
+      </plugin>
+
+      <plugin>
+        <artifactId>maven-jar-plugin</artifactId>
+        <configuration>
+          <archive>
+            <manifest>
+              <addClasspath>true</addClasspath>
+              <mainClass>${mainClass}</mainClass>
+            </manifest>
+          </archive>
+        </configuration>
+      </plugin>
+    </plugins>
+
+  </build>
+
+</project>

src/main/java/com/albertoventurini/parsley/Grammar.java

@@ -0,0 +1,89 @@
+package com.albertoventurini.parsley;
+
+import com.albertoventurini.parsley.rules.AnyCharacter;
+import com.albertoventurini.parsley.rules.MatchCharacter;
+import com.albertoventurini.parsley.rules.MatchString;
+import com.albertoventurini.parsley.rules.OneOf;
+import com.albertoventurini.parsley.rules.OneOrMore;
+import com.albertoventurini.parsley.rules.Rule;
+import com.albertoventurini.parsley.rules.Sequence;
+import com.albertoventurini.parsley.rules.TakeWhileCharacter;
+import com.albertoventurini.parsley.rules.UntilString;
+import com.albertoventurini.parsley.rules.Wrapper;
+import com.albertoventurini.parsley.rules.ZeroOrMore;
+import com.albertoventurini.parsley.rules.ZeroOrOne;
+
+import java.util.Optional;
+import java.util.function.Predicate;
+
+public class Grammar {
+
+    private final Rule startRule;
+
+    private final Rule commentRule;
+
+    public Grammar(
+            final Rule startRule,
+            final Rule commentRule) {
+        this.startRule = startRule;
+        this.commentRule = commentRule;
+
+        // TODO: better than this
+        if (commentRule != null) {
+            commentRule.setComment(true);
+        }
+    }
+
+    public Optional<ParseTree> parse(final String text) {
+        final var ctx = new GrammarContext(text, commentRule);
+        return startRule.apply(ctx);
+    }
+
+    public static MatchCharacter character(final char c) {
+        return new MatchCharacter(c);
+    }
+
+    public static AnyCharacter anyChar() {
+        return new AnyCharacter();
+    }
+
+    public static MatchString string(final String s) {
+        return new MatchString(s);
+    }
+
+    public static TakeWhileCharacter token() {
+        return new TakeWhileCharacter();
+    }
+
+    public static TakeWhileCharacter takeWhile(final Predicate<Character> characterPredicate) {
+        return new TakeWhileCharacter(characterPredicate);
+    }
+
+    public static UntilString until(final String s) {
+        return new UntilString(s);
+    }
+
+    public static Sequence sequence(final Rule... rules) {
+        return new Sequence(rules);
+    }
+
+    public static OneOf oneOf(final Rule... rules) {
+        return new OneOf(rules);
+    }
+
+    public static ZeroOrMore zeroOrMore(final Rule childRule) {
+        return new ZeroOrMore(childRule);
+    }
+
+    public static ZeroOrOne zeroOrOne(final Rule childRule) {
+        return new ZeroOrOne(childRule);
+    }
+
+    public static OneOrMore oneOrMore(final Rule childRule) {
+        return new OneOrMore(childRule);
+    }
+
+    public static Wrapper wrapper() {
+        return new Wrapper();
+    }
+}

src/main/java/com/albertoventurini/parsley/GrammarContext.java

@@ -0,0 +1,47 @@
+package com.albertoventurini.parsley;
+
+import com.albertoventurini.parsley.rules.Rule;
+
+public class GrammarContext extends ParseContext {
+    private final Rule commentRule;
+    private boolean inComment;
+
+    GrammarContext(
+            final String string,
+            final Rule commentRule) {
+        super(string);
+        this.commentRule = commentRule;
+    }
+
+    public void advanceToNextToken() {
+        discardWhitespaces();
+        if (!inComment) {
+            discardComments();
+            discardWhitespaces();
+        }
+    }
+
+    public boolean isInComment() {
+        return inComment;
+    }
+
+    public void setInComment(final boolean inComment) {
+        this.inComment = inComment;
+    }
+
+    private void discardComments() {
+        if (hasNext() && commentRule != null) {
+            commentRule.apply(this);
+        }
+    }
+
+    private void discardWhitespaces() {
+        while (hasNext()) {
+            final char c = peek();
+            if (!(Character.isWhitespace(c) || c == '\n')) {
+                break;
+            }
+            advance();
+        }
+    }
+}

