/*

 * Copyright (c) 1998, 2014, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.  Oracle designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Oracle in the LICENSE file that accompanied this code.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

package javax.swing.plaf.basic;

import java.io.*;

import java.awt.*;

import java.net.URL;

import javax.swing.*;

import javax.swing.text.*;

import javax.swing.text.html.*;

import sun.swing.SwingUtilities2;

/**

 * Support for providing html views for the swing components.

 * This translates a simple html string to a javax.swing.text.View

 * implementation that can render the html and provide the necessary

 * layout semantics.

 *

 * @author  Timothy Prinzing

 * @since 1.3

 */

public class BasicHTML {

    /**

     * Create an html renderer for the given component and

     * string of html.

     */

    public static View createHTMLView(JComponent c, String html) {

        BasicEditorKit kit = getFactory();

        Document doc = kit.createDefaultDocument(c.getFont(),

                                                 c.getForeground());

        Object base = c.getClientProperty(documentBaseKey);

        if (base instanceof URL) {

            ((HTMLDocument)doc).setBase((URL)base);

        }

        Reader r = new StringReader(html);

        try {

            kit.read(r, doc, 0);

        } catch (Throwable e) {

        }

        ViewFactory f = kit.getViewFactory();

        View hview = f.create(doc.getDefaultRootElement());

        View v = new Renderer(c, f, hview);

        return v;

    }

    /**

     * Returns the baseline for the html renderer.

     *

     * @param view the View to get the baseline for

     * @param w the width to get the baseline for

     * @param h the height to get the baseline for

     * @throws IllegalArgumentException if width or height is < 0

     * @return baseline or a value < 0 indicating there is no reasonable

     *                  baseline

     * @see java.awt.FontMetrics

     * @see javax.swing.JComponent#getBaseline(int,int)

     * @since 1.6

     */

    public static int getHTMLBaseline(View view, int w, int h) {

        if (w < 0 || h < 0) {

            throw new IllegalArgumentException(

                    "Width and height must be >= 0");

        }

        if (view instanceof Renderer) {

            return getBaseline(view.getView(0), w, h);

        }

        return -1;

    }

    /**

     * Gets the baseline for the specified component.  This digs out

     * the View client property, and if non-null the baseline is calculated

     * from it.  Otherwise the baseline is the value <code>y + ascent</code>.

     */

    static int getBaseline(JComponent c, int y, int ascent,

                                  int w, int h) {

        View view = (View)c.getClientProperty(BasicHTML.propertyKey);

        if (view != null) {

            int baseline = getHTMLBaseline(view, w, h);

            if (baseline < 0) {

                return baseline;

            }

            return y + baseline;

        }

        return y + ascent;

    }

    /**

     * Gets the baseline for the specified View.

     */

    static int getBaseline(View view, int w, int h) {

        if (hasParagraph(view)) {

            view.setSize(w, h);

            return getBaseline(view, new Rectangle(0, 0, w, h));

        }

        return -1;

    }

    private static int getBaseline(View view, Shape bounds) {

        if (view.getViewCount() == 0) {

            return -1;

        }

        AttributeSet attributes = view.getElement().getAttributes();

        Object name = null;

        if (attributes != null) {

            name = attributes.getAttribute(StyleConstants.NameAttribute);

        }

        int index = 0;

        if (name == HTML.Tag.HTML && view.getViewCount() > 1) {

            // For html on widgets the header is not visible, skip it.

            index++;

        }

        bounds = view.getChildAllocation(index, bounds);

        if (bounds == null) {

            return -1;

        }

        View child = view.getView(index);

        if (view instanceof javax.swing.text.ParagraphView) {

            Rectangle rect;

            if (bounds instanceof Rectangle) {

                rect = (Rectangle)bounds;

            }

            else {

                rect = bounds.getBounds();

            }

            return rect.y + (int)(rect.height *

                                  child.getAlignment(View.Y_AXIS));

        }

        return getBaseline(child, bounds);

    }

    private static boolean hasParagraph(View view) {

        if (view instanceof javax.swing.text.ParagraphView) {

            return true;

        }

        if (view.getViewCount() == 0) {

            return false;

        }

        AttributeSet attributes = view.getElement().getAttributes();

        Object name = null;

        if (attributes != null) {

            name = attributes.getAttribute(StyleConstants.NameAttribute);

        }

        int index = 0;

        if (name == HTML.Tag.HTML && view.getViewCount() > 1) {

            // For html on widgets the header is not visible, skip it.

            index = 1;

        }

        return hasParagraph(view.getView(index));

    }

    /**

     * Check the given string to see if it should trigger the

     * html rendering logic in a non-text component that supports

     * html rendering.

     */

    public static boolean isHTMLString(String s) {

        if (s != null) {

            if ((s.length() >= 6) && (s.charAt(0) == '<') && (s.charAt(5) == '>')) {

                String tag = s.substring(1,5);

                return tag.equalsIgnoreCase(propertyKey);

            }

        }

        return false;

    }

    /**

     * Stash the HTML render for the given text into the client

     * properties of the given JComponent. If the given text is

     * <em>NOT HTML</em> the property will be cleared of any

     * renderer.

