/*
 * 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.
 */

/* $Id$ */
 
package org.apache.fop.image.analyser;

// Java
import java.io.InputStream;
import java.io.IOException;
import java.awt.geom.AffineTransform;

// XML
import org.w3c.dom.Element;
import org.w3c.dom.svg.SVGDocument;

// Batik
import org.apache.batik.dom.svg.SAXSVGDocumentFactory;
import org.apache.batik.dom.svg.SVGOMDocument;
import org.apache.batik.bridge.BridgeContext;
import org.apache.batik.bridge.UnitProcessor;
import org.apache.batik.dom.svg.SVGDOMImplementation;
import org.apache.commons.io.IOUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

// FOP
import org.apache.fop.image.XMLImage;
import org.apache.fop.image.FopImage;
import org.apache.fop.apps.FOUserAgent;
import org.apache.fop.svg.SVGUserAgent;
import org.apache.fop.util.UnclosableInputStream;

/** 
 * ImageReader object for SVG document image type.
 */
public class SVGReader implements ImageReader {

    /** Logger instance */
    protected static Log log = LogFactory.getLog(SVGReader.class);
    
    /** SVG's MIME type */
    public static final String SVG_MIME_TYPE = "image/svg+xml";

    private boolean batik = true;

    /** @see org.apache.fop.image.analyser.ImageReader */
    public FopImage.ImageInfo verifySignature(String uri, InputStream fis,
            FOUserAgent ua) throws IOException {
        FopImage.ImageInfo info = loadImage(uri, fis, ua);
        if (info != null) {
            IOUtils.closeQuietly(fis);
        }
        return info;
    }

    /**
     * Returns the MIME type supported by this implementation.
     *
     * @return   The MIME type
     */
    public String getMimeType() {
        return SVG_MIME_TYPE;
    }

    /**
     * This means the external svg document will be loaded twice. Possibly need
     * a slightly different design for the image stuff.
     *
     * @param uri  @todo Description of the Parameter
     * @param fis  @todo Description of the Parameter
     * @param ua   @todo Description of the Parameter
     * @return     @todo Description of the Return Value
     */
    private FopImage.ImageInfo loadImage(String uri, InputStream bis,
            FOUserAgent ua) {
        if (batik) {
            try {
                Loader loader = new Loader();
                return loader.getImage(uri, bis, 
                    ua.getSourcePixelUnitToMillimeter());
            } catch (NoClassDefFoundError e) {
                batik = false;
                log.warn("Batik not in class path", e);
                return null;
            }
        }
        return null;
    }

    /**
     * This method is put in another class so that the classloader does not
     * attempt to load batik related classes when constructing the SVGReader
     * class.
     */
    class Loader {
        private FopImage.ImageInfo getImage(String uri, InputStream fis,
                float pixelUnitToMM) {
            // parse document and get the size attributes of the svg element

            try {
                fis = new UnclosableInputStream(fis);

                FopImage.ImageInfo info = new FopImage.ImageInfo();

                //Set the resolution to that of the FOUserAgent
                info.dpiHorizontal = 25.4f / pixelUnitToMM;
                info.dpiVertical = info.dpiHorizontal;
                
                info.originalURI = uri;
                info.mimeType = getMimeType();
                info.str = SVGDOMImplementation.SVG_NAMESPACE_URI;

                int length = fis.available();
                fis.mark(length + 1);
                SAXSVGDocumentFactory factory = new SAXSVGDocumentFactory(
                        XMLImage.getParserName());
                SVGDocument doc = (SVGDocument) factory.createSVGDocument(uri, fis);
                info.data = doc;

                Element e = doc.getRootElement();
                String s;
                SVGUserAgent userAg = new SVGUserAgent(pixelUnitToMM,
                            new AffineTransform());
                BridgeContext ctx = new BridgeContext(userAg);
                UnitProcessor.Context uctx = UnitProcessor.createContext(ctx, e);

                // 'width' attribute - default is 100%
                s = e.getAttributeNS(null,
                        SVGOMDocument.SVG_WIDTH_ATTRIBUTE);
                if (s.length() == 0) {
                    s = SVGOMDocument.SVG_SVG_WIDTH_DEFAULT_VALUE;
                }
                info.width = Math.round(UnitProcessor.svgHorizontalLengthToUserSpace(
                        s, SVGOMDocument.SVG_WIDTH_ATTRIBUTE, uctx));

                // 'height' attribute - default is 100%
                s = e.getAttributeNS(null,
                        SVGOMDocument.SVG_HEIGHT_ATTRIBUTE);
                if (s.length() == 0) {
                    s = SVGOMDocument.SVG_SVG_HEIGHT_DEFAULT_VALUE;
                }
                info.height = Math.round(UnitProcessor.svgVerticalLengthToUserSpace(
                        s, SVGOMDocument.SVG_HEIGHT_ATTRIBUTE, uctx));

                return info;
            } catch (NoClassDefFoundError ncdfe) {
                try {
                    fis.reset();
                } catch (IOException ioe) {
                    // we're more interested in the original exception
                }
                batik = false;
                log.warn("Batik not in class path", ncdfe);
                return null;
            } catch (IOException e) {
                // If the svg is invalid then it throws an IOException
                // so there is no way of knowing if it is an svg document

                log.debug("Error while trying to load stream as an SVG file: "
                                       + e.getMessage());
                // assuming any exception means this document is not svg
                // or could not be loaded for some reason
                try {
                    fis.reset();
                } catch (IOException ioe) {
                    // we're more interested in the original exception
                }
                return null;
            }
        }
    }

}