/**********************************************
    * Copyright (C) 2010 Lukas Laag
    * This file is part of lib-gwt-svg.
    * 
    * libgwtsvg is free software: you can redistribute it and/or modify
    * it under the terms of the GNU Lesser General Public License as published by
    * the Free Software Foundation, either version 3 of the License, or
    * (at your option) any later version.
    * 
   * libgwtsvg 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 Lesser General Public License for more details.
   * 
   * You should have received a copy of the GNU Lesser General Public License
   * along with libgwtsvg.  If not, see http://www.gnu.org/licenses/
   **********************************************/
  package org.vectomatic.dev.svg.impl.gen;
  
  import java.io.ByteArrayInputStream;
  import java.io.InputStream;
  import java.io.Reader;
  import java.io.StringReader;
  import java.net.URL;
  
  import javax.xml.XMLConstants;
  import javax.xml.transform.Source;
  import javax.xml.transform.stream.StreamSource;
  import javax.xml.validation.Schema;
  import javax.xml.validation.SchemaFactory;
  import javax.xml.validation.Validator;
  
  import org.w3c.dom.ls.LSInput;
  import org.w3c.dom.ls.LSResourceResolver;
  import org.xml.sax.SAXParseException;
  
  import com.google.gwt.core.ext.TreeLogger;
  import com.google.gwt.core.ext.UnableToCompleteException;
  import com.google.gwt.uibinder.rebind.UiBinderWriter;
  
  /**
   * Class to validate an SVG file against the SVG 1.1 XSD schema
   * @author laaglu
   */
  public class SVGValidator {
  	private static Validator validator;
  	
  	/**
  	 * Constructor (block instantiation)
  	 */
  	private SVGValidator() {
  	}
  	/**
  	 * Validates the specified SVG input
  	 * @param rawSvg The SVG input to validate 
  	 * @param systemId The URL of the resource being validated
  	 * @param logger A logger to report validation errors (if the method is invoked
  	 * to validate an {@link org.vectomatic.dom.svg.ui.SVGResource} or an
  	 * {@link org.vectomatic.dom.svg.ui.ExternalSVGResource})
  	 * @param writer A writer to report validation errors (if the method is
  	 * invoked to validate a UiBinder template)
  	 * @throws UnableToCompleteException If validation error occur
  	 */
  	public static void validate(String rawSvg, String systemId, final TreeLogger logger, final UiBinderWriter writer) throws UnableToCompleteException {
  	    try {
  	    	if (validator == null) {
  	    		SchemaFactory factory = SchemaFactory.newInstance(XMLConstants.W3C_XML_SCHEMA_NS_URI);
  	    		URL svgSchemaURL = SVGValidator.class.getResource("SVG.xsd");
  	    	    Source schemaFile = new StreamSource(svgSchemaURL.openStream(), svgSchemaURL.toExternalForm());
  	    	    Schema schema = factory.newSchema(schemaFile);
  	    	    validator = schema.newValidator();
  	    	    validator.setResourceResolver(new LSResourceResolver() {
  					@Override
  					public LSInput resolveResource(String type, String namespaceURI,
  							final String publicId, final String systemId, final String baseURI) {
  						if (logger != null) {
  				    		logger.log(TreeLogger.INFO, "resolveResource(" + type + ", " + namespaceURI + ", " + publicId + ", " + systemId + ", " + baseURI + ")");
  				    	}
  						return new LSInput() {
  
  							@Override
  							public Reader getCharacterStream() {
  								return new StringReader("");
  							}
  
  							@Override
  							public void setCharacterStream(
  									Reader characterStream) {
  							}
  
  							@Override
  							public InputStream getByteStream() {
  								return new ByteArrayInputStream(new byte[0]);
  							}
  
  							@Override
  							public void setByteStream(InputStream byteStream) {
  							}
  
 							@Override
 							public String getStringData() {
 								return "";
 							}
 
 							@Override
 							public void setStringData(String stringData) {							
 							}
 
 							@Override
 							public String getSystemId() {
 								return systemId;
 							}
 
 							@Override
 							public void setSystemId(String systemId) {
 							}
 
 							@Override
 							public String getPublicId() {
 								return publicId;
 							}
 
 							@Override
 							public void setPublicId(String publicId) {
 							}
 
 							@Override
 							public String getBaseURI() {
 								return baseURI;
 							}
 
 							@Override
 							public void setBaseURI(String baseURI) {
 							}
 
 							@Override
 							public String getEncoding() {
 								return null;
 							}
 
 							@Override
 							public void setEncoding(String encoding) {
 							}
 
 							@Override
 							public boolean getCertifiedText() {
 								return false;
 							}
 
 							@Override
 							public void setCertifiedText(boolean certifiedText) {
 							}
 							
 						};
 					}
 				});
 	    	}
 	        validator.validate(new StreamSource(new StringReader(rawSvg), systemId));
 	    } catch (SAXParseException e) {
 	    	if (writer != null) {
 	    		writer.die(e.getMessage() + " @" + e.getSystemId() + " L:" + e.getLineNumber() + ",C:" + e.getColumnNumber());
 	    	} else if (logger != null) {
 	    		logger.log(TreeLogger.ERROR, "Invalid SVG input @" + e.getSystemId() + " L:" + e.getLineNumber() + ",C:" + e.getColumnNumber(), e);
 				throw new UnableToCompleteException();
 	    	}
 	    } catch (Throwable t) {
 	    	if (writer != null) {
 	    		writer.die(t.getMessage());
 	    	} else if (logger != null) {
 	    		logger.log(TreeLogger.ERROR, "Invalid SVG input", t);
 				throw new UnableToCompleteException();
 	    	}
 	    }
 	}
 }