     * <p>

     * This method is useful for ComponentUI implementations

     * that are static (i.e. shared) and get their state

     * entirely from the JComponent.

     */

    public static void updateRenderer(JComponent c, String text) {

        View value = null;

        View oldValue = (View)c.getClientProperty(BasicHTML.propertyKey);

        Boolean htmlDisabled = (Boolean) c.getClientProperty(htmlDisable);

        if (htmlDisabled != Boolean.TRUE && BasicHTML.isHTMLString(text)) {

            value = BasicHTML.createHTMLView(c, text);

        }

        if (value != oldValue && oldValue != null) {

            for (int i = 0; i < oldValue.getViewCount(); i++) {

                oldValue.getView(i).setParent(null);

            }

        }

        c.putClientProperty(BasicHTML.propertyKey, value);

    }

    /**

     * If this client property of a JComponent is set to Boolean.TRUE

     * the component's 'text' property is never treated as HTML.

     */

    private static final String htmlDisable = "html.disable";

    /**

     * Key to use for the html renderer when stored as a

     * client property of a JComponent.

     */

    public static final String propertyKey = "html";

    /**

     * Key stored as a client property to indicate the base that relative

     * references are resolved against. For example, lets say you keep

     * your images in the directory resources relative to the code path,

     * you would use the following the set the base:

     * <pre>

     *   jComponent.putClientProperty(documentBaseKey,

     *                                xxx.class.getResource("resources/"));

     * </pre>

     */

    public static final String documentBaseKey = "html.base";

    static BasicEditorKit getFactory() {

        if (basicHTMLFactory == null) {

            basicHTMLViewFactory = new BasicHTMLViewFactory();

            basicHTMLFactory = new BasicEditorKit();

        }

        return basicHTMLFactory;

    }

    /**

     * The source of the html renderers

     */

    private static BasicEditorKit basicHTMLFactory;

    /**

     * Creates the Views that visually represent the model.

     */

    private static ViewFactory basicHTMLViewFactory;

    /**

     * Overrides to the default stylesheet.  Should consider

     * just creating a completely fresh stylesheet.

     */

    private static final String styleChanges =

    "p { margin-top: 0; margin-bottom: 0; margin-left: 0; margin-right: 0 }" +

    "body { margin-top: 0; margin-bottom: 0; margin-left: 0; margin-right: 0 }";

    /**

     * The views produced for the ComponentUI implementations aren't

     * going to be edited and don't need full html support.  This kit

     * alters the HTMLEditorKit to try and trim things down a bit.

     * It does the following:

     * <ul>

     * <li>It doesn't produce Views for things like comments,

     * head, title, unknown tags, etc.

     * <li>It installs a different set of css settings from the default

     * provided by HTMLEditorKit.

     * </ul>

     */

    @SuppressWarnings("serial") // JDK-implementation class

    static class BasicEditorKit extends HTMLEditorKit {

        /** Shared base style for all documents created by us use. */

        private static StyleSheet defaultStyles;

        /**

         * Overriden to return our own slimmed down style sheet.

         */

        public StyleSheet getStyleSheet() {

            if (defaultStyles == null) {

                defaultStyles = new StyleSheet();

                StringReader r = new StringReader(styleChanges);

                try {

                    defaultStyles.loadRules(r, null);

                } catch (Throwable e) {

                    // don't want to die in static initialization...

                    // just display things wrong.

                }

                r.close();

                defaultStyles.addStyleSheet(super.getStyleSheet());

            }

            return defaultStyles;

        }

        /**

         * Sets the async policy to flush everything in one chunk, and

         * to not display unknown tags.

         */

        public Document createDefaultDocument(Font defaultFont,

                                              Color foreground) {

            StyleSheet styles = getStyleSheet();

            StyleSheet ss = new StyleSheet();

            ss.addStyleSheet(styles);

            BasicDocument doc = new BasicDocument(ss, defaultFont, foreground);

            doc.setAsynchronousLoadPriority(Integer.MAX_VALUE);

            doc.setPreservesUnknownTags(false);

            return doc;

        }

        /**

         * Returns the ViewFactory that is used to make sure the Views don't

         * load in the background.

         */

        public ViewFactory getViewFactory() {

            return basicHTMLViewFactory;

        }

    }

    /**

     * BasicHTMLViewFactory extends HTMLFactory to force images to be loaded

     * synchronously.

     */

    static class BasicHTMLViewFactory extends HTMLEditorKit.HTMLFactory {

        public View create(Element elem) {

            View view = super.create(elem);

            if (view instanceof ImageView) {

                ((ImageView)view).setLoadsSynchronously(true);

            }

            return view;

        }

    }

    /**

     * The subclass of HTMLDocument that is used as the model. getForeground

     * is overridden to return the foreground property from the Component this

     * was created for.