src/main/java/com/albertoventurini/parsley/ParseContext.java

@@ -0,0 +1,78 @@
+package com.albertoventurini.parsley;
+
+import java.util.Arrays;
+
+public class ParseContext {
+    private final char[] charArr;
+    private int cursor;
+
+    public ParseContext(final String string) {
+        charArr = string.toCharArray();
+    }
+
+    public char next() {
+        char c = peek();
+        cursor++;
+        return c;
+    }
+
+    public char peek() {
+        if (cursor >= charArr.length) {
+            throw new ParseException("No more characters to parse");
+        }
+        return charArr[cursor];
+    }
+
+    public boolean hasNext() {
+        return cursor < charArr.length;
+    }
+
+    public int getCursor() {
+        return cursor;
+    }
+
+    public void advance() {
+        advance(1);
+    }
+
+    public void advance(final int i) {
+        cursor += i;
+    }
+
+    public void setCursor(final int cursor) {
+        this.cursor = cursor;
+    }
+
+    public void consume(final char c) {
+        final char n = next();
+        if (n != c) {
+            throw new ParseException("Expected character " + c + ", instead found " + n);
+        }
+    }
+
+    public String substring(final int start, final int end) {
+        return String.valueOf(Arrays.copyOfRange(charArr, start, end));
+    }
+
+    public String substring(final int start) {
+        return substring(start, cursor);
+    }
+
+    public String substring() {
+        return String.valueOf(Arrays.copyOfRange(charArr, cursor, charArr.length));
+    }
+
+    public boolean matches(final String s) {
+        if (cursor + s.length() > charArr.length) {
+            return false;
+        }
+
+        for (int i = 0; i < s.length(); i++) {
+            if (charArr[cursor + i] != s.charAt(i)) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+}

src/main/java/com/albertoventurini/parsley/ParseException.java

@@ -0,0 +1,8 @@
+package com.albertoventurini.parsley;
+
+public class ParseException extends RuntimeException {
+
+    public ParseException(final String message) {
+        super(message);
+    }
+}

src/main/java/com/albertoventurini/parsley/ParseTree.java

@@ -0,0 +1,75 @@
+package com.albertoventurini.parsley;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.Optional;
+
+public class ParseTree {
+
+    private final String text;
+
+    private final List<ParseTree> children;
+
+    public static final class Leaf extends ParseTree {
+        public Leaf(final String text) {
+            super(text, Collections.emptyList());
+        }
+    }
+
+    public static final class Node extends ParseTree {
+        public Node(final String text, final List<ParseTree> children) {
+            super(text, children);
+        }
+    }
+
+    public ParseTree(final String text, final List<ParseTree> children) {
+        this.text = text;
+        this.children = children;
+    }
+
+    public static Leaf leaf(final String text) {
+        return new Leaf(text);
+    }
+
+    public static Node node(final String text, final List<ParseTree> children) {
+        return new Node(text, children);
+    }
+
+    public String getText() {
+        return text;
+    }
+
+    public List<ParseTree> getChildren() {
+        return children;
+    }
+
+    public ParseTree child(final int i) {
+        return children.get(i);
+    }
+
+    public Optional<ParseTree> getFirstDescendantByName(final String name) {
+        if (name.equals(text)) {
+            return Optional.of(this);
+        }
+
+        for (final ParseTree child : children) {
+            final Optional<ParseTree> descendant = child.getFirstDescendantByName(name);
+            if (descendant.isPresent()) {
+                return descendant;
+            }
+        }
+
+        return Optional.empty();
+    }
+
+    public ParseTree child(final String name) {
+        return children.stream().filter(c -> name.equals(c.text))
+                .findFirst()
+                .orElseThrow(() -> new RuntimeException("Child not found: " + name));
+    }
+
+    @Override
+    public String toString() {
+        return text;
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/AnyCharacter.java

@@ -0,0 +1,18 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public final class AnyCharacter extends Rule {
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        return Optional.of(ParseTree.leaf(Character.toString(ctx.next())));
+    }
+
+    @Override
+    public String toString() {
+        return "AnyCharacter{}";
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/MatchCharacter.java

