/*
 * Reference ETL Parser for Java
 * Copyright (c) 2000-2009 Constantine A Plotnikov
 *
 * Permission is hereby granted, free of charge, to any person 
 * obtaining a copy of this software and associated documentation 
 * files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, 
 * publish, distribute, sublicense, and/or sell copies of the Software, 
 * and to permit persons to whom the Software is furnished to do so, 
 * subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be 
 * included in all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 
 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 
 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 
 * SOFTWARE. 
 */
package net.sf.etl.parsers;

/**
 * <p>
 * A lexer interface. This interface is used to iterate stream of token. Note
 * that the design is intentionally different from Iterator interfaces because
 * lexer is supposed to be used by different methods and these methods need to
 * check current value and depending on value either consume to or delegate
 * processing to other context.
 * </p>
 * 
 * <p>
 * When lexer is created it has position before any token and {@link #advance()}
 * operation should be performed on it.
 * </p>
 * 
 * @author const
 */
public interface Lexer extends AbstractParser<Token> {
	/**
	 * Start reparsing fragment of source. This method is usually used by
	 * editors to reparse some fragment of source code.
	 * 
	 * @param systemId
	 *            a system identifier
	 * @param r
	 *            reader
	 * @param start
	 *            initial position for lexer
	 * @param state
	 *            a state of lexer (one of Lexer.*_STATE constants)
	 */
	void reparse(String systemId, java.io.Reader r, TextPos start,
			LexerStates state);

	/**
	 * @return next token. The token is not consumed.
	 * @throws IllegalStateException
	 *             if lexer is past end of file or before first token.
	 * @see AbstractParser#advance()
	 */
	Token current();
}