package net.jxta.edutella.provider.datalog;

import java.io.InputStreamReader;
import java.io.Reader;
import java.io.StringReader;
import java.net.URL;

import net.jxta.edutella.eqm.EQMException;
import net.jxta.edutella.eqm.Query;
import net.jxta.edutella.eqm.io.QueryParser;




/**
 * Supports import and export of Datalog queries. For query import this class provides its 
 * own native Datalog parser.
 * 
 * @author Boris Wolf
 * @version $Revision: 1.1 $ $Date: 2002/03/06 16:12:40 $
 */
public class DatalogQueryParser implements QueryParser {
	public Query read(Reader src) {
		return read(src, null);
	}
	
	public Query parse(String src) {
		return read(new StringReader(src), null);
	}

    public Query parse(String src, String base) {
        return read(new StringReader(src), base);
    }

	public Query read(URL src) {
		try {
			InputStreamReader input =
				new InputStreamReader(src.openStream());
			return read(input, src.toString());
		} catch (Exception e) {
            System.out.println(e.getMessage());
			throw new EQMException(e.getMessage());
		}
	}
    
    public Query read(Reader src, String base) {
        try{
            AntlrDatalogLexer lexer = new AntlrDatalogLexer(src);
            AntlrDatalogParser parser = new AntlrDatalogParser(lexer);
            if ( base == null ) {
                base = "";
            } 

            Query eduquery = parser.query(base);
            return eduquery;
        } catch (Exception e){
            throw new EQMException(e);
        }
    }
}