@@ -0,0 +1,34 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public final class MatchCharacter extends Rule {
+    private final char c;
+
+    public MatchCharacter(final char c) {
+        this.c = c;
+
+        discard = true;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        ctx.advanceToNextToken();
+
+        if (ctx.peek() == c) {
+            return Optional.of(ParseTree.leaf(Character.toString(ctx.next())));
+        } else {
+            return Optional.empty();
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Character{" +
+                "c=" + c +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/MatchString.java

@@ -0,0 +1,35 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public final class MatchString extends Rule {
+    private final String s;
+
+    public MatchString(final String s) {
+        this.s = s;
+
+        discard = true;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        ctx.advanceToNextToken();
+
+        if (ctx.matches(s)) {
+            ctx.advance(s.length());
+            return Optional.of(ParseTree.leaf(s));
+        } else {
+            return Optional.empty();
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "MatchString{" +
+                "s='" + s + '\'' +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/OneOf.java

@@ -0,0 +1,37 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Arrays;
+import java.util.Optional;
+
+public final class OneOf extends Rule {
+    private final Rule[] rules;
+
+    public OneOf(final Rule... rules) {
+        this.rules = rules;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        final int start = ctx.getCursor();
+
+        for (final Rule rule : rules) {
+            final Optional<ParseTree> result = rule.apply(ctx);
+            if (result.isPresent()) {
+                return result;
+            }
+        }
+
+        ctx.setCursor(start);
+        return Optional.empty();
+    }
+
+    @Override
+    public String toString() {
+        return "OneOf{" +
+                "rules=" + Arrays.toString(rules) +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/OneOrMore.java

@@ -0,0 +1,46 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public class OneOrMore extends Rule {
+    private final Rule childRule;
+
+    public OneOrMore(final Rule childRule) {
+        this.childRule = childRule;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        final List<ParseTree> children = new ArrayList<>();
+
+        final Optional<ParseTree> firstChild = childRule.apply(ctx);
+        if (firstChild.isEmpty()) {
+            return Optional.empty();
+        }
+
+        children.add(firstChild.get());
+
+        while (ctx.hasNext()) {
+            final Optional<ParseTree> child = childRule.apply(ctx);
+            if (child.isEmpty()) {
+                break;
+            } else {
+                children.add(child.get());
+            }
+        }
+
+        return Optional.of(ParseTree.node(name, children));
+    }
+
+    @Override
+    public String toString() {
+        return "OneOrMore{" +
+                childRule +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/Rule.java

@@ -0,0 +1,48 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public abstract class Rule {
+    protected String name;
+
+    public boolean isComment = false;
+
+    protected boolean discard = false;
+
+    public Rule as(final String name) {
+        this.name = name;
+        return this;
+    }
+
+    public Rule discard() {
+        discard = true;
+        return this;
+    }
+
+    public Rule discard(final boolean discard) {
+        this.discard = discard;
+        return this;
+    }
+
+    public Optional<ParseTree> apply(final GrammarContext ctx) {
+        final boolean inComment = ctx.isInComment();
+
+        try {
+            if (!inComment && isComment) {
+                ctx.setInComment(true);
+            }
+            return tryApply(ctx);
+        } finally {
+            ctx.setInComment(inComment);
+        }
+    }
+
+    public abstract Optional<ParseTree> tryApply(final GrammarContext ctx);
+
+    public void setComment(final boolean comment) {
+        isComment = comment;
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/Sequence.java

@@ -0,0 +1,48 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Optional;
+
+public final class Sequence extends Rule {
+    private final Rule[] rules;
+
+    public Sequence(final Rule... rules) {
+        this.rules = rules;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        final int start = ctx.getCursor();
+        final List<ParseTree> children = new ArrayList<>(rules.length);
+
+        for (final Rule rule : rules) {
+            if (!ctx.hasNext()) {
+                ctx.setCursor(start);
+                return Optional.empty();
+            }
+
+            final Optional<ParseTree> child = rule.apply(ctx);
+
+            if (child.isEmpty()) {
+                ctx.setCursor(start);
+                return Optional.empty();
+            } else if (!rule.discard) {
+                children.add(child.get());
+            }
+        }
+
+        return Optional.of(ParseTree.node(name, children));
+    }
+
+    @Override
+    public String toString() {
+        return "Sequence{" +
+                "rules=" + Arrays.toString(rules) +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/TakeWhileCharacter.java

