IndentWatcher.java

/**
 *  Copyright 2011 Oliver Buchtala
 *
 *	This file is part of ndogen.
 *
 *  ndogen is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  ndogen is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with ndogen.  If not, see <http://www.gnu.org/licenses/>.
 */
package org.ndogen.antlr;

import java.util.Stack;

import org.antlr.runtime.*;

public class IndentWatcher {

	Lexer lexer;
	
	Stack<Integer> indentStack;

	private CharStream input;

	private final int DEDENT;

	private final int INDENT;
	
	public IndentWatcher(Lexer lexer, int INDENT, int DEDENT) {
		super();
		this.lexer = lexer;
		this.INDENT = INDENT;
		this.DEDENT = DEDENT;
		input = lexer.getCharStream();
		
		indentStack = new Stack<Integer>();
	}
	
	public void checkIndent(CharStream input) {
		if(indentStack.isEmpty()) {
			indentStack.push(0);
		}
		
		// look ahead and emit INDENTs and DEDENTS if necessary
		int idx = 1;
		int level = 0;
		int pos = 0;
		while(true) {
			int c = input.LA(idx++);
			pos++;
			if(c == '\n') {
				return;
			} else if (c == -1) {
				for (int i = 0; i < indentStack.size()-1; i++) {
					lexer.emit(new CommonToken(DEDENT));
				}
				return;
			} else if (c == ' ') {
				level++;
			} else if (c == '\t') {
				level+=4;
			} else break;
		}
		
		if(level>0) {
			input.seek(input.index()+pos-1);
		}
		
		if (level > indentStack.peek()) {
			indentStack.push(level);
			CommonToken indent = new CommonToken(INDENT);
			indent.setStartIndex(input.index()+1);
			indent.setStopIndex(input.index()+pos);
			lexer.emit(indent);
		} else if (level < indentStack.peek()) {
			while (indentStack.peek() > level) {
				indentStack.pop();
				lexer.emit(new CommonToken(DEDENT));
			}
		}
	}
	
}