PomUtils

package org.apache.maven.archetype.common.util;

/*
 * 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.
 */

import org.apache.maven.archetype.exception.InvalidPackaging;
import org.apache.maven.archetype.old.ArchetypeTemplateProcessingException;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;

import javax.xml.XMLConstants;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.OutputKeys;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;
import java.io.IOException;
import java.io.Reader;
import java.io.Writer;

/**
 * POM helper class.
 */
public final class PomUtils
{
    private PomUtils()
    {
        throw new IllegalStateException( "no instantiable constructor" );
    }

    /**
     * Adds module {@code artifactId} unless the module already presents in {@code fileReader}.
     *
     * @param artifactId artifactId of module to add
     * @param fileReader source POM XML
     * @param fileWriter target XML
     * @return {@code true} if modules section in POM is empty or does not exist or {@code artifactId} does not appear
     * a module in {@code fileReader} XML.
     * @throws IOException if I/O error
     * @throws InvalidPackaging if packaging is not "pom" or not exist in POM
     * @throws ArchetypeTemplateProcessingException if "project" does not exist or "modules" element is duplicated
     * @throws ParserConfigurationException if parser error
     * @throws SAXException if parser error
     * @throws TransformerException if an error writing to {@code fileWriter}
     */
    public static boolean addNewModule( String artifactId, Reader fileReader, Writer fileWriter )
            throws ArchetypeTemplateProcessingException, InvalidPackaging, IOException,
            ParserConfigurationException, SAXException, TransformerException
    {
        DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
        dbf.setFeature( "http://apache.org/xml/features/disallow-doctype-decl", true );
        dbf.setFeature( "http://xml.org/sax/features/external-general-entities", false );
        dbf.setFeature( "http://xml.org/sax/features/external-parameter-entities", false );
        dbf.setFeature( "http://apache.org/xml/features/nonvalidating/load-external-dtd", false );
        dbf.setXIncludeAware( false );
        dbf.setExpandEntityReferences( false );

        DocumentBuilder db = dbf.newDocumentBuilder();
        InputSource inputSource = new InputSource();
        inputSource.setCharacterStream( fileReader );
        Document document = db.parse( inputSource );

        Element project = document.getDocumentElement();
        if ( !"project".equals( project.getNodeName() ) )
        {
            throw new ArchetypeTemplateProcessingException( "Unable to find root element 'project'." );
        }

        String packaging = null;
        NodeList packagingElement = project.getElementsByTagName( "packaging" );
        if ( packagingElement != null && packagingElement.getLength() == 1 )
        {
            packaging = packagingElement.item( 0 ).getTextContent();
        }
        if ( !"pom".equals( packaging ) )
        {
            throw new InvalidPackaging(
                    "Unable to add module to the current project as it is not of packaging type 'pom'" );
        }

        Node modules = getModulesNode( project );

        if ( !hasArtifactIdInModules( artifactId, modules ) )
        {
            Element module = document.createElement( "module" );
            module.setTextContent( artifactId );
            if ( modules == null )
            {
                modules = document.createElement( "modules" );
                project.appendChild( modules );
            }

            // shift the child node by next two spaces after the parent node spaces
            modules.appendChild( document.createTextNode( "  " ) );

            modules.appendChild( module );

            // shift the end tag </modules>
            modules.appendChild( document.createTextNode( "\n  " ) );

            TransformerFactory tf = TransformerFactory.newInstance();
            tf.setAttribute( XMLConstants.ACCESS_EXTERNAL_DTD, "" );
            tf.setAttribute( XMLConstants.ACCESS_EXTERNAL_STYLESHEET, "" );

            tf.setAttribute( "indent-number", 2 );
            Transformer tr = tf.newTransformer();
            tr.setOutputProperty( OutputKeys.INDENT, "yes" );
            tr.setOutputProperty( OutputKeys.METHOD, "xml" );
            tr.setOutputProperty( OutputKeys.ENCODING, "UTF-8" );
            tr.setOutputProperty( "{http://xml.apache.org/xslt}indent-amount", "2" );
            document.getDomConfig().setParameter( "infoset", Boolean.TRUE );
            document.getDocumentElement().normalize();
            tr.transform( new DOMSource( document ), new StreamResult( fileWriter ) );
            return true;
        }
        else
        {
            return false;
        }
    }

    private static Node getModulesNode( Element project )
    {
        Node modules = null;
        NodeList nodes = project.getChildNodes();
        for ( int len = nodes.getLength(), i = 0; i < len; i++ )
        {
            Node node = nodes.item( i );
            if ( node.getNodeType() == Node.ELEMENT_NODE && "modules".equals( node.getNodeName() ) )
            {
                modules = node;
                break;
            }
        }
        return modules;
    }

    private static boolean hasArtifactIdInModules( String artifactId, Node modules )
    {
        if ( modules != null )
        {
            Node module = modules.getFirstChild();
            while ( module != null )
            {
                if ( module.getNodeType() == Node.ELEMENT_NODE && artifactId.equals( module.getTextContent() ) )
                {
                    return true;
                }
                module = module.getNextSibling();
            }
        }
        return false;
    }
}