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Open Source (LGPL) JavaFX PDF Viewer
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/*
 * ===========================================
 * Java Pdf Extraction Decoding Access Library
 * ===========================================
 *
 * Project Info:  http://www.idrsolutions.com
 * Help section for developers at http://www.idrsolutions.com/support/
 *
 * (C) Copyright 1997-2017 IDRsolutions and Contributors.
 *
 * This file is part of JPedal/JPDF2HTML5
 *
 @LICENSE@
 *
 * ---------------
 * BaseTransferHandler.java
 * ---------------
 */
package org.jpedal.examples.viewer.gui;

import java.awt.datatransfer.DataFlavor;
import java.awt.datatransfer.Transferable;
import java.io.BufferedReader;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.Reader;
import javax.swing.JComponent;
import javax.swing.TransferHandler;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;

import org.jpedal.examples.viewer.Commands;
import org.jpedal.examples.viewer.Values;
import org.jpedal.gui.GUIFactory;
import org.jpedal.utils.LogWriter;
import org.jpedal.utils.StringUtils;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NamedNodeMap;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

public class BaseTransferHandler extends TransferHandler {
    protected final Commands currentCommands;
    protected final GUIFactory currentGUI;
    protected final Values commonValues;

    public BaseTransferHandler(final Values commonValues, final GUIFactory currentGUI, final Commands currentCommands) {
        this.commonValues = commonValues;
        this.currentGUI = currentGUI;
        this.currentCommands = currentCommands;
    }

    @Override
    public boolean canImport(final JComponent dest, final DataFlavor[] flavors) {
        return true;
    }

    protected Object getImport(final Transferable transferable) throws Exception {
        final DataFlavor[] flavors = transferable.getTransferDataFlavors();
        DataFlavor listFlavor = null;
        final int lastFlavor = flavors.length - 1;

        // Check the flavors and see if we find one we like.
        // If we do, save it.
        for (int f = 0; f <= lastFlavor; f++) {
            if (flavors[f].isFlavorJavaFileListType()) {
                listFlavor = flavors[f];
            }
        }

        // Ok, now try to display the content of the drop.
        try {
            final DataFlavor bestTextFlavor = DataFlavor.selectBestTextFlavor(flavors);
            if (bestTextFlavor != null) { // this could be a file from a web page being dragged in
                final Reader r = bestTextFlavor.getReaderForText(transferable);

                String textData = readTextDate(r);

                // need to remove all the 0 characters that will appear in the String when importing on Linux
                textData = removeChar(textData, (char) 0);

                if (textData.contains("ftp:/")) {
                    currentGUI.showMessageDialog("Files cannot be opened via FTP");
                    return null;
                }

                textData = getURL(textData);

                // replace URL spaces
                textData = textData.replaceAll("%20", " ");

                return textData;

            } else if (listFlavor != null) { // this is most likely a file being dragged in
                return transferable.getTransferData(listFlavor);
            }
        } catch (final Exception e) {
            LogWriter.writeLog("Caught exception decoding transfer:" + e.getMessage());

            return null;
        }

        return null;
    }

    private static String removeChar(final String s, final char c) {
        final StringBuilder r = new StringBuilder();
        for (int i = 0; i < s.length(); i++) {
            if (s.charAt(i) != c) {
                r.append(s.charAt(i));
            }
        }
        return r.toString();
    }

    /**
     * Returns the URL from the text data acquired from the transferable object.
     *
     * @param textData text data acquired from the transferable.
     * @return the URL of the file to open
     * @throws ParserConfigurationException
     * @throws SAXException
     * @throws IOException
     */
    private static String getURL(String textData) throws ParserConfigurationException, SAXException, IOException {
        if (!textData.startsWith("http://") && !textData.startsWith("file://")) { // its not a url so it must be a file
            final DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance();
            final DocumentBuilder db = dbf.newDocumentBuilder();
            final Document doc = db.parse(new ByteArrayInputStream(StringUtils.toBytes(textData)));

            final Element a = (Element) doc.getElementsByTagName("a").item(0);
            textData = getHrefAttribute(a);
        }

        return textData;
    }

    /**
     * Acquire text data from a reader. 


     * Firefox this will be some html containing an "a" element with the "href" attribute linking to the to the PDF. 


     * IE a simple one line String containing the URL will be returned
     *
     * @param r the reader to read from
     * @return the text data from the reader
     * @throws IOException
     */
    private static String readTextDate(final Reader r) throws IOException {
        final BufferedReader br = new BufferedReader(r);

        final StringBuilder textData = new StringBuilder();
        String line = br.readLine();
        while (line != null) {
            textData.append(line);
            line = br.readLine();
        }
        br.close();

        return textData.toString();
    }

    /**
     * Returns the URL held in the href attribute from an element
     *
     * @param element the element containing the href attribute
     * @return the URL held in the href attribute
     */
    private static String getHrefAttribute(final Element element) {
        final NamedNodeMap attrs = element.getAttributes();

        final Node nameNode = attrs.getNamedItem("href");
        if (nameNode != null) {
            return nameNode.getNodeValue();
        }

        return null;
    }
}