@@ -0,0 +1,48 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+import java.util.function.Predicate;
+
+public final class TakeWhileCharacter extends Rule {
+    private final Predicate<Character> characterPredicate;
+
+    private static final Predicate<Character> DEFAULT_PREDICATE = (c) -> !Character.isWhitespace(c);
+
+    public TakeWhileCharacter() {
+        this(DEFAULT_PREDICATE);
+    }
+
+    public TakeWhileCharacter(final Predicate<Character> characterPredicate) {
+        this.characterPredicate = characterPredicate;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        ctx.advanceToNextToken();
+
+        final int start = ctx.getCursor();
+
+        while (ctx.hasNext()) {
+            if (!characterPredicate.test(ctx.peek())) {
+                break;
+            }
+            ctx.advance();
+        }
+
+        if (ctx.getCursor() > start) {
+            return Optional.of(ParseTree.leaf(ctx.substring(start)));
+        } else {
+            return Optional.empty();
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Token{" +
+                "characterPredicate=" + characterPredicate +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/UntilString.java

@@ -0,0 +1,45 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Arrays;
+import java.util.Optional;
+
+public final class UntilString extends Rule {
+    private final char[] charArr;
+
+    public UntilString(final String s) {
+        this.charArr = s.toCharArray();
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        ctx.advanceToNextToken();
+
+        final int start = ctx.getCursor();
+
+        int matched = 0;
+        while (ctx.hasNext() && matched < charArr.length) {
+            if (ctx.next() == charArr[matched]) {
+                matched++;
+            } else {
+                matched = 0;
+            }
+        }
+
+        if (!ctx.hasNext()) {
+            return Optional.of(ParseTree.leaf(ctx.substring(start)));
+        } else {
+            return Optional.of(ParseTree.leaf(ctx.substring(start, ctx.getCursor())));
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "UntilString{" +
+                "name='" + name + '\'' +
+                ", charArr=" + Arrays.toString(charArr) +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/Wrapper.java

@@ -0,0 +1,32 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public final class Wrapper extends Rule {
+    private Rule childRule;
+
+    public Rule getChildRule() {
+        return childRule;
+    }
+
+    public void setChildRule(final Rule childRule) {
+        this.childRule = childRule;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        if (childRule != null) {
+            return childRule.apply(ctx);
+        } else {
+            return Optional.empty();
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "Wrapper{" + childRule.toString() + "}";
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/ZeroOrMore.java

@@ -0,0 +1,39 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public final class ZeroOrMore extends Rule {
+    private final Rule childRule;
+
+    public ZeroOrMore(final Rule childRule) {
+        this.childRule = childRule;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        final List<ParseTree> children = new ArrayList<>();
+
+        while (ctx.hasNext()) {
+            final Optional<ParseTree> child = childRule.apply(ctx);
+            if (child.isEmpty()) {
+                break;
+            } else {
+                children.add(child.get());
+            }
+        }
+
+        return Optional.of(ParseTree.node(name, children));
+    }
+
+    @Override
+    public String toString() {
+        return "ZeroOrMore{" +
+                childRule +
+                '}';
+    }
+}

src/main/java/com/albertoventurini/parsley/rules/ZeroOrOne.java

@@ -0,0 +1,31 @@
+package com.albertoventurini.parsley.rules;
+
+import com.albertoventurini.parsley.GrammarContext;
+import com.albertoventurini.parsley.ParseTree;
+
+import java.util.Optional;
+
+public final class ZeroOrOne extends Rule {
+    private final Rule childRule;
+
+    public ZeroOrOne(final Rule childRule) {
+        this.childRule = childRule;
+    }
+
+    @Override
+    public Optional<ParseTree> tryApply(final GrammarContext ctx) {
+        final Optional<ParseTree> child = childRule.apply(ctx);
+        if (child.isPresent()) {
+            return child;
+        } else {
+            return Optional.of(ParseTree.leaf(""));
+        }
+    }
+
+    @Override
+    public String toString() {
+        return "ZeroOrOne{" +
+                childRule +
+                '}';
+    }
+}