/*
 *  JFLAP - Formal Languages and Automata Package
 * 
 * 
 *  Susan H. Rodger
 *  Computer Science Department
 *  Duke University
 *  August 27, 2009

 *  Copyright (c) 2002-2009
 *  All rights reserved.

 *  JFLAP is open source software. Please see the LICENSE for terms.
 *
 */





package file.xml;

import file.ParseException;
import java.util.Map;
import org.w3c.dom.*;
import regular.*;

/**
 * This transducer is the codec for {@link regular.RegularExpression} objects.
 * 
 * @author Thomas Finley
 */

public class RETransducer extends AbstractTransducer {
	/**
	 * Returns the type this transducer recognizes, "re".
	 * 
	 * @return the string "re"
	 */
	public String getType() {
		return "re";
	}

	/**
	 * Given a document, this will return the corresponding regular expression
	 * encoded in the DOM document.
	 * 
	 * @param document
	 *            the DOM document to convert
	 * @return the {@link regular.RegularExpression} instance
	 */
	public java.io.Serializable fromDOM(Document document) {
		Map e2t = elementsToText(document.getDocumentElement());
		String expression = (String) e2t.get(EXPRESSION_NAME);
		if (expression == null)
			if (e2t.containsKey(EXPRESSION_NAME))
				throw new ParseException("Regular expression structure has no "
						+ EXPRESSION_NAME + " tag!");
			else
				expression = "";
		return new RegularExpression(expression);
	}

	/**
	 * Given a JFLAP regular expression, this will return the corresponding DOM
	 * encoding of the structure.
	 * 
	 * @param structure
	 *            the regular expression to encode
	 * @return a DOM document instance
	 */
	public Document toDOM(java.io.Serializable structure) {
		RegularExpression re = (RegularExpression) structure;
		Document doc = newEmptyDocument();
		Element se = doc.getDocumentElement();
		// Add the regular expression tag.
		se.appendChild(createComment(doc, COMMENT_EXPRESSION));
		se
				.appendChild(createElement(doc, EXPRESSION_NAME, null, re
						.asString()));
		// Return the completed document.
		return doc;
	}

	/** The tag name for the regular expression itself. */
	public static final String EXPRESSION_NAME = "expression";

	/** The comment for the list of productions. */
	private static final String COMMENT_EXPRESSION = "The regular expression.";
}