/*
 * RestorableTokenSource.java
 *
 * comments here.
 *
 * @author   Michiaki Tatsubori
 * @version  %VERSION% %DATE%
 * @see      java.lang.Object
 *
 * COPYRIGHT 1998 by Michiaki Tatsubori, ALL RIGHTS RESERVED.
 */
package io.devnulllabs.openjava.syntax;

import io.devnulllabs.openjava.mop.Environment;
import io.devnulllabs.openjava.tools.parser.Token;

/**
 * The class <code>RestorableTokenSource</code>
 * <p>
 * For example
 * <pre>
 * </pre>
 * <p>
 *
 * @author   Michiaki Tatsubori
 * @version  1.0
 * @since    $Id: RestorableTokenSource.java,v 1.2 2003/02/19 02:54:31 tatsubori Exp $
 * @see java.lang.Object
 */
public class RestorableTokenSource implements TokenSource {
    private TokenSource tokenSource;
    private Environment env;
    private int pointer = 0;
    private int offset = 0;

    public RestorableTokenSource(TokenSource src, Environment env) {
        this.tokenSource = src;
        this.env = env;
    }

    public RestorableTokenSource(TokenSource src) {
        this(src, null);
    }

    public Environment getEnvironment() {
        return ((env == null) ? tokenSource.getEnvironment() : env);
    }

    public void assume() {
        offset = pointer;
    }
    public void restore() {
        pointer = offset;
    }
    public void fix() {
        for (int i = offset; i < pointer; ++i) {
            tokenSource.getNextToken();
        }
        pointer = 0;
        offset = 0;
    }
    public Token getNextToken() {
        return tokenSource.getToken(++pointer);
    }

    public Token getToken(int i) {
        return tokenSource.getToken(pointer + i);
    }

}