/**
 * The class to handle the before-page event while converting an XPS document.
 */
public static class NavigationInjector extends BeforePageSavingEventHandler
{
    private final XpsFont _font;
    private List<Integer> _pageNumbers;

    public NavigationInjector(XpsFont font, int[] pageNumbers)
    {
        _font = font;
        if (pageNumbers == null || pageNumbers.length == 0)
            return;

        // Turn the page number array into a sorted collection of unique values.
        SortedMap<Integer, Integer> map = new TreeMap<Integer, Integer>();
        for (int pn : pageNumbers)
            map.put(pn, 0);
        _pageNumbers = new ArrayList<Integer>(map.keySet());
    }

    /**
     * The action itself to be triggered on a before-page event.
     * @param args The even arguments.
     */
    @Override
    public void handle(BeforeSavingEventArgs<PageAPI> args)
    {
        PageAPI api = args.getElementAPI();

        XpsGlyphs glyphs;
        // For all pages in the output PDF except the first one...
        if (args.getOutputPageNumber() > 1)
        {
          // ...insert a hyperlink to the first page...
            glyphs = api.createGlyphs(_font, 15f, 5f, api.getHeight() - 10f, "[First]");
            glyphs.setFill(api.createSolidColorBrush(Color.BLUE));
            glyphs.setHyperlinkTarget(new XpsPageLinkTarget(_pageNumbers == null ? 1 : _pageNumbers.get(0)));
            api.add(glyphs);

            // ...and to the previous page.
            glyphs = api.createGlyphs(_font, 15f, 60f, api.getHeight() - 10f, "[Prev]");
            glyphs.setFill(api.createSolidColorBrush(Color.BLUE));
            glyphs.setHyperlinkTarget(new XpsPageLinkTarget(
                _pageNumbers == null ? args.getAbsolutePageNumber() - 1 : _pageNumbers.get(args.getOutputPageNumber() - 2)));
            api.add(glyphs);
        }

        // For all pages in the output PDF except the last one...
        if ((_pageNumbers != null && args.getOutputPageNumber() < _pageNumbers.size()) ||
            (_pageNumbers == null && args.getOutputPageNumber() < api.getTotalPageCount()))
        {
          // ...insert a hyperlink to the next page...
            glyphs = api.createGlyphs(_font, 15f, 110f, api.getHeight() - 10f, "[Next]");
            glyphs.setFill(api.createSolidColorBrush(Color.BLUE));
            glyphs.setHyperlinkTarget(new XpsPageLinkTarget(
                _pageNumbers == null ? args.getAbsolutePageNumber() + 1 : _pageNumbers.get(args.getOutputPageNumber())));
            api.add(glyphs);

            // ...and to the last page.
            glyphs = api.createGlyphs(_font, 15f, 160f, api.getHeight() - 10f, "[Last]");
            glyphs.setFill(api.createSolidColorBrush(Color.BLUE));
            glyphs.setHyperlinkTarget(new XpsPageLinkTarget(
                _pageNumbers == null ? api.getTotalPageCount() : _pageNumbers.get(_pageNumbers.size() - 1)));
            api.add(glyphs);
        }

        // Insert a page number in the bottom-right corner.
        glyphs = api.createGlyphs(_font, 15f, api.getWidth() - 20f, api.getHeight() - 10f, Integer.toString(args.getOutputPageNumber()));
        glyphs.setFill(api.createSolidColorBrush(Color.BLACK));
        api.add(glyphs);

        // Add an outline entry to display the links to the converted pages in the navigation pane of a PDF viewer.
        api.addOutlineEntry(MessageFormat.format("Page {0}", args.getOutputPageNumber()), 1, args.getAbsolutePageNumber());
    }
}