     */

    @SuppressWarnings("serial") // Superclass is not serializable across versions

    static class BasicDocument extends HTMLDocument {

        /** The host, that is where we are rendering. */

        // private JComponent host;

        BasicDocument(StyleSheet s, Font defaultFont, Color foreground) {

            super(s);

            setPreservesUnknownTags(false);

            setFontAndColor(defaultFont, foreground);

        }

        /**

         * Sets the default font and default color. These are set by

         * adding a rule for the body that specifies the font and color.

         * This allows the html to override these should it wish to have

         * a custom font or color.

         */

        private void setFontAndColor(Font font, Color fg) {

            getStyleSheet().addRule(sun.swing.SwingUtilities2.

                                    displayPropertiesToCSS(font,fg));

        }

    }

    /**

     * Root text view that acts as an HTML renderer.

     */

    static class Renderer extends View {

        Renderer(JComponent c, ViewFactory f, View v) {

            super(null);

            host = c;

            factory = f;

            view = v;

            view.setParent(this);

            // initially layout to the preferred size

            setSize(view.getPreferredSpan(X_AXIS), view.getPreferredSpan(Y_AXIS));

        }

        /**

         * Fetches the attributes to use when rendering.  At the root

         * level there are no attributes.  If an attribute is resolved

         * up the view hierarchy this is the end of the line.

         */

        public AttributeSet getAttributes() {

            return null;

        }

        /**

         * Determines the preferred span for this view along an axis.

         *

         * @param axis may be either X_AXIS or Y_AXIS

         * @return the span the view would like to be rendered into.

         *         Typically the view is told to render into the span

         *         that is returned, although there is no guarantee.

         *         The parent may choose to resize or break the view.

         */

        public float getPreferredSpan(int axis) {

            if (axis == X_AXIS) {

                // width currently laid out to

                return width;

            }

            return view.getPreferredSpan(axis);

        }

        /**

         * Determines the minimum span for this view along an axis.

         *

         * @param axis may be either X_AXIS or Y_AXIS

         * @return the span the view would like to be rendered into.

         *         Typically the view is told to render into the span

         *         that is returned, although there is no guarantee.

         *         The parent may choose to resize or break the view.

         */

        public float getMinimumSpan(int axis) {

            return view.getMinimumSpan(axis);

        }

        /**

         * Determines the maximum span for this view along an axis.

         *

         * @param axis may be either X_AXIS or Y_AXIS

         * @return the span the view would like to be rendered into.

         *         Typically the view is told to render into the span

         *         that is returned, although there is no guarantee.

         *         The parent may choose to resize or break the view.

         */

        public float getMaximumSpan(int axis) {

            return Integer.MAX_VALUE;

        }

        /**

         * Specifies that a preference has changed.

         * Child views can call this on the parent to indicate that

         * the preference has changed.  The root view routes this to

         * invalidate on the hosting component.

         * <p>

         * This can be called on a different thread from the

         * event dispatching thread and is basically unsafe to

         * propagate into the component.  To make this safe,

         * the operation is transferred over to the event dispatching

         * thread for completion.  It is a design goal that all view

         * methods be safe to call without concern for concurrency,

         * and this behavior helps make that true.

         *

         * @param child the child view

         * @param width true if the width preference has changed

         * @param height true if the height preference has changed

         */

        public void preferenceChanged(View child, boolean width, boolean height) {

            host.revalidate();

            host.repaint();

        }

        /**

         * Determines the desired alignment for this view along an axis.

         *

         * @param axis may be either X_AXIS or Y_AXIS

         * @return the desired alignment, where 0.0 indicates the origin

         *     and 1.0 the full span away from the origin

         */

        public float getAlignment(int axis) {

            return view.getAlignment(axis);

        }

        /**

         * Renders the view.

         *

         * @param g the graphics context

         * @param allocation the region to render into

         */

        public void paint(Graphics g, Shape allocation) {

            Rectangle alloc = allocation.getBounds();

            view.setSize(alloc.width, alloc.height);

            view.paint(g, allocation);

        }

        /**

         * Sets the view parent.

         *

         * @param parent the parent view

         */

        public void setParent(View parent) {

            throw new Error("Can't set parent on root view");

        }

        /**

         * Returns the number of views in this view.  Since

         * this view simply wraps the root of the view hierarchy

         * it has exactly one child.

         *

         * @return the number of views

         * @see #getView

         */

        public int getViewCount() {

            return 1;

        }

        /**

         * Gets the n-th view in this container.

         *

         * @param n the number of the view to get

         * @return the view

         */

        public View getView(int n) {

            return view;

        }

        /**

         * Provides a mapping from the document model coordinate space

         * to the coordinate space of the view mapped to it.

         *

         * @param pos the position to convert

         * @param a the allocated region to render into

         * @return the bounding box of the given position

         */

        public Shape modelToView(int pos, Shape a, Position.Bias b) throws BadLocationException {

            return view.modelToView(pos, a, b);

        }