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 * CruiseControl, a Continuous Integration Toolkit
 * Copyright (c) 2001-2003, 2006, ThoughtWorks, Inc.
 * 200 E. Randolph, 25th Floor
 * Chicago, IL 60601 USA
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
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 * are met:
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 *     + Redistributions of source code must retain the above copyright
 *       notice, this list of conditions and the following disclaimer.
 *
 *     + Redistributions in binary form must reproduce the above
 *       copyright notice, this list of conditions and the following
 *       disclaimer in the documentation and/or other materials provided
 *       with the distribution.
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 *       names of its contributors may be used to endorse or promote
 *       products derived from this software without specific prior
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 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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package net.sourceforge.cruisecontrol.gendoc;

import java.io.IOException;
import java.io.StringReader;

import javax.xml.parsers.ParserConfigurationException;
import javax.xml.parsers.SAXParser;
import javax.xml.parsers.SAXParserFactory;

import org.xml.sax.InputSource;
import org.xml.sax.SAXException;
import org.xml.sax.SAXParseException;
import org.xml.sax.helpers.DefaultHandler;

/**
 * Utility class for validating the XML in plugin descriptions and notes.
 * @author pollens@msoe.edu
 */
class XMLValidator {

    private final SAXParser parser;
    
    private final ErrorHandler handler;
    
    private SAXParseException error;
    
    public XMLValidator() {
        try {
            parser = SAXParserFactory.newInstance().newSAXParser();
        } catch (ParserConfigurationException e) {
            // This shouldn't happen.
            throw new RuntimeException(e);
        } catch (SAXException e) {
            // This shouldn't happen.
            throw new RuntimeException(e);
        }
        
        handler = new ErrorHandler();
    }
    
    /**
     * Validates text as well-formed XML.
     * @param text Text to validate.
     * @param field Name of the field being validated (used in error messages).
     * @throws PluginInfoParsingException Iff the text is not valid XML.
     */
    public void validateWellFormed(String text, String field) throws PluginInfoParsingException {
        // Surround the string with <p> tags, in case it doesn't have any surrounding
        // tags already.
        text = String.format("<p>%s</p>", text);
        
        // Reset the error state.
        error = null;
        
        // Try to parse the text as XML.
        try {
            parser.parse(new InputSource(new StringReader(text)), handler);
        } catch (SAXException e) {
            // Fall through to the error handling code below.
        } catch (IOException e) {
            // This shouldn't happen.
            throw new RuntimeException(e);
        }
        
        if (error != null) {
            throw new PluginInfoParsingException(
                    "Invalid XML content in " + field + ": " + error.getMessage());
        }
    }
    
    /**
     * SAX handler to catch XML errors.
     * @author pollens
     */
    private class ErrorHandler extends DefaultHandler {
        
        @Override
        public void fatalError(SAXParseException e) {
            XMLValidator.this.error = e;
        }
        
    }
    
}