/*

   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.

 */

package org.apache.batik.ext.awt.font;

import java.awt.Shape;
import java.awt.font.GlyphMetrics;
import java.awt.font.GlyphVector;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;
import java.awt.geom.Point2D;

import org.apache.batik.ext.awt.geom.PathLength;

/**
 * PathLayout can layout text along a Shape, usually a Path object.
 * <p>
 * There are a number of improvements that could be made to this class.
 * I'll try to list some of them:
 * <ul>
 * <li> The layout should really only modify the GlyphVector, rather
 *      than converting to a Shape.
 * <li> Maybe the functions should take a AttributedCharacterIterator
 *      or something? Should this class do the entire layout?
 * <li> The layout code works, but it's definitely not perfect.
 * </ul>
 * @author <a href="mailto:dean.jackson@cmis.csiro.au">Dean Jackson</a>
 * @version $Id$
 */

public class TextPathLayout {

    /**
     * Align the text at the start of the path.
     */
    public static final int ALIGN_START = 0;
    /**
     * Align the text at the middle of the path.
     */
    public static final int ALIGN_MIDDLE = 1;
    /**
     * Align the text at the end of the path.
     */
    public static final int ALIGN_END = 2;

    /**
     * Use the spacing between the glyphs to adjust for textLength.
     */
    public static final int ADJUST_SPACING = 0;
    /**
     * Use the entire glyph to adjust for textLength.
     */
    public static final int ADJUST_GLYPHS = 1;

    /**
     * Wraps the GlyphVector around the given path. The results
     * are mostly quite nice but you need to be careful choosing
     * the size of the font that created the GlyphVector, as
     * well as the "curvyness" of the path (really dynamic curves
     * don't look so great, abrupt changes/vertices look worse).
     *
     * @param glyphs The GlyphVector to layout.
     * @param path The path (or shape) to wrap around
     * @param align The text alignment to use. Should be one
     *              of ALIGN_START, ALIGN_MIDDLE or ALIGN_END.
     * @param startOffset The offset from the start of the path for the initial
     *              text position.
     * @param textLength The length that the text should fill.
     * @param lengthAdjustMode The method used to expand or contract
     *                         the text to meet the textLength.
     * @return A shape that is the outline of the glyph vector
     * wrapped along the path
     */


    public static Shape layoutGlyphVector(GlyphVector glyphs,
                                          Shape path, int align,
                                          float startOffset,
                                          float textLength,
                                          int lengthAdjustMode) {

        GeneralPath newPath = new GeneralPath();
        PathLength pl = new PathLength(path);
        float pathLength = pl.lengthOfPath();

        if ( glyphs == null ){
            return newPath;
        }
        float glyphsLength = (float) glyphs.getVisualBounds().getWidth();

        // return from the ugly cases
        if (path == null ||
            glyphs.getNumGlyphs() == 0 ||
            pl.lengthOfPath() == 0f ||
            glyphsLength == 0f) {
            return newPath;
        }

        // work out the expansion/contraction per character
        float lengthRatio = textLength / glyphsLength;

        // the current start point of the character on the path
        float currentPosition = startOffset;

        // if align is START then a currentPosition of 0f
        // is correct.
        // if align is END then the currentPosition should
        // be enough to place the last character on the end
        // of the path
        // if align is MIDDLE then the currentPosition should
        // be enough to center the glyphs on the path

        if (align == ALIGN_END) {
            currentPosition += pathLength - textLength;
        } else if (align == ALIGN_MIDDLE) {
            currentPosition += (pathLength - textLength) / 2;
        }

        // iterate through the GlyphVector placing each glyph

        for (int i = 0; i < glyphs.getNumGlyphs(); i++) {

            GlyphMetrics gm = glyphs.getGlyphMetrics(i);

            float charAdvance = gm.getAdvance();

            Shape glyph = glyphs.getGlyphOutline(i);

            // if lengthAdjust was GLYPHS, then scale the glyph
            // by the lengthRatio in the X direction
            // FIXME: for vertical text this will be the Y direction
            if (lengthAdjustMode == ADJUST_GLYPHS) {
                AffineTransform scale = AffineTransform.getScaleInstance(lengthRatio, 1.0f);
                glyph = scale.createTransformedShape(glyph);

                // charAdvance has to scale accordingly
                charAdvance *= lengthRatio;
            }

            float glyphWidth = (float) glyph.getBounds2D().getWidth();

            // Use either of these to calculate the mid point
            // of the character along the path.
            // If you change this, you must also change the
            // transform on the glyph down below
            // In some case this gives better layout, but
            // the way it is at the moment is a closer match
            // to the textPath layout from the SVG spec

            //float charMidPos = currentPosition + charAdvance / 2f;
            float charMidPos = currentPosition + glyphWidth / 2f;

            // Calculate the actual point to place the glyph around
            Point2D charMidPoint = pl.pointAtLength(charMidPos);

            // Check if the glyph is actually on the path

            if (charMidPoint != null) {

                // Calculate the normal to the path (midline of glyph)
                float angle = pl.angleAtLength(charMidPos);

                // Define the transform of the glyph
                AffineTransform glyphTrans = new AffineTransform();

                // translate to the point on the path
                glyphTrans.translate(charMidPoint.getX(), charMidPoint.getY());

                // rotate midline of glyph to be normal to path
                glyphTrans.rotate(angle);

                // translate glyph backwards so we rotate about the
                // center of the glyph
                // Choose one of these translations - see the comments
                // in the charMidPos calculation above
                glyphTrans.translate(charAdvance / -2f, 0f);
                //glyphTrans.translate(glyphWidth / -2f, 0f);

                glyph = glyphTrans.createTransformedShape(glyph);
                newPath.append(glyph, false);

            }

            // move along by the advance value
            // if the lengthAdjustMode was SPACING then
            // we have to take this into account here
            if (lengthAdjustMode == ADJUST_SPACING) {
                currentPosition += (charAdvance * lengthRatio);
            } else {
                currentPosition += charAdvance;
            }

        }

        return newPath;
    }

    /**
     * Wraps the GlyphVector around the given path.
     *
     * @param glyphs The GlyphVector to layout.
     * @param path The path (or shape) to wrap around
     * @param align The text alignment to use. Should be one
     *              of ALIGN_START, ALIGN_MIDDLE or ALIGN_END.
     * @return A shape that is the outline of the glyph vector
     * wrapped along the path
     */

    public static Shape layoutGlyphVector(GlyphVector glyphs,
                                          Shape path, int align) {

        return layoutGlyphVector(glyphs, path, align, 0f,
                                 (float) glyphs.getVisualBounds().getWidth(),
                                 ADJUST_SPACING);
    }

    /**
     * Wraps the GlyphVector around the given path.
     *
     * @param glyphs The GlyphVector to layout.
     * @param path The path (or shape) to wrap around
     * @return A shape that is the outline of the glyph vector
     * wrapped along the path
     */

    public static Shape layoutGlyphVector(GlyphVector glyphs,
                                          Shape path) {

        return layoutGlyphVector(glyphs, path, ALIGN_START);
    }


} // TextPathLayout
