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package com.sun.tools.xjc.reader.internalizer;

import java.io.IOException;

import com.sun.xml.xsom.parser.XMLParser;

import org.w3c.dom.Document;
import org.xml.sax.ContentHandler;
import org.xml.sax.EntityResolver;
import org.xml.sax.ErrorHandler;
import org.xml.sax.InputSource;
import org.xml.sax.SAXException;


/**
 * {@link XMLParser} implementation that 
 * parses XML from a DOM forest instead of parsing it from
 * its original location.
 * 
 * @author
 *     Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
 */
class DOMForestParser implements XMLParser {
    
    /** DOM forest to be "parsed". */
    private final DOMForest forest;
    
    /** Scanner object will do the actual SAX events generation. */
    private final DOMForestScanner scanner;
    
    private final XMLParser fallbackParser;
    
    /**
     * @param fallbackParser
     *      This parser will be used when DOMForestParser needs to parse
     *      documents that are not in the forest.
     */
    DOMForestParser( DOMForest forest, XMLParser fallbackParser ) {
        this.forest = forest;
        this.scanner = new DOMForestScanner(forest);
        this.fallbackParser = fallbackParser;
    }

    public void parse(
        InputSource source,
        ContentHandler contentHandler,
        ErrorHandler errorHandler,
        EntityResolver entityResolver )
        throws SAXException, IOException {
        
        String systemId = source.getSystemId();
        Document dom = forest.get(systemId);
        
        if(dom==null) {
            // if no DOM tree is built for it,
            // let the fall back parser parse the original document.
            //
            // for example, XSOM parses datatypes.xsd (XML Schema part 2)
            // but this will never be built into the forest.
            fallbackParser.parse( source, contentHandler, errorHandler, entityResolver );
            return;
        }
        
        scanner.scan( dom, contentHandler );
    }
}
