libhover/org.eclipse.linuxtools.cdt.libhover.devhelp/src/org/eclipse/linuxtools/internal/cdt/libhover/devhelp/DevHelpTopic.java

/*******************************************************************************
 * Copyright (c) 2012, 2018 Red Hat Inc. and others.
 * 
 * This program and the accompanying materials are made
 * available under the terms of the Eclipse Public License 2.0
 * which is available at https://www.eclipse.org/legal/epl-2.0/
 *
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 * Red Hat Inc. - Initial implementation
 *******************************************************************************/
package org.eclipse.linuxtools.internal.cdt.libhover.devhelp;

import java.io.File;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;

import org.eclipse.core.expressions.IEvaluationContext;
import org.eclipse.core.runtime.IPath;
import org.eclipse.core.runtime.Path;
import org.eclipse.help.ITopic;
import org.eclipse.help.IUAElement;
import org.eclipse.jface.preference.IPreferenceStore;
import org.eclipse.linuxtools.internal.cdt.libhover.devhelp.preferences.PreferenceConstants;
import org.w3c.dom.Document;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.xml.sax.SAXException;

public class DevHelpTopic implements ITopic {

    private String name;
    private XPath xpath;
    private String label;
    private String link;
    private List<ITopic> subTopics;

    DevHelpTopic(String name) {
        this.name = name;
        xpath = XPathFactory.newInstance().newXPath();
        subTopics = new ArrayList<>();
        label = name;
        init();
    }

    private void init() {
        IPreferenceStore ps = DevHelpPlugin.getDefault().getPreferenceStore();
        IPath devhelpLocation = new Path(
                ps.getString(PreferenceConstants.DEVHELP_DIRECTORY)).append(
                name).append(name + ".devhelp2"); //$NON-NLS-1$
        File devhelpFile = devhelpLocation.toFile();
        if (devhelpFile.exists()) {
            DocumentBuilderFactory docfactory = DocumentBuilderFactory
                    .newInstance();
            docfactory.setValidating(false);
            try {
                docfactory.setFeature("http://xml.org/sax/features/namespaces", //$NON-NLS-1$
                        false);
                docfactory.setFeature("http://xml.org/sax/features/validation", //$NON-NLS-1$
                        false);
                docfactory
                        .setFeature(
                                "http://apache.org/xml/features/nonvalidating/load-dtd-grammar", //$NON-NLS-1$
                                false);
                docfactory
                        .setFeature(
                                "http://apache.org/xml/features/nonvalidating/load-external-dtd", //$NON-NLS-1$
                                false);

                DocumentBuilder docbuilder = docfactory.newDocumentBuilder();
                Document docroot = docbuilder.parse(devhelpLocation.toFile());

                // set label
                label = xpathEval("/book/@title", docroot); //$NON-NLS-1$
                if (label.isEmpty()) {
                    label = name;
                }
                link = xpathEval("/book/@link", docroot); //$NON-NLS-1$

                // set subtopics
                NodeList nodes = xpathEvalNodes("/book/chapters/sub", docroot); //$NON-NLS-1$
                for (int i = 0; i < nodes.getLength(); i++) {
                    Node node = nodes.item(i);
                    subTopics.add(new SimpleTopic(name, node));
                }
            } catch (ParserConfigurationException e) {
                e.printStackTrace();
            } catch (SAXException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private String xpathEval(String path, Document docroot) {
        String result = ""; //$NON-NLS-1$
        try {
            result = xpath.evaluate(path, docroot);
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return result;
    }

    private NodeList xpathEvalNodes(String path, Document docroot) {
        NodeList result = null;
        try {
            result = (NodeList) xpath.evaluate(path, docroot,
                    XPathConstants.NODESET);
        } catch (XPathExpressionException e) {
            e.printStackTrace();
        }
        return result;
    }

    @Override
    public boolean isEnabled(IEvaluationContext context) {
        return true;
    }

    @Override
    public IUAElement[] getChildren() {
        return getSubtopics();
    }

    @Override
    public String getHref() {
        return "/" + DevHelpPlugin.PLUGIN_ID + "/" + name + "/"+link; //$NON-NLS-1$  //$NON-NLS-2$ //$NON-NLS-3$

    }

    @Override
    public String getLabel() {
        return label;
    }

    @Override
    public ITopic[] getSubtopics() {
        return subTopics.toArray(new ITopic[subTopics.size()]);
